Autosomal Dominant Cerebellar Ataxia

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Inheritance

1

Autosomal dominant HP:0000006

Autosomal dominant transmission is characteristic. Each child of a heterozygous affected parent has a 50% probability of inheriting the disease allele, with clinical risk modified by penetrance and repeat structure. An apparently negative family history can reflect late onset, reduced penetrance, an unrecognized affected relative, de novo variation or parental mosaicism. Anticipation occurs in several unstable-repeat disorders but is not universal: SCA6 generally lacks anticipation and it is infrequent in SCA17.

Autosomal dominant inheritance

Show evidence (2 references)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Human Clinical

"hereditary ataxia has a 50% chance of inheriting the"

In the autosomal-dominant offspring section, the chapter specifies allele-transmission risk, not guaranteed age or severity of disease.

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"Normal SCA17 alleles contain 25 to 40 repeats while alleles with 41 to 49 repeats have incomplete penetrance."

The review illustrates allele-dependent penetrance; locus-specific interpretation is required.

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Subtypes

8

clinical

ADCA Type I (ataxia with extracerebellar features) MONDO:0019792

Historical Harding type I describes cerebellar ataxia with extracerebellar neurological findings, such as pyramidal, extrapyramidal, cognitive or oculomotor abnormalities. Expression varies within families and across molecular causes; the clinical class is not a single genotype.

Show evidence (2 references)

PMID:7066668 SUPPORT PRIMARY RESULT Human Clinical

"The clinical features of 11 families containing 73 individuals with dominantly inherited cerebellar ataxia of late onset are described."

The original clinical classification was derived from 11 families and predates molecular subtype definitions.

PMID:7066668 SUPPORT PRIMARY RESULT Human Clinical

"Many of the patients had physical signs in addition to cerebellar ataxia, which included dementia, supranuclear ophthalmoplegia, extrapyramidal dysfunction, optic atrophy, pigmentary retinal degeneration, myoclonus and deafness."

The original cohort documents the broader neurological spectrum.

ADCA Type II (ataxia with pigmentary retinopathy) MONDO:0016163

ATXN7 hgnc:10560

Historical Harding type II combines cerebellar ataxia with pigmentary retinal degeneration. ATXN7-related SCA7 is the major molecular example and can cause cone-rod dystrophy with progressive visual loss. MONDO carries the historical ADCA type II class name as a synonym of spinocerebellar ataxia 7 (MONDO:0016163), rather than providing a separate ADCA-II term.

Show evidence (2 references)

PMID:7066668 SUPPORT PRIMARY RESULT Human Clinical

"cerebellar ataxia with pigmentary retinal degeneration"

The original classification specifically identifies the retinal-associated presentation.

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"Retinal degeneration is a distinctive feature of SCA7 with progressive cone-rod dystrophy leading to even- tual blindness [100]."

The review connects the retinal clinical class with SCA7.

ADCA Type III (pure cerebellar ataxia) MONDO:0019793

Historical Harding type III describes a predominantly cerebellar syndrome, often slowly progressive and later in onset. SCA6 is a common example; the roster and degree of permitted extracerebellar involvement differ between clinical classifications. The Roman numeral III does not denote SCA3.

Show evidence (2 references)

PMID:7066668 SUPPORT PRIMARY RESULT Human Clinical

"a later onset (over 60 years) 'pure' cerebellar syndrome"

The original classification identifies a late-onset predominantly cerebellar presentation.

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"SCA6 is considered a pure cerebellar ataxia."

The molecular SCA6 example has predominantly cerebellar disease.

molecular

SCA10 (ATXN10 intronic ATTCT expansion) MONDO:0011330

ATXN10 hgnc:10549

An intronic pentanucleotide (ATTCT) expansion in ATXN10, and therefore a noncoding-repeat rather than a polyglutamine disease. The reported syndrome combines slowly progressive cerebellar ataxia with seizures. MONDO parents this term under autosomal dominant cerebellar ataxia type IV, a Harding class this entry does not carry as a clinical row, so it is placed on the family entry rather than on the ADCA-I or ADCA-III entries.

Show evidence (2 references)

PMID:11017075 SUPPORT PRIMARY RESULT Human Clinical

"We found an expansion of a pentanucleotide (ATTCT) repeat in intron 9 of SCA10 in all patients in five Mexican SCA10 families."

The discovery study locates the causal expansion in an intron of the gene now called ATXN10, in all affected members of five families.

PMID:11017075 SUPPORT BACKGROUND Human Clinical

"Spinocerebellar ataxia type 10 (SCA10; MIM 603516; refs 1,2) is an autosomal dominant disorder characterized by cerebellar ataxia and seizures."

Source for the dominant inheritance and the ataxia-with-seizures clinical description of this subtype.

SCA44 (GRM1) MONDO:0033479

GRM1 hgnc:4593

Caused by heterozygous dominant variants in GRM1, which encodes the metabotropic glutamate receptor mGluR1. The reported alleles are not mechanistically uniform: gain-of-function missense variants segregated with adult-onset cerebellar ataxia in two families, while a de novo truncating variant acting as a dominant negative was associated with juvenile-onset ataxia and intellectual disability. A conventional-variant subtype, not a repeat expansion.

Show evidence (1 reference)

PMID:28886343 SUPPORT PRIMARY RESULT Human Clinical

"Here, we describe heterozygous dominant mutations in GRM1, which encodes mGluR1, that are associated with distinct disease phenotypes: gain-of-function missense mutations, linked in two different families to adult-onset cerebellar ataxia, and a de novo truncation mutation resulting in a..."

Source for the GRM1 gene assignment and for the two distinct dominant allele mechanisms recorded in this row.

SCA50 (NPTX1) MONDO:0859334

NPTX1 hgnc:7952

Caused by heterozygous missense variants in NPTX1, which encodes the secreted protein neuronal pentraxin 1. The reported phenotype is a late-onset, slowly progressive cerebellar ataxia with downbeat nystagmus, cerebellar cognitive-affective features, myoclonic tremor and mild vermian atrophy. Note that the SCA50 designation has also been applied to GAA-FGF14 disease: the title of PMID:36493768 reads "An intronic GAA repeat expansion in FGF14 causes the autosomal-dominant adult-onset ataxia SCA50/ATX-FGF14." This row is scoped to the NPTX1 disease that MONDO:0859334 denotes (OMIM:620158), resolved through that cross-reference rather than through the label.

Show evidence (2 references)

PMID:34788392 SUPPORT PRIMARY RESULT Human Clinical

"Our results establish NPTX1 as a new causative gene in autosomal dominant cerebellar ataxias."

Source for the NPTX1 gene assignment in a dominant cerebellar ataxia.

PMID:34788392 SUPPORT PRIMARY RESULT Human Clinical

"The NPTX1-associated phenotype consists of a late-onset, slowly progressive, cerebellar ataxia, with downbeat nystagmus, cognitive impairment reminiscent of cerebellar cognitive affective syndrome, myoclonic tremor and mild cerebellar vermian atrophy on brain imaging."

Source for the clinical description recorded in this row.

SCA51 (THAP11 CAG expansion) MONDO:0975800

THAP11 hgnc:23194

Caused by a coding CAG repeat expansion in THAP11, so a polyglutamine rather than a conventional-variant subtype. Reported expanded alleles carried 45 to 100 repeats against 20 to 38 in controls, and the length of the uninterrupted 3-prime CAG tract rather than the total repeat length tracked with polyglutamine toxicity. Detection has so far been concentrated in Chinese-ancestry pedigrees; a population survey of Genomics England, a UCL neurology cohort and UK Biobank concluded the expansion is rare in the British population. The gene symbol THAP11 (hgnc:23194) is not THAP1 (hgnc:20856), the DYT6 dystonia gene.

Show evidence (2 references)

PMID:37148549 SUPPORT PRIMARY RESULT Human Clinical

"We identified THAP11 as the novel causative SCA gene with CAG repeats ranging from 45 to 100 in patients with ataxia and from 20 to 38 in healthy control subjects."

Source for the THAP11 gene assignment and for the patient and control repeat ranges quoted in this row.

PMID:39651830 SUPPORT PRIMARY RESULT Human Clinical

"These results indicate that THAP11 expansions are rare in the British population and that sequence structures predisposed to expansions may be more common in non-British ancestries."

Population survey establishing that this subtype is rare outside the ancestries in which it was discovered. It qualifies the expected yield of testing rather than contradicting the gene-disease association.

SCA52 (RAB3A) MONDO:0981162

RAB3A hgnc:9777

Caused by a heterozygous missense variant in RAB3A, a small GTPase of regulated exocytosis, reported in two families with adult-onset progressive cerebellar ataxia and cerebellar atrophy. The variant retains GTP binding but fails to bind the effectors RIM1 and Rabphilin-3A, so the proposed lesion is presynaptic rather than a repeat-expansion or protein-aggregation mechanism. A conventional-variant subtype.

Show evidence (2 references)

PMID:41492970 SUPPORT PRIMARY RESULT Human Clinical

"In this study, we identified the c.247C > T p.(Arg83Trp) variant in RAB3A, encoding a small GTPase involved in membrane-associated regulated exocytosis, in two families with cerebellar ataxia."

Source for the RAB3A gene assignment and for the two-family basis of this subtype.

PMID:41492970 SUPPORT PRIMARY RESULT Human Clinical

"Affected individuals presented with adult-onset, gradually progressive cerebellar symptoms, often accompanied by mild gait spasticity and tremors."

Source for the clinical description recorded in this row.

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Discussions and Knowledge Gaps

2

Which expanded-protein species drive injury in each molecular subtype?

KNOWLEDGE GAP adca_inclusion_toxicity

Attached to

pathophysiology#Neuronal Polyglutamine Inclusions

Large inclusions are pathological observations but are not established as the universally toxic species. Soluble species, fragments, native-protein interactions and RNA-related processes can contribute differently. Therefore inclusion formation is a parallel observed endpoint, not a required bridge to neuronal death.

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Other

"Whether these large aggregates, a hallmark of all polyQ SCAs, are neurotox- ic or neuroprotective is still under debate [ 47]."

The review explicitly identifies unresolved direction of inclusion effects.

Which molecular and cellular abnormalities explain each subtype-specific clinical trajectory?

KNOWLEDGE GAP adca_molecular_and_clinical_heterogeneity

Attached to

pathophysiology#Cerebellar Network Dysfunction

Historical clinical classes cross molecular diagnoses, and similar ataxia can arise from different neuronal compartments and genetic lesions. Human SCA3 cortical sparing, episodic SCA6 and restricted FGF14 ocular presentations preclude a universal Purkinje-loss or fixed-progression model. Selected regional cohorts also cannot establish one worldwide subtype distribution.

Show evidence (2 references)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"SCA3 affects various different regions of the brain and spinal cord, although the cerebellar cortex and olivary nuclei Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias 265 are relatively spared. The brain weight of SCA3 patients is significantly reduced,..."

Human SCA3 neuropathology demonstrates relative cerebellar-cortex sparing and dentate-nucleus involvement.

PMID:38507876 SUPPORT BACKGROUND Human Clinical

"A dominantly inherited GAA repeat expansion in intron 1 of the fibroblast growth factor 14 (FGF14) gene has recently been identified as the cause of GAA-FGF14 disease/spinocerebellar ataxia 27B (SCA27B)"

The primary cohort introduces an established noncoding expansion cause, distinct from the polyglutamine group.

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Pathophysiology

12

Coding Polyglutamine Repeat Expansion

Expanded coding CAG tracts cause the polyglutamine SCAs, including SCA1, SCA2, SCA3, SCA6, SCA7 and SCA17. Repeat thresholds and interruption effects are locus-specific.

ATXN1 hgnc:10548 THAP11 hgnc:23194 ATXN2 hgnc:10555 ATXN3 hgnc:7106 CACNA1A hgnc:1388 ATXN7 hgnc:10560 TBP hgnc:11588

Experimental models

SCA2 patient fibroblast ASO target-engagement assay PRIMARY CELL CULTURE Patient-derived fibroblasts retain the expanded coding allele used for the target-engagement assay.

Downstream

Expanded Polyglutamine Protein Translation of a pathogenic coding expansion lengthens the encoded glutamine tract.

Show evidence (2 references)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"These diseases are all caused by a CAG repeat expansion in the coding region of a gene."

The review defines the six polyglutamine SCAs; this mechanism does not describe every ADCA.

PMID:37148549 SUPPORT PRIMARY RESULT Human Clinical

"We identified THAP11 as the novel causative SCA gene with CAG repeats ranging from 45 to 100 in patients with ataxia and from 20 to 38 in healthy control subjects."

Adds THAP11 to this node as a coding CAG expansion identified after the 2019 review that defined the original six.

Expanded Polyglutamine Protein

Translation produces an abnormally long glutamine tract within the affected protein. Toxic gain of function and altered native protein interactions can coexist; the normal functions of the different proteins are not interchangeable.

ATXN1 hgnc:10548 ATXN2 hgnc:10555 ATXN3 hgnc:7106 CACNA1A hgnc:1388 ATXN7 hgnc:10560 TBP hgnc:11588

Animal models

Purkinje-directed ATXN2-Q127 transgenic mouse Mouse recapitulates Expresses expanded human ATXN2 in Purkinje cells.

BAC-ATXN2-Q72 transgenic mouse Mouse recapitulates Models expanded human ATXN2 in a BAC genomic context.

Downstream

Polyglutamine Protein Misfolding Polyglutamine expansion favors abnormal protein conformation.

Altered Neuronal Gene Expression Expanded proteins perturb transcriptional regulators through subtype-specific interactions.

Reduced Purkinje Cell Firing The mutant-ATXN2 branch impairs Purkinje physiology in SCA2 models; intervening molecular mechanisms remain incompletely resolved.

Extracerebellar Neural Dysfunction In multisystem polyglutamine SCAs, expanded-protein disease also injures selected neurons outside the cerebellar cortex.

Retinal Photoreceptor Degeneration Expanded ATXN7 is associated with retinal degeneration through subtype-specific mechanisms; this route is not assigned to every expanded polyglutamine protein.

Show evidence (1 reference)

PMID:28405024 SUPPORT BACKGROUND Human Clinical

"SCA2 is caused by DNA CAG repeat expansion leading to an increase in the polyglutamine (polyQ) domain in the N-terminal part of the ATXN2 protein."

The SCA2 background directly describes translation of the coding expansion.

Polyglutamine Protein Misfolding

Expanded polyglutamine proteins adopt abnormal conformations. Misfolded soluble species and cleavage fragments can perturb cellular homeostasis; their importance differs among subtypes.

Downstream

Neuronal Polyglutamine Inclusions Misfolded expanded proteins can accumulate in inclusions.

Cerebellar Neuron Degeneration Misfolded-protein toxicity contributes through incompletely resolved, interacting cellular pathways; visible inclusion formation is not required by this edge.

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Other

"For the polyQ SCAs, the misfolded mutant polyQ proteins present a major challenge to cellular protein quality control systems."

Misfolded expanded proteins challenge proteostasis; this is a synthesis across polyglutamine models.

Neuronal Polyglutamine Inclusions

Large insoluble inclusions containing expanded proteins occur in the polyglutamine SCAs. Their causal contribution is unresolved; this graph does not assume visible inclusions are the lethal species or a necessary intermediate to neuron loss.

inclusion body assembly GO:0070841 ↑ INCREASED

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Other

"the expanded polyQ sequence leads to the formation of large insoluble protein aggregates containing the expanded diseased protein mainly in neurons of the cerebellum."

The review distinguishes large insoluble inclusions from the unresolved toxic protein species.

Altered Neuronal Gene Expression

Expanded proteins alter transcriptional regulation in experimental polyglutamine disease systems. Loss of normal interactions and abnormal interactions both contribute; the affected transcripts and degree of mediation are subtype-dependent.

Downstream

Cerebellar Neuron Degeneration Transcriptional disruption is one proposed contributor to degeneration. The review explicitly leaves unresolved how much it mediates toxicity or whether targeting it alone is sufficient.

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Other

"One well-established effect of the mutant polyQ proteins is that these proteins lead to transcriptional dysregulation."

Altered gene expression is one experimentally supported consequence of expanded proteins; its contribution varies by subtype.

Cerebellar Neuron Degeneration

Neurons of the cerebellum and its connections degenerate in established disease. Vulnerability varies: SCA2 prominently affects Purkinje cells, whereas SCA3 relatively spares the cerebellar cortex and prominently affects dentate neurons. A single universal Purkinje-death pathway would misrepresent this family.

cerebellum UBERON:0002037

Downstream

Cerebellar Network Dysfunction Loss of vulnerable neurons disrupts cerebellar circuitry and its connections.

Cerebellar atrophy Neuron loss contributes to anatomical atrophy in degenerative subtypes, as described for SCA2; MRI alone does not establish a cellular or molecular mechanism.

Show evidence (2 references)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"Autosomal dominant cerebellar ataxias (ADCAs) are a group of neurodegenerative disorders characterized by degeneration of the cerebellum and its connections."

The family definition includes the cerebellum and its connected pathways, rather than one universal vulnerable cell type.

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"SCA3 affects various different regions of the brain and spinal cord, although the cerebellar cortex and olivary nuclei Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias 265 are relatively spared. The brain weight of SCA3 patients is significantly reduced,..."

Human SCA3 neuropathology demonstrates relative cerebellar-cortex sparing and dentate-nucleus involvement.

Reduced Purkinje Cell Firing

Reduced spontaneous Purkinje-cell firing is demonstrated in SCA2 transgenic mouse cerebellar slices and is reversible after ATXN2 lowering. This physiological defect is distinct from neuron loss and is not asserted to occur identically in every ADCA subtype.

Purkinje cell CL:0000121

Animal models

Purkinje-directed ATXN2-Q127 transgenic mouse Mouse recapitulates Mutant physiology is measured in acute slices after animal treatment.

BAC-ATXN2-Q72 transgenic mouse Mouse recapitulates Firing frequency is restored in acute slices after delayed treatment.

Downstream

Cerebellar Network Dysfunction Abnormal Purkinje output can impair cerebellar motor circuits. The model links physiology and behavior but does not selectively restore firing independently of other ATXN2 effects.

Show evidence (1 reference)

PMID:28405024 SUPPORT BACKGROUND In Vitro

"In acute slice preparations, we had previously shown that mutant ATXN2 caused a slowing of PC firing."

Slice electrophysiology documents reduced Purkinje firing in mutant-ATXN2 mice.

Cerebellar Network Dysfunction

Disordered activity in cerebellar circuits and their connections impairs motor coordination. Functional disruption can accompany degeneration but need not require loss of all affected neurons; the SCA2 model demonstrates reversibility of a firing defect.

cerebellum UBERON:0002037

Animal models

Purkinje-directed ATXN2-Q127 transgenic mouse Mouse recapitulates Motor performance improves after ATXN2 lowering.

BAC-ATXN2-Q72 transgenic mouse Mouse recapitulates ASO-treated mice have improved but incomplete motor recovery.

Downstream

Progressive cerebellar ataxia Cerebellar circuit dysfunction contributes to this manifestation; expression varies by molecular subtype and stage.

Dysarthria Cerebellar circuit dysfunction contributes to this manifestation; expression varies by molecular subtype and stage.

Nystagmus Cerebellar circuit dysfunction contributes to this manifestation; expression varies by molecular subtype and stage.

Downbeat nystagmus Cerebellar circuit dysfunction contributes to this manifestation; expression varies by molecular subtype and stage.

Intention tremor Cerebellar circuit dysfunction contributes to this manifestation; expression varies by molecular subtype and stage.

Show evidence (2 references)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"Autosomal dominant cerebellar ataxias (ADCAs) are a group of neurodegenerative disorders characterized by degeneration of the cerebellum and its connections."

The family definition includes the cerebellum and its connected pathways, rather than one universal vulnerable cell type.

PMID:28405024 SUPPORT INDIRECT PRIMARY RESULT Model Organism

"Both models recreate the progressive adult-onset dysfunction and degeneration of a neuronal network that are seen in patients, including decreased firing frequency of cerebellar Purkinje cells and a decline in motor function."

Two SCA2 transgenic models link abnormal Purkinje physiology with impaired motor behavior.

Noncoding Repeat Expansion

Noncoding repeat expansions are a separate genetic route. FGF14 intronic GAA expansion is a contemporary example; other loci can involve altered RNA biology. A noncoding location does not establish one common RNA-toxicity mechanism.

FGF14 hgnc:3671 ATXN10 hgnc:10549

Downstream

Cerebellar Network Dysfunction The FGF14 expansion is associated with cerebellar dysfunction and variable ocular or ataxic presentations. Reduced FGF14 function and altered excitability are proposed intermediates, not directly assayed in the cited clinical cohort.

Show evidence (2 references)

PMID:38507876 SUPPORT BACKGROUND Human Clinical

"A dominantly inherited GAA repeat expansion in intron 1 of the fibroblast growth factor 14 (FGF14) gene has recently been identified as the cause of GAA-FGF14 disease/spinocerebellar ataxia 27B (SCA27B)"

The primary cohort introduces an established noncoding expansion cause, distinct from the polyglutamine group.

PMID:11017075 SUPPORT PRIMARY RESULT Human Clinical

"We found an expansion of a pentanucleotide (ATTCT) repeat in intron 9 of SCA10 in all patients in five Mexican SCA10 families."

A second, independent noncoding expansion class at this node - a pentanucleotide rather than a trinucleotide repeat, in an intron of ATXN10.

Conventional Dominant Disease Variant

Dominant sequence variants and rearrangements in genes such as ITPR1, SPTBN2, PRKCG and AFG3L2 affect different cellular functions. Variant-specific loss of function, altered regulation or dominant interference should be resolved in molecular subtype entries, rather than assigned uniformly here.

GRM1 hgnc:4593 NPTX1 hgnc:7952 RAB3A hgnc:9777 ITPR1 hgnc:6180 SPTBN2 hgnc:11276 PRKCG hgnc:9402 AFG3L2 hgnc:315

Downstream

Cerebellar Network Dysfunction Diverse conventional alleles converge on cerebellar impairment through gene-specific pathways.

Show evidence (4 references)

PMID:20723845 SUPPORT REVIEW SYNTHESIS Human Clinical

"All other SCAs are caused by either conventional mutations or large rearrangements in genes with different functions, including glutamate signalling (SCA5/SPTBN2) and calcium signalling (SCA15/16/ITPR1), channel function (SCA13/KCNC3, SCA14/PRKCG, SCA27/FGF14), tau regulation (SCA11/TTBK2), and..."

The historical review supports heterogeneous conventional-variant mechanisms; its old gene counts and inclusion of noncoding SCA31 are not treated as current exhaustive classification.

PMID:28886343 SUPPORT PRIMARY RESULT Human Clinical

"Here, we describe heterozygous dominant mutations in GRM1, which encodes mGluR1, that are associated with distinct disease phenotypes: gain-of-function missense mutations, linked in two different families to adult-onset cerebellar ataxia, and a de novo truncation mutation resulting in a..."

A conventional dominant allele class at this node, and an instance where gain-of-function and dominant-negative variants in one gene give different phenotypes.

