Infantile Spasms

Complex MONDO:0018097 Pathograph 12 Show in embeddings browser Epilepsy Neurodevelopmental Disorder Neurological Disease

Infantile spasms, now classified as infantile epileptic spasms syndrome (IESS), is an age-dependent developmental and epileptic encephalopathy of infancy. It is characterized by epileptic spasms, usually in clusters, hypsarrhythmia or a related epileptiform EEG pattern, and developmental stagnation or regression. Etiology is heterogeneous, including structural, prenatal, perinatal, postnatal, metabolic, and genetic causes.

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1
Mappings
2
Definitions
3
Inheritance
4
Pathophys.
7
Phenotypes
3
Gaps
12
Pathograph
5
Medical Actions
2
Subtypes
2
Datasets
2
Trials
2
Deep Research
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Mappings

MONDO
MONDO:0018097 infantile spasms
skos:exactMatch Orphanet ORPHA:697160
Orphanet ORPHA:697160 is the current infantile epileptic spasms syndrome disease record and MONDO maps infantile spasms to this concept.
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Definitions

2
ILAE neonatal and infant epilepsy syndrome definition
ILAE classifies infantile spasms/IESS among epilepsy syndromes with onset in neonates and infants, emphasizing syndrome diagnosis together with etiology.
OTHER
Show evidence (1 reference)
PMID:35503712 SUPPORT Human Clinical
"The International League Against Epilepsy (ILAE) Task Force on Nosology and Definitions proposes a classification and definition of epilepsy syndromes in the neonate and infant with seizure onset up to 2 years of age. "
The ILAE position statement defines epilepsy syndromes with onset in infancy, including infantile epileptic spasms syndrome.
West syndrome electroclinical triad
West syndrome is the historical triad of infantile spasms, hypsarrhythmia on EEG, and developmental regression.
OTHER
Show evidence (1 reference)
PMID:37736852 SUPPORT Human Clinical
"When infantile spasms occur with a concomitant hypsarrhythmia on electroencephalogram (EEG) and developmental regression, it is known as West Syndrome. "
Review article states the clinical-EEG-developmental triad that historically defines West syndrome.
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Inheritance

3
Autosomal dominant HP:0000006
A subset of genetic IESS is caused by monoallelic variants in genes recorded by Orphanet, including dominant mechanisms.
Autosomal dominant inheritance
Show evidence (1 reference)
ORPHA:697160 SUPPORT Other
"Autosomal dominant"
Orphanet records autosomal dominant inheritance among the inherited IESS etiologies.
Autosomal recessive HP:0000007
A subset of genetic IESS is caused by biallelic pathogenic variants in autosomal genes.
Autosomal recessive inheritance
Show evidence (1 reference)
ORPHA:697160 SUPPORT Other
"Autosomal recessive"
Orphanet records autosomal recessive inheritance among the inherited IESS etiologies.
X-linked dominant HP:0001423
X-linked genes such as ARX, CDKL5, PIGA, and WDR45 contribute to the inherited IESS spectrum.
X-linked dominant inheritance
Show evidence (1 reference)
ORPHA:697160 SUPPORT Other
"X-linked dominant"
Orphanet records X-linked dominant inheritance for part of the IESS spectrum.
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Subtypes

2
IESS with known etiology
IESS with a structural, prenatal, perinatal, postnatal, metabolic, or genetic etiology identified by clinical evaluation.
IESS of unknown etiology
IESS in which standard clinical evaluation does not identify the underlying cause at the time of diagnosis.
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Discussions and Knowledge Gaps