PMID:34788392 SUPPORT PRIMARY RESULT Human Clinical

"Our results establish NPTX1 as a new causative gene in autosomal dominant cerebellar ataxias."

Adds NPTX1 missense variants to the conventional-variant allele classes at this node.

+ 1 more reference

Extracerebellar Neural Dysfunction

Some molecular subtypes additionally impair brainstem, spinal, basal-ganglia or peripheral pathways. SCA3 provides evidence of structural degeneration, but a clinical feature alone does not demonstrate neuron loss in its specific circuit. The affected regions and balance of dysfunction versus degeneration differ among molecular forms.

Downstream

Slow saccades Subtype-dependent extra-cerebellar involvement can contribute; the specific cellular mediators are not resolved by the cited clinical synthesis.

Peripheral neuropathy Subtype-dependent extra-cerebellar involvement can contribute; the specific cellular mediators are not resolved by the cited clinical synthesis.

Parkinsonism Subtype-dependent extra-cerebellar involvement can contribute; the specific cellular mediators are not resolved by the cited clinical synthesis.

Spasticity Subtype-dependent extra-cerebellar involvement can contribute; the specific cellular mediators are not resolved by the cited clinical synthesis.

Dysphagia Subtype-dependent extra-cerebellar involvement can contribute; the specific cellular mediators are not resolved by the cited clinical synthesis.

Dystonia Subtype-dependent extra-cerebellar involvement can contribute; the specific cellular mediators are not resolved by the cited clinical synthesis.

Cognitive impairment Subtype-dependent extra-cerebellar involvement can contribute; the specific cellular mediators are not resolved by the cited clinical synthesis.

Dementia Subtype-dependent extra-cerebellar involvement can contribute; the specific cellular mediators are not resolved by the cited clinical synthesis.

Hyporeflexia Subtype-dependent extra-cerebellar involvement can contribute; the specific cellular mediators are not resolved by the cited clinical synthesis.

Show evidence (2 references)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"SCA3 affects various different regions of the brain and spinal cord, although the cerebellar cortex and olivary nuclei Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias 265 are relatively spared. The brain weight of SCA3 patients is significantly reduced,..."

Human SCA3 neuropathology demonstrates relative cerebellar-cortex sparing and dentate-nucleus involvement.

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"In the spinal cord, the dorsal root ganglia, dorsal nuclei, and anterior horn are affected [57, 88]."

The SCA3 neuropathology section documents additional spinal involvement.

Retinal Photoreceptor Degeneration

ATXN7-related disease causes degeneration of retinal photoreceptors in addition to neurological disease. This retinal branch is specific to SCA7 within the examples summarized here.

retina UBERON:0000966

Downstream

Retinal dystrophy Photoreceptor degeneration manifests as progressive cone-rod dystrophy.

Visual impairment Progressive photoreceptor loss impairs vision and can lead to blindness.

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"Retinal degeneration is a distinctive feature of SCA7 with progressive cone-rod dystrophy leading to even- tual blindness [100]."

SCA7 can cause progressive cone-rod dystrophy. This retinal phenotype is central to the historical ADCA-II class.

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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

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Phenotypes

17

Digestive 1

Dysphagia HP:0002015

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"Adult-onset SCA7 is characterized by progressive cerebellar ataxia, slowed ocular saccades, dysarthria, dyspha- gia, and pyramidal symptoms, such as hyperreflexia and spas- ticity [ 99]."

Bulbar or cerebellar dysfunction can impair swallowing and increase aspiration or nutritional risk as disease advances. This is especially relevant in multisystem subtypes.

Eye 5

Nystagmus HP:0000639

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"SCA2 is characterized by progressive cerebellar ataxia, dysarthria, and oculomotor deficits, including abnormally slow saccades and nystagmus [ 69]."

Nystagmus is one possible cerebellar ocular-motor finding. Slow saccades, abnormal pursuit and other signs vary by molecular subtype.

Slow saccades Slow saccadic eye movements HP:0000514

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"SCA2 is characterized by progressive cerebellar ataxia, dysarthria, and oculomotor deficits, including abnormally slow saccades and nystagmus [ 69]."

Abnormally slow saccades are particularly associated with SCA2 and also occur in other subtypes; they are not obligatory across ADCA.

Downbeat nystagmus HP:0010545

Show evidence (1 reference)

PMID:38507876 SUPPORT PRIMARY RESULT Human Clinical

"a late-onset slowly progressive cerebellar syndrome that is frequently associated with episodic symptoms and downbeat nystagmus (DBN)."

Downbeat nystagmus is prominent in a subset of molecular forms, including FGF14-associated disease. The 2024 FGF14 cohort was selected for this finding and cannot establish its frequency among all affected carriers.

Retinal dystrophy HP:0000556

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"Retinal degeneration is a distinctive feature of SCA7 with progressive cone-rod dystrophy leading to even- tual blindness [100]."

SCA7 can cause progressive cone-rod dystrophy. This retinal phenotype is central to the historical ADCA-II class.

Visual impairment HP:0000505

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"Retinal degeneration is a distinctive feature of SCA7 with progressive cone-rod dystrophy leading to even- tual blindness [100]."

Progressive retinal visual loss can culminate in blindness in SCA7. Other ocular complaints in ADCA can instead arise from disordered eye movements.

Musculoskeletal 1

Spasticity HP:0001257

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"Adult-onset SCA7 is characterized by progressive cerebellar ataxia, slowed ocular saccades, dysarthria, dyspha- gia, and pyramidal symptoms, such as hyperreflexia and spas- ticity [ 99]."

Pyramidal involvement may cause spasticity in multisystem ADCA, including adult SCA7.

Nervous System 10

Progressive cerebellar ataxia HP:0002073

Show evidence (2 references)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"All ADCAs have progressive ataxia as their main clinical feature, frequently accompanied by dysarthria and oculomotor deficits."

Progressive gait and limb incoordination is characteristic of classic ADCA, but need not be present at the first visit or in every restricted ocular presentation.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Human Clinical

"dysmetria, dysdiadochokinesis, tremor, dysarthria, nystagmus, saccades"

The hereditary-ataxia baseline describes the cerebellar examination; manifestations remain subtype-dependent.

Dysarthria HP:0001260

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"All ADCAs have progressive ataxia as their main clinical feature, frequently accompanied by dysarthria and oculomotor deficits."

Speech can become slurred or poorly coordinated. Its presence and severity vary by subtype and disease stage.

Cerebellar atrophy HP:0001272

Show evidence (1 reference)

PMID:38507876 SUPPORT PRIMARY RESULT Human Clinical

"Brain MRI of eight patients showed cerebellar atrophy (13%; 8/60), which was limited to the vermis in three patients and extended to the hemispheres in five patients."

Cerebellar atrophy may be visible on MRI, with variable regional and extracerebellar involvement. Its absence does not exclude a genetic cerebellar disorder, particularly early or in restricted FGF14 ocular presentations.

Intention tremor HP:0002080

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"Patients can also suffer from intention and postural tremors, myoclonus, Parkinsonism, sleep disturbances, autonomic dysfunction, and initial hyperreflexia followed by peripheral neuropathy with hyporeflexia or areflexia [70]."

Intention tremor can accompany cerebellar incoordination, with subtype-dependent expression.

Peripheral neuropathy HP:0009830

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"Patients can also suffer from intention and postural tremors, myoclonus, Parkinsonism, sleep disturbances, autonomic dysfunction, and initial hyperreflexia followed by peripheral neuropathy with hyporeflexia or areflexia [70]."

Sensory or sensorimotor neuropathy occurs in multisystem forms, including SCA2 and later-onset SCA3, but is not universal.

Hyporeflexia HP:0001265

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"Patients can also suffer from intention and postural tremors, myoclonus, Parkinsonism, sleep disturbances, autonomic dysfunction, and initial hyperreflexia followed by peripheral neuropathy with hyporeflexia or areflexia [70]."

Reduced tendon reflexes can accompany peripheral involvement; some patients instead show brisk reflexes earlier in disease.

Parkinsonism HP:0001300

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"Patients can also suffer from intention and postural tremors, myoclonus, Parkinsonism, sleep disturbances, autonomic dysfunction, and initial hyperreflexia followed by peripheral neuropathy with hyporeflexia or areflexia [70]."

Parkinsonian presentations occur in selected SCA2, SCA3 and SCA17 families and may be clinically prominent.

Dystonia HP:0001332

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"SCA17 presents itself with cerebellar ataxia, pyramidal signs, and involuntary movements including chorea and dys- tonia."

Dystonia occurs in some molecular forms, including SCA17.

Cognitive impairment HP:0100543

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"different stud- ies have reported late cognitive deficits [71]"

Cognitive involvement varies considerably; late cognitive deficits are reported in SCA2 and dementia is prominent in some SCA17 presentations.

Dementia HP:0000726

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"SCA17 patients are known to suffer from psychiatric symp- toms, as well as dementia [108, 109]."

Dementia is a subtype-associated feature, particularly in SCA17; it is not a defining feature of every cerebellar ataxia.

🧬

Genetic Associations

8

Polyglutamine SCA genes (Causative coding repeat expansions in a subset of ADCA)

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"These diseases are all caused by a CAG repeat expansion in the coding region of a gene."

The review defines the six polyglutamine SCAs; this mechanism does not describe every ADCA.

Noncoding-repeat and conventional-variant causes (Additional distinct dominant genetic mechanisms)

Show evidence (2 references)

PMID:38507876 SUPPORT BACKGROUND Human Clinical

"A dominantly inherited GAA repeat expansion in intron 1 of the fibroblast growth factor 14 (FGF14) gene has recently been identified as the cause of GAA-FGF14 disease/spinocerebellar ataxia 27B (SCA27B)"

The primary cohort introduces an established noncoding expansion cause, distinct from the polyglutamine group.

PMID:20723845 SUPPORT REVIEW SYNTHESIS Human Clinical

"All other SCAs are caused by either conventional mutations or large rearrangements in genes with different functions, including glutamate signalling (SCA5/SPTBN2) and calcium signalling (SCA15/16/ITPR1), channel function (SCA13/KCNC3, SCA14/PRKCG, SCA27/FGF14), tau regulation (SCA11/TTBK2), and..."

The historical review supports heterogeneous conventional-variant mechanisms; its old gene counts and inclusion of noncoding SCA31 are not treated as current exhaustive classification.

ATXN7 (Causative coding CAG expansion in SCA7)

Gene: ATXN7 hgnc:10560 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (1 reference)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"Retinal degeneration is a distinctive feature of SCA7 with progressive cone-rod dystrophy leading to even- tual blindness [100]."

The review connects SCA7 to the retinal class, which is the clinical subtype this gene entry is scoped to.

ATXN10 (Causative intronic ATTCT pentanucleotide expansion in SCA10)

Gene: ATXN10 hgnc:10549 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (2 references)

PMID:11017075 SUPPORT PRIMARY RESULT Human Clinical

"We found an expansion of a pentanucleotide (ATTCT) repeat in intron 9 of SCA10 in all patients in five Mexican SCA10 families."

Establishes the causal intronic expansion in the gene now named ATXN10.

PMID:11017075 SUPPORT PRIMARY RESULT Human Clinical

"Analysis of 562 chromosomes from unaffected individuals of various ethnic origins (including 242 chromosomes from Mexican persons) showed a range of 10 to 22 ATTCT repeats with no evidence of expansions."

The control range reported in the discovery study, which is what separates a normal allele from a pathogenic one at this locus.

GRM1 (Causative heterozygous dominant variants in SCA44)

Gene: GRM1 hgnc:4593 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (1 reference)

PMID:28886343 SUPPORT PRIMARY RESULT Human Clinical

"Here, we describe heterozygous dominant mutations in GRM1, which encodes mGluR1, that are associated with distinct disease phenotypes: gain-of-function missense mutations, linked in two different families to adult-onset cerebellar ataxia, and a de novo truncation mutation resulting in a..."

Establishes dominant GRM1 variants as causal and records both allele classes.

NPTX1 (Causative heterozygous missense variants in SCA50)

Gene: NPTX1 hgnc:7952 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (2 references)

PMID:34788392 SUPPORT PRIMARY RESULT Human Clinical

"Our results establish NPTX1 as a new causative gene in autosomal dominant cerebellar ataxias."

Establishes NPTX1 as a dominant ataxia gene.

PMID:34788392 SUPPORT PRIMARY RESULT Human Clinical

"Further investigations with whole-exome sequencing and an amplicon-based panel identified four additional unrelated families segregating the same variant, for whom a common founder effect could be excluded."

Source for the independent recurrence of the p.G389R allele recorded in this entry's notes.

THAP11 (Causative coding CAG repeat expansion in SCA51)

Gene: THAP11 hgnc:23194 gene page relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (3 references)

PMID:37148549 SUPPORT PRIMARY RESULT Human Clinical

"We identified THAP11 as the novel causative SCA gene with CAG repeats ranging from 45 to 100 in patients with ataxia and from 20 to 38 in healthy control subjects."

Establishes THAP11 as causal and gives the patient and control repeat ranges.

PMID:37148549 SUPPORT PRIMARY RESULT Human Clinical

"Among the patients, the number of CAA interruptions within CAG repeats was decreased to 3 (up to 5-6 in controls), whereas the number of 3' pure CAG repeats was up to 32 to 87 (4-16 in controls), suggesting that the toxicity of polyQ protein was length dependent on the pure CAG repeats."

Source for the claim that the uninterrupted CAG tract, not total repeat length, is the pathogenic measure at this locus.

PMID:39651830 SUPPORT PRIMARY RESULT Human Clinical

"These results indicate that THAP11 expansions are rare in the British population and that sequence structures predisposed to expansions may be more common in non-British ancestries."

Population survey qualifying the expected yield of testing this locus outside the ancestries of discovery. It does not contradict the gene-disease association.

RAB3A (Causative heterozygous missense variant in SCA52)

Gene: RAB3A hgnc:9777 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (2 references)

PMID:41492970 SUPPORT PRIMARY RESULT Human Clinical

"In this study, we identified the c.247C > T p.(Arg83Trp) variant in RAB3A, encoding a small GTPase involved in membrane-associated regulated exocytosis, in two families with cerebellar ataxia."

Establishes RAB3A as causal in two families.

PMID:41492970 SUPPORT In Vitro

"Although the mutant Rab3A R83W retained GTP-binding affinity, it failed to bind the key effector proteins RIM1 and Rabphilin-3A, highlighting the functional importance of R83 in effector complex formation, as supported by structural analysis."

Source for the effector-binding rather than GTP-binding lesion recorded in this entry's notes.

💊

Medical Actions

14

Physical rehabilitation and mobility support

Category: Therapeutic Action: Physical Therapy NCIT:C15302

Platform: Behavioral / lifestyle

Individualized balance, gait and strength training, mobility aids and fall-prevention adaptations support function. Goals and intensity depend on impairment and safety; rehabilitation is not established as a cure or proof of slowed molecular degeneration. A 62-person assessor-masked trial found greater SARA improvement with aerobic than dose-matched balance training; 43 participants had genetically confirmed SCA and the remainder had idiopathic ataxia or MSA-C. Selection required ambulatory function and safe cycling. This supports functional rehabilitation, not subtype-specific neuroprotection. In a separate uncontrolled seven-person SCA6/SCA31 cohort, annual intensive rehabilitation accompanied relative pre-session SARA stability through year six, while balance declined earlier; six-month follow-up SARA worsened from year three. Absence of a concurrent control prevents attributing long-term disease slowing to that regimen.

Mechanism Target:

MODULATES Progressive cerebellar ataxia — Symptomatic intervention addresses the functional manifestation; it is not evidence of reversal of the underlying genetic lesion.

Show evidence (4 references)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Other

"PT (balance exercises, gait training, muscle strengthening) to maintain mobility & function"

GeneReviews recommends physical rehabilitation to preserve functional mobility; this is broad hereditary-ataxia guidance.

PMID:40946705 SUPPORT PRIMARY RESULT Human Clinical

"Compared to the balance group, the aerobic training group demonstrated significantly better improvements in SARA (time-by-group interaction, 6 months: β, −1.53; 95% CI, −2.44 to −0.61;"

Primary randomized between-group SARA result; the full body establishes a mixed ataxia population and selected exercise eligibility.

PMID:40946705 SUPPORT PRIMARY RESULT Human Clinical

"Most participants in the aerobic and balance groups had genetically confirmed spinocerebellar ataxia (21/31 and 22/31, respectively)"

The randomized cohort includes 43 genetically confirmed SCA participants, not 62 people with ADCA.

+ 1 more reference

Show evidence (4 references)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Other

"PT (balance exercises, gait training, muscle strengthening) to maintain mobility & function"

GeneReviews recommends physical rehabilitation to preserve functional mobility; this is broad hereditary-ataxia guidance.

PMID:40946705 SUPPORT PRIMARY RESULT Human Clinical

"Compared to the balance group, the aerobic training group demonstrated significantly better improvements in SARA (time-by-group interaction, 6 months: β, −1.53; 95% CI, −2.44 to −0.61;"

Primary randomized between-group SARA result; the full body establishes a mixed ataxia population and selected exercise eligibility.

PMID:40946705 SUPPORT PRIMARY RESULT Human Clinical

"Most participants in the aerobic and balance groups had genetically confirmed spinocerebellar ataxia (21/31 and 22/31, respectively)"

The randomized cohort includes 43 genetically confirmed SCA participants, not 62 people with ADCA.

+ 1 more reference

Occupational therapy and adaptive equipment

Category: Therapeutic Action: Occupational Therapy NCIT:C121351

Platform: Behavioral / lifestyle

Occupational therapy and adaptive utensils, dressing aids, mobility equipment and home adaptations can help maintain independence. Reassess needs with progression.

Mechanism Target:

BYPASSES Progressive cerebellar ataxia — Adaptive equipment compensates for impaired daily function; the guideline does not show restoration of cerebellar molecular or neuronal function.

Show evidence (1 reference)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Other

"Inpatient rehab w/OT/PT may improve ataxia & functional abilities in persons w/degenerative ataxias."

GeneReviews recommends occupational and physical rehabilitation for functional abilities.

Show evidence (2 references)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Other

"Inpatient rehab w/OT/PT may improve ataxia & functional abilities in persons w/degenerative ataxias."

GeneReviews recommends occupational and physical rehabilitation for functional abilities.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Other

"Home adaptations to prevent falls (e.g., grab bars, raised toilet seats)"

The chapter gives concrete fall-prevention adaptations.

Speech-language and communication support

Category: Therapeutic Action: Speech Language Therapy NCIT:C159273

Platform: Other

Speech-language therapy addresses dysarthria and communication needs; writing or digital communication can be added as speech becomes less intelligible.

Mechanism Target:

BYPASSES Dysarthria — Writing or digital devices compensate for impaired spoken communication without demonstrating recovery of dysarthria.

Show evidence (1 reference)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Other

"Consider alternative communication methods as needed (e.g., writing pads & digital devices)."

Speech-language care includes alternative communication when dysarthria limits speech.

Show evidence (1 reference)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Other

"Consider alternative communication methods as needed (e.g., writing pads & digital devices)."

Speech-language care includes alternative communication when dysarthria limits speech.

Swallowing and nutritional support

Category: Therapeutic Action: Nutritional Support NCIT:C15433

Platform: Other

Assess choking, swallowing safety, weight and intake. Modify food consistency and provide dietetic or nutritional support; discuss enteral feeding when intake cannot be maintained despite supplements. Decisions are individualized and do not presume all patients eventually require a feeding tube.

Mechanism Target:

MODULATES Dysphagia — Symptomatic intervention addresses the functional manifestation; it is not evidence of reversal of the underlying genetic lesion.

Show evidence (3 references)

PMID:30786918 SUPPORT REVIEW SYNTHESIS Other

"If patients show symptoms of dysphagia a referral to a speech and language therapist should be made"

The progressive-ataxia guideline recommends symptomatic swallowing assessment and support.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Other

"Modify food consistency to ↓ aspiration risk."

GeneReviews provides a specific compensatory swallowing intervention.

PMID:30786918 SUPPORT REVIEW SYNTHESIS Other

"If calorie intake cannot be maintained despite supplements, discuss the possibility of a percutaneous gastronomy (PEG) to provide secure feeding."

The guideline makes feeding-tube discussion conditional on inadequate intake.

Show evidence (3 references)

PMID:30786918 SUPPORT REVIEW SYNTHESIS Other

"If patients show symptoms of dysphagia a referral to a speech and language therapist should be made"

The progressive-ataxia guideline recommends symptomatic swallowing assessment and support.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Other

"Modify food consistency to ↓ aspiration risk."

GeneReviews provides a specific compensatory swallowing intervention.

PMID:30786918 SUPPORT REVIEW SYNTHESIS Other

"If calorie intake cannot be maintained despite supplements, discuss the possibility of a percutaneous gastronomy (PEG) to provide secure feeding."

The guideline makes feeding-tube discussion conditional on inadequate intake.

Treatment of spasticity

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Platform: Other

Use physiotherapy and individualized antispasticity treatment when pyramidal symptoms impair function. Oral agents or selected focal botulinum treatment are symptomatic options; tolerability and effects on mobility guide decisions.

Mechanism Target:

MODULATES Spasticity — Symptomatic intervention addresses the functional manifestation; it is not evidence of reversal of the underlying genetic lesion.

Show evidence (2 references)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Other

"Baclofen, tizanidine, or dantrolene may relieve muscle spasms & spasticity."

The guidance identifies symptomatic antispasticity options.

PMID:30786918 SUPPORT REVIEW SYNTHESIS Other

"To treat focal spasticity refer to a specialised clinic for treatment with intramuscular botulinum toxin injections, followed by physiotherapy."

The guideline distinguishes focal from generalized treatment.

Show evidence (2 references)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Other

"Baclofen, tizanidine, or dantrolene may relieve muscle spasms & spasticity."

The guidance identifies symptomatic antispasticity options.

PMID:30786918 SUPPORT REVIEW SYNTHESIS Other

"To treat focal spasticity refer to a specialised clinic for treatment with intramuscular botulinum toxin injections, followed by physiotherapy."

The guideline distinguishes focal from generalized treatment.

Treatment of dystonia

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Platform: Other

Focal dystonia may be treated with botulinum toxin, while generalized dystonia needs individualized specialist management. Recommendations largely extrapolate symptomatic practice across neurological disorders.

Mechanism Target:

MODULATES Dystonia — Symptomatic intervention addresses the functional manifestation; it is not evidence of reversal of the underlying genetic lesion.

Show evidence (1 reference)

PMID:30786918 SUPPORT REVIEW SYNTHESIS Other

"Focal dystonia should be treated with botulinum toxin injections."

This is a good-practice recommendation for focal dystonia in progressive ataxia.

Show evidence (1 reference)

PMID:30786918 SUPPORT REVIEW SYNTHESIS Other

"Focal dystonia should be treated with botulinum toxin injections."

This is a good-practice recommendation for focal dystonia in progressive ataxia.

Neuro-ophthalmic symptomatic treatment

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Platform: Other

Neuro-ophthalmic assessment distinguishes nystagmus, diplopia, ocular-motor impairment and retinal visual loss. Selected medication or prism treatment and low-vision aids may improve symptoms; retinal degeneration and ocular-motor dysfunction require different support.