3
By what shared developmental mechanism do etiologically diverse insults (tuberous sclerosis and other mTORopathies, hypoxic-ischemic injury, trisomy 21, and monogenic developmental and epileptic encephalopathies) converge on the SAME age-dependent electroclinical syndrome of epileptic spasms and hypsarrhythmia?
KNOWLEDGE GAP OPEN gap_iess_final_common_pathway_convergence
Attached to
pathophysiology#Heterogeneous developmental brain etiologies pathophysiology#Developing brain epileptic network hyperexcitability
IESS is defined precisely by this convergence: structural, metabolic, and genetic causes producing an indistinguishable spasms/hypsarrhythmia phenotype within a narrow infantile window. The entry currently models the convergence descriptively (diverse etiologies -> abnormal epileptic network activity) but the physiological hub that unifies them is unresolved. Candidate convergent nodes proposed in the literature include CRH/stress-axis hyperactivity, a mistimed GABA developmental switch (NKCC1/KCC2 imbalance), and brainstem/cortical dysmaturation. Identifying the shared hub matters because it would define the syndrome mechanistically rather than by list of causes, and could reveal an etiology-agnostic therapeutic target.
Proposed experiments
Cross-etiology convergent-hub profiling in IESS models
cross-model convergent-pathway profiling experiment Relation: this experiment is of type this experiment type This experiment is of type cross-model convergent-pathway profiling experiment.
exp_iess_convergent_hub_crossetiology_profiling
Assemble a panel of distinct IESS etiologic models (e.g., TSC/mTOR, ARX interneuronopathy, and an acquired hypoxic-ischemic model) and test whether they share a common physiological signature at the proposed convergence hubs (CRH/stress-axis tone, NKCC1/KCC2 ratio and GABA reversal potential, and brainstem-cortical network maturation) during the spasm-susceptible developmental window.
Readouts
Chloride-handling and GABA-switch readout
pathophysiology#Developing brain epileptic network hyperexcitability
GABA signaling GO:0007214 Gene Ontology (GO) Relation: this readout reports on this biological process This readout reports on dysregulated GABA signaling, annotated with gamma-aminobutyric acid signaling pathway (GO:0007214). GO:0007214 is a biological process from the Gene Ontology. ↕ DYSREGULATED
gramicidin perforated-patch recording Relation: this readout is measured by this assay This readout is measured by gramicidin perforated-patch recording.
Direction: POSITIVE
Controls
Age-matched wild-type
Littermate controls profiled in the same developmental window.
Decision criterion
A convergence hub is supported if mechanistically distinct etiologic models share the same abnormality at that node (e.g., a common shift in GABA reversal potential or CRH tone) that is absent in age-matched controls; divergent signatures argue against a single unifying mechanism.
Would support
pathophysiology#Developing brain epileptic network hyperexcitability pathophysiology#Heterogeneous developmental brain etiologies
Show evidence (2 references)
PMID:39029407 SUPPORT Human Clinical
"Aetiology was prenatal (40.3 %), perinatal (10.5 %), postnatal (3.7 %), with unknown timing (10.2 %) or with unknown aetiology (33.5 %)."
Documents the etiologic heterogeneity that nonetheless converges on one electroclinical syndrome, framing the open convergence question.
PMID:38540325 SUPPORT Human Clinical
"some of the most commonly reported genetic aetiologies include trisomy 21 and pathogenic variants in genes such as TSC1, TSC2, CDKL5, ARX, KCNQ2, STXBP1 and SCN2A."
Illustrates the mechanistically diverse genetic causes (transcription factor, ion channel, synaptic, mTOR-pathway) that all produce IESS, underscoring the unresolved final common pathway.
Do rodent models of infantile spasms (ARX interneuronopathy mice and the CRH/stress model) faithfully reproduce the human syndrome, given that these models generate spasm-like or limbic events but do not clearly reproduce human hypsarrhythmia or the human developmental timing window?
HUMAN MODEL MISMATCH OPEN gap_iess_rodent_model_human_fidelity
Attached to
pathophysiology#Developing brain epileptic network hyperexcitability
The mechanistic case for the excitation-inhibition (ARX interneuronopathy) and stress/CRH arms rests largely on rodent models, yet their fidelity to human IESS is uncertain. The CRH model produces only limbic seizures rather than the classic epileptic (flexion) spasms, and no rodent model convincingly reproduces the human hypsarrhythmic EEG signature or the tightly age-restricted human window. This is a HUMAN_MODEL_MISMATCH rather than a plain knowledge gap: model-system evidence EXISTS, but its translational validity is the open question. Resolving it matters because the CRH model is the principal mechanistic rationale offered for hormonal (ACTH) therapy, and the ARX model underpins the interneuronopathy account of the syndrome.
Proposed experiments
Model-to-human EEG and developmental-window concordance study
cross-species electroclinical concordance experiment Relation: this experiment is of type this experiment type This experiment is of type cross-species electroclinical concordance experiment.
exp_iess_model_eeg_phenotype_concordance
Systematically compare long-term video-EEG from ARX and CRH rodent models against human IESS, scoring for a hypsarrhythmia-equivalent interictal pattern, epileptic-spasm (rather than limbic-seizure) semiology, and the developmental timing of onset and offset relative to human infancy.
Readouts
Hypsarrhythmia-equivalent EEG signature
pathophysiology#Developing brain epileptic network hyperexcitability
trans-synaptic signaling GO:0099537 Gene Ontology (GO) Relation: this readout reports on this biological process This readout reports on abnormal trans-synaptic signaling (GO:0099537). GO:0099537 is a biological process from the Gene Ontology. ⚠ ABNORMAL
continuous video-EEG recording Relation: this readout is measured by this assay This readout is measured by continuous video-EEG recording.
Direction: POSITIVE
Controls
Age-matched non-epileptic animals
Littermate controls recorded across the equivalent developmental window.
Decision criterion
Model fidelity is supported only if a model reproduces a hypsarrhythmia-equivalent interictal EEG pattern together with genuine epileptic-spasm semiology within a developmentally restricted window analogous to human infancy; absence of the hypsarrhythmic signature keeps the mechanistic inference model-limited.
Would support
pathophysiology#Developing brain epileptic network hyperexcitability
Show evidence (2 references)
PMID:23312951 SUPPORT Model Organism
"The stress theory of spasms yielded the corticotropin releasing hormone (CRH)-induced model, which showed the higher proconvulsant potency of CRH in developing rats, although only limbic seizures were observed."
Explicitly notes that the CRH model reproduces only limbic (not classic flexion) seizures, the core of the model-to-human mismatch.
PMID:23312951 SUPPORT Model Organism
"two genetic mouse models of interneuronopathies with infantile spasms due to loss of function of the aristaless X-linked homeobox-related gene (ARX)."
Identifies the ARX interneuronopathy mouse models whose fidelity to human hypsarrhythmia and the human developmental window remains to be established.
Is rapid cessation of spasms and hypsarrhythmia after first-line therapy itself disease-modifying for neurodevelopment, or is it mainly a marker of a milder underlying etiology that would have had a better developmental trajectory regardless?
OPEN QUESTION OPEN gap_iess_early_cessation_disease_modifying
Attached to
pathophysiology#Developmental and epileptic encephalopathy burden treatments#Hormonal therapy with ACTH or high-dose prednisolone
Observational data consistently associate shorter lead-time to effective treatment and early spasm control with better developmental outcome, which is often read as evidence that the epileptic encephalopathy itself drives developmental harm and that stopping it early rescues development. But because etiology strongly confounds both treatment response and baseline developmental potential, the association is equally compatible with early responders simply having milder underlying brain disease. Distinguishing a causal disease-modifying effect from a prognostic marker is decision-relevant: it determines whether aggressive early treatment escalation changes long-term outcome or only changes the seizure course.
Proposed experiments
Etiology-stratified lead-time and outcome analysis
etiology-stratified prospective cohort analysis Relation: this experiment is of type this experiment type This experiment is of type etiology-stratified prospective cohort analysis.
exp_iess_etiology_stratified_leadtime_analysis
Using a prospective IESS cohort with uniform etiologic workup, test whether the association between early electroclinical response and developmental outcome persists WITHIN etiologic strata (e.g., within TSC, within trisomy 21, within unknown-etiology cases) and after adjustment for baseline development, rather than being explained by etiology differences between fast and slow responders.
Readouts
Developmental outcome within etiologic strata
pathophysiology#Developmental and epileptic encephalopathy burden
standardized developmental assessment Relation: this readout is measured by this assay This readout is measured by standardized developmental assessment.
Direction: POSITIVE
Controls
Etiology-matched slow/non-responders
Within each etiologic stratum, compare early responders against matched slow or non-responders.
Decision criterion
A disease-modifying effect is supported if earlier spasm cessation predicts better developmental outcome WITHIN etiologic strata and after baseline-development adjustment; if the association collapses once etiology and baseline are controlled, early cessation is better interpreted as a prognostic marker.
Would support
pathophysiology#Developmental and epileptic encephalopathy burden
Show evidence (2 references)
PMID:30236380 SUPPORT Human Clinical
"Increasing lead-time to treatment was associated with lower VABS scores"
Establishes the lead-time-to-treatment association with developmental outcome that motivates, but does not by itself resolve, the disease-modifying-versus-marker question.
PMID:30236380 SUPPORT Human Clinical
"Initial control of spasms between days 14 and 42 of treatment was associated with higher mean VABS scores at 18 months"
Shows the early-cessation/outcome association whose causal versus prognostic interpretation is the open question.
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Pathophysiology

4
Heterogeneous developmental brain etiologies
Structural, prenatal, perinatal, postnatal, metabolic, and genetic causes disrupt the developing infant brain and converge on an IESS electroclinical phenotype.
ARX hgnc:18060 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves ARX (hgnc:18060). hgnc:18060 is a gene from the HUGO Gene Nomenclature Committee. CDKL5 hgnc:11411 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves CDKL5 (hgnc:11411). hgnc:11411 is a gene from the HUGO Gene Nomenclature Committee. GRIN2B hgnc:4586 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves GRIN2B (hgnc:4586). hgnc:4586 is a gene from the HUGO Gene Nomenclature Committee. SCN2A hgnc:10588 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves SCN2A (hgnc:10588). hgnc:10588 is a gene from the HUGO Gene Nomenclature Committee.
nervous system development GO:0007399 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal nervous system development (GO:0007399). GO:0007399 is a biological process from the Gene Ontology. ⚠ ABNORMAL
brain UBERON:0000955 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in brain (UBERON:0000955). UBERON:0000955 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Developing brain epileptic network hyperexcitability Diverse etiologies converge on abnormal epileptic network activity in the infant brain.
mTOR pathway hyperactivation A major structural/genetic etiologic class (tuberous sclerosis complex and related mTORopathies) acts through constitutive mTORC1 signaling.
Developmental and epileptic encephalopathy burden Underlying etiologies contribute to developmental impairment independent of epileptiform activity.
Show evidence (2 references)
PMID:39029407 SUPPORT Human Clinical
"Aetiology was prenatal (40.3 %), perinatal (10.5 %), postnatal (3.7 %), with unknown timing (10.2 %) or with unknown aetiology (33.5 %). "
National cohort demonstrates etiologic heterogeneity across prenatal, perinatal, postnatal, and unknown causes.
ORPHA:697160 SUPPORT Other
"SCN2A | sodium voltage-gated channel alpha subunit 2 | hgnc:10588 | Disease-causing germline mutation(s) in"
Orphanet records SCN2A and other genes as disease-causing in genetic IESS.
mTOR pathway hyperactivation
In tuberous sclerosis complex and related mTORopathies, loss of function of TSC1/TSC2 (or activating variants in the wider PI3K-AKT-mTOR pathway, and brain-restricted somatic mTOR-pathway variants) disinhibits mTORC1 signaling. This drives abnormal cortical cytoarchitecture (cortical tubers, focal cortical dysplasia, dysmorphic neurons) that seeds the epileptogenic network, and provides the mechanistic rationale for mTOR-inhibitor precision therapy.
TSC1 hgnc:12362 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves TSC1 (hgnc:12362). hgnc:12362 is a gene from the HUGO Gene Nomenclature Committee. TSC2 hgnc:12363 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves TSC2 (hgnc:12363). hgnc:12363 is a gene from the HUGO Gene Nomenclature Committee.
positive regulation of TOR signaling GO:0032008 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased positive regulation of TOR signaling (GO:0032008). GO:0032008 is a biological process from the Gene Ontology. ↑ INCREASED
cerebral cortex UBERON:0000956 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in cerebral cortex (UBERON:0000956). UBERON:0000956 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Developing brain epileptic network hyperexcitability mTORC1 hyperactivation and the resulting dysplastic cortex generate the hyperexcitable epileptic network.
Show evidence (3 references)
PMID:33892851 SUPPORT Human Clinical
"the identification of the responsible genes and gene products forming the mechanistic target of rapamycin complex, previously termed the mammalian target of rapamycin, not only has expanded our understanding of tuberous sclerosis pathophysiology, but has also inspired the search for targeted..."
Establishes the mTORC1 pathway as the molecular basis of TSC pathophysiology and the rationale for targeted (mTOR-inhibitor) intervention.
PMID:33892851 SUPPORT Human Clinical
"the pediatric neurologist is often responsible for making the initial diagnosis when the affected individual presents with infantile spasms or another early-onset epilepsy syndrome. "
Links TSC (the prototypical mTORopathy) directly to infantile-spasms presentation.
PMID:38540325 SUPPORT Human Clinical
"some of the most commonly reported genetic aetiologies include trisomy 21 and pathogenic variants in genes such as TSC1, TSC2, CDKL5, ARX, KCNQ2, STXBP1 and SCN2A. "
Confirms TSC1/TSC2 (and ARX) among the most commonly reported genetic etiologies of IESS.
Developing brain epileptic network hyperexcitability
The IESS phenotype reflects abnormal synchronized activity in immature cortical-subcortical networks, producing epileptic spasms and the hypsarrhythmic EEG pattern. A recurrent mechanistic theme is a shift toward net excitation in the developing cortex through impaired GABAergic interneuron development/function (interneuronopathy, exemplified by ARX loss of function), consistent with the conserved epilepsy excitation-inhibition imbalance pattern and with the efficacy of the GABA-augmenting drug vigabatrin.
neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology. cortical GABAergic interneuron CL:0000617 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves cortical GABAergic interneuron, annotated with GABAergic neuron (CL:0000617). CL:0000617 is a cell type from the Cell Ontology.
ARX hgnc:18060 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves ARX (hgnc:18060). hgnc:18060 is a gene from the HUGO Gene Nomenclature Committee.
trans-synaptic signaling GO:0099537 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal trans-synaptic signaling (GO:0099537). GO:0099537 is a biological process from the Gene Ontology. ⚠ ABNORMAL GABA signaling GO:0007214 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased GABA signaling, annotated with gamma-aminobutyric acid signaling pathway (GO:0007214). GO:0007214 is a biological process from the Gene Ontology. ↓ DECREASED
brain UBERON:0000955 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in brain (UBERON:0000955). UBERON:0000955 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Infantile spasms Epileptic network discharges produce clusters of infantile spasms.
Hypsarrhythmia The same epileptic encephalopathy produces the hypsarrhythmic EEG pattern.
Developmental and epileptic encephalopathy burden Epileptic encephalopathy contributes to developmental impairment alongside the underlying etiology.
Show evidence (3 references)
PMID:37736852 SUPPORT Human Clinical
"Infantile spasms, newly classified as infantile epileptic spasm syndrome (IESS), occur in children under 2 years of age and present as an occur as brief, symmetrical, contractions of the musculature of the neck, trunk, and extremities. "
Review describes the age-dependent epileptic spasm phenotype produced by the abnormal infantile network state.
PMID:27838190 SUPPORT Human Clinical
"enrolled infants who had a clinical diagnosis of infantile spasms and a hypsarrhythmic (or similar) EEG no more than 7 days before enrolment. "
Trial inclusion criteria show that infantile spasms and hypsarrhythmic or similar EEG activity form the electroclinical syndrome.
PMID:23312951 SUPPORT Model Organism
"two genetic mouse models of interneuronopathies with infantile spasms due to loss of function of the aristaless X-linked homeobox-related gene (ARX). "
ARX loss-of-function mouse interneuronopathy models link GABAergic interneuron dysfunction to the generation of infantile spasms, supporting the excitation-inhibition imbalance arm.
Developmental and epileptic encephalopathy burden
IESS is part of the developmental and epileptic encephalopathy spectrum: developmental impairment reflects both the underlying etiology and the epileptic encephalopathy.
nervous system development GO:0007399 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal nervous system development (GO:0007399). GO:0007399 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Downstream
Developmental regression Epileptic encephalopathy is associated with loss of developmental skills.
Global developmental delay The combined etiologic and epileptic burden contributes to global developmental delay.
Show evidence (4 references)
PMID:35503712 SUPPORT Human Clinical
"developmental and epileptic encephalopathies, diseases where there is developmental impairment related to both the underlying etiology independent of epileptiform activity and the epileptic encephalopathy. "
ILAE statement defines developmental and epileptic encephalopathies as disorders where etiology and epileptiform activity both contribute to developmental impairment.
PMID:39029407 SUPPORT Human Clinical
"At latest follow-up severe neurodevelopmental outcome was seen in 44.2 % and 76.4 % still had epilepsy."
Danish cohort quantifies long-term neurodevelopmental and epilepsy burden after IESS.
PMID:30236380 SUPPORT Human Clinical
"Increasing lead-time to treatment was associated with lower VABS scores "
ICISS 18-month follow-up shows that longer lead-time to effective treatment predicts worse developmental (Vineland Adaptive Behaviour Scales) outcome, consistent with the developmental-and-epileptic-encephalopathy model in which the epileptic activity itself drives developmental harm.
+ 1 more reference
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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Infantile Spasms Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
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Phenotypes