Mechanism Target:

MODULATES Nystagmus — Symptomatic intervention addresses the functional manifestation; it is not evidence of reversal of the underlying genetic lesion.

Show evidence (2 references)

PMID:30786918 SUPPORT REVIEW SYNTHESIS Other

"If disabling nystagmus or oscillopsia is present treatment is recommended, often with either gabapentin or baclofen."

The guideline addresses symptomatic eye-movement disability, not every genetic subtype equally.

PMID:30786918 SUPPORT REVIEW SYNTHESIS Other

"Patients with visual impairment should be offered low vision aids and the possibility of having their visual disability registered."

Low-vision support is recommended when visual function is impaired.

Show evidence (2 references)

PMID:30786918 SUPPORT REVIEW SYNTHESIS Other

"If disabling nystagmus or oscillopsia is present treatment is recommended, often with either gabapentin or baclofen."

The guideline addresses symptomatic eye-movement disability, not every genetic subtype equally.

PMID:30786918 SUPPORT REVIEW SYNTHESIS Other

"Patients with visual impairment should be offered low vision aids and the possibility of having their visual disability registered."

Low-vision support is recommended when visual function is impaired.

Selected 4-aminopyridine use in FGF14-associated disease

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Agent: 4-aminopyridine CHEBI:34385

Platform: Small molecule

Specialist-directed 4-aminopyridine may provide symptomatic benefit in selected FGF14-associated downbeat-nystagmus or ataxia presentations. Evidence includes retrospective open-label responses and a four-person post hoc genotype subgroup from an earlier crossover trial. All four received active drug first, and phase baselines differed; larger randomized trials are needed. Disease modification and family-wide benefit are not established.

Mechanism Target:

MODULATES Downbeat nystagmus — Symptomatic intervention addresses the functional manifestation; it is not evidence of reversal of the underlying genetic lesion.

Show evidence (2 references)

PMID:38507876 SUPPORT PRIMARY RESULT Human Clinical

"A clinician-reported treatment response was recorded for 29 of 36 patients carrying a (GAA)≥250 allele"

The selected FGF14 downbeat-nystagmus cohort supplies retrospective clinician-reported response, not a general ADCA efficacy estimate.

PMID:38507876 SUPPORT PRIMARY RESULT Human Clinical

"the benefits reported herein need validation in a larger randomised placebo-controlled trial."

The authors explicitly limit the efficacy inference.

Show evidence (2 references)

PMID:38507876 SUPPORT PRIMARY RESULT Human Clinical

"A clinician-reported treatment response was recorded for 29 of 36 patients carrying a (GAA)≥250 allele"

The selected FGF14 downbeat-nystagmus cohort supplies retrospective clinician-reported response, not a general ADCA efficacy estimate.

PMID:38507876 SUPPORT PRIMARY RESULT Human Clinical

"the benefits reported herein need validation in a larger randomised placebo-controlled trial."

The authors explicitly limit the efficacy inference.

Riluzole evidence remains subtype-dependent

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Agent: Riluzole NCIT:C47704

Platform: Small molecule

Earlier mixed-etiology ataxia studies prompted consideration of off-label riluzole, with liver-enzyme monitoring. In ATRIL, 45 moderately affected SCA2 participants received riluzole or placebo for 12 months, without a clinical or MRI benefit. This does not establish routine efficacy across ADCA and does not prove absence of benefit in every other subtype.

Show evidence (2 references)

PMID:35063116 SUPPORT PRIMARY RESULT Human Clinical

"Riluzole did not improve clinical or radiological outcomes in these patients."

The negative result concerns 45 moderately affected SCA2 participants in ATRIL.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Other

"use requires monitoring of liver enzymes."

GeneReviews notes monitoring when riluzole is considered.

Cognitive and psychological support

Category: Therapeutic Action: Supportive Care NCIT:C15747

Platform: Other

Assess cognitive, mood and behavioral concerns, with neuropsychological rehabilitation, psychotherapy or standard psychiatric treatment as appropriate. Cognitive impairment is subtype-dependent; it should not be presumed from motor severity alone.

Show evidence (2 references)

PMID:30786918 SUPPORT REVIEW SYNTHESIS Other

"Cognitive rehabilitation is recommended for those patients with cognitive impairment."

The guideline recommends rehabilitation for an identified cognitive problem.

PMID:30786918 SUPPORT REVIEW SYNTHESIS Other

"In many cases depression can be treated in primary care using medications, counselling or cognitive behavioural therapy."

The guideline supplies symptomatic mental-health care.

Longitudinal neurological and functional monitoring

Category: Monitoring Action: Supportive Care NCIT:C15747

Platform: Other

Follow neurological function, falls, mobility, speech, swallowing, nutrition and cognitive or psychiatric concerns. GeneReviews suggests annual neurological review, with more frequent assessment for deterioration and symptom-based allied-health review. These are broad hereditary-ataxia recommendations; the chapter notes the absence of general published surveillance guidelines.

Show evidence (2 references)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Other

"Monitor ataxia progression w/standardized scale (SARA)."

The chapter supports structured neurological follow-up.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Other

"Annually; more often for an acute exacerbation"

The surveillance table suggests this frequency for neurological and functional assessment.

Genetic counseling and family testing

Category: Counseling / Informational Action: Genetic Counseling NCIT:C15240

Platform: Other

Offer voluntary pre- and post-test counseling covering inheritance, variable penetrance, uncertain results, psychological implications and reproductive options. Test a known familial pathogenic variant when appropriate. Predictive testing for adult-onset disease in asymptomatic minors is generally deferred unless childhood actionability justifies it; symptomatic children warrant diagnostic evaluation.

Show evidence (2 references)

PMID:40883955 SUPPORT REVIEW SYNTHESIS Other

"This does not obligate the person to proceed with testing but is recommended to better understand the risk of the familial condition and the potential impact of results should they proceed with testing."

The predictive-testing recommendation preserves informed choice.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Other

"Genetic counseling and risk assessment depend on determination of the specific cause of an inherited ataxia in an individual."

The broad chapter makes family counseling molecularly specific.

Palliative and family support

Category: Therapeutic Action: Palliative Therapy NCIT:C15292

Platform: Other

Advanced functional impairment may warrant coordinated palliative care, symptom relief, respite and support for caregivers. These services can accompany active rehabilitation and are individualized; the progressive-ataxia guideline bases much of this advice on other neurodegenerative disorders.

Show evidence (1 reference)

PMID:30786918 SUPPORT REVIEW SYNTHESIS Other

"In the absence of available literature on palliative and end-of-life care in the ataxias specifically, these recommendations are derived in part from evidence of these interventions in other progressive neurodegenerative conditions"

The source explicitly states the extrapolated evidence base.

Troriluzole investigational treatment

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Agent: troriluzole CHEBI:757061

Platform: Small molecule

In its November 4, 2025 complete-response letter, FDA concluded that the submitted trials and external-control analysis did not establish substantial evidence of efficacy for spinocerebellar ataxia. Concerns included a failed prespecified randomized primary endpoint, residual confounding, substantial missing data and nonprespecified analyses; the external-control result is not established disease modification. That decision did not approve the submitted SCA application; this dated regulatory conclusion does not assert a subsequent development outcome or established clinical benefit.

Show evidence (1 reference)

url:https://download.open.fda.gov/crl/CRL_NDA210862_20251104.pdf SUPPORT REVIEW SYNTHESIS Other

"substantial evidence of effectiveness has not been established for troriluzole for the treatment of spinocerebellar ataxia."

The dated regulatory review is evidence of the submitted-data conclusion, not a prediction about future development.

🔬

Diagnosis

4

Neurological, family-history and acquired-cause assessment

Establish the pattern and tempo of cerebellar dysfunction, obtain a multigeneration pedigree and evaluate additional neurological findings. Consider acquired, nutritional, immune, toxic and structural causes, particularly when onset or rapid progression is atypical. A negative family history does not exclude dominant ataxia.

Show evidence (2 references)

PMID:30786918 SUPPORT REVIEW SYNTHESIS Other

"The clinical context (speed of evolution, episodic/fluctuating versus progressive etc.) should determine the investigation of individual cases."

The guideline prioritizes phenotype and tempo rather than a universal test sequence.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Other

"A three-generation family history should be taken with attention to relatives with manifestations of hereditary ataxia"

The hereditary-ataxia chapter recommends a detailed multigeneration family history.

MRI and functional baseline

Brain MRI defines the distribution of atrophy and helps assess alternative causes. Document cerebellar and extracerebellar examination findings, using SARA or another appropriate scale for follow-up. Normal or minimally abnormal imaging does not exclude early or restricted FGF14-associated disease.

Show evidence (2 references)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Other

"Brain MRI to evaluate presence & severity of cerebellar atrophy"

GeneReviews recommends imaging to assess structural involvement.

PMID:38507876 SUPPORT PRIMARY RESULT Human Clinical

"Brain MRI of eight patients showed cerebellar atrophy (13%; 8/60), which was limited to the vermis in three patients and extended to the hemispheres in five patients."

Cerebellar atrophy may be visible on MRI, with variable regional and extracerebellar involvement. Its absence does not exclude a genetic cerebellar disorder, particularly early or in restricted FGF14 ocular presentations.

Molecular testing that detects repeat expansions

Testing must detect the relevant expansion classes as well as sequence and copy-number variants. The 2025 recommendations favor comprehensive testing, ideally genome sequencing with validated short-tandem-repeat sizing, sometimes complemented by repeat-primed PCR or long-read sequencing. A dedicated expansion panel followed by genome testing is an alternative. Standard sequence-only panels or exomes may miss expansions; familial targeted testing can be appropriate.

Show evidence (2 references)

PMID:40883955 SUPPORT REVIEW SYNTHESIS Other

"The initial genetic test ordered should be as comprehensive as possible, include the most ataxia‐relevant genes, and reliably detect pathogenic repeat expansions."

The consensus recommendation explicitly requires repeat detection.

PMID:40883955 SUPPORT REVIEW SYNTHESIS Other

"If WGS as a first approach is fiscally impossible or otherwise not feasible, then a dedicated repeat expansion panel with eventual reflex to WGS would be appropriate."

The guideline provides an alternative pathway when comprehensive genome testing is unavailable.

Interpretation and reassessment of unresolved results

Interpret variants with phenotype, segregation, repeat structure and current classification; a variant of uncertain significance alone does not establish a molecular diagnosis. Negative testing may reflect assay limitations or an unresolved cause. Consider reanalysis after at least two years or new symptoms, including newly detectable repeat expansions where available.

Show evidence (1 reference)

PMID:40883955 SUPPORT REVIEW SYNTHESIS Other

"Reanalysis of previously negative genomic testing should be considered after a period of at least 2 years or a change in symptomology."

The consensus recommends periodic reassessment rather than treating every negative result as final.

📈

Progression

1

Variable onset and progression

Age at onset ranges from childhood to late adulthood by gene, allele and family. The classic course is progressive, but episodes or ocular-motor symptoms may precede sustained ataxia. There is no family-wide rate of progression or survival estimate; slowly progressive SCA6 and FGF14-associated disease differ from severe childhood repeat-expansion presentations.

Show evidence (3 references)

PMID:30607747 SUPPORT REVIEW SYNTHESIS Human Clinical

"Clinical features differ between patients with an adult onset and patients with an onset in infancy or early childhood with the disease starting in childhood showing a more rapid and aggressive progression within a few years. When disease symptoms first appear later in life, the disease..."

The SCA7 section explicitly contrasts rapid childhood and slower adult courses.

PMID:38507876 SUPPORT PRIMARY RESULT Human Clinical

"episodic symptoms and oscillopsia preceded gait impairment in 1 of 10 (10%) and 3 of 28 (11%) patients for whom information on age at onset of these features was available, respectively."

Selected FGF14-associated downbeat-nystagmus cases illustrate variable initial manifestations, not family-wide frequencies.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/ SUPPORT REVIEW SYNTHESIS Human Clinical

"May begin w/episodic ataxia, very slow progression; onset often after age 50 yrs; normal life span"

The SCA6 row supplies a subtype-specific counterexample to a universal early-onset or shortened-survival course.

🌍

Epidemiology

2

Historical Singapore family estimate

In the 2002 series, 204 people with ataxia underwent a nine-locus testing panel; 58 positive patients belonged to 36 families. The estimated lower bound was one affected family per 27,000 Singaporean families. This family-unit estimate is not a person-level prevalence or a contemporary comprehensive-panel yield.

Show evidence (1 reference)

PMID:12485197 SUPPORT PRIMARY RESULT Human Clinical

"The estimated prevalence of ADCA in Singaporean families was at least 1 : 27,000."

The denominator is families, so conversion to persons per 100,000 is inappropriate.

Regional subtype distributions

SCA3 accounted for 31 of 58 molecularly classified Singaporean patients, whereas SCA6 accounted for 59 of 76 classified Aomori cases in the 2007–2009 Japanese series. Aomori enrolled 80 people, including 15 apparently sporadic cases. These selected, historically tested cohorts have different ascertainment and denominators; founder effects cannot be separated from referral and assay coverage by this comparison.

Show evidence (2 references)

PMID:12485197 SUPPORT PRIMARY RESULT Human Clinical

"SCA 3 was identified in 31 (53.4%) patients from 15 families, SCA 2 in 17 (29.3%) patients from 12 families and SCA 1 in four (6.9%) patients from four families."

The proportions concern 58 positive patients, not all 204 tested individuals.

PMID:21088341 SUPPORT PRIMARY RESULT Human Clinical

"SCA6 was found to be the most common form of SCA in Aomori Prefecture, with a polyglutamine expansion in the CACNA1A gene being found in 59 of the 80 cases analyzed (77.7% of cases)."

The prose establishes regional SCA6 predominance but incorrectly pairs 59 of 80 with 77.7%; Table 2 shows that 76 cases were molecularly classified. The description preserves the corrected denominator and source discrepancy.

🔬

Clinical Trials

2

NCT03347344 PHASE_III COMPLETED

ATRIL randomized 45 participants with moderately affected, genetically defined SCA2 to riluzole or placebo for 12 months. Improvement of at least one SARA point occurred in 7/22 versus 9/23; neither clinical nor MRI outcomes improved with riluzole. The result is specific to the enrolled SCA2 population.

Show evidence (1 reference)

PMID:35063116 SUPPORT PRIMARY RESULT Human Clinical

"Riluzole did not improve clinical or radiological outcomes in these patients."

The randomized SCA2 trial did not meet the intended clinical efficacy goal.

NCT05002218 NOT_APPLICABLE COMPLETED

Single-center assessor-masked randomized comparison of home aerobic versus balance training in 62 selected ambulatory adults with mixed cerebellar ataxias, including 43 genetically confirmed SCAs. At six months, the between-group SARA effect favored aerobic training by 1.53 points (95% CI 0.61–2.44 in the direction of improvement). Training support stopped after six months; 11/62 participants had dropped out by one year. Adherence subgroup comparisons were not randomized, missing-at-random assumptions limit inference, and structural MRI results were not reported in this paper.

Show evidence (2 references)

PMID:40946705 SUPPORT PRIMARY RESULT Human Clinical

"Of 62 participants randomized, 31 were randomized to home aerobic training and 31 were randomized to home balance training."

The primary report establishes the randomized comparator design.

PMID:40946705 SUPPORT PRIMARY RESULT Human Clinical

"The inferences from analyses with missing data are valid under the missing-at-random assumption (ie, the missing mechanism does not depend on the value of the unobserved outcome), which is not testable in this study."

The authors state the missing-data assumption explicitly.

🧫

Experimental Models

1

SCA2 patient fibroblast ASO target-engagement assay PRIMARY_CELL_CULTURE

Electroporated ASO7 lowers total ATXN2 transcript and both mutant and wild-type allele products by PCR assays. This supplies human-cell target engagement without measuring neuronal firing or survival.

Cell source

Patient-derived skin fibroblasts carrying CAG35 and CAG22 ATXN2 alleles

Publication

PMID:28405024

Pathograph links

Coding Polyglutamine Repeat Expansion recapitulates observes: molecular Patient-derived fibroblasts retain the expanded coding allele used for the target-engagement assay.

Limitations: This link records the disease-associated genotype. The RNA-lowering endpoint is described in the model; it is not a measurement or correction of the DNA expansion, neuronal firing or survival.

Show evidence (1 reference)

PMID:28405024 SUPPORT PRIMARY RESULT In Vitro

"SCA2 patient-derived skin fibroblasts (SCA2-CAG35) were cultured and maintained in DMEM medium"

The patient-derived culture carries the disease-associated coding expansion.

No broad donor panel or functional neuronal rescue was tested in this assay. Methods state harvest at five days whereas the extended-data caption states 72 hours; no exact exposure interval is promoted. The result does not establish allele selectivity or clinical efficacy.

Show evidence (1 reference)

PMID:28405024 SUPPORT PRIMARY RESULT In Vitro

"ASO7 lowered expression of wildtype and mutant ATXN2 in SCA2 patient-derived fibroblasts"

The human-cell experiment demonstrates non-allele-specific transcript lowering.

🐁

Animal Models

2

Purkinje-directed ATXN2-Q127 transgenic mouse

The SCA2 model develops motor impairment and reduced Purkinje-cell firing. Intracerebroventricular ASO7 begun around motor-phenotype onset lowers human ATXN2 and partly lowers endogenous mouse Atxn2, improving rotarod performance. Subsequent acute-slice recordings show restoration of firing.

Species

Mouse

Genotype

Pcp 2-driven full-length human ATXN2 with 127 CAG repeats

Background

B6;D2 hybrid background

Publication

PMID:28405024

Pathograph links

Expanded Polyglutamine Protein recapitulates observes: molecular Expresses expanded human ATXN2 in Purkinje cells.

Limitations: Overexpression, promoter and repeat length constrain generalization to other polyglutamine disorders.

Show evidence (1 reference)

PMID:28405024 SUPPORT PRIMARY RESULT Model Organism

"Pcp2-ATXN2-Q127 (ATXN2-Q127) transgenic mice express the full-length human ATXN2-[CAG]127 cDNA under the control of the mouse Purkinje cell protein 2 (L7) promoter (Pcp2)."

The model uses Purkinje-directed expression of a human expanded transgene rather than a humanized endogenous allele.

Reduced Purkinje Cell Firing recapitulates observes: cellular Mutant physiology is measured in acute slices after animal treatment.

Limitations: The assay is ex vivo; ASO lowers multiple downstream abnormalities and does not isolate firing as the necessary mediator of behavioral rescue.

Readouts

Purkinje firing frequency

Reduced baseline firing approaches wild-type values after ASO7.

Show evidence (1 reference)

PMID:28405024 SUPPORT PRIMARY RESULT In Vitro

"In both models, a single injection of ASO7 resulted in near complete restoration of normal PC firing frequency"

Electrophysiology in acute cerebellar slices measures firing after in-vivo treatment.

Show evidence (1 reference)

PMID:28405024 SUPPORT PRIMARY RESULT In Vitro

"In both models, a single injection of ASO7 resulted in near complete restoration of normal PC firing frequency"

Electrophysiology in acute cerebellar slices measures firing after in-vivo treatment.

Cerebellar Network Dysfunction recapitulates observes: organism Motor performance improves after ATXN2 lowering.

Limitations: Rotarod is a functional surrogate rather than a complete measure of human ataxia.

Show evidence (1 reference)

PMID:28405024 SUPPORT PRIMARY RESULT Model Organism

"Mice injected with ASO7 had significantly improved motor performance compared to saline-treated control mice"

The mouse motor result supports target-dependent experimental improvement.

Cell-restricted transgene expression and a very long repeat differ from typical human heterozygosity. The study demonstrates preclinical target engagement and functional rescue, not human efficacy, a cure, lifespan extension in these SCA2 cohorts or recovery of lost neurons. Electrophysiological cell counts are nested within only one to four mice per genotype.

Show evidence (2 references)

PMID:28405024 SUPPORT PRIMARY RESULT Model Organism

"Pcp2-ATXN2-Q127 (ATXN2-Q127) transgenic mice express the full-length human ATXN2-[CAG]127 cDNA under the control of the mouse Purkinje cell protein 2 (L7) promoter (Pcp2)."

The model uses Purkinje-directed expression of a human expanded transgene rather than a humanized endogenous allele.

PMID:28405024 SUPPORT PRIMARY RESULT Model Organism

"Mice injected with ASO7 had significantly improved motor performance compared to saline-treated control mice"

The mouse motor result supports target-dependent experimental improvement.

BAC-ATXN2-Q72 transgenic mouse

The BAC model expresses expanded ATXN2 across multiple neuronal tissues and has slower disease progression than the Purkinje-directed Q127 model. ASO7 reduces ATXN2 and improves motor behavior; a separate delayed-treatment cohort shows firing recovery when injected more than 12 weeks after motor onset.

Species

Mouse

Genotype

Human ATXN2 BAC with 72 CAG repeats

Background

FVB;B6 hybrid background

Publication

PMID:28405024

Pathograph links

Expanded Polyglutamine Protein recapitulates observes: molecular Models expanded human ATXN2 in a BAC genomic context.

Limitations: Transgene context is more extensive but does not reproduce every aspect of human disease.

Show evidence (1 reference)

PMID:28405024 SUPPORT PRIMARY RESULT Model Organism

"BAC-ATXN2-Q72 (BAC-Q72) mice were created using a contiguous 169 kb human ATXN2 gene sequence including 16 kb upstream ATXN2 sequence, the entire ATXN2-[CAG]72 coding region (with introns) and 3 kb of ATXN2 3’-UTR and downstream sequence."

The BAC preserves the human regulatory and intronic context but remains a transgenic mouse model.

Reduced Purkinje Cell Firing recapitulates observes: cellular Firing frequency is restored in acute slices after delayed treatment.

Limitations: No isolated manipulation of firing or neuronal replacement was performed.

Readouts

Late-treatment firing recovery

Purkinje physiology was assessed 10 weeks after treatment at 30 weeks.

Show evidence (1 reference)

PMID:28405024 SUPPORT PRIMARY RESULT In Vitro

"In both models, a single injection of ASO7 resulted in near complete restoration of normal PC firing frequency"

Electrophysiology in acute cerebellar slices measures firing after in-vivo treatment.

Show evidence (1 reference)

PMID:28405024 SUPPORT PRIMARY RESULT In Vitro

"In both models, a single injection of ASO7 resulted in near complete restoration of normal PC firing frequency"

Electrophysiology in acute cerebellar slices measures firing after in-vivo treatment.

Cerebellar Network Dysfunction recapitulates observes: organism ASO-treated mice have improved but incomplete motor recovery.

Limitations: Motor and delayed physiological experiments have different treatment schedules; their results must not be pooled into a late-onset motor-rescue claim.

Show evidence (1 reference)

PMID:28405024 SUPPORT PRIMARY RESULT Model Organism

"However, the rotarod performance of the ASO7 treated mice did not perfectly mirror that of wildtype mice."

The BAC model motor rescue is incomplete.