7
Integument 1
Cutaneous signs of underlying etiology FREQUENT Abnormal skin morphology HP:0011121 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abnormal skin morphology (HP:0011121). HP:0011121 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
ORPHA:697160 SUPPORT Other
"HP:0011121 | Abnormal skin morphology | Frequent (79-30%)"
Orphanet records abnormal skin morphology as frequent for the IESS spectrum.
Nervous System 5
Epileptic spasms VERY_FREQUENT HP:0011097 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Epileptic spasm (HP:0011097). HP:0011097 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38540325 SUPPORT Human Clinical
"Infantile epileptic spasms syndrome (IESS) is a devastating developmental epileptic encephalopathy (DEE) consisting of epileptic spasms, as well as one or both of developmental regression or stagnation and hypsarrhythmia on EEG. "
Defines epileptic spasms as the mandatory seizure type of IESS, with developmental regression/stagnation and hypsarrhythmia as the associated (not both-required) features.
Hypsarrhythmia VERY_FREQUENT HP:0002521 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypsarrhythmia (HP:0002521). HP:0002521 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
ORPHA:697160 SUPPORT Other
"HP:0002521 | Hypsarrhythmia | Very frequent (99-80%)"
Orphanet records hypsarrhythmia as very frequent in IESS.
PMID:27838190 SUPPORT Human Clinical
"clinical diagnosis of infantile spasms and a hypsarrhythmic (or similar) EEG"
ICISS trial used hypsarrhythmic or similar EEG as part of the electroclinical inclusion criteria.
Developmental regression VERY_FREQUENT HP:0002376 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Developmental regression (HP:0002376). HP:0002376 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
ORPHA:697160 SUPPORT Other
"HP:0002376 | Developmental regression | Very frequent (99-80%)"
Orphanet records developmental regression as very frequent in IESS.
PMID:37736852 SUPPORT Human Clinical
"concomitant hypsarrhythmia on electroencephalogram (EEG) and developmental regression"
Review includes developmental regression in the West syndrome triad.
Myoclonus VERY_FREQUENT HP:0001336 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Myoclonus (HP:0001336). HP:0001336 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
ORPHA:697160 SUPPORT Other
"HP:0001336 | Myoclonus | Very frequent (99-80%)"
Orphanet records myoclonus as very frequent in IESS.
Global developmental delay HP:0001263 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Global developmental delay (HP:0001263). HP:0001263 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:35503712 SUPPORT Human Clinical
"developmental impairment related to both the underlying etiology independent of epileptiform activity and the epileptic encephalopathy"
ILAE statement supports developmental impairment as intrinsic to developmental and epileptic encephalopathy syndromes.
PMID:39029407 SUPPORT Human Clinical
"severe neurodevelopmental outcome was seen in 44.2 %"
National cohort documents severe neurodevelopmental outcome in a large fraction of children with IESS.
Other 1
Infantile spasms VERY_FREQUENT HP:0012469 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Infantile spasms (HP:0012469). HP:0012469 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
ORPHA:697160 SUPPORT Other
"HP:0012469 | Infantile spasms | Very frequent (99-80%)"
Orphanet records infantile spasms as very frequent in IESS.
🗃️

External Assertions

2
Orphanet infantile epileptic spasms syndrome record
Orphanet structured disease record ORPHA:697160
Orphanet's ORPHA:697160 structured record for infantile epileptic spasms syndrome includes the inheritance modes, disease-gene assertions, HPO phenotype rows, and external cross-references used in this entry.
Show evidence (2 references)
ORPHA:697160 SUPPORT Other
"HP:0012469 | Infantile spasms | Very frequent (99-80%)"
Orphanet lists infantile spasms as a very frequent phenotype for ORPHA:697160.
ORPHA:697160 SUPPORT Other
"ARX | aristaless related homeobox | hgnc:18060 | Disease-causing germline mutation(s) in"
Orphanet records ARX among disease-causing genes for the IESS spectrum.
Orphanet West syndrome legacy record
Orphanet structured disease record ORPHA:3451
Orphanet's ORPHA:3451 West syndrome record is retained as a legacy exact cross-reference to MONDO:0018097 and the ICD-11 IESS/West syndrome concept.
Show evidence (1 reference)
ORPHA:3451 SUPPORT Other
"MONDO:0018097 | Exact"
ORPHA:3451 maps exactly to the MONDO infantile spasms concept used by this entry.
💊