The late-treatment result is physiological recovery, not direct evidence that established neuron loss or all behavioral deficits were reversed at that late stage. Normalized Purkinje protein levels and mRNA changes do not establish one serial transcription-to-firing mechanism. The Methods and extended weight caption differ in stated BAC dosing; no unique dosing regimen is inferred here.

Show evidence (3 references)

PMID:28405024 SUPPORT PRIMARY RESULT Model Organism

"BAC-ATXN2-Q72 (BAC-Q72) mice were created using a contiguous 169 kb human ATXN2 gene sequence including 16 kb upstream ATXN2 sequence, the entire ATXN2-[CAG]72 coding region (with introns) and 3 kb of ATXN2 3’-UTR and downstream sequence."

The BAC preserves the human regulatory and intronic context but remains a transgenic mouse model.

PMID:28405024 SUPPORT PRIMARY RESULT Model Organism

"However, the rotarod performance of the ASO7 treated mice did not perfectly mirror that of wildtype mice."

The BAC model motor rescue is incomplete.

PMID:28405024 SUPPORT PRIMARY RESULT Model Organism

"Similarly, we injected BAC-Q72 mice at 30 wks, >12 weeks after motor phenotype onset, and analyzed PC firing 10 wks later."

The primary body defines the timing and physiological endpoint of delayed treatment.

{ }

Source YAML

click to show

name: Autosomal Dominant Cerebellar Ataxia
creation_date: '2026-08-19T12:00:00Z'
category: Mendelian
description: Autosomal dominant cerebellar ataxia (ADCA) comprises genetically heterogeneous disorders that impair the cerebellum and its connections. Progressive gait or limb incoordination, dysarthria and abnormal eye movements are characteristic, but the combination, onset and course vary by molecular subtype; episodic or predominantly ocular presentations also occur. Historical Harding classes distinguish predominantly cerebellar disease, disease with extracerebellar features, and ataxia with retinal degeneration. These clinical classes differ from numbered molecular spinocerebellar ataxias. Coding repeat expansions, noncoding repeat expansions and conventional pathogenic variants cause distinct molecular disturbances, with subtype-dependent neuronal vulnerability rather than universal Purkinje-cell loss.
disease_term:
  preferred_term: autosomal dominant cerebellar ataxia
  term:
    id: MONDO:0020380
    label: autosomal dominant cerebellar ataxia
synonyms:
- ADCA
- autosomal dominant spinocerebellar ataxia
categories:
- Neurodegenerative Disorder
- Hereditary Ataxia
parents:
- Hereditary ataxia
- Cerebellar degeneration
inheritance:
- name: Autosomal dominant
  description: 'Autosomal dominant transmission is characteristic. Each child of a heterozygous affected parent has a 50% probability of inheriting the disease allele, with clinical risk modified by penetrance and repeat structure. An apparently negative family history can reflect late onset, reduced penetrance, an unrecognized affected relative, de novo variation or parental mosaicism. Anticipation occurs in several unstable-repeat disorders but is not universal: SCA6 generally lacks anticipation and it is infrequent in SCA17.'
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
    reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: hereditary ataxia has a 50% chance of inheriting the
    explanation: In the autosomal-dominant offspring section, the chapter specifies allele-transmission risk, not guaranteed age or severity of disease.
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Normal SCA17 alleles contain 25 to 40 repeats while alleles with 41 to 49 repeats have incomplete penetrance.
    explanation: The review illustrates allele-dependent penetrance; locus-specific interpretation is required.
has_subtypes:
- name: ADCA-I
  display_name: ADCA Type I (ataxia with extracerebellar features)
  classification: clinical
  description: Historical Harding type I describes cerebellar ataxia with extracerebellar neurological findings, such as pyramidal, extrapyramidal, cognitive or oculomotor abnormalities. Expression varies within families and across molecular causes; the clinical class is not a single genotype.
  evidence:
  - reference: PMID:7066668
    reference_title: The clinical features and classification of the late onset autosomal dominant cerebellar ataxias. A study of 11 families, including descendants of the 'the Drew family of Walworth'.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The clinical features of 11 families containing 73 individuals with dominantly inherited cerebellar ataxia of late onset are described.
    explanation: The original clinical classification was derived from 11 families and predates molecular subtype definitions.
  - reference: PMID:7066668
    reference_title: The clinical features and classification of the late onset autosomal dominant cerebellar ataxias. A study of 11 families, including descendants of the 'the Drew family of Walworth'.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Many of the patients had physical signs in addition to cerebellar ataxia, which included dementia, supranuclear ophthalmoplegia, extrapyramidal dysfunction, optic atrophy, pigmentary retinal degeneration, myoclonus and deafness.
    explanation: The original cohort documents the broader neurological spectrum.
  subtype_term:
    preferred_term: autosomal dominant cerebellar ataxia type I
    term:
      id: MONDO:0019792
      label: autosomal dominant cerebellar ataxia type I
- name: ADCA-II
  display_name: ADCA Type II (ataxia with pigmentary retinopathy)
  classification: clinical
  description: Historical Harding type II combines cerebellar ataxia with pigmentary retinal degeneration. ATXN7-related SCA7 is the major molecular example and can cause cone-rod dystrophy with progressive visual loss. MONDO carries the historical ADCA type II class name as a synonym of spinocerebellar ataxia 7 (MONDO:0016163), rather than providing a separate ADCA-II term.
  evidence:
  - reference: PMID:7066668
    reference_title: The clinical features and classification of the late onset autosomal dominant cerebellar ataxias. A study of 11 families, including descendants of the 'the Drew family of Walworth'.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: cerebellar ataxia with pigmentary retinal degeneration
    explanation: The original classification specifically identifies the retinal-associated presentation.
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Retinal degeneration is a distinctive feature of SCA7 with progressive cone-rod dystrophy leading to even- tual blindness [100].
    explanation: The review connects the retinal clinical class with SCA7.
  subtype_term:
    preferred_term: spinocerebellar ataxia 7
    term:
      id: MONDO:0016163
      label: spinocerebellar ataxia 7
  genes:
  - preferred_term: ATXN7
    term:
      id: hgnc:10560
      label: ATXN7
- name: ADCA-III
  display_name: ADCA Type III (pure cerebellar ataxia)
  classification: clinical
  description: Historical Harding type III describes a predominantly cerebellar syndrome, often slowly progressive and later in onset. SCA6 is a common example; the roster and degree of permitted extracerebellar involvement differ between clinical classifications. The Roman numeral III does not denote SCA3.
  evidence:
  - reference: PMID:7066668
    reference_title: The clinical features and classification of the late onset autosomal dominant cerebellar ataxias. A study of 11 families, including descendants of the 'the Drew family of Walworth'.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: a later onset (over 60 years) 'pure' cerebellar syndrome
    explanation: The original classification identifies a late-onset predominantly cerebellar presentation.
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: SCA6 is considered a pure cerebellar ataxia.
    explanation: The molecular SCA6 example has predominantly cerebellar disease.
  subtype_term:
    preferred_term: autosomal dominant cerebellar ataxia type III
    term:
      id: MONDO:0019793
      label: autosomal dominant cerebellar ataxia type III
- name: SCA10
  display_name: SCA10 (ATXN10 intronic ATTCT expansion)
  classification: molecular
  description: An intronic pentanucleotide (ATTCT) expansion in ATXN10, and therefore a noncoding-repeat rather than a polyglutamine disease. The reported syndrome combines slowly progressive cerebellar ataxia with seizures. MONDO parents this term under autosomal dominant cerebellar ataxia type IV, a Harding class this entry does not carry as a clinical row, so it is placed on the family entry rather than on the ADCA-I or ADCA-III entries.
  subtype_term:
    preferred_term: spinocerebellar ataxia type 10
    term:
      id: MONDO:0011330
      label: spinocerebellar ataxia type 10
  genes:
  - preferred_term: ATXN10
    term:
      id: hgnc:10549
      label: ATXN10
  evidence:
  - reference: PMID:11017075
    reference_title: Large expansion of the ATTCT pentanucleotide repeat in spinocerebellar ataxia type 10.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: We found an expansion of a pentanucleotide (ATTCT) repeat in intron 9 of SCA10 in all patients in five Mexican SCA10 families.
    explanation: The discovery study locates the causal expansion in an intron of the gene now called ATXN10, in all affected members of five families.
  - reference: PMID:11017075
    reference_title: Large expansion of the ATTCT pentanucleotide repeat in spinocerebellar ataxia type 10.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: Spinocerebellar ataxia type 10 (SCA10; MIM 603516; refs 1,2) is an autosomal dominant disorder characterized by cerebellar ataxia and seizures.
    explanation: Source for the dominant inheritance and the ataxia-with-seizures clinical description of this subtype.
- name: SCA44
  display_name: SCA44 (GRM1)
  classification: molecular
  description: 'Caused by heterozygous dominant variants in GRM1, which encodes the metabotropic glutamate receptor mGluR1. The reported alleles are not mechanistically uniform: gain-of-function missense variants segregated with adult-onset cerebellar ataxia in two families, while a de novo truncating variant acting as a dominant negative was associated with juvenile-onset ataxia and intellectual disability. A conventional-variant subtype, not a repeat expansion.'
  subtype_term:
    preferred_term: spinocerebellar ataxia 44
    term:
      id: MONDO:0033479
      label: spinocerebellar ataxia 44
  genes:
  - preferred_term: GRM1
    term:
      id: hgnc:4593
      label: GRM1
  evidence:
  - reference: PMID:28886343
    reference_title: Dominant Mutations in GRM1 Cause Spinocerebellar Ataxia Type 44.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: 'Here, we describe heterozygous dominant mutations in GRM1, which encodes mGluR1, that are associated with distinct disease phenotypes: gain-of-function missense mutations, linked in two different families to adult-onset cerebellar ataxia, and a de novo truncation mutation resulting in a dominant-negative effect that is associated with juvenile-onset ataxia and intellectual disability.'
    explanation: Source for the GRM1 gene assignment and for the two distinct dominant allele mechanisms recorded in this row.
- name: SCA50
  display_name: SCA50 (NPTX1)
  classification: molecular
  description: 'Caused by heterozygous missense variants in NPTX1, which encodes the secreted protein neuronal pentraxin 1. The reported phenotype is a late-onset, slowly progressive cerebellar ataxia with downbeat nystagmus, cerebellar cognitive-affective features, myoclonic tremor and mild vermian atrophy. Note that the SCA50 designation has also been applied to GAA-FGF14 disease: the title of PMID:36493768 reads "An intronic GAA repeat expansion in FGF14 causes the autosomal-dominant adult-onset ataxia SCA50/ATX-FGF14." This row is scoped to the NPTX1 disease that MONDO:0859334 denotes (OMIM:620158), resolved through that cross-reference rather than through the label.'
  subtype_term:
    preferred_term: spinocerebellar ataxia 50
    term:
      id: MONDO:0859334
      label: spinocerebellar ataxia 50
  genes:
  - preferred_term: NPTX1
    term:
      id: hgnc:7952
      label: NPTX1
  evidence:
  - reference: PMID:34788392
    reference_title: NPTX1 mutations trigger endoplasmic reticulum stress and cause autosomal dominant cerebellar ataxia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Our results establish NPTX1 as a new causative gene in autosomal dominant cerebellar ataxias.
    explanation: Source for the NPTX1 gene assignment in a dominant cerebellar ataxia.
  - reference: PMID:34788392
    reference_title: NPTX1 mutations trigger endoplasmic reticulum stress and cause autosomal dominant cerebellar ataxia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: 'The NPTX1-associated phenotype consists of a late-onset, slowly progressive, cerebellar ataxia, with downbeat nystagmus, cognitive impairment reminiscent of cerebellar cognitive affective syndrome, myoclonic tremor and mild cerebellar vermian atrophy on brain imaging.'
    explanation: Source for the clinical description recorded in this row.
- name: SCA51
  display_name: SCA51 (THAP11 CAG expansion)
  classification: molecular
  description: Caused by a coding CAG repeat expansion in THAP11, so a polyglutamine rather than a conventional-variant subtype. Reported expanded alleles carried 45 to 100 repeats against 20 to 38 in controls, and the length of the uninterrupted 3-prime CAG tract rather than the total repeat length tracked with polyglutamine toxicity. Detection has so far been concentrated in Chinese-ancestry pedigrees; a population survey of Genomics England, a UCL neurology cohort and UK Biobank concluded the expansion is rare in the British population. The gene symbol THAP11 (hgnc:23194) is not THAP1 (hgnc:20856), the DYT6 dystonia gene.
  subtype_term:
    preferred_term: spinocerebellar ataxia 51
    term:
      id: MONDO:0975800
      label: spinocerebellar ataxia 51
  genes:
  - preferred_term: THAP11
    term:
      id: hgnc:23194
      label: THAP11
  evidence:
  - reference: PMID:37148549
    reference_title: CAG Repeat Expansion in THAP11 Is Associated with a Novel Spinocerebellar Ataxia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: 'We identified THAP11 as the novel causative SCA gene with CAG repeats ranging from 45 to 100 in patients with ataxia and from 20 to 38 in healthy control subjects.'
    explanation: Source for the THAP11 gene assignment and for the patient and control repeat ranges quoted in this row.
  - reference: PMID:39651830
    reference_title: A Population-Wide Exploration of the THAP11 CAG Repeat Size and Structure in the 100,000 Genomes Project and UK Biobank.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: 'These results indicate that THAP11 expansions are rare in the British population and that sequence structures predisposed to expansions may be more common in non-British ancestries.'
    explanation: Population survey establishing that this subtype is rare outside the ancestries in which it was discovered. It qualifies the expected yield of testing rather than contradicting the gene-disease association.
- name: SCA52
  display_name: SCA52 (RAB3A)
  classification: molecular
  description: Caused by a heterozygous missense variant in RAB3A, a small GTPase of regulated exocytosis, reported in two families with adult-onset progressive cerebellar ataxia and cerebellar atrophy. The variant retains GTP binding but fails to bind the effectors RIM1 and Rabphilin-3A, so the proposed lesion is presynaptic rather than a repeat-expansion or protein-aggregation mechanism. A conventional-variant subtype.
  subtype_term:
    preferred_term: spinocerebellar ataxia 52
    term:
      id: MONDO:0981162
      label: spinocerebellar ataxia 52
  genes:
  - preferred_term: RAB3A
    term:
      id: hgnc:9777
      label: RAB3A
  evidence:
  - reference: PMID:41492970
    reference_title: An R83W mutation in Rab3A causes autosomal-dominant cerebellar ataxia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: 'In this study, we identified the c.247C > T p.(Arg83Trp) variant in RAB3A, encoding a small GTPase involved in membrane-associated regulated exocytosis, in two families with cerebellar ataxia.'
    explanation: Source for the RAB3A gene assignment and for the two-family basis of this subtype.
  - reference: PMID:41492970
    reference_title: An R83W mutation in Rab3A causes autosomal-dominant cerebellar ataxia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: 'Affected individuals presented with adult-onset, gradually progressive cerebellar symptoms, often accompanied by mild gait spasticity and tremors.'
    explanation: Source for the clinical description recorded in this row.
pathophysiology:
- name: Coding Polyglutamine Repeat Expansion
  biological_scale: MOLECULAR
  description: Expanded coding CAG tracts cause the polyglutamine SCAs, including SCA1, SCA2, SCA3, SCA6, SCA7 and SCA17. Repeat thresholds and interruption effects are locus-specific.
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: These diseases are all caused by a CAG repeat expansion in the coding region of a gene.
    explanation: The review defines the six polyglutamine SCAs; this mechanism does not describe every ADCA.
  - reference: PMID:37148549
    reference_title: CAG Repeat Expansion in THAP11 Is Associated with a Novel Spinocerebellar Ataxia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: 'We identified THAP11 as the novel causative SCA gene with CAG repeats ranging from 45 to 100 in patients with ataxia and from 20 to 38 in healthy control subjects.'
    explanation: Adds THAP11 to this node as a coding CAG expansion identified after the 2019 review that defined the original six.
  role: trigger
  genes:
  - preferred_term: ATXN1
    term:
      id: hgnc:10548
      label: ATXN1
  - preferred_term: THAP11
    term:
      id: hgnc:23194
      label: THAP11
  - preferred_term: ATXN2
    term:
      id: hgnc:10555
      label: ATXN2
  - preferred_term: ATXN3
    term:
      id: hgnc:7106
      label: ATXN3
  - preferred_term: CACNA1A
    term:
      id: hgnc:1388
      label: CACNA1A
  - preferred_term: ATXN7
    term:
      id: hgnc:10560
      label: ATXN7
  - preferred_term: TBP
    term:
      id: hgnc:11588
      label: TBP
  downstream:
  - target: Expanded Polyglutamine Protein
    description: Translation of a pathogenic coding expansion lengthens the encoded glutamine tract.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:28405024
      reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: SCA2 is caused by DNA CAG repeat expansion leading to an increase in the polyglutamine (polyQ) domain in the N-terminal part of the ATXN2 protein.
      explanation: The SCA2 background directly describes translation of the coding expansion.
- name: Expanded Polyglutamine Protein
  biological_scale: MOLECULAR
  description: Translation produces an abnormally long glutamine tract within the affected protein. Toxic gain of function and altered native protein interactions can coexist; the normal functions of the different proteins are not interchangeable.
  evidence:
  - reference: PMID:28405024
    reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: SCA2 is caused by DNA CAG repeat expansion leading to an increase in the polyglutamine (polyQ) domain in the N-terminal part of the ATXN2 protein.
    explanation: The SCA2 background directly describes translation of the coding expansion.
  genes:
  - preferred_term: ATXN1
    term:
      id: hgnc:10548
      label: ATXN1
  - preferred_term: ATXN2
    term:
      id: hgnc:10555
      label: ATXN2
  - preferred_term: ATXN3
    term:
      id: hgnc:7106
      label: ATXN3
  - preferred_term: CACNA1A
    term:
      id: hgnc:1388
      label: CACNA1A
  - preferred_term: ATXN7
    term:
      id: hgnc:10560
      label: ATXN7
  - preferred_term: TBP
    term:
      id: hgnc:11588
      label: TBP
  downstream:
  - target: Polyglutamine Protein Misfolding
    description: Polyglutamine expansion favors abnormal protein conformation.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: For the polyQ SCAs, the misfolded mutant polyQ proteins present a major challenge to cellular protein quality control systems.
      explanation: Misfolded expanded proteins challenge proteostasis; this is a synthesis across polyglutamine models.
  - target: Altered Neuronal Gene Expression
    description: Expanded proteins perturb transcriptional regulators through subtype-specific interactions.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: One well-established effect of the mutant polyQ proteins is that these proteins lead to transcriptional dysregulation.
      explanation: Altered gene expression is one experimentally supported consequence of expanded proteins; its contribution varies by subtype.
  - target: Reduced Purkinje Cell Firing
    description: The mutant-ATXN2 branch impairs Purkinje physiology in SCA2 models; intervening molecular mechanisms remain incompletely resolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:28405024
      reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: BACKGROUND
      snippet: In acute slice preparations, we had previously shown that mutant ATXN2 caused a slowing of PC firing.
      explanation: Slice electrophysiology documents reduced Purkinje firing in mutant-ATXN2 mice.
  - target: Extracerebellar Neural Dysfunction
    description: In multisystem polyglutamine SCAs, expanded-protein disease also injures selected neurons outside the cerebellar cortex.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: SCA3 affects various different regions of the brain and spinal cord, although the cerebellar cortex and olivary nuclei Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias 265 are relatively spared. The brain weight of SCA3 patients is significantly reduced, and neuronal cell loss is most prominent in the cerebellar dentate nucleus and substantia nigra.
      explanation: Human SCA3 neuropathology demonstrates relative cerebellar-cortex sparing and dentate-nucleus involvement.
      directness: INDIRECT
  - target: Retinal Photoreceptor Degeneration
    description: Expanded ATXN7 is associated with retinal degeneration through subtype-specific mechanisms; this route is not assigned to every expanded polyglutamine protein.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: Retinal degeneration is a distinctive feature of SCA7 with progressive cone-rod dystrophy leading to even- tual blindness [100].
      explanation: SCA7 can cause progressive cone-rod dystrophy. This retinal phenotype is central to the historical ADCA-II class.
      directness: INDIRECT
- name: Polyglutamine Protein Misfolding
  biological_scale: MOLECULAR
  description: Expanded polyglutamine proteins adopt abnormal conformations. Misfolded soluble species and cleavage fragments can perturb cellular homeostasis; their importance differs among subtypes.
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: For the polyQ SCAs, the misfolded mutant polyQ proteins present a major challenge to cellular protein quality control systems.
    explanation: Misfolded expanded proteins challenge proteostasis; this is a synthesis across polyglutamine models.
  downstream:
  - target: Neuronal Polyglutamine Inclusions
    description: Misfolded expanded proteins can accumulate in inclusions.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: the expanded polyQ sequence leads to the formation of large insoluble protein aggregates containing the expanded diseased protein mainly in neurons of the cerebellum.
      explanation: The review distinguishes large insoluble inclusions from the unresolved toxic protein species.
  - target: Cerebellar Neuron Degeneration
    description: Misfolded-protein toxicity contributes through incompletely resolved, interacting cellular pathways; visible inclusion formation is not required by this edge.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: Together, these disrupted cellular processes cause perturbations of the intra- cellular homeostasis and eventually lead to the death of neu- ronal cells, inducing the characteristic neurodegenerative symptoms of the polyQ SCAs.
      explanation: Several molecular disturbances are synthesized as contributors to neuronal death; the passage does not isolate one necessary pathway.
      directness: INDIRECT
- name: Neuronal Polyglutamine Inclusions
  biological_scale: CELLULAR
  description: Large insoluble inclusions containing expanded proteins occur in the polyglutamine SCAs. Their causal contribution is unresolved; this graph does not assume visible inclusions are the lethal species or a necessary intermediate to neuron loss.
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: the expanded polyQ sequence leads to the formation of large insoluble protein aggregates containing the expanded diseased protein mainly in neurons of the cerebellum.
    explanation: The review distinguishes large insoluble inclusions from the unresolved toxic protein species.
  biological_processes:
  - preferred_term: inclusion body assembly
    term:
      id: GO:0070841
      label: inclusion body assembly
    modifier: INCREASED
- name: Altered Neuronal Gene Expression
  biological_scale: CELLULAR
  description: Expanded proteins alter transcriptional regulation in experimental polyglutamine disease systems. Loss of normal interactions and abnormal interactions both contribute; the affected transcripts and degree of mediation are subtype-dependent.
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: One well-established effect of the mutant polyQ proteins is that these proteins lead to transcriptional dysregulation.
    explanation: Altered gene expression is one experimentally supported consequence of expanded proteins; its contribution varies by subtype.
  downstream:
  - target: Cerebellar Neuron Degeneration
    description: Transcriptional disruption is one proposed contributor to degeneration. The review explicitly leaves unresolved how much it mediates toxicity or whether targeting it alone is sufficient.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: Firstly, it is not cur- rently established to what extent the transcriptional dysregu- lation is a key component of polyQ toxicity and whether targeting this pathway is enough to achieve clinically mean- ingful effects.
      explanation: The source limits inference from transcriptional changes to neuronal injury.
      directness: INDIRECT
- name: Cerebellar Neuron Degeneration
  biological_scale: CELLULAR
  description: 'Neurons of the cerebellum and its connections degenerate in established disease. Vulnerability varies: SCA2 prominently affects Purkinje cells, whereas SCA3 relatively spares the cerebellar cortex and prominently affects dentate neurons. A single universal Purkinje-death pathway would misrepresent this family.'
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Autosomal dominant cerebellar ataxias (ADCAs) are a group of neurodegenerative disorders characterized by degeneration of the cerebellum and its connections.
    explanation: The family definition includes the cerebellum and its connected pathways, rather than one universal vulnerable cell type.
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: SCA3 affects various different regions of the brain and spinal cord, although the cerebellar cortex and olivary nuclei Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias 265 are relatively spared. The brain weight of SCA3 patients is significantly reduced, and neuronal cell loss is most prominent in the cerebellar dentate nucleus and substantia nigra.
    explanation: Human SCA3 neuropathology demonstrates relative cerebellar-cortex sparing and dentate-nucleus involvement.
  role: central_effector
  locations:
  - preferred_term: cerebellum
    term:
      id: UBERON:0002037
      label: cerebellum
  downstream:
  - target: Cerebellar Network Dysfunction
    description: Loss of vulnerable neurons disrupts cerebellar circuitry and its connections.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: Autosomal dominant cerebellar ataxias (ADCAs) are a group of neurodegenerative disorders characterized by degeneration of the cerebellum and its connections.
      explanation: The family definition includes the cerebellum and its connected pathways, rather than one universal vulnerable cell type.
      directness: INDIRECT
  - target: Cerebellar atrophy
    description: Neuron loss contributes to anatomical atrophy in degenerative subtypes, as described for SCA2; MRI alone does not establish a cellular or molecular mechanism.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: SCA2 presents with atrophy of the cerebellum characterized by severe loss of cerebellar Purkinje cells (PCs) while the deep cerebellar nuclei (DCN) are relatively spared.
      explanation: The SCA2 neuropathological synthesis directly associates cerebellar atrophy with severe Purkinje-cell loss.
      directness: INDIRECT
- name: Reduced Purkinje Cell Firing
  biological_scale: CELLULAR
  description: Reduced spontaneous Purkinje-cell firing is demonstrated in SCA2 transgenic mouse cerebellar slices and is reversible after ATXN2 lowering. This physiological defect is distinct from neuron loss and is not asserted to occur identically in every ADCA subtype.
  evidence:
  - reference: PMID:28405024
    reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: BACKGROUND
    snippet: In acute slice preparations, we had previously shown that mutant ATXN2 caused a slowing of PC firing.
    explanation: Slice electrophysiology documents reduced Purkinje firing in mutant-ATXN2 mice.
  cell_types:
  - preferred_term: Purkinje cell
    term:
      id: CL:0000121
      label: Purkinje cell
  downstream:
  - target: Cerebellar Network Dysfunction
    description: Abnormal Purkinje output can impair cerebellar motor circuits. The model links physiology and behavior but does not selectively restore firing independently of other ATXN2 effects.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:28405024
      reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: PRIMARY_RESULT
      snippet: Both models recreate the progressive adult-onset dysfunction and degeneration of a neuronal network that are seen in patients, including decreased firing frequency of cerebellar Purkinje cells and a decline in motor function.
      explanation: Two SCA2 transgenic models link abnormal Purkinje physiology with impaired motor behavior.
      directness: INDIRECT
- name: Cerebellar Network Dysfunction
  biological_scale: TISSUE
  description: Disordered activity in cerebellar circuits and their connections impairs motor coordination. Functional disruption can accompany degeneration but need not require loss of all affected neurons; the SCA2 model demonstrates reversibility of a firing defect.
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Autosomal dominant cerebellar ataxias (ADCAs) are a group of neurodegenerative disorders characterized by degeneration of the cerebellum and its connections.
    explanation: The family definition includes the cerebellum and its connected pathways, rather than one universal vulnerable cell type.
  - reference: PMID:28405024
    reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: Both models recreate the progressive adult-onset dysfunction and degeneration of a neuronal network that are seen in patients, including decreased firing frequency of cerebellar Purkinje cells and a decline in motor function.
    explanation: Two SCA2 transgenic models link abnormal Purkinje physiology with impaired motor behavior.
    directness: INDIRECT
  locations:
  - preferred_term: cerebellum
    term:
      id: UBERON:0002037
      label: cerebellum
  role: central_effector
  downstream:
  - target: Progressive cerebellar ataxia
    description: Cerebellar circuit dysfunction contributes to this manifestation; expression varies by molecular subtype and stage.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: All ADCAs have progressive ataxia as their main clinical feature, frequently accompanied by dysarthria and oculomotor deficits.
      explanation: Progressive gait and limb incoordination is characteristic of classic ADCA, but need not be present at the first visit or in every restricted ocular presentation.
      directness: INDIRECT
  - target: Dysarthria
    description: Cerebellar circuit dysfunction contributes to this manifestation; expression varies by molecular subtype and stage.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: All ADCAs have progressive ataxia as their main clinical feature, frequently accompanied by dysarthria and oculomotor deficits.
      explanation: Speech can become slurred or poorly coordinated. Its presence and severity vary by subtype and disease stage.
      directness: INDIRECT
  - target: Nystagmus
    description: Cerebellar circuit dysfunction contributes to this manifestation; expression varies by molecular subtype and stage.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: SCA2 is characterized by progressive cerebellar ataxia, dysarthria, and oculomotor deficits, including abnormally slow saccades and nystagmus [ 69].
      explanation: Nystagmus is one possible cerebellar ocular-motor finding. Slow saccades, abnormal pursuit and other signs vary by molecular subtype.
      directness: INDIRECT
  - target: Downbeat nystagmus
    description: Cerebellar circuit dysfunction contributes to this manifestation; expression varies by molecular subtype and stage.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:38507876
      reference_title: 'GAA-FGF14 disease: defining its frequency, molecular basis, and 4-aminopyridine response in a large downbeat nystagmus cohort.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: a late-onset slowly progressive cerebellar syndrome that is frequently associated with episodic symptoms and downbeat nystagmus (DBN).
      explanation: Downbeat nystagmus is prominent in a subset of molecular forms, including FGF14-associated disease. The 2024 FGF14 cohort was selected for this finding and cannot establish its frequency among all affected carriers.
      directness: INDIRECT
  - target: Intention tremor
    description: Cerebellar circuit dysfunction contributes to this manifestation; expression varies by molecular subtype and stage.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: Patients can also suffer from intention and postural tremors, myoclonus, Parkinsonism, sleep disturbances, autonomic dysfunction, and initial hyperreflexia followed by peripheral neuropathy with hyporeflexia or areflexia [70].
      explanation: Intention tremor can accompany cerebellar incoordination, with subtype-dependent expression.
      directness: INDIRECT
- name: Noncoding Repeat Expansion
  biological_scale: MOLECULAR
  description: Noncoding repeat expansions are a separate genetic route. FGF14 intronic GAA expansion is a contemporary example; other loci can involve altered RNA biology. A noncoding location does not establish one common RNA-toxicity mechanism.
  evidence:
  - reference: PMID:38507876
    reference_title: 'GAA-FGF14 disease: defining its frequency, molecular basis, and 4-aminopyridine response in a large downbeat nystagmus cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: A dominantly inherited GAA repeat expansion in intron 1 of the fibroblast growth factor 14 (FGF14) gene has recently been identified as the cause of GAA-FGF14 disease/spinocerebellar ataxia 27B (SCA27B)
    explanation: The primary cohort introduces an established noncoding expansion cause, distinct from the polyglutamine group.
  - reference: PMID:11017075
    reference_title: Large expansion of the ATTCT pentanucleotide repeat in spinocerebellar ataxia type 10.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: We found an expansion of a pentanucleotide (ATTCT) repeat in intron 9 of SCA10 in all patients in five Mexican SCA10 families.
    explanation: A second, independent noncoding expansion class at this node - a pentanucleotide rather than a trinucleotide repeat, in an intron of ATXN10.
  role: trigger
  genes:
  - preferred_term: FGF14
    term:
      id: hgnc:3671
      label: FGF14
  - preferred_term: ATXN10
    term:
      id: hgnc:10549
      label: ATXN10
  downstream:
  - target: Cerebellar Network Dysfunction
    description: The FGF14 expansion is associated with cerebellar dysfunction and variable ocular or ataxic presentations. Reduced FGF14 function and altered excitability are proposed intermediates, not directly assayed in the cited clinical cohort.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:38507876
      reference_title: 'GAA-FGF14 disease: defining its frequency, molecular basis, and 4-aminopyridine response in a large downbeat nystagmus cohort.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: BACKGROUND
      snippet: A dominantly inherited GAA repeat expansion in intron 1 of the fibroblast growth factor 14 (FGF14) gene has recently been identified as the cause of GAA-FGF14 disease/spinocerebellar ataxia 27B (SCA27B)
      explanation: The primary cohort introduces an established noncoding expansion cause, distinct from the polyglutamine group.
      directness: INDIRECT
- name: Conventional Dominant Disease Variant
  biological_scale: MOLECULAR
  description: Dominant sequence variants and rearrangements in genes such as ITPR1, SPTBN2, PRKCG and AFG3L2 affect different cellular functions. Variant-specific loss of function, altered regulation or dominant interference should be resolved in molecular subtype entries, rather than assigned uniformly here.
  evidence:
  - reference: PMID:20723845
    reference_title: 'Autosomal dominant cerebellar ataxias: polyglutamine expansions and beyond.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: All other SCAs are caused by either conventional mutations or large rearrangements in genes with different functions, including glutamate signalling (SCA5/SPTBN2) and calcium signalling (SCA15/16/ITPR1), channel function (SCA13/KCNC3, SCA14/PRKCG, SCA27/FGF14), tau regulation (SCA11/TTBK2), and mitochondrial activity (SCA28/AFG3L2) or RNA alteration (SCA31/BEAN-TK2).
    explanation: The historical review supports heterogeneous conventional-variant mechanisms; its old gene counts and inclusion of noncoding SCA31 are not treated as current exhaustive classification.
  - reference: PMID:28886343
    reference_title: Dominant Mutations in GRM1 Cause Spinocerebellar Ataxia Type 44.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: 'Here, we describe heterozygous dominant mutations in GRM1, which encodes mGluR1, that are associated with distinct disease phenotypes: gain-of-function missense mutations, linked in two different families to adult-onset cerebellar ataxia, and a de novo truncation mutation resulting in a dominant-negative effect that is associated with juvenile-onset ataxia and intellectual disability.'
    explanation: A conventional dominant allele class at this node, and an instance where gain-of-function and dominant-negative variants in one gene give different phenotypes.
  - reference: PMID:34788392
    reference_title: NPTX1 mutations trigger endoplasmic reticulum stress and cause autosomal dominant cerebellar ataxia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Our results establish NPTX1 as a new causative gene in autosomal dominant cerebellar ataxias.
    explanation: Adds NPTX1 missense variants to the conventional-variant allele classes at this node.
  - reference: PMID:41492970
    reference_title: An R83W mutation in Rab3A causes autosomal-dominant cerebellar ataxia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: 'In this study, we identified the c.247C > T p.(Arg83Trp) variant in RAB3A, encoding a small GTPase involved in membrane-associated regulated exocytosis, in two families with cerebellar ataxia.'
    explanation: Adds RAB3A to the conventional-variant allele classes at this node.
  role: trigger
  genes:
  - preferred_term: GRM1
    term:
      id: hgnc:4593
      label: GRM1
  - preferred_term: NPTX1
    term:
      id: hgnc:7952
      label: NPTX1
  - preferred_term: RAB3A
    term:
      id: hgnc:9777
      label: RAB3A
  - preferred_term: ITPR1
    term:
      id: hgnc:6180
      label: ITPR1
  - preferred_term: SPTBN2
    term:
      id: hgnc:11276
      label: SPTBN2
  - preferred_term: PRKCG
    term:
      id: hgnc:9402
      label: PRKCG
  - preferred_term: AFG3L2
    term:
      id: hgnc:315
      label: AFG3L2
  downstream:
  - target: Cerebellar Network Dysfunction
    description: Diverse conventional alleles converge on cerebellar impairment through gene-specific pathways.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:20723845
      reference_title: 'Autosomal dominant cerebellar ataxias: polyglutamine expansions and beyond.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: All other SCAs are caused by either conventional mutations or large rearrangements in genes with different functions, including glutamate signalling (SCA5/SPTBN2) and calcium signalling (SCA15/16/ITPR1), channel function (SCA13/KCNC3, SCA14/PRKCG, SCA27/FGF14), tau regulation (SCA11/TTBK2), and mitochondrial activity (SCA28/AFG3L2) or RNA alteration (SCA31/BEAN-TK2).
      explanation: The historical review supports heterogeneous conventional-variant mechanisms; its old gene counts and inclusion of noncoding SCA31 are not treated as current exhaustive classification.
      directness: INDIRECT
- name: Extracerebellar Neural Dysfunction
  biological_scale: CELLULAR
  description: Some molecular subtypes additionally impair brainstem, spinal, basal-ganglia or peripheral pathways. SCA3 provides evidence of structural degeneration, but a clinical feature alone does not demonstrate neuron loss in its specific circuit. The affected regions and balance of dysfunction versus degeneration differ among molecular forms.