Medical Actions

5
Hormonal therapy with ACTH or high-dose prednisolone
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: corticotropin CHEBI:3892 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses corticotropin (CHEBI:3892). CHEBI:3892 is a therapeutic agent from Chemical Entities of Biological Interest. prednisolone CHEBI:8378 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses prednisolone (CHEBI:8378). CHEBI:8378 is a therapeutic agent from Chemical Entities of Biological Interest.
ACTH, tetracosactide, or high-dose prednisolone are first-line hormonal therapies for IESS, aiming for rapid cessation of spasms and EEG improvement. A leading mechanistic hypothesis for hormonal efficacy is the stress/corticotropin-releasing-hormone (CRH) model, in which CRH acts as an endogenous convulsant in the immature brain and ACTH suppresses CRH through negative feedback; this remains a hypothesis supported chiefly by animal models.
Mechanism Target:
MODULATES Developing brain epileptic network hyperexcitability — Hormonal therapy reduces the epileptic network activity that produces spasms and hypsarrhythmia.
Target Phenotypes: Infantile spasms HP:0012469 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Infantile spasms (HP:0012469). HP:0012469 is a phenotype from the Human Phenotype Ontology. Hypsarrhythmia HP:0002521 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Hypsarrhythmia (HP:0002521). HP:0002521 is a phenotype from the Human Phenotype Ontology.
Show evidence (4 references)
PMID:35765990 SUPPORT Human Clinical
"Treatments including ACTH and high dose prednisolone are more effective in achieving electroclinical and clinical remissions for infantile spasms."
Network meta-analysis supports ACTH and high-dose prednisolone as effective first-line therapies.
PMID:31903560 SUPPORT Human Clinical
"Prednisolone/prednisone elicits a similar electroclinical response as ACTH for infantile spasms"
RCT meta-analysis supports prednisolone/prednisone as an ACTH alternative for electroclinical response.
PMID:29105055 SUPPORT Human Clinical
"First-line treatment with standard therapy was by far the most important variable in determining likelihood of response to treatment of infantile spasms with or without hypsarrhythmia. "
National Infantile Spasms Consortium cohort shows that using standard first-line therapy (hormonal therapy or vigabatrin) is the strongest determinant of treatment response.
+ 1 more reference
Vigabatrin
Action: anticonvulsant agent therapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is anticonvulsant agent therapy, annotated with Anticonvulsant Therapy (NCIT:C64172). NCIT:C64172 is a clinical intervention from the NCI Thesaurus. Ontology label: Anticonvulsant Therapy NCIT:C64172
Agent: vigabatrin CHEBI:63638 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses vigabatrin (CHEBI:63638). CHEBI:63638 is a therapeutic agent from Chemical Entities of Biological Interest.
Vigabatrin is an antiseizure medication used for IESS, especially when tuberous sclerosis complex is the underlying cause; it increases brain GABA concentrations but requires visual-field toxicity risk management.
Mechanism Target:
MODULATES Developing brain epileptic network hyperexcitability — Vigabatrin increases inhibitory GABA tone and reduces epileptic spasm frequency.
Target Phenotypes: Infantile spasms HP:0012469 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Infantile spasms (HP:0012469). HP:0012469 is a phenotype from the Human Phenotype Ontology.
Show evidence (4 references)
PMID:22364326 SUPPORT Human Clinical
"Clinical studies have shown that vigabatrin is superior to placebo in decreasing the frequency of infantile spasms."
Review summarizes clinical trial evidence for vigabatrin reducing infantile spasms.
PMID:22364326 SUPPORT Human Clinical
"In tuberous sclerosis, vigabatrin may be considered the first-line treatment for IS."
Supports the specific first-line role of vigabatrin in TSC-associated IESS.
PMID:22364326 SUPPORT Human Clinical
"The mode of action is increasing concentrations of the inhibitory neurotransmitter GABA in the brain."
Provides the mechanism rationale for vigabatrin modulation of epileptic network activity.
+ 1 more reference
Combination hormonal therapy plus vigabatrin
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: corticotropin CHEBI:3892 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses corticotropin (CHEBI:3892). CHEBI:3892 is a therapeutic agent from Chemical Entities of Biological Interest. prednisolone CHEBI:8378 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses prednisolone (CHEBI:8378). CHEBI:8378 is a therapeutic agent from Chemical Entities of Biological Interest. vigabatrin CHEBI:63638 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses vigabatrin (CHEBI:63638). CHEBI:63638 is a therapeutic agent from Chemical Entities of Biological Interest.
Combined hormonal therapy with vigabatrin can be used as initial therapy to increase early spasm cessation compared with hormonal therapy alone.
Target Phenotypes: Infantile spasms HP:0012469 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Infantile spasms (HP:0012469). HP:0012469 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:27838190 SUPPORT Human Clinical
"Between days 14 and 42 inclusive no spasms were witnessed in 133 (72%) of 186 patients on hormonal therapy with vigabatrin compared with 108 (57%) of 191 patients on hormonal therapy alone "
ICISS randomized trial shows higher early spasm cessation with combination hormonal therapy plus vigabatrin.
PMID:27838190 SUPPORT Human Clinical
"Hormonal therapy with vigabatrin is significantly more effective at stopping infantile spasms than hormonal therapy alone."
ICISS interpretation directly supports combination therapy efficacy.
mTOR inhibitor therapy (everolimus)
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: everolimus CHEBI:68478 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses everolimus (CHEBI:68478). CHEBI:68478 is a therapeutic agent from Chemical Entities of Biological Interest.
Everolimus is an mTOR inhibitor used as mechanism-matched precision therapy for tuberous sclerosis complex-associated epilepsy, targeting the mTORC1 hyperactivation that underlies TSC. It is an adjunctive option for treatment-resistant TSC seizures rather than a first-line therapy for infantile spasms.
Mechanism Target:
INHIBITS mTOR pathway hyperactivation — Everolimus inhibits mTORC1, the hyperactivated node driving TSC-associated epileptogenesis.
Show evidence (2 references)
PMID:27613521 SUPPORT Human Clinical
"Everolimus, a mammalian target of rapamycin (mTOR) inhibitor, has been used for various benign tumours associated with tuberous sclerosis complex."
Identifies everolimus as an mTOR inhibitor used in tuberous sclerosis complex, the prototypical mTORopathy cause of infantile spasms.
PMID:27613521 SUPPORT Human Clinical
"Adjunctive everolimus treatment significantly reduced seizure frequency with a tolerable safety profile compared with placebo in patients with tuberous sclerosis complex and treatment-resistant seizures."
Phase 3 RCT shows adjunctive everolimus reduces seizures in TSC, supporting mechanism-matched mTOR-inhibitor therapy for the TSC-associated etiologic class.
Genetic counseling
Action: Genetic CounselingNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Genetic Counseling (NCIT:C15240). NCIT:C15240 is a clinical intervention from the NCI Thesaurus. NCIT:C15240
Genetic counseling is indicated when IESS has an inherited or de novo genetic etiology, because the spectrum includes autosomal dominant, autosomal recessive, and X-linked genetic causes.
Show evidence (1 reference)
ORPHA:697160 SUPPORT Other
"Autosomal dominant"
Orphanet's genetic inheritance assertions support counseling for recurrence-risk assessment.
🔬

Diagnosis

2
Video EEG and electroclinical syndrome diagnosis
Diagnosis is based on recognizing the spasm semiology together with EEG evidence of hypsarrhythmia or a similar epileptiform pattern; video-EEG is used to confirm events and assess electroclinical response.
electroencephalography NCIT:C38054 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:27838190 SUPPORT Human Clinical
"enrolled infants who had a clinical diagnosis of infantile spasms and a hypsarrhythmic (or similar) EEG no more than 7 days before enrolment. "
Trial criteria demonstrate the diagnostic pairing of clinical spasms with a hypsarrhythmic or similar EEG pattern.
Etiologic evaluation with neuroimaging and genetic testing
After electroclinical diagnosis, evaluation should seek an underlying structural, metabolic, or genetic cause using neuroimaging, metabolic assessment, and genetic testing as clinically appropriate.
genetic testing NCIT:C15709 NCI Thesaurus (NCIT)
Show evidence (2 references)
PMID:35503712 SUPPORT Human Clinical
"For each syndrome, we report epidemiology, clinical course, seizure types, electroencephalography (EEG), neuroimaging, genetics, and differential diagnosis."
ILAE syndrome framework includes EEG, neuroimaging, genetics, and differential diagnosis for infant epilepsy syndromes.
PMID:35503712 SUPPORT Human Clinical
"Guidance is given on the criteria for syndrome diagnosis in resource-limited regions where laboratory confirmation, including EEG, MRI, and genetic testing, might not be available."
ILAE notes EEG, MRI, and genetic testing as usual confirmatory resources for syndrome diagnosis and etiologic evaluation.
📊