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: SCA3 affects various different regions of the brain and spinal cord, although the cerebellar cortex and olivary nuclei Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias 265 are relatively spared. The brain weight of SCA3 patients is significantly reduced, and neuronal cell loss is most prominent in the cerebellar dentate nucleus and substantia nigra.
    explanation: Human SCA3 neuropathology demonstrates relative cerebellar-cortex sparing and dentate-nucleus involvement.
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: In the spinal cord, the dorsal root ganglia, dorsal nuclei, and anterior horn are affected [57, 88].
    explanation: The SCA3 neuropathology section documents additional spinal involvement.
  downstream:
  - target: Slow saccades
    description: Subtype-dependent extra-cerebellar involvement can contribute; the specific cellular mediators are not resolved by the cited clinical synthesis.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: SCA2 is characterized by progressive cerebellar ataxia, dysarthria, and oculomotor deficits, including abnormally slow saccades and nystagmus [ 69].
      explanation: Abnormally slow saccades are particularly associated with SCA2 and also occur in other subtypes; they are not obligatory across ADCA.
      directness: INDIRECT
  - target: Peripheral neuropathy
    description: Subtype-dependent extra-cerebellar involvement can contribute; the specific cellular mediators are not resolved by the cited clinical synthesis.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: Patients can also suffer from intention and postural tremors, myoclonus, Parkinsonism, sleep disturbances, autonomic dysfunction, and initial hyperreflexia followed by peripheral neuropathy with hyporeflexia or areflexia [70].
      explanation: Sensory or sensorimotor neuropathy occurs in multisystem forms, including SCA2 and later-onset SCA3, but is not universal.
      directness: INDIRECT
  - target: Parkinsonism
    description: Subtype-dependent extra-cerebellar involvement can contribute; the specific cellular mediators are not resolved by the cited clinical synthesis.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: Patients can also suffer from intention and postural tremors, myoclonus, Parkinsonism, sleep disturbances, autonomic dysfunction, and initial hyperreflexia followed by peripheral neuropathy with hyporeflexia or areflexia [70].
      explanation: Parkinsonian presentations occur in selected SCA2, SCA3 and SCA17 families and may be clinically prominent.
      directness: INDIRECT
  - target: Spasticity
    description: Subtype-dependent extra-cerebellar involvement can contribute; the specific cellular mediators are not resolved by the cited clinical synthesis.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: Adult-onset SCA7 is characterized by progressive cerebellar ataxia, slowed ocular saccades, dysarthria, dyspha- gia, and pyramidal symptoms, such as hyperreflexia and spas- ticity [ 99].
      explanation: Pyramidal involvement may cause spasticity in multisystem ADCA, including adult SCA7.
      directness: INDIRECT
  - target: Dysphagia
    description: Subtype-dependent extra-cerebellar involvement can contribute; the specific cellular mediators are not resolved by the cited clinical synthesis.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: Adult-onset SCA7 is characterized by progressive cerebellar ataxia, slowed ocular saccades, dysarthria, dyspha- gia, and pyramidal symptoms, such as hyperreflexia and spas- ticity [ 99].
      explanation: Bulbar or cerebellar dysfunction can impair swallowing and increase aspiration or nutritional risk as disease advances. This is especially relevant in multisystem subtypes.
      directness: INDIRECT
  - target: Dystonia
    description: Subtype-dependent extra-cerebellar involvement can contribute; the specific cellular mediators are not resolved by the cited clinical synthesis.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: SCA17 presents itself with cerebellar ataxia, pyramidal signs, and involuntary movements including chorea and dys- tonia.
      explanation: Dystonia occurs in some molecular forms, including SCA17.
      directness: INDIRECT
  - target: Cognitive impairment
    description: Subtype-dependent extra-cerebellar involvement can contribute; the specific cellular mediators are not resolved by the cited clinical synthesis.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: different stud- ies have reported late cognitive deficits [71]
      explanation: Cognitive involvement varies considerably; late cognitive deficits are reported in SCA2 and dementia is prominent in some SCA17 presentations.
      directness: INDIRECT
  - target: Dementia
    description: Subtype-dependent extra-cerebellar involvement can contribute; the specific cellular mediators are not resolved by the cited clinical synthesis.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: SCA17 patients are known to suffer from psychiatric symp- toms, as well as dementia [108, 109].
      explanation: Dementia is a subtype-associated feature, particularly in SCA17; it is not a defining feature of every cerebellar ataxia.
      directness: INDIRECT
  - target: Hyporeflexia
    description: Subtype-dependent extra-cerebellar involvement can contribute; the specific cellular mediators are not resolved by the cited clinical synthesis.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: Patients can also suffer from intention and postural tremors, myoclonus, Parkinsonism, sleep disturbances, autonomic dysfunction, and initial hyperreflexia followed by peripheral neuropathy with hyporeflexia or areflexia [70].
      explanation: Reduced tendon reflexes can accompany peripheral involvement; some patients instead show brisk reflexes earlier in disease.
      directness: INDIRECT
- name: Retinal Photoreceptor Degeneration
  biological_scale: CELLULAR
  description: ATXN7-related disease causes degeneration of retinal photoreceptors in addition to neurological disease. This retinal branch is specific to SCA7 within the examples summarized here.
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Retinal degeneration is a distinctive feature of SCA7 with progressive cone-rod dystrophy leading to even- tual blindness [100].
    explanation: SCA7 can cause progressive cone-rod dystrophy. This retinal phenotype is central to the historical ADCA-II class.
  locations:
  - preferred_term: retina
    term:
      id: UBERON:0000966
      label: retina
  downstream:
  - target: Retinal dystrophy
    description: Photoreceptor degeneration manifests as progressive cone-rod dystrophy.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: Retinal degeneration is a distinctive feature of SCA7 with progressive cone-rod dystrophy leading to even- tual blindness [100].
      explanation: SCA7 can cause progressive cone-rod dystrophy. This retinal phenotype is central to the historical ADCA-II class.
  - target: Visual impairment
    description: Progressive photoreceptor loss impairs vision and can lead to blindness.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30607747
      reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: REVIEW_SYNTHESIS
      snippet: Retinal degeneration is a distinctive feature of SCA7 with progressive cone-rod dystrophy leading to even- tual blindness [100].
      explanation: Progressive retinal visual loss can culminate in blindness in SCA7. Other ocular complaints in ADCA can instead arise from disordered eye movements.
progression:
- phase: Variable onset and progression
  notes: Age at onset ranges from childhood to late adulthood by gene, allele and family. The classic course is progressive, but episodes or ocular-motor symptoms may precede sustained ataxia. There is no family-wide rate of progression or survival estimate; slowly progressive SCA6 and FGF14-associated disease differ from severe childhood repeat-expansion presentations.
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Clinical features differ between patients with an adult onset and patients with an onset in infancy or early childhood with the disease starting in childhood showing a more rapid and aggressive progression within a few years. When disease symptoms first appear later in life, the disease progresses more slowly and the degree of disability will vary accordingly [103].
    explanation: The SCA7 section explicitly contrasts rapid childhood and slower adult courses.
  - reference: PMID:38507876
    reference_title: 'GAA-FGF14 disease: defining its frequency, molecular basis, and 4-aminopyridine response in a large downbeat nystagmus cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: episodic symptoms and oscillopsia preceded gait impairment in 1 of 10 (10%) and 3 of 28 (11%) patients for whom information on age at onset of these features was available, respectively.
    explanation: Selected FGF14-associated downbeat-nystagmus cases illustrate variable initial manifestations, not family-wide frequencies.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
    reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: May begin w/episodic ataxia, very slow progression; onset often after age 50 yrs; normal life span
    explanation: The SCA6 row supplies a subtype-specific counterexample to a universal early-onset or shortened-survival course.
phenotypes:
- name: Progressive cerebellar ataxia
  category: Neurologic
  description: Progressive gait and limb incoordination is characteristic of classic ADCA, but need not be present at the first visit or in every restricted ocular presentation.
  phenotype_term:
    preferred_term: Progressive cerebellar ataxia
    term:
      id: HP:0002073
      label: Progressive cerebellar ataxia
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: All ADCAs have progressive ataxia as their main clinical feature, frequently accompanied by dysarthria and oculomotor deficits.
    explanation: Progressive gait and limb incoordination is characteristic of classic ADCA, but need not be present at the first visit or in every restricted ocular presentation.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
    reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: dysmetria, dysdiadochokinesis, tremor, dysarthria, nystagmus, saccades
    explanation: The hereditary-ataxia baseline describes the cerebellar examination; manifestations remain subtype-dependent.
- name: Dysarthria
  category: Neurologic
  description: Speech can become slurred or poorly coordinated. Its presence and severity vary by subtype and disease stage.
  phenotype_term:
    preferred_term: Dysarthria
    term:
      id: HP:0001260
      label: Dysarthria
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: All ADCAs have progressive ataxia as their main clinical feature, frequently accompanied by dysarthria and oculomotor deficits.
    explanation: Speech can become slurred or poorly coordinated. Its presence and severity vary by subtype and disease stage.
- name: Nystagmus
  category: Neurologic
  description: Nystagmus is one possible cerebellar ocular-motor finding. Slow saccades, abnormal pursuit and other signs vary by molecular subtype.
  phenotype_term:
    preferred_term: Nystagmus
    term:
      id: HP:0000639
      label: Nystagmus
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: SCA2 is characterized by progressive cerebellar ataxia, dysarthria, and oculomotor deficits, including abnormally slow saccades and nystagmus [ 69].
    explanation: Nystagmus is one possible cerebellar ocular-motor finding. Slow saccades, abnormal pursuit and other signs vary by molecular subtype.
- name: Cerebellar atrophy
  category: Imaging
  description: Cerebellar atrophy may be visible on MRI, with variable regional and extracerebellar involvement. Its absence does not exclude a genetic cerebellar disorder, particularly early or in restricted FGF14 ocular presentations.
  phenotype_term:
    preferred_term: Cerebellar atrophy
    term:
      id: HP:0001272
      label: Cerebellar atrophy
  evidence:
  - reference: PMID:38507876
    reference_title: 'GAA-FGF14 disease: defining its frequency, molecular basis, and 4-aminopyridine response in a large downbeat nystagmus cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Brain MRI of eight patients showed cerebellar atrophy (13%; 8/60), which was limited to the vermis in three patients and extended to the hemispheres in five patients.
    explanation: Cerebellar atrophy may be visible on MRI, with variable regional and extracerebellar involvement. Its absence does not exclude a genetic cerebellar disorder, particularly early or in restricted FGF14 ocular presentations.
- name: Slow saccades
  category: Neurologic
  description: Abnormally slow saccades are particularly associated with SCA2 and also occur in other subtypes; they are not obligatory across ADCA.
  phenotype_term:
    preferred_term: Slow saccadic eye movements
    term:
      id: HP:0000514
      label: Slow saccadic eye movements
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: SCA2 is characterized by progressive cerebellar ataxia, dysarthria, and oculomotor deficits, including abnormally slow saccades and nystagmus [ 69].
    explanation: Abnormally slow saccades are particularly associated with SCA2 and also occur in other subtypes; they are not obligatory across ADCA.
- name: Downbeat nystagmus
  category: Neurologic
  description: Downbeat nystagmus is prominent in a subset of molecular forms, including FGF14-associated disease. The 2024 FGF14 cohort was selected for this finding and cannot establish its frequency among all affected carriers.
  phenotype_term:
    preferred_term: Downbeat nystagmus
    term:
      id: HP:0010545
      label: Downbeat nystagmus
  evidence:
  - reference: PMID:38507876
    reference_title: 'GAA-FGF14 disease: defining its frequency, molecular basis, and 4-aminopyridine response in a large downbeat nystagmus cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: a late-onset slowly progressive cerebellar syndrome that is frequently associated with episodic symptoms and downbeat nystagmus (DBN).
    explanation: Downbeat nystagmus is prominent in a subset of molecular forms, including FGF14-associated disease. The 2024 FGF14 cohort was selected for this finding and cannot establish its frequency among all affected carriers.
- name: Intention tremor
  category: Neurologic
  description: Intention tremor can accompany cerebellar incoordination, with subtype-dependent expression.
  phenotype_term:
    preferred_term: Intention tremor
    term:
      id: HP:0002080
      label: Intention tremor
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Patients can also suffer from intention and postural tremors, myoclonus, Parkinsonism, sleep disturbances, autonomic dysfunction, and initial hyperreflexia followed by peripheral neuropathy with hyporeflexia or areflexia [70].
    explanation: Intention tremor can accompany cerebellar incoordination, with subtype-dependent expression.
- name: Peripheral neuropathy
  category: Neurologic
  description: Sensory or sensorimotor neuropathy occurs in multisystem forms, including SCA2 and later-onset SCA3, but is not universal.
  phenotype_term:
    preferred_term: Peripheral neuropathy
    term:
      id: HP:0009830
      label: Peripheral neuropathy
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Patients can also suffer from intention and postural tremors, myoclonus, Parkinsonism, sleep disturbances, autonomic dysfunction, and initial hyperreflexia followed by peripheral neuropathy with hyporeflexia or areflexia [70].
    explanation: Sensory or sensorimotor neuropathy occurs in multisystem forms, including SCA2 and later-onset SCA3, but is not universal.
- name: Hyporeflexia
  category: Neurologic
  description: Reduced tendon reflexes can accompany peripheral involvement; some patients instead show brisk reflexes earlier in disease.
  phenotype_term:
    preferred_term: Hyporeflexia
    term:
      id: HP:0001265
      label: Hyporeflexia
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Patients can also suffer from intention and postural tremors, myoclonus, Parkinsonism, sleep disturbances, autonomic dysfunction, and initial hyperreflexia followed by peripheral neuropathy with hyporeflexia or areflexia [70].
    explanation: Reduced tendon reflexes can accompany peripheral involvement; some patients instead show brisk reflexes earlier in disease.
- name: Parkinsonism
  category: Neurologic
  description: Parkinsonian presentations occur in selected SCA2, SCA3 and SCA17 families and may be clinically prominent.
  phenotype_term:
    preferred_term: Parkinsonism
    term:
      id: HP:0001300
      label: Parkinsonism
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Patients can also suffer from intention and postural tremors, myoclonus, Parkinsonism, sleep disturbances, autonomic dysfunction, and initial hyperreflexia followed by peripheral neuropathy with hyporeflexia or areflexia [70].
    explanation: Parkinsonian presentations occur in selected SCA2, SCA3 and SCA17 families and may be clinically prominent.
- name: Spasticity
  category: Neurologic
  description: Pyramidal involvement may cause spasticity in multisystem ADCA, including adult SCA7.
  phenotype_term:
    preferred_term: Spasticity
    term:
      id: HP:0001257
      label: Spasticity
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Adult-onset SCA7 is characterized by progressive cerebellar ataxia, slowed ocular saccades, dysarthria, dyspha- gia, and pyramidal symptoms, such as hyperreflexia and spas- ticity [ 99].
    explanation: Pyramidal involvement may cause spasticity in multisystem ADCA, including adult SCA7.
- name: Dysphagia
  category: Neurologic
  description: Bulbar or cerebellar dysfunction can impair swallowing and increase aspiration or nutritional risk as disease advances. This is especially relevant in multisystem subtypes.
  phenotype_term:
    preferred_term: Dysphagia
    term:
      id: HP:0002015
      label: Dysphagia
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Adult-onset SCA7 is characterized by progressive cerebellar ataxia, slowed ocular saccades, dysarthria, dyspha- gia, and pyramidal symptoms, such as hyperreflexia and spas- ticity [ 99].
    explanation: Bulbar or cerebellar dysfunction can impair swallowing and increase aspiration or nutritional risk as disease advances. This is especially relevant in multisystem subtypes.
- name: Dystonia
  category: Neurologic
  description: Dystonia occurs in some molecular forms, including SCA17.
  phenotype_term:
    preferred_term: Dystonia
    term:
      id: HP:0001332
      label: Dystonia
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: SCA17 presents itself with cerebellar ataxia, pyramidal signs, and involuntary movements including chorea and dys- tonia.
    explanation: Dystonia occurs in some molecular forms, including SCA17.
- name: Cognitive impairment
  category: Neurologic
  description: Cognitive involvement varies considerably; late cognitive deficits are reported in SCA2 and dementia is prominent in some SCA17 presentations.
  phenotype_term:
    preferred_term: Cognitive impairment
    term:
      id: HP:0100543
      label: Cognitive impairment
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: different stud- ies have reported late cognitive deficits [71]
    explanation: Cognitive involvement varies considerably; late cognitive deficits are reported in SCA2 and dementia is prominent in some SCA17 presentations.
- name: Dementia
  category: Neurologic
  description: Dementia is a subtype-associated feature, particularly in SCA17; it is not a defining feature of every cerebellar ataxia.
  phenotype_term:
    preferred_term: Dementia
    term:
      id: HP:0000726
      label: Dementia
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: SCA17 patients are known to suffer from psychiatric symp- toms, as well as dementia [108, 109].
    explanation: Dementia is a subtype-associated feature, particularly in SCA17; it is not a defining feature of every cerebellar ataxia.
- name: Retinal dystrophy
  category: Ophthalmologic
  description: SCA7 can cause progressive cone-rod dystrophy. This retinal phenotype is central to the historical ADCA-II class.
  phenotype_term:
    preferred_term: Retinal dystrophy
    term:
      id: HP:0000556
      label: Retinal dystrophy
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Retinal degeneration is a distinctive feature of SCA7 with progressive cone-rod dystrophy leading to even- tual blindness [100].
    explanation: SCA7 can cause progressive cone-rod dystrophy. This retinal phenotype is central to the historical ADCA-II class.
- name: Visual impairment
  category: Ophthalmologic
  description: Progressive retinal visual loss can culminate in blindness in SCA7. Other ocular complaints in ADCA can instead arise from disordered eye movements.
  phenotype_term:
    preferred_term: Visual impairment
    term:
      id: HP:0000505
      label: Visual impairment
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Retinal degeneration is a distinctive feature of SCA7 with progressive cone-rod dystrophy leading to even- tual blindness [100].
    explanation: Progressive retinal visual loss can culminate in blindness in SCA7. Other ocular complaints in ADCA can instead arise from disordered eye movements.
epidemiology:
- name: Historical Singapore family estimate
  description: In the 2002 series, 204 people with ataxia underwent a nine-locus testing panel; 58 positive patients belonged to 36 families. The estimated lower bound was one affected family per 27,000 Singaporean families. This family-unit estimate is not a person-level prevalence or a contemporary comprehensive-panel yield.
  evidence:
  - reference: PMID:12485197
    reference_title: Prevalence and ethnic differences of autosomal-dominant cerebellar ataxia in Singapore.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: 'The estimated prevalence of ADCA in Singaporean families was at least 1 : 27,000.'
    explanation: The denominator is families, so conversion to persons per 100,000 is inappropriate.
- name: Regional subtype distributions
  description: SCA3 accounted for 31 of 58 molecularly classified Singaporean patients, whereas SCA6 accounted for 59 of 76 classified Aomori cases in the 2007–2009 Japanese series. Aomori enrolled 80 people, including 15 apparently sporadic cases. These selected, historically tested cohorts have different ascertainment and denominators; founder effects cannot be separated from referral and assay coverage by this comparison.
  evidence:
  - reference: PMID:12485197
    reference_title: Prevalence and ethnic differences of autosomal-dominant cerebellar ataxia in Singapore.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: SCA 3 was identified in 31 (53.4%) patients from 15 families, SCA 2 in 17 (29.3%) patients from 12 families and SCA 1 in four (6.9%) patients from four families.
    explanation: The proportions concern 58 positive patients, not all 204 tested individuals.
  - reference: PMID:21088341
    reference_title: Prevalence of autosomal dominant cerebellar ataxia in Aomori, the northernmost prefecture of Honshu, Japan.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: SCA6 was found to be the most common form of SCA in Aomori Prefecture, with a polyglutamine expansion in the CACNA1A gene being found in 59 of the 80 cases analyzed (77.7% of cases).
    explanation: The prose establishes regional SCA6 predominance but incorrectly pairs 59 of 80 with 77.7%; Table 2 shows that 76 cases were molecularly classified. The description preserves the corrected denominator and source discrepancy.
genetic:
- name: Polyglutamine SCA genes
  association: Causative coding repeat expansions in a subset of ADCA
  notes: ATXN1, ATXN2, ATXN3, CACNA1A, ATXN7 and TBP are the six polyglutamine SCA genes covered by the mechanistic review. DRPLA is a related ATN1 expansion disorder. Repeat length, interruptions, penetrance and transmission behavior require locus-specific interpretation.
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: These diseases are all caused by a CAG repeat expansion in the coding region of a gene.
    explanation: The review defines the six polyglutamine SCAs; this mechanism does not describe every ADCA.
- name: Noncoding-repeat and conventional-variant causes
  association: Additional distinct dominant genetic mechanisms
  notes: FGF14 intronic GAA expansion is an important late-onset cause that may present with downbeat nystagmus before overt ataxia. Conventional dominant variants or rearrangements in ITPR1, SPTBN2, PRKCG, AFG3L2 and other genes are mechanistically heterogeneous. Coding sequencing alone cannot exclude these families of repeat disorders.
  evidence:
  - reference: PMID:38507876
    reference_title: 'GAA-FGF14 disease: defining its frequency, molecular basis, and 4-aminopyridine response in a large downbeat nystagmus cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: A dominantly inherited GAA repeat expansion in intron 1 of the fibroblast growth factor 14 (FGF14) gene has recently been identified as the cause of GAA-FGF14 disease/spinocerebellar ataxia 27B (SCA27B)
    explanation: The primary cohort introduces an established noncoding expansion cause, distinct from the polyglutamine group.
  - reference: PMID:20723845
    reference_title: 'Autosomal dominant cerebellar ataxias: polyglutamine expansions and beyond.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: All other SCAs are caused by either conventional mutations or large rearrangements in genes with different functions, including glutamate signalling (SCA5/SPTBN2) and calcium signalling (SCA15/16/ITPR1), channel function (SCA13/KCNC3, SCA14/PRKCG, SCA27/FGF14), tau regulation (SCA11/TTBK2), and mitochondrial activity (SCA28/AFG3L2) or RNA alteration (SCA31/BEAN-TK2).
    explanation: The historical review supports heterogeneous conventional-variant mechanisms; its old gene counts and inclusion of noncoding SCA31 are not treated as current exhaustive classification.
- name: ATXN7
  association: Causative coding CAG expansion in SCA7
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  gene_term:
    preferred_term: ATXN7
    term:
      id: hgnc:10560
      label: ATXN7
  subtype: ADCA-II
  notes: ATXN7 is one of the six polyglutamine SCA genes in the cited mechanistic review. It is recorded as its own causal-gene entry because the retinal clinical class this entry carries as ADCA-II is bound to the SCA7 disease term.
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: Retinal degeneration is a distinctive feature of SCA7 with progressive cone-rod dystrophy leading to even- tual blindness [100].
    explanation: The review connects SCA7 to the retinal class, which is the clinical subtype this gene entry is scoped to.
- name: ATXN10
  association: Causative intronic ATTCT pentanucleotide expansion in SCA10
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  gene_term:
    preferred_term: ATXN10
    term:
      id: hgnc:10549
      label: ATXN10
  subtype: SCA10
  notes: A noncoding expansion, in intron 9, and a pentanucleotide rather than a trinucleotide repeat. Repeat-primed or long-read assays are required; coding sequencing does not detect it.
  evidence:
  - reference: PMID:11017075
    reference_title: Large expansion of the ATTCT pentanucleotide repeat in spinocerebellar ataxia type 10.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: We found an expansion of a pentanucleotide (ATTCT) repeat in intron 9 of SCA10 in all patients in five Mexican SCA10 families.
    explanation: Establishes the causal intronic expansion in the gene now named ATXN10.
  - reference: PMID:11017075
    reference_title: Large expansion of the ATTCT pentanucleotide repeat in spinocerebellar ataxia type 10.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Analysis of 562 chromosomes from unaffected individuals of various ethnic origins (including 242 chromosomes from Mexican persons) showed a range of 10 to 22 ATTCT repeats with no evidence of expansions.
    explanation: The control range reported in the discovery study, which is what separates a normal allele from a pathogenic one at this locus.
- name: GRM1
  association: Causative heterozygous dominant variants in SCA44
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  gene_term:
    preferred_term: GRM1
    term:
      id: hgnc:4593
      label: GRM1
  subtype: SCA44
  notes: 'Two dominant allele classes with different consequences were reported together: gain-of-function missense variants in adult-onset ataxia, and a de novo truncating variant acting as a dominant negative in juvenile-onset ataxia with intellectual disability. Recessive GRM1 variants cause a separate disease, SCAR13, which is not this entry.'
  evidence:
  - reference: PMID:28886343
    reference_title: Dominant Mutations in GRM1 Cause Spinocerebellar Ataxia Type 44.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: 'Here, we describe heterozygous dominant mutations in GRM1, which encodes mGluR1, that are associated with distinct disease phenotypes: gain-of-function missense mutations, linked in two different families to adult-onset cerebellar ataxia, and a de novo truncation mutation resulting in a dominant-negative effect that is associated with juvenile-onset ataxia and intellectual disability.'
    explanation: Establishes dominant GRM1 variants as causal and records both allele classes.
- name: NPTX1
  association: Causative heterozygous missense variants in SCA50
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  gene_term:
    preferred_term: NPTX1
    term:
      id: hgnc:7952
      label: NPTX1
  subtype: SCA50
  notes: Two missense variants were reported. Beyond the index family, p.G389R was found in four further unrelated families for which a common founder effect could be excluded, which is what supports recurrence rather than a single-family observation.
  evidence:
  - reference: PMID:34788392
    reference_title: NPTX1 mutations trigger endoplasmic reticulum stress and cause autosomal dominant cerebellar ataxia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Our results establish NPTX1 as a new causative gene in autosomal dominant cerebellar ataxias.
    explanation: Establishes NPTX1 as a dominant ataxia gene.
  - reference: PMID:34788392
    reference_title: NPTX1 mutations trigger endoplasmic reticulum stress and cause autosomal dominant cerebellar ataxia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Further investigations with whole-exome sequencing and an amplicon-based panel identified four additional unrelated families segregating the same variant, for whom a common founder effect could be excluded.
    explanation: Source for the independent recurrence of the p.G389R allele recorded in this entry's notes.
- name: THAP11
  association: Causative coding CAG repeat expansion in SCA51
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  gene_term:
    preferred_term: THAP11
    term:
      id: hgnc:23194
      label: THAP11
  subtype: SCA51
  notes: 'THAP11 (hgnc:23194) must not be confused with THAP1 (hgnc:20856), the DYT6 dystonia gene. The pathogenic measure at this locus is the uninterrupted 3-prime CAG tract rather than total repeat length, so an assay reporting only total length can be misleading. Expansions have so far been found predominantly in Chinese-ancestry pedigrees.'
  evidence:
  - reference: PMID:37148549
    reference_title: CAG Repeat Expansion in THAP11 Is Associated with a Novel Spinocerebellar Ataxia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: 'We identified THAP11 as the novel causative SCA gene with CAG repeats ranging from 45 to 100 in patients with ataxia and from 20 to 38 in healthy control subjects.'
    explanation: Establishes THAP11 as causal and gives the patient and control repeat ranges.
  - reference: PMID:37148549
    reference_title: CAG Repeat Expansion in THAP11 Is Associated with a Novel Spinocerebellar Ataxia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: 'Among the patients, the number of CAA interruptions within CAG repeats was decreased to 3 (up to 5-6 in controls), whereas the number of 3'' pure CAG repeats was up to 32 to 87 (4-16 in controls), suggesting that the toxicity of polyQ protein was length dependent on the pure CAG repeats.'
    explanation: Source for the claim that the uninterrupted CAG tract, not total repeat length, is the pathogenic measure at this locus.
  - reference: PMID:39651830
    reference_title: A Population-Wide Exploration of the THAP11 CAG Repeat Size and Structure in the 100,000 Genomes Project and UK Biobank.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: 'These results indicate that THAP11 expansions are rare in the British population and that sequence structures predisposed to expansions may be more common in non-British ancestries.'
    explanation: Population survey qualifying the expected yield of testing this locus outside the ancestries of discovery. It does not contradict the gene-disease association.
- name: RAB3A
  association: Causative heterozygous missense variant in SCA52
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  gene_term:
    preferred_term: RAB3A
    term:
      id: hgnc:9777
      label: RAB3A
  subtype: SCA52
  notes: One recurrent variant, p.Arg83Trp, in two families. The proposed lesion is a failure of effector binding rather than loss of GTP binding, which is why this is recorded as a conventional dominant variant and not as a null allele.
  evidence:
  - reference: PMID:41492970
    reference_title: An R83W mutation in Rab3A causes autosomal-dominant cerebellar ataxia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: 'In this study, we identified the c.247C > T p.(Arg83Trp) variant in RAB3A, encoding a small GTPase involved in membrane-associated regulated exocytosis, in two families with cerebellar ataxia.'
    explanation: Establishes RAB3A as causal in two families.
  - reference: PMID:41492970
    reference_title: An R83W mutation in Rab3A causes autosomal-dominant cerebellar ataxia.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Although the mutant Rab3A R83W retained GTP-binding affinity, it failed to bind the key effector proteins RIM1 and Rabphilin-3A, highlighting the functional importance of R83 in effector complex formation, as supported by structural analysis.
    explanation: Source for the effector-binding rather than GTP-binding lesion recorded in this entry's notes.
treatments:
- name: Physical rehabilitation and mobility support
  description: Individualized balance, gait and strength training, mobility aids and fall-prevention adaptations support function. Goals and intensity depend on impairment and safety; rehabilitation is not established as a cure or proof of slowed molecular degeneration. A 62-person assessor-masked trial found greater SARA improvement with aerobic than dose-matched balance training; 43 participants had genetically confirmed SCA and the remainder had idiopathic ataxia or MSA-C. Selection required ambulatory function and safe cycling. This supports functional rehabilitation, not subtype-specific neuroprotection. In a separate uncontrolled seven-person SCA6/SCA31 cohort, annual intensive rehabilitation accompanied relative pre-session SARA stability through year six, while balance declined earlier; six-month follow-up SARA worsened from year three. Absence of a concurrent control prevents attributing long-term disease slowing to that regimen.
  action_category: THERAPEUTIC
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Physical Therapy
    term:
      id: NCIT:C15302
      label: Physical Therapy
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
    reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: PT (balance exercises, gait training, muscle strengthening) to maintain mobility &#x00026; function
    explanation: GeneReviews recommends physical rehabilitation to preserve functional mobility; this is broad hereditary-ataxia guidance.
  - reference: PMID:40946705
    reference_title: 'Home Training for Cerebellar Ataxias: A Randomized Clinical Trial.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: 'Compared to the balance group, the aerobic training group demonstrated significantly better improvements in SARA (time-by-group interaction, 6 months: β, −1.53; 95% CI, −2.44 to −0.61;'
    explanation: Primary randomized between-group SARA result; the full body establishes a mixed ataxia population and selected exercise eligibility.
  - reference: PMID:40946705
    reference_title: 'Home Training for Cerebellar Ataxias: A Randomized Clinical Trial.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Most participants in the aerobic and balance groups had genetically confirmed spinocerebellar ataxia (21/31 and 22/31, respectively)
    explanation: The randomized cohort includes 43 genetically confirmed SCA participants, not 62 people with ADCA.
  - reference: PMID:40906249
    reference_title: 'Long-Term Effects of Annual Intensive Rehabilitation in Patients with Hereditary Pure Cerebellar Ataxia: A 7-year Follow-up Study.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Additionally, the absence of a control group prevents direct comparison with the natural history of the condition
    explanation: The seven-person retrospective cohort cannot establish a causal effect on long-term disease progression.
  target_mechanisms:
  - target: Progressive cerebellar ataxia
    treatment_effect: MODULATES
    description: Symptomatic intervention addresses the functional manifestation; it is not evidence of reversal of the underlying genetic lesion.
    evidence:
    - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
      reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: PT (balance exercises, gait training, muscle strengthening) to maintain mobility &#x00026; function
      explanation: GeneReviews recommends physical rehabilitation to preserve functional mobility; this is broad hereditary-ataxia guidance.
    - reference: PMID:40946705
      reference_title: 'Home Training for Cerebellar Ataxias: A Randomized Clinical Trial.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: 'Compared to the balance group, the aerobic training group demonstrated significantly better improvements in SARA (time-by-group interaction, 6 months: β, −1.53; 95% CI, −2.44 to −0.61;'
      explanation: Primary randomized between-group SARA result; the full body establishes a mixed ataxia population and selected exercise eligibility.
    - reference: PMID:40946705
      reference_title: 'Home Training for Cerebellar Ataxias: A Randomized Clinical Trial.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: Most participants in the aerobic and balance groups had genetically confirmed spinocerebellar ataxia (21/31 and 22/31, respectively)
      explanation: The randomized cohort includes 43 genetically confirmed SCA participants, not 62 people with ADCA.
    - reference: PMID:40906249
      reference_title: 'Long-Term Effects of Annual Intensive Rehabilitation in Patients with Hereditary Pure Cerebellar Ataxia: A 7-year Follow-up Study.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: Additionally, the absence of a control group prevents direct comparison with the natural history of the condition
      explanation: The seven-person retrospective cohort cannot establish a causal effect on long-term disease progression.
- name: Occupational therapy and adaptive equipment
  description: Occupational therapy and adaptive utensils, dressing aids, mobility equipment and home adaptations can help maintain independence. Reassess needs with progression.
  action_category: THERAPEUTIC
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Occupational Therapy
    term:
      id: NCIT:C121351
      label: Occupational Therapy
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
    reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Inpatient rehab w/OT/PT may improve ataxia &#x00026; functional abilities in persons w/degenerative ataxias.  # codespell:ignore ot
    explanation: GeneReviews recommends occupational and physical rehabilitation for functional abilities.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
    reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Home adaptations to prevent falls (e.g., grab bars, raised toilet seats)
    explanation: The chapter gives concrete fall-prevention adaptations.
  target_mechanisms:
  - target: Progressive cerebellar ataxia
    treatment_effect: BYPASSES
    description: Adaptive equipment compensates for impaired daily function; the guideline does not show restoration of cerebellar molecular or neuronal function.
    evidence:
    - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
      reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: Inpatient rehab w/OT/PT may improve ataxia &#x00026; functional abilities in persons w/degenerative ataxias.  # codespell:ignore ot
      explanation: GeneReviews recommends occupational and physical rehabilitation for functional abilities.
- name: Speech-language and communication support
  description: Speech-language therapy addresses dysarthria and communication needs; writing or digital communication can be added as speech becomes less intelligible.
  action_category: THERAPEUTIC
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Speech Language Therapy
    term:
      id: NCIT:C159273
      label: Speech Language Therapy
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
    reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Consider alternative communication methods as needed (e.g., writing pads &#x00026; digital devices).
    explanation: Speech-language care includes alternative communication when dysarthria limits speech.
  target_mechanisms:
  - target: Dysarthria
    treatment_effect: BYPASSES
    description: Writing or digital devices compensate for impaired spoken communication without demonstrating recovery of dysarthria.
    evidence:
    - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
      reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: Consider alternative communication methods as needed (e.g., writing pads &#x00026; digital devices).
      explanation: Speech-language care includes alternative communication when dysarthria limits speech.
- name: Swallowing and nutritional support
  description: Assess choking, swallowing safety, weight and intake. Modify food consistency and provide dietetic or nutritional support; discuss enteral feeding when intake cannot be maintained despite supplements. Decisions are individualized and do not presume all patients eventually require a feeding tube.
  action_category: THERAPEUTIC
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Nutritional Support
    term:
      id: NCIT:C15433
      label: Nutritional Support
  evidence:
  - reference: PMID:30786918
    reference_title: Guidelines on the diagnosis and management of the progressive ataxias.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: If patients show symptoms of dysphagia a referral to a speech and language therapist should be made
    explanation: The progressive-ataxia guideline recommends symptomatic swallowing assessment and support.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
    reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Modify food consistency to &#x02193; aspiration risk.
    explanation: GeneReviews provides a specific compensatory swallowing intervention.
  - reference: PMID:30786918
    reference_title: Guidelines on the diagnosis and management of the progressive ataxias.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: If calorie intake cannot be maintained despite supplements, discuss the possibility of a percutaneous gastronomy (PEG) to provide secure feeding.
    explanation: The guideline makes feeding-tube discussion conditional on inadequate intake.
  target_mechanisms:
  - target: Dysphagia
    treatment_effect: MODULATES
    description: Symptomatic intervention addresses the functional manifestation; it is not evidence of reversal of the underlying genetic lesion.
    evidence:
    - reference: PMID:30786918
      reference_title: Guidelines on the diagnosis and management of the progressive ataxias.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: If patients show symptoms of dysphagia a referral to a speech and language therapist should be made
      explanation: The progressive-ataxia guideline recommends symptomatic swallowing assessment and support.
    - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
      reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: Modify food consistency to &#x02193; aspiration risk.
      explanation: GeneReviews provides a specific compensatory swallowing intervention.
    - reference: PMID:30786918
      reference_title: Guidelines on the diagnosis and management of the progressive ataxias.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: If calorie intake cannot be maintained despite supplements, discuss the possibility of a percutaneous gastronomy (PEG) to provide secure feeding.
      explanation: The guideline makes feeding-tube discussion conditional on inadequate intake.
- name: Treatment of spasticity
  description: Use physiotherapy and individualized antispasticity treatment when pyramidal symptoms impair function. Oral agents or selected focal botulinum treatment are symptomatic options; tolerability and effects on mobility guide decisions.
  action_category: THERAPEUTIC
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
    reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Baclofen, tizanidine, or dantrolene may relieve muscle spasms &#x00026; spasticity.
    explanation: The guidance identifies symptomatic antispasticity options.
  - reference: PMID:30786918
    reference_title: Guidelines on the diagnosis and management of the progressive ataxias.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: To treat focal spasticity refer to a specialised clinic for treatment with intramuscular botulinum toxin injections, followed by physiotherapy.
    explanation: The guideline distinguishes focal from generalized treatment.
  target_mechanisms:
  - target: Spasticity
    treatment_effect: MODULATES
    description: Symptomatic intervention addresses the functional manifestation; it is not evidence of reversal of the underlying genetic lesion.
    evidence:
    - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
      reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: Baclofen, tizanidine, or dantrolene may relieve muscle spasms &#x00026; spasticity.
      explanation: The guidance identifies symptomatic antispasticity options.
    - reference: PMID:30786918
      reference_title: Guidelines on the diagnosis and management of the progressive ataxias.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: To treat focal spasticity refer to a specialised clinic for treatment with intramuscular botulinum toxin injections, followed by physiotherapy.
      explanation: The guideline distinguishes focal from generalized treatment.
- name: Treatment of dystonia
  description: Focal dystonia may be treated with botulinum toxin, while generalized dystonia needs individualized specialist management. Recommendations largely extrapolate symptomatic practice across neurological disorders.
  action_category: THERAPEUTIC
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  evidence:
  - reference: PMID:30786918
    reference_title: Guidelines on the diagnosis and management of the progressive ataxias.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Focal dystonia should be treated with botulinum toxin injections.
    explanation: This is a good-practice recommendation for focal dystonia in progressive ataxia.
  target_mechanisms:
  - target: Dystonia
    treatment_effect: MODULATES
    description: Symptomatic intervention addresses the functional manifestation; it is not evidence of reversal of the underlying genetic lesion.
    evidence:
    - reference: PMID:30786918
      reference_title: Guidelines on the diagnosis and management of the progressive ataxias.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: Focal dystonia should be treated with botulinum toxin injections.
      explanation: This is a good-practice recommendation for focal dystonia in progressive ataxia.
- name: Neuro-ophthalmic symptomatic treatment
  description: Neuro-ophthalmic assessment distinguishes nystagmus, diplopia, ocular-motor impairment and retinal visual loss. Selected medication or prism treatment and low-vision aids may improve symptoms; retinal degeneration and ocular-motor dysfunction require different support.
  action_category: THERAPEUTIC
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  evidence:
  - reference: PMID:30786918
    reference_title: Guidelines on the diagnosis and management of the progressive ataxias.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: If disabling nystagmus or oscillopsia is present treatment is recommended, often with either gabapentin or baclofen.
    explanation: The guideline addresses symptomatic eye-movement disability, not every genetic subtype equally.
  - reference: PMID:30786918
    reference_title: Guidelines on the diagnosis and management of the progressive ataxias.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Patients with visual impairment should be offered low vision aids and the possibility of having their visual disability registered.
    explanation: Low-vision support is recommended when visual function is impaired.
  target_mechanisms:
  - target: Nystagmus
    treatment_effect: MODULATES
    description: Symptomatic intervention addresses the functional manifestation; it is not evidence of reversal of the underlying genetic lesion.
    evidence:
    - reference: PMID:30786918
      reference_title: Guidelines on the diagnosis and management of the progressive ataxias.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: If disabling nystagmus or oscillopsia is present treatment is recommended, often with either gabapentin or baclofen.
      explanation: The guideline addresses symptomatic eye-movement disability, not every genetic subtype equally.
    - reference: PMID:30786918
      reference_title: Guidelines on the diagnosis and management of the progressive ataxias.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: Patients with visual impairment should be offered low vision aids and the possibility of having their visual disability registered.
      explanation: Low-vision support is recommended when visual function is impaired.
- name: Selected 4-aminopyridine use in FGF14-associated disease
  description: Specialist-directed 4-aminopyridine may provide symptomatic benefit in selected FGF14-associated downbeat-nystagmus or ataxia presentations. Evidence includes retrospective open-label responses and a four-person post hoc genotype subgroup from an earlier crossover trial. All four received active drug first, and phase baselines differed; larger randomized trials are needed. Disease modification and family-wide benefit are not established.
  action_category: THERAPEUTIC
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: 4-aminopyridine
      term:
        id: CHEBI:34385
        label: 4-aminopyridine
  evidence:
  - reference: PMID:38507876
    reference_title: 'GAA-FGF14 disease: defining its frequency, molecular basis, and 4-aminopyridine response in a large downbeat nystagmus cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: A clinician-reported treatment response was recorded for 29 of 36 patients carrying a (GAA)≥250 allele
    explanation: The selected FGF14 downbeat-nystagmus cohort supplies retrospective clinician-reported response, not a general ADCA efficacy estimate.
  - reference: PMID:38507876
    reference_title: 'GAA-FGF14 disease: defining its frequency, molecular basis, and 4-aminopyridine response in a large downbeat nystagmus cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: the benefits reported herein need validation in a larger randomised placebo-controlled trial.
    explanation: The authors explicitly limit the efficacy inference.
  target_mechanisms:
  - target: Downbeat nystagmus
    treatment_effect: MODULATES
    description: Symptomatic intervention addresses the functional manifestation; it is not evidence of reversal of the underlying genetic lesion.
    evidence:
    - reference: PMID:38507876
      reference_title: 'GAA-FGF14 disease: defining its frequency, molecular basis, and 4-aminopyridine response in a large downbeat nystagmus cohort.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: A clinician-reported treatment response was recorded for 29 of 36 patients carrying a (GAA)≥250 allele
      explanation: The selected FGF14 downbeat-nystagmus cohort supplies retrospective clinician-reported response, not a general ADCA efficacy estimate.
    - reference: PMID:38507876
      reference_title: 'GAA-FGF14 disease: defining its frequency, molecular basis, and 4-aminopyridine response in a large downbeat nystagmus cohort.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      snippet: the benefits reported herein need validation in a larger randomised placebo-controlled trial.
      explanation: The authors explicitly limit the efficacy inference.
- name: Riluzole evidence remains subtype-dependent
  description: Earlier mixed-etiology ataxia studies prompted consideration of off-label riluzole, with liver-enzyme monitoring. In ATRIL, 45 moderately affected SCA2 participants received riluzole or placebo for 12 months, without a clinical or MRI benefit. This does not establish routine efficacy across ADCA and does not prove absence of benefit in every other subtype.
  action_category: THERAPEUTIC
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: Riluzole
      term:
        id: NCIT:C47704
        label: Riluzole
  evidence:
  - reference: PMID:35063116
    reference_title: 'Safety and efficacy of riluzole in spinocerebellar ataxia type 2 in France (ATRIL): a multicentre, randomised, double-blind, placebo-controlled trial.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Riluzole did not improve clinical or radiological outcomes in these patients.
    explanation: The negative result concerns 45 moderately affected SCA2 participants in ATRIL.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
    reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: use requires monitoring of liver enzymes.
    explanation: GeneReviews notes monitoring when riluzole is considered.
- name: Cognitive and psychological support
  description: Assess cognitive, mood and behavioral concerns, with neuropsychological rehabilitation, psychotherapy or standard psychiatric treatment as appropriate. Cognitive impairment is subtype-dependent; it should not be presumed from motor severity alone.
  action_category: THERAPEUTIC
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:30786918
    reference_title: Guidelines on the diagnosis and management of the progressive ataxias.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Cognitive rehabilitation is recommended for those patients with cognitive impairment.
    explanation: The guideline recommends rehabilitation for an identified cognitive problem.
  - reference: PMID:30786918
    reference_title: Guidelines on the diagnosis and management of the progressive ataxias.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: In many cases depression can be treated in primary care using medications, counselling or cognitive behavioural therapy.
    explanation: The guideline supplies symptomatic mental-health care.
- name: Longitudinal neurological and functional monitoring
  description: Follow neurological function, falls, mobility, speech, swallowing, nutrition and cognitive or psychiatric concerns. GeneReviews suggests annual neurological review, with more frequent assessment for deterioration and symptom-based allied-health review. These are broad hereditary-ataxia recommendations; the chapter notes the absence of general published surveillance guidelines.
  action_category: MONITORING
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
    reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Monitor ataxia progression w/standardized scale (SARA).
    explanation: The chapter supports structured neurological follow-up.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
    reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Annually; more often for an acute exacerbation
    explanation: The surveillance table suggests this frequency for neurological and functional assessment.
- name: Genetic counseling and family testing
  description: Offer voluntary pre- and post-test counseling covering inheritance, variable penetrance, uncertain results, psychological implications and reproductive options. Test a known familial pathogenic variant when appropriate. Predictive testing for adult-onset disease in asymptomatic minors is generally deferred unless childhood actionability justifies it; symptomatic children warrant diagnostic evaluation.
  action_category: COUNSELING_INFORMATIONAL
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:40883955
    reference_title: Practice Recommendations for Genetic Testing of Ataxias.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: This does not obligate the person to proceed with testing but is recommended to better understand the risk of the familial condition and the potential impact of results should they proceed with testing.
    explanation: The predictive-testing recommendation preserves informed choice.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
    reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Genetic counseling and risk assessment depend on determination of the specific cause of an inherited ataxia in an individual.
    explanation: The broad chapter makes family counseling molecularly specific.
- name: Palliative and family support
  description: Advanced functional impairment may warrant coordinated palliative care, symptom relief, respite and support for caregivers. These services can accompany active rehabilitation and are individualized; the progressive-ataxia guideline bases much of this advice on other neurodegenerative disorders.
  action_category: THERAPEUTIC
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Palliative Therapy
    term:
      id: NCIT:C15292
      label: Palliative Therapy
  evidence:
  - reference: PMID:30786918
    reference_title: Guidelines on the diagnosis and management of the progressive ataxias.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: In the absence of available literature on palliative and end-of-life care in the ataxias specifically, these recommendations are derived in part from evidence of these interventions in other progressive neurodegenerative conditions
    explanation: The source explicitly states the extrapolated evidence base.
- name: Troriluzole investigational treatment
  description: In its November 4, 2025 complete-response letter, FDA concluded that the submitted trials and external-control analysis did not establish substantial evidence of efficacy for spinocerebellar ataxia. Concerns included a failed prespecified randomized primary endpoint, residual confounding, substantial missing data and nonprespecified analyses; the external-control result is not established disease modification. That decision did not approve the submitted SCA application; this dated regulatory conclusion does not assert a subsequent development outcome or established clinical benefit.
  evidence:
  - reference: url:https://download.open.fda.gov/crl/CRL_NDA210862_20251104.pdf
    reference_title: https://download.open.fda.gov/crl/CRL_NDA210862_20251104.pdf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: substantial evidence of effectiveness has not been established for troriluzole for the treatment of spinocerebellar ataxia.
    explanation: The dated regulatory review is evidence of the submitted-data conclusion, not a prediction about future development.
  action_category: THERAPEUTIC
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: troriluzole
      term:
        id: CHEBI:757061
        label: troriluzole
diagnosis:
- name: Neurological, family-history and acquired-cause assessment
  description: Establish the pattern and tempo of cerebellar dysfunction, obtain a multigeneration pedigree and evaluate additional neurological findings. Consider acquired, nutritional, immune, toxic and structural causes, particularly when onset or rapid progression is atypical. A negative family history does not exclude dominant ataxia.
  evidence:
  - reference: PMID:30786918
    reference_title: Guidelines on the diagnosis and management of the progressive ataxias.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: The clinical context (speed of evolution, episodic/fluctuating versus progressive etc.) should determine the investigation of individual cases.
    explanation: The guideline prioritizes phenotype and tempo rather than a universal test sequence.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
    reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: A three-generation family history should be taken with attention to relatives with manifestations of hereditary ataxia
    explanation: The hereditary-ataxia chapter recommends a detailed multigeneration family history.
- name: MRI and functional baseline
  description: Brain MRI defines the distribution of atrophy and helps assess alternative causes. Document cerebellar and extracerebellar examination findings, using SARA or another appropriate scale for follow-up. Normal or minimally abnormal imaging does not exclude early or restricted FGF14-associated disease.
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
    reference_title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Brain MRI to evaluate presence &#x00026; severity of cerebellar atrophy
    explanation: GeneReviews recommends imaging to assess structural involvement.
  - reference: PMID:38507876
    reference_title: 'GAA-FGF14 disease: defining its frequency, molecular basis, and 4-aminopyridine response in a large downbeat nystagmus cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Brain MRI of eight patients showed cerebellar atrophy (13%; 8/60), which was limited to the vermis in three patients and extended to the hemispheres in five patients.
    explanation: Cerebellar atrophy may be visible on MRI, with variable regional and extracerebellar involvement. Its absence does not exclude a genetic cerebellar disorder, particularly early or in restricted FGF14 ocular presentations.
- name: Molecular testing that detects repeat expansions
  description: Testing must detect the relevant expansion classes as well as sequence and copy-number variants. The 2025 recommendations favor comprehensive testing, ideally genome sequencing with validated short-tandem-repeat sizing, sometimes complemented by repeat-primed PCR or long-read sequencing. A dedicated expansion panel followed by genome testing is an alternative. Standard sequence-only panels or exomes may miss expansions; familial targeted testing can be appropriate.
  evidence:
  - reference: PMID:40883955
    reference_title: Practice Recommendations for Genetic Testing of Ataxias.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: The initial genetic test ordered should be as comprehensive as possible, include the most ataxia‐relevant genes, and reliably detect pathogenic repeat expansions.
    explanation: The consensus recommendation explicitly requires repeat detection.
  - reference: PMID:40883955
    reference_title: Practice Recommendations for Genetic Testing of Ataxias.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: If WGS as a first approach is fiscally impossible or otherwise not feasible, then a dedicated repeat expansion panel with eventual reflex to WGS would be appropriate.
    explanation: The guideline provides an alternative pathway when comprehensive genome testing is unavailable.
- name: Interpretation and reassessment of unresolved results
  description: Interpret variants with phenotype, segregation, repeat structure and current classification; a variant of uncertain significance alone does not establish a molecular diagnosis. Negative testing may reflect assay limitations or an unresolved cause. Consider reanalysis after at least two years or new symptoms, including newly detectable repeat expansions where available.
  evidence:
  - reference: PMID:40883955
    reference_title: Practice Recommendations for Genetic Testing of Ataxias.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Reanalysis of previously negative genomic testing should be considered after a period of at least 2 years or a change in symptomology.
    explanation: The consensus recommends periodic reassessment rather than treating every negative result as final.
clinical_trials:
- name: NCT03347344
  status: COMPLETED
  description: ATRIL randomized 45 participants with moderately affected, genetically defined SCA2 to riluzole or placebo for 12 months. Improvement of at least one SARA point occurred in 7/22 versus 9/23; neither clinical nor MRI outcomes improved with riluzole. The result is specific to the enrolled SCA2 population.
  evidence:
  - reference: PMID:35063116
    reference_title: 'Safety and efficacy of riluzole in spinocerebellar ataxia type 2 in France (ATRIL): a multicentre, randomised, double-blind, placebo-controlled trial.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Riluzole did not improve clinical or radiological outcomes in these patients.
    explanation: The randomized SCA2 trial did not meet the intended clinical efficacy goal.
  phase: PHASE_III
- name: NCT05002218
  status: COMPLETED
  description: Single-center assessor-masked randomized comparison of home aerobic versus balance training in 62 selected ambulatory adults with mixed cerebellar ataxias, including 43 genetically confirmed SCAs. At six months, the between-group SARA effect favored aerobic training by 1.53 points (95% CI 0.61–2.44 in the direction of improvement). Training support stopped after six months; 11/62 participants had dropped out by one year. Adherence subgroup comparisons were not randomized, missing-at-random assumptions limit inference, and structural MRI results were not reported in this paper.
  evidence:
  - reference: PMID:40946705
    reference_title: 'Home Training for Cerebellar Ataxias: A Randomized Clinical Trial.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: Of 62 participants randomized, 31 were randomized to home aerobic training and 31 were randomized to home balance training.
    explanation: The primary report establishes the randomized comparator design.
  - reference: PMID:40946705
    reference_title: 'Home Training for Cerebellar Ataxias: A Randomized Clinical Trial.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: The inferences from analyses with missing data are valid under the missing-at-random assumption (ie, the missing mechanism does not depend on the value of the unobserved outcome), which is not testable in this study.
    explanation: The authors state the missing-data assumption explicitly.
  phase: NOT_APPLICABLE
animal_models:
- name: Purkinje-directed ATXN2-Q127 transgenic mouse
  species: Mouse
  background: B6;D2 hybrid background
  genotype: Pcp 2-driven full-length human ATXN2 with 127 CAG repeats
  publication: PMID:28405024
  description: The SCA2 model develops motor impairment and reduced Purkinje-cell firing. Intracerebroventricular ASO7 begun around motor-phenotype onset lowers human ATXN2 and partly lowers endogenous mouse Atxn2, improving rotarod performance. Subsequent acute-slice recordings show restoration of firing.
  notes: Cell-restricted transgene expression and a very long repeat differ from typical human heterozygosity. The study demonstrates preclinical target engagement and functional rescue, not human efficacy, a cure, lifespan extension in these SCA2 cohorts or recovery of lost neurons. Electrophysiological cell counts are nested within only one to four mice per genotype.
  evidence:
  - reference: PMID:28405024
    reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: Pcp2-ATXN2-Q127 (ATXN2-Q127) transgenic mice express the full-length human ATXN2-[CAG]127 cDNA under the control of the mouse Purkinje cell protein 2 (L7) promoter (Pcp2).
    explanation: The model uses Purkinje-directed expression of a human expanded transgene rather than a humanized endogenous allele.
  - reference: PMID:28405024
    reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: Mice injected with ASO7 had significantly improved motor performance compared to saline-treated control mice
    explanation: The mouse motor result supports target-dependent experimental improvement.
  modeled_mechanisms:
  - target: Expanded Polyglutamine Protein
    relationship: RECAPITULATES
    limitations: Overexpression, promoter and repeat length constrain generalization to other polyglutamine disorders.
    description: Expresses expanded human ATXN2 in Purkinje cells.
    evidence:
    - reference: PMID:28405024
      reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: PRIMARY_RESULT
      snippet: Pcp2-ATXN2-Q127 (ATXN2-Q127) transgenic mice express the full-length human ATXN2-[CAG]127 cDNA under the control of the mouse Purkinje cell protein 2 (L7) promoter (Pcp2).
      explanation: The model uses Purkinje-directed expression of a human expanded transgene rather than a humanized endogenous allele.
    model_scale: MOLECULAR
  - target: Reduced Purkinje Cell Firing
    relationship: RECAPITULATES
    limitations: The assay is ex vivo; ASO lowers multiple downstream abnormalities and does not isolate firing as the necessary mediator of behavioral rescue.
    readouts:
    - name: Purkinje firing frequency
      description: Reduced baseline firing approaches wild-type values after ASO7.
      evidence:
      - reference: PMID:28405024
        reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
        supports: SUPPORT
        evidence_source: IN_VITRO
        quote_role: PRIMARY_RESULT
        snippet: In both models, a single injection of ASO7 resulted in near complete restoration of normal PC firing frequency
        explanation: Electrophysiology in acute cerebellar slices measures firing after in-vivo treatment.
      target: Reduced Purkinje Cell Firing
    description: Mutant physiology is measured in acute slices after animal treatment.
    evidence:
    - reference: PMID:28405024
      reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: In both models, a single injection of ASO7 resulted in near complete restoration of normal PC firing frequency
      explanation: Electrophysiology in acute cerebellar slices measures firing after in-vivo treatment.
    model_scale: CELLULAR
  - target: Cerebellar Network Dysfunction
    relationship: RECAPITULATES
    limitations: Rotarod is a functional surrogate rather than a complete measure of human ataxia.
    description: Motor performance improves after ATXN2 lowering.
    evidence:
    - reference: PMID:28405024
      reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: PRIMARY_RESULT
      snippet: Mice injected with ASO7 had significantly improved motor performance compared to saline-treated control mice
      explanation: The mouse motor result supports target-dependent experimental improvement.
    model_scale: ORGANISM
- name: BAC-ATXN2-Q72 transgenic mouse
  species: Mouse
  background: FVB;B6 hybrid background
  genotype: Human ATXN2 BAC with 72 CAG repeats
  publication: PMID:28405024
  description: The BAC model expresses expanded ATXN2 across multiple neuronal tissues and has slower disease progression than the Purkinje-directed Q127 model. ASO7 reduces ATXN2 and improves motor behavior; a separate delayed-treatment cohort shows firing recovery when injected more than 12 weeks after motor onset.
  notes: The late-treatment result is physiological recovery, not direct evidence that established neuron loss or all behavioral deficits were reversed at that late stage. Normalized Purkinje protein levels and mRNA changes do not establish one serial transcription-to-firing mechanism. The Methods and extended weight caption differ in stated BAC dosing; no unique dosing regimen is inferred here.
  evidence:
  - reference: PMID:28405024
    reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: BAC-ATXN2-Q72 (BAC-Q72) mice were created using a contiguous 169 kb human ATXN2 gene sequence including 16 kb upstream ATXN2 sequence, the entire ATXN2-[CAG]72 coding region (with introns) and 3 kb of ATXN2 3’-UTR and downstream sequence.
    explanation: The BAC preserves the human regulatory and intronic context but remains a transgenic mouse model.
  - reference: PMID:28405024
    reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: However, the rotarod performance of the ASO7 treated mice did not perfectly mirror that of wildtype mice.
    explanation: The BAC model motor rescue is incomplete.
  - reference: PMID:28405024
    reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    snippet: Similarly, we injected BAC-Q72 mice at 30 wks, >12 weeks after motor phenotype onset, and analyzed PC firing 10 wks later.
    explanation: The primary body defines the timing and physiological endpoint of delayed treatment.
  modeled_mechanisms:
  - target: Expanded Polyglutamine Protein
    relationship: RECAPITULATES
    limitations: Transgene context is more extensive but does not reproduce every aspect of human disease.
    description: Models expanded human ATXN2 in a BAC genomic context.
    evidence:
    - reference: PMID:28405024
      reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: PRIMARY_RESULT
      snippet: BAC-ATXN2-Q72 (BAC-Q72) mice were created using a contiguous 169 kb human ATXN2 gene sequence including 16 kb upstream ATXN2 sequence, the entire ATXN2-[CAG]72 coding region (with introns) and 3 kb of ATXN2 3’-UTR and downstream sequence.
      explanation: The BAC preserves the human regulatory and intronic context but remains a transgenic mouse model.
    model_scale: MOLECULAR
  - target: Reduced Purkinje Cell Firing
    relationship: RECAPITULATES
    limitations: No isolated manipulation of firing or neuronal replacement was performed.
    readouts:
    - name: Late-treatment firing recovery
      description: Purkinje physiology was assessed 10 weeks after treatment at 30 weeks.
      evidence:
      - reference: PMID:28405024
        reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
        supports: SUPPORT
        evidence_source: IN_VITRO
        quote_role: PRIMARY_RESULT
        snippet: In both models, a single injection of ASO7 resulted in near complete restoration of normal PC firing frequency
        explanation: Electrophysiology in acute cerebellar slices measures firing after in-vivo treatment.
      target: Reduced Purkinje Cell Firing
    description: Firing frequency is restored in acute slices after delayed treatment.
    evidence:
    - reference: PMID:28405024
      reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: In both models, a single injection of ASO7 resulted in near complete restoration of normal PC firing frequency
      explanation: Electrophysiology in acute cerebellar slices measures firing after in-vivo treatment.
    model_scale: CELLULAR
  - target: Cerebellar Network Dysfunction
    relationship: RECAPITULATES
    limitations: Motor and delayed physiological experiments have different treatment schedules; their results must not be pooled into a late-onset motor-rescue claim.
    description: ASO-treated mice have improved but incomplete motor recovery.
    evidence:
    - reference: PMID:28405024
      reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: PRIMARY_RESULT
      snippet: However, the rotarod performance of the ASO7 treated mice did not perfectly mirror that of wildtype mice.
      explanation: The BAC model motor rescue is incomplete.
    model_scale: ORGANISM
experimental_models:
- name: SCA2 patient fibroblast ASO target-engagement assay
  experimental_model_type: PRIMARY_CELL_CULTURE
  cell_source: Patient-derived skin fibroblasts carrying CAG35 and CAG22 ATXN2 alleles
  publication: PMID:28405024
  description: Electroporated ASO7 lowers total ATXN2 transcript and both mutant and wild-type allele products by PCR assays. This supplies human-cell target engagement without measuring neuronal firing or survival.
  notes: No broad donor panel or functional neuronal rescue was tested in this assay. Methods state harvest at five days whereas the extended-data caption states 72 hours; no exact exposure interval is promoted. The result does not establish allele selectivity or clinical efficacy.
  evidence:
  - reference: PMID:28405024
    reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    snippet: ASO7 lowered expression of wildtype and mutant ATXN2 in SCA2 patient-derived fibroblasts
    explanation: The human-cell experiment demonstrates non-allele-specific transcript lowering.
  modeled_mechanisms:
  - target: Coding Polyglutamine Repeat Expansion
    relationship: RECAPITULATES
    limitations: This link records the disease-associated genotype. The RNA-lowering endpoint is described in the model; it is not a measurement or correction of the DNA expansion, neuronal firing or survival.
    description: Patient-derived fibroblasts retain the expanded coding allele used for the target-engagement assay.
    evidence:
    - reference: PMID:28405024
      reference_title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      snippet: SCA2 patient-derived skin fibroblasts (SCA2-CAG35) were cultured and maintained in DMEM medium
      explanation: The patient-derived culture carries the disease-associated coding expansion.
    model_scale: MOLECULAR
discussions:
- discussion_id: adca_inclusion_toxicity
  kind: KNOWLEDGE_GAP
  attaches_to:
  - pathophysiology#Neuronal Polyglutamine Inclusions
  prompt: Which expanded-protein species drive injury in each molecular subtype?
  rationale: Large inclusions are pathological observations but are not established as the universally toxic species. Soluble species, fragments, native-protein interactions and RNA-related processes can contribute differently. Therefore inclusion formation is a parallel observed endpoint, not a required bridge to neuronal death.
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: Whether these large aggregates, a hallmark of all polyQ SCAs, are neurotox- ic or neuroprotective is still under debate [ 47].
    explanation: The review explicitly identifies unresolved direction of inclusion effects.
- discussion_id: adca_molecular_and_clinical_heterogeneity
  kind: KNOWLEDGE_GAP
  attaches_to:
  - pathophysiology#Cerebellar Network Dysfunction
  prompt: Which molecular and cellular abnormalities explain each subtype-specific clinical trajectory?
  rationale: Historical clinical classes cross molecular diagnoses, and similar ataxia can arise from different neuronal compartments and genetic lesions. Human SCA3 cortical sparing, episodic SCA6 and restricted FGF14 ocular presentations preclude a universal Purkinje-loss or fixed-progression model. Selected regional cohorts also cannot establish one worldwide subtype distribution.
  evidence:
  - reference: PMID:30607747
    reference_title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: SCA3 affects various different regions of the brain and spinal cord, although the cerebellar cortex and olivary nuclei Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias 265 are relatively spared. The brain weight of SCA3 patients is significantly reduced, and neuronal cell loss is most prominent in the cerebellar dentate nucleus and substantia nigra.
    explanation: Human SCA3 neuropathology demonstrates relative cerebellar-cortex sparing and dentate-nucleus involvement.
  - reference: PMID:38507876
    reference_title: 'GAA-FGF14 disease: defining its frequency, molecular basis, and 4-aminopyridine response in a large downbeat nystagmus cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: A dominantly inherited GAA repeat expansion in intron 1 of the fibroblast growth factor 14 (FGF14) gene has recently been identified as the cause of GAA-FGF14 disease/spinocerebellar ataxia 27B (SCA27B)
    explanation: The primary cohort introduces an established noncoding expansion cause, distinct from the polyglutamine group.
notes: 'Subtype placement rule used here. MONDO:0020380 has 64 hierarchical descendants (OLS4 hierarchicalDescendants endpoint). A numbered molecular SCA is carried on this family entry only when MONDO parents it directly on MONDO:0020380, or on a Harding class this entry does not itself carry as a clinical row. SCA44, SCA50, SCA51 and SCA52 are parented directly on MONDO:0020380; SCA10 is parented on autosomal dominant cerebellar ataxia type IV (MONDO:0019794), for which no dismech entry exists. Descendants parented on ADCA type I (MONDO:0019792) belong to Autosomal_Dominant_Cerebellar_Ataxia_Type_I, which already curates fifteen of them, and are not duplicated here.