Prevalence

1
Denmark, births 1996-2019
Birth Prevalence 22.0 per 100,000 1–9 per 10,000
Show evidence (1 reference)
PMID:39029407 SUPPORT Human Clinical
"The incidence of IESS was 22 per 100.000 live births."
National retrospective Danish cohort provides a population incidence estimate for IESS.
📊

Related Datasets

2
Dual developmental effects of ARX poly-alanine mutations in human cortical excitatory and inhibitory neurons geo:GSE215362
Infantile spasms (IS), a severe childhood epilepsy with an incidence of 1.6–4.5 per 10,000 live births, often lead to lifelong intellectual disability. Up to 5% of affected males carry mutations in the Aristaless-related homeobox (ARX) gene. The lack of human-specific models for developmental epilepsy limits progress, making organoids a promising alternative. We use human cortical (CO) and ganglionic eminence organoids (GEO) to model poly-alanine expansion (PAE) mutations in ARX. PAE mutations increase cortical progenitor proliferation and accelerate early cortical development.
human BULK RNA SEQ n=24
PMID:41422506
Identified by GEO DataSets index search for Infantile Spasms (scripts/discover_datasets.py); accession and metadata verified against NCBI E-utilities on 2026-07-31. Title, sample count, and organism are GEO's own values.
Remodeling of synaptic transmission genomic fabrics in the hypothalamic arcuate nucleus of a rat female model of infantile spasms geo:GSE84585
We profiled the whole transcriptomes of female rat hypothalamic arcuate nuclei to determine the remodeling of the genomic fabrics responsible for the glutamatergic, GABAergic, dopaminergic, cholinergic and serotonergic transmission in epilepsy and recovery following different treatments. The rats were prenatally exposed (G15) to betamethasone (or just saline for control) followed by repeated adiministration of N-Methyl-D-Aspartic acid (NMDA) on postnatal days 12, 13 and 15 which triggered infantile spasms.
rat MICROARRAY n=20
PMID:29636502
Identified by GEO DataSets index search for Infantile Spasms (scripts/discover_datasets.py); accession and metadata verified against NCBI E-utilities on 2026-07-31. Title, sample count, and organism are GEO's own values.
🔬

Clinical Trials

2
NCT04302116 NOT_APPLICABLE RECRUITING
Randomized trial comparing vigabatrin plus high-dose prednisolone combination therapy with vigabatrin alone for infantile spasms.
Target Phenotypes: Infantile spasms HP:0012469 Human Phenotype Ontology (HP) Relation: this clinical trial targets this phenotype This clinical trial targets Infantile spasms (HP:0012469). HP:0012469 is a phenotype from the Human Phenotype Ontology. Hypsarrhythmia HP:0002521 Human Phenotype Ontology (HP) Relation: this clinical trial targets this phenotype This clinical trial targets Hypsarrhythmia (HP:0002521). HP:0002521 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
clinicaltrials:NCT04302116 SUPPORT Human Clinical
"this study is aimed to compare the efficacy of vigabatrin with high dose prednisolone combination therapy and vigabatrin alone."
ClinicalTrials.gov record describes the active randomized comparison of combination therapy versus vigabatrin alone.
NCT04289467 PHASE_II RECRUITING
Phase II trial of fenfluramine for refractory infantile spasms that have not responded to vigabatrin and ACTH.
Target Phenotypes: Refractory infantile spasms HP:0012469 Human Phenotype Ontology (HP) Relation: this clinical trial targets this phenotype This clinical trial targets Refractory infantile spasms, annotated with Infantile spasms (HP:0012469). HP:0012469 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
clinicaltrials:NCT04289467 SUPPORT Human Clinical
"children with refractory infantile spasms (also called epileptic spasms or West syndrome) will be treated with fenfluramine"
ClinicalTrials.gov record describes fenfluramine evaluation for refractory infantile spasms.
{ }