  Claims left to the entries that own them. SCA27B / GAA-FGF14 disease is curated on Spinocerebellar_Ataxia_27B, which also records SCA27A (MONDO:0008654, OMIM:609307, the childhood-onset FGF14 coding-variant disease) as a differential; SCA27A is therefore not bound as a subtype row here. SCA1, SCA2, SCA6, SCA8, SCA15/16, SCA17, SCA23, SCA31, SCA36, SCA43 and SCA48 have their own dismech entries. The polyglutamine genes ATXN1, ATXN2, ATXN3, CACNA1A and TBP reach the pathograph as gene descriptors on the coding-expansion nodes rather than as separate causal-gene entries, because this entry is the family umbrella and their locus-specific thresholds belong in the molecular subtype entries.


  Nomenclature hazard. The SCA50 label has been used for two different diseases. MONDO:0859334 (OMIM:620158) denotes the NPTX1 disease curated here. PMID:36493768, already cited by Spinocerebellar_Ataxia_27B, is titled "An intronic GAA repeat expansion in FGF14 causes the autosomal-dominant adult-onset ataxia SCA50/ATX-FGF14" and so applies the same number to the FGF14 repeat disease. The subtype row was resolved through the OMIM cross-reference rather than through the label.


  This is a family-level entry. Molecular subtype entries carry detailed variant thresholds and allele-specific pathways. The reviewed graph separates measured or reviewed events and retains unknown intermediates where the evidence does not establish a unique sequence. GeneReviews is a broader hereditary-ataxia overview; only applicable dominant-ataxia and general supportive-care content is used. The 2019 polyglutamine review is not treated as current proof of clinical availability, and the 2025 FDA conclusion is explicitly dated.'
references:
- reference: PMID:40906249
  title: 'Long-Term Effects of Annual Intensive Rehabilitation in Patients with Hereditary Pure Cerebellar Ataxia: A 7-year Follow-up Study.'
  findings:
  - statement: Complete primary main body, Methods, Results, tables and Discussion read. Selected seven-person retrospective cohort (two SCA6, five SCA31), no concurrent control, differing pre/post/six-month trajectories and early balance deterioration preclude proof of disease slowing.
- reference: PMID:40946705
  title: 'Home Training for Cerebellar Ataxias: A Randomized Clinical Trial.'
  findings:
  - statement: Genuine full primary PMC HTML for PMID40946705 generated and read through Methods, Results, Tables 1–3, figures and Discussion. Sixty-two selected ambulatory adults,43 genetically confirmed SCAs; subtype efficacy not separately established. Missing-at-random assumption,17.7% one-year attrition, nonrandomized adherence comparison and unpublished MRI endpoints are retained. This entry now cites PMID:40946705, whose full-text HTML cache carries every quoted snippet.
- reference: PMID:12485197
  title: Prevalence and ethnic differences of autosomal-dominant cerebellar ataxia in Singapore.
  findings:
  - statement: Original and regenerated abstract reviewed; full primary body was not recovered. Singapore 2002 ascertained 204 tested people and 58 positive people from 36 families. Family-unit prevalence is retained only in epidemiology, without conversion to person-level frequency.
- reference: PMID:21088341
  title: Prevalence of autosomal dominant cerebellar ataxia in Aomori, the northernmost prefecture of Honshu, Japan.
  findings:
  - statement: Entire primary PDF, Methods, Results, tables, figures and Discussion reviewed. Aomori 76 classified/80 enrolled denominators, historical assay scope and unproven founder explanation are preserved.
- reference: PMID:30607747
  title: Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.
  findings:
  - statement: Entire available full PDF main body, subtype sections and therapeutic/model tables reviewed. Human SCA3 cerebellar-cortex sparing, uncertain inclusion toxicity, interacting gain/loss effects and model-to-human treatment limits replace universal Purkinje and therapy claims.
- reference: PMID:7066668
  title: The clinical features and classification of the late onset autosomal dominant cerebellar ataxias. A study of 11 families, including descendants of the 'the Drew family of Walworth'.
  findings:
  - statement: Complete original classification abstract reviewed. Eleven families and 73 individuals establish the historical clinical framework; full primary article was not available in the generated cache.
- reference: PMID:20723845
  title: 'Autosomal dominant cerebellar ataxias: polyglutamine expansions and beyond.'
  findings:
  - statement: Complete review abstract reviewed. Used for broad mechanistic heterogeneity only; its historical gene count and mapped loci are not a current exhaustive catalogue.
- reference: PMID:30786918
  title: Guidelines on the diagnosis and management of the progressive ataxias.
  findings:
  - statement: Complete full guideline main body and all six included tables reviewed. Mostly good-practice recommendations and extrapolation from other neurological diseases; Friedreich-specific and other recessive/acquired-disease treatments are not applied to ADCA.
- reference: PMID:40883955
  title: Practice Recommendations for Genetic Testing of Ataxias.
  findings:
  - statement: Complete 2025 full main body, methods,20 recommendations and tables reviewed. U.S.-based consensus emphasizes comprehensive testing with explicit repeat-detection capability, informed choice and reassessment; no universal sensitivity is claimed.
- reference: PMID:35063116
  title: 'Safety and efficacy of riluzole in spinocerebellar ataxia type 2 in France (ATRIL): a multicentre, randomised, double-blind, placebo-controlled trial.'
  findings:
  - statement: Complete ATRIL abstract reviewed.45 moderate SCA2 participants,12-month randomized comparison and negative clinical/MRI result are kept subtype-specific; full primary body was not recovered.
- reference: PMID:38507876
  title: 'GAA-FGF14 disease: defining its frequency, molecular basis, and 4-aminopyridine response in a large downbeat nystagmus cohort.'
  findings:
  - statement: Entire regenerated full primary body, Methods, Results, Discussion,Table 1 and figures reviewed. The 170-person DBN-ascertained, mainlyEuropean single-center cohort does not provide general ADCA penetrance; 4-AP response is retrospective with only four post hoc genotype-positive crossover participants and phase/order limitations.
- reference: PMID:28405024
  title: Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.
  findings:
  - statement: Entire cached main body, Methods and available extended-data captions reviewed. Two transgenic mouse models, motor versus ex-vivo firing assays, partial motor rescue, limited mouse-level physiology replication and non-allele-specific fibroblast RNA lowering are distinct. Main figure captions and separate supplementary discussion were not available in this representation; no missing denominators are inferred.
- reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/
  title: Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf
  findings:
  - statement: Hereditary Ataxia Overview, updatedJuly 9,2026. Complete chapter clinical, genetic, diagnostic, management and counseling sections and relevant tables reviewed. This broader GeneReviews chapter supplies all four applicable baseline domains; subtype-specific prognosis and anticipation exceptions are retained.
  tags:
  - GeneReviews
- reference: url:https://download.open.fda.gov/crl/CRL_NDA210862_20251104.pdf
  title: https://download.open.fda.gov/crl/CRL_NDA210862_20251104.pdf
  findings:
  - statement: 'FDA complete-response letter for NDA210862, November 4,2025. Entire available substantive assessment reviewed: failed randomized primary endpoint and external-control confounding/missing-data limitations prevent treating the submitted analysis as established SCA disease modification.'
review_notes: Comprehensive source and claim review of the original three references, full GeneReviews overview, current genetic-testing guidance, progressive-ataxia care guideline and selected contemporary clinical/model sources. Related Harding-I manual report and Harding-III provider synthesis/report leads were inspected for family-level relevance; subtype-specific experimental or pharmacologic claims were not promoted without source verification. Human findings, clinical recommendations, experimental readouts and unresolved intermediates are separated. No family-wide phenotype frequency bands are inferred from subtype cohorts.
updated_date: '2026-09-21T14:15:08Z'

📚

References & Deep Research

References

14

PMID:40906249

Long-Term Effects of Annual Intensive Rehabilitation in Patients with Hereditary Pure Cerebellar Ataxia: A 7-year Follow-up Study.

1 finding

Complete primary main body, Methods, Results, tables and Discussion read. Selected seven-person retrospective cohort (two SCA6, five SCA31), no concurrent control, differing pre/post/six-month trajectories and early balance deterioration preclude proof of disease slowing.

PMID:40946705

Home Training for Cerebellar Ataxias: A Randomized Clinical Trial.

1 finding

Genuine full primary PMC HTML for PMID40946705 generated and read through Methods, Results, Tables 1–3, figures and Discussion. Sixty-two selected ambulatory adults,43 genetically confirmed SCAs; subtype efficacy not separately established. Missing-at-random assumption,17.7% one-year attrition, nonrandomized adherence comparison and unpublished MRI endpoints are retained. This entry now cites PMID:40946705, whose full-text HTML cache carries every quoted snippet.

PMID:12485197

Prevalence and ethnic differences of autosomal-dominant cerebellar ataxia in Singapore.

1 finding

Original and regenerated abstract reviewed; full primary body was not recovered. Singapore 2002 ascertained 204 tested people and 58 positive people from 36 families. Family-unit prevalence is retained only in epidemiology, without conversion to person-level frequency.

PMID:21088341

Prevalence of autosomal dominant cerebellar ataxia in Aomori, the northernmost prefecture of Honshu, Japan.

1 finding

Entire primary PDF, Methods, Results, tables, figures and Discussion reviewed. Aomori 76 classified/80 enrolled denominators, historical assay scope and unproven founder explanation are preserved.

PMID:30607747

Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias.

1 finding

Entire available full PDF main body, subtype sections and therapeutic/model tables reviewed. Human SCA3 cerebellar-cortex sparing, uncertain inclusion toxicity, interacting gain/loss effects and model-to-human treatment limits replace universal Purkinje and therapy claims.

PMID:7066668

The clinical features and classification of the late onset autosomal dominant cerebellar ataxias. A study of 11 families, including descendants of the 'the Drew family of Walworth'.

1 finding

Complete original classification abstract reviewed. Eleven families and 73 individuals establish the historical clinical framework; full primary article was not available in the generated cache.

PMID:20723845

Autosomal dominant cerebellar ataxias: polyglutamine expansions and beyond.

1 finding

Complete review abstract reviewed. Used for broad mechanistic heterogeneity only; its historical gene count and mapped loci are not a current exhaustive catalogue.

PMID:30786918

Guidelines on the diagnosis and management of the progressive ataxias.

1 finding

Complete full guideline main body and all six included tables reviewed. Mostly good-practice recommendations and extrapolation from other neurological diseases; Friedreich-specific and other recessive/acquired-disease treatments are not applied to ADCA.

PMID:40883955

Practice Recommendations for Genetic Testing of Ataxias.

1 finding

Complete 2025 full main body, methods,20 recommendations and tables reviewed. U.S.-based consensus emphasizes comprehensive testing with explicit repeat-detection capability, informed choice and reassessment; no universal sensitivity is claimed.

PMID:35063116

Safety and efficacy of riluzole in spinocerebellar ataxia type 2 in France (ATRIL): a multicentre, randomised, double-blind, placebo-controlled trial.

1 finding

Complete ATRIL abstract reviewed.45 moderate SCA2 participants,12-month randomized comparison and negative clinical/MRI result are kept subtype-specific; full primary body was not recovered.

PMID:38507876

GAA-FGF14 disease: defining its frequency, molecular basis, and 4-aminopyridine response in a large downbeat nystagmus cohort.

1 finding

Entire regenerated full primary body, Methods, Results, Discussion,Table 1 and figures reviewed. The 170-person DBN-ascertained, mainlyEuropean single-center cohort does not provide general ADCA penetrance; 4-AP response is retrospective with only four post hoc genotype-positive crossover participants and phase/order limitations.

PMID:28405024

Antisense oligonucleotide therapy for spinocerebellar ataxia type 2.

1 finding

Entire cached main body, Methods and available extended-data captions reviewed. Two transgenic mouse models, motor versus ex-vivo firing assays, partial motor rescue, limited mouse-level physiology replication and non-allele-specific fibroblast RNA lowering are distinct. Main figure captions and separate supplementary discussion were not available in this representation; no missing denominators are inferred.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1138/

Hereditary Ataxia Overview - GeneReviews® - NCBI Bookshelf

1 finding

Hereditary Ataxia Overview, updatedJuly 9,2026. Complete chapter clinical, genetic, diagnostic, management and counseling sections and relevant tables reviewed. This broader GeneReviews chapter supplies all four applicable baseline domains; subtype-specific prognosis and anticipation exceptions are retained.

url:https://download.open.fda.gov/crl/CRL_NDA210862_20251104.pdf

https://download.open.fda.gov/crl/CRL_NDA210862_20251104.pdf

1 finding

FDA complete-response letter for NDA210862, November 4,2025. Entire available substantive assessment reviewed: failed randomized primary endpoint and external-control confounding/missing-data limitations prevent treating the submitted analysis as established SCA disease modification.

Autosomal Dominant Cerebellar Ataxia

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