Source YAML

click to show 
name: Infantile Spasms
creation_date: "2026-05-07T12:19:58Z"
description: >
  Infantile spasms, now classified as infantile epileptic spasms syndrome
  (IESS), is an age-dependent developmental and epileptic encephalopathy of
  infancy. It is characterized by epileptic spasms, usually in clusters,
  hypsarrhythmia or a related epileptiform EEG pattern, and developmental
  stagnation or regression. Etiology is heterogeneous, including structural,
  prenatal, perinatal, postnatal, metabolic, and genetic causes.
category: Complex
parents:
- Epilepsy
- Neurodevelopmental Disorder
- Neurological Disease
synonyms:
- West syndrome
- West's syndrome
- Infantile epileptic spasms syndrome
- IESS
disease_term:
  preferred_term: infantile spasms
  term:
    id: MONDO:0018097
    label: infantile spasms
mappings:
  mondo_mappings:
  - term:
      id: MONDO:0018097
      label: infantile spasms
    mapping_predicate: skos:exactMatch
    mapping_source: Orphanet ORPHA:697160
    mapping_justification: >
      Orphanet ORPHA:697160 is the current infantile epileptic spasms syndrome
      disease record and MONDO maps infantile spasms to this concept.
external_assertions:
- name: Orphanet infantile epileptic spasms syndrome record
  source: Orphanet
  assertion_type: structured_disease_record
  external_id: ORPHA:697160
  url: http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=en&Expert=697160
  description: >
    Orphanet's ORPHA:697160 structured record for infantile epileptic spasms
    syndrome includes the inheritance modes, disease-gene assertions, HPO
    phenotype rows, and external cross-references used in this entry.
  evidence:
  - reference: ORPHA:697160
    reference_title: "Infantile epileptic spasms syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0012469 | Infantile spasms | Very frequent (99-80%)"
    explanation: Orphanet lists infantile spasms as a very frequent phenotype for ORPHA:697160.
  - reference: ORPHA:697160
    reference_title: "Infantile epileptic spasms syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "ARX | aristaless related homeobox | hgnc:18060 | Disease-causing germline mutation(s) in"
    explanation: Orphanet records ARX among disease-causing genes for the IESS spectrum.
- name: Orphanet West syndrome legacy record
  source: Orphanet
  assertion_type: structured_disease_record
  external_id: ORPHA:3451
  url: http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=en&Expert=3451
  description: >
    Orphanet's ORPHA:3451 West syndrome record is retained as a legacy exact
    cross-reference to MONDO:0018097 and the ICD-11 IESS/West syndrome concept.
  evidence:
  - reference: ORPHA:3451
    reference_title: "West syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "MONDO:0018097 | Exact"
    explanation: ORPHA:3451 maps exactly to the MONDO infantile spasms concept used by this entry.
definitions:
- name: ILAE neonatal and infant epilepsy syndrome definition
  definition_type: OTHER
  description: >
    ILAE classifies infantile spasms/IESS among epilepsy syndromes with onset in
    neonates and infants, emphasizing syndrome diagnosis together with etiology.
  evidence:
  - reference: PMID:35503712
    reference_title: "ILAE classification and definition of epilepsy syndromes with onset in neonates and infants: Position statement by the ILAE Task Force on Nosology and Definitions."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >
      The International League Against Epilepsy (ILAE) Task Force on Nosology and Definitions proposes a classification and definition of epilepsy syndromes in the neonate and infant with seizure onset up to 2 years of age.
    explanation: The ILAE position statement defines epilepsy syndromes with onset in infancy, including infantile epileptic spasms syndrome.
- name: West syndrome electroclinical triad
  definition_type: OTHER
  description: >
    West syndrome is the historical triad of infantile spasms, hypsarrhythmia on
    EEG, and developmental regression.
  evidence:
  - reference: PMID:37736852
    reference_title: "Treatment modalities for infantile spasms: current considerations and evolving strategies in clinical practice."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >
      When infantile spasms occur with a concomitant hypsarrhythmia on electroencephalogram (EEG) and developmental regression, it is known as West Syndrome.
    explanation: Review article states the clinical-EEG-developmental triad that historically defines West syndrome.
prevalence:
- population: Denmark, births 1996-2019
  measure_type: BIRTH_PREVALENCE
  prevalence_class: BAND_1_5_PER_10000
  rate_per_100000: 22.0
  percentage: 22 per 100,000 live births
  evidence:
  - reference: PMID:39029407
    reference_title: "Epidemiology and outcome of infantile spasms in Denmark in 1996-2019."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The incidence of IESS was 22 per 100.000 live births.
    explanation: National retrospective Danish cohort provides a population incidence estimate for IESS.
has_subtypes:
- name: Known etiology
  display_name: IESS with known etiology
  description: >
    IESS with a structural, prenatal, perinatal, postnatal, metabolic, or
    genetic etiology identified by clinical evaluation.
- name: Unknown etiology
  display_name: IESS of unknown etiology
  description: >
    IESS in which standard clinical evaluation does not identify the underlying
    cause at the time of diagnosis.
inheritance:
- name: Autosomal dominant
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  description: >
    A subset of genetic IESS is caused by monoallelic variants in genes recorded
    by Orphanet, including dominant mechanisms.
  evidence:
  - reference: ORPHA:697160
    reference_title: "Infantile epileptic spasms syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Autosomal dominant"
    explanation: Orphanet records autosomal dominant inheritance among the inherited IESS etiologies.
- name: Autosomal recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >
    A subset of genetic IESS is caused by biallelic pathogenic variants in
    autosomal genes.
  evidence:
  - reference: ORPHA:697160
    reference_title: "Infantile epileptic spasms syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Autosomal recessive"
    explanation: Orphanet records autosomal recessive inheritance among the inherited IESS etiologies.
- name: X-linked dominant
  inheritance_term:
    preferred_term: X-linked dominant inheritance
    term:
      id: HP:0001423
      label: X-linked dominant inheritance
  description: >
    X-linked genes such as ARX, CDKL5, PIGA, and WDR45 contribute to the
    inherited IESS spectrum.
  evidence:
  - reference: ORPHA:697160
    reference_title: "Infantile epileptic spasms syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "X-linked dominant"
    explanation: Orphanet records X-linked dominant inheritance for part of the IESS spectrum.
pathophysiology:
- name: Heterogeneous developmental brain etiologies
  description: >
    Structural, prenatal, perinatal, postnatal, metabolic, and genetic causes
    disrupt the developing infant brain and converge on an IESS electroclinical
    phenotype.
  genes:
  - preferred_term: ARX
    term:
      id: hgnc:18060
      label: ARX
  - preferred_term: CDKL5
    term:
      id: hgnc:11411
      label: CDKL5
  - preferred_term: GRIN2B
    term:
      id: hgnc:4586
      label: GRIN2B
  - preferred_term: SCN2A
    term:
      id: hgnc:10588
      label: SCN2A
  biological_processes:
  - preferred_term: nervous system development
    term:
      id: GO:0007399
      label: nervous system development
    modifier: ABNORMAL
  locations:
  - preferred_term: brain
    term:
      id: UBERON:0000955
      label: brain
  evidence:
  - reference: PMID:39029407
    reference_title: "Epidemiology and outcome of infantile spasms in Denmark in 1996-2019."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >
      Aetiology was prenatal (40.3 %), perinatal (10.5 %), postnatal (3.7 %), with unknown timing (10.2 %) or with unknown aetiology (33.5 %).
    explanation: National cohort demonstrates etiologic heterogeneity across prenatal, perinatal, postnatal, and unknown causes.
  - reference: ORPHA:697160
    reference_title: "Infantile epileptic spasms syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "SCN2A | sodium voltage-gated channel alpha subunit 2 | hgnc:10588 | Disease-causing germline mutation(s) in"
    explanation: Orphanet records SCN2A and other genes as disease-causing in genetic IESS.
  downstream:
  - target: Developing brain epileptic network hyperexcitability
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Diverse etiologies converge on abnormal epileptic network activity in the infant brain.
  - target: mTOR pathway hyperactivation
    causal_link_type: DIRECT
    description: A major structural/genetic etiologic class (tuberous sclerosis complex and related mTORopathies) acts through constitutive mTORC1 signaling.
  - target: Developmental and epileptic encephalopathy burden
    causal_link_type: DIRECT
    description: Underlying etiologies contribute to developmental impairment independent of epileptiform activity.
- name: mTOR pathway hyperactivation
  description: >
    In tuberous sclerosis complex and related mTORopathies, loss of function of
    TSC1/TSC2 (or activating variants in the wider PI3K-AKT-mTOR pathway, and
    brain-restricted somatic mTOR-pathway variants) disinhibits mTORC1 signaling.
    This drives abnormal cortical cytoarchitecture (cortical tubers, focal
    cortical dysplasia, dysmorphic neurons) that seeds the epileptogenic network,
    and provides the mechanistic rationale for mTOR-inhibitor precision therapy.
  genes:
  - preferred_term: TSC1
    term:
      id: hgnc:12362
      label: TSC1
  - preferred_term: TSC2
    term:
      id: hgnc:12363
      label: TSC2
  biological_processes:
  - preferred_term: positive regulation of TOR signaling
    term:
      id: GO:0032008
      label: positive regulation of TOR signaling
    modifier: INCREASED
  locations:
  - preferred_term: cerebral cortex
    term:
      id: UBERON:0000956
      label: cerebral cortex
  evidence:
  - reference: PMID:33892851
    reference_title: "Tuberous Sclerosis Complex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >
      the identification of the responsible genes and gene products forming the mechanistic target of rapamycin complex, previously termed the mammalian target of rapamycin, not only has expanded our understanding of tuberous sclerosis pathophysiology, but has also inspired the search for targeted interventions.
    explanation: Establishes the mTORC1 pathway as the molecular basis of TSC pathophysiology and the rationale for targeted (mTOR-inhibitor) intervention.
  - reference: PMID:33892851
    reference_title: "Tuberous Sclerosis Complex."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >
      the pediatric neurologist is often responsible for making the initial diagnosis when the affected individual presents with infantile spasms or another early-onset epilepsy syndrome.
    explanation: Links TSC (the prototypical mTORopathy) directly to infantile-spasms presentation.
  - reference: PMID:38540325
    reference_title: "Genetic Advancements in Infantile Epileptic Spasms Syndrome and Opportunities for Precision Medicine."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >
      some of the most commonly reported genetic aetiologies include trisomy 21 and pathogenic variants in genes such as TSC1, TSC2, CDKL5, ARX, KCNQ2, STXBP1 and SCN2A.
    explanation: Confirms TSC1/TSC2 (and ARX) among the most commonly reported genetic etiologies of IESS.
  downstream:
  - target: Developing brain epileptic network hyperexcitability
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - mTORC1 hyperactivation produces cortical tubers, focal cortical dysplasia, and dysmorphic neurons that form the epileptogenic substrate.
    description: mTORC1 hyperactivation and the resulting dysplastic cortex generate the hyperexcitable epileptic network.
- name: Developing brain epileptic network hyperexcitability
  conforms_to: "epilepsy_excitation_inhibition_imbalance#Excitation-Inhibition Imbalance"
  description: >
    The IESS phenotype reflects abnormal synchronized activity in immature
    cortical-subcortical networks, producing epileptic spasms and the
    hypsarrhythmic EEG pattern. A recurrent mechanistic theme is a shift toward
    net excitation in the developing cortex through impaired GABAergic
    interneuron development/function (interneuronopathy, exemplified by ARX
    loss of function), consistent with the conserved epilepsy
    excitation-inhibition imbalance pattern and with the efficacy of the
    GABA-augmenting drug vigabatrin.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  - preferred_term: cortical GABAergic interneuron
    term:
      id: CL:0000617
      label: GABAergic neuron
  genes:
  - preferred_term: ARX
    term:
      id: hgnc:18060
      label: ARX
  biological_processes:
  - preferred_term: trans-synaptic signaling
    term:
      id: GO:0099537
      label: trans-synaptic signaling
    modifier: ABNORMAL
  - preferred_term: GABA signaling
    term:
      id: GO:0007214
      label: gamma-aminobutyric acid signaling pathway
    modifier: DECREASED
  locations:
  - preferred_term: brain
    term:
      id: UBERON:0000955
      label: brain
  evidence:
  - reference: PMID:37736852
    reference_title: "Treatment modalities for infantile spasms: current considerations and evolving strategies in clinical practice."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >
      Infantile spasms, newly classified as infantile epileptic spasm syndrome (IESS), occur in children under 2 years of age and present as an occur as brief, symmetrical, contractions of the musculature of the neck, trunk, and extremities.
    explanation: Review describes the age-dependent epileptic spasm phenotype produced by the abnormal infantile network state.
  - reference: PMID:27838190
    reference_title: "Safety and effectiveness of hormonal treatment versus hormonal treatment with vigabatrin for infantile spasms (ICISS): a randomised, multicentre, open-label trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >
      enrolled infants who had a clinical diagnosis of infantile spasms and a hypsarrhythmic (or similar) EEG no more than 7 days before enrolment.
    explanation: Trial inclusion criteria show that infantile spasms and hypsarrhythmic or similar EEG activity form the electroclinical syndrome.
  - reference: PMID:23312951
    reference_title: "Basic mechanisms of catastrophic epilepsy--overview from animal models."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >
      two genetic mouse models of interneuronopathies with infantile spasms due to loss of function of the aristaless X-linked homeobox-related gene (ARX).
    explanation: ARX loss-of-function mouse interneuronopathy models link GABAergic interneuron dysfunction to the generation of infantile spasms, supporting the excitation-inhibition imbalance arm.
  downstream:
  - target: Infantile spasms
    causal_link_type: DIRECT
    description: Epileptic network discharges produce clusters of infantile spasms.
  - target: Hypsarrhythmia
    causal_link_type: DIRECT
    description: The same epileptic encephalopathy produces the hypsarrhythmic EEG pattern.
  - target: Developmental and epileptic encephalopathy burden
    causal_link_type: DIRECT
    description: Epileptic encephalopathy contributes to developmental impairment alongside the underlying etiology.
- name: Developmental and epileptic encephalopathy burden
  description: >
    IESS is part of the developmental and epileptic encephalopathy spectrum:
    developmental impairment reflects both the underlying etiology and the
    epileptic encephalopathy.
  biological_processes:
  - preferred_term: nervous system development
    term:
      id: GO:0007399
      label: nervous system development
    modifier: ABNORMAL
  evidence:
  - reference: PMID:35503712
    reference_title: "ILAE classification and definition of epilepsy syndromes with onset in neonates and infants: Position statement by the ILAE Task Force on Nosology and Definitions."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >
      developmental and epileptic encephalopathies, diseases where there is developmental impairment related to both the underlying etiology independent of epileptiform activity and the epileptic encephalopathy.
    explanation: ILAE statement defines developmental and epileptic encephalopathies as disorders where etiology and epileptiform activity both contribute to developmental impairment.
  - reference: PMID:39029407
    reference_title: "Epidemiology and outcome of infantile spasms in Denmark in 1996-2019."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: At latest follow-up severe neurodevelopmental outcome was seen in 44.2 % and 76.4 % still had epilepsy.
    explanation: Danish cohort quantifies long-term neurodevelopmental and epilepsy burden after IESS.
  - reference: PMID:30236380
    reference_title: "Vigabatrin with hormonal treatment versus hormonal treatment alone (ICISS) for infantile spasms: 18-month outcomes of an open-label, randomised controlled trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >
      Increasing lead-time to treatment was associated with lower VABS scores
    explanation: ICISS 18-month follow-up shows that longer lead-time to effective treatment predicts worse developmental (Vineland Adaptive Behaviour Scales) outcome, consistent with the developmental-and-epileptic-encephalopathy model in which the epileptic activity itself drives developmental harm.
  - reference: PMID:30236380
    reference_title: "Vigabatrin with hormonal treatment versus hormonal treatment alone (ICISS) for infantile spasms: 18-month outcomes of an open-label, randomised controlled trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >
      Initial control of spasms between days 14 and 42 of treatment was associated with higher mean VABS scores at 18 months
    explanation: Early cessation of spasms is associated with better developmental outcome, supporting the prognostic value of rapid, effective treatment.
  downstream:
  - target: Developmental regression
    causal_link_type: DIRECT
    description: Epileptic encephalopathy is associated with loss of developmental skills.
  - target: Global developmental delay
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Developmental impairment is related to both underlying etiology and epileptic encephalopathy.
    description: The combined etiologic and epileptic burden contributes to global developmental delay.
phenotypes:
- name: Infantile spasms
  category: Clinical
  frequency: VERY_FREQUENT
  diagnostic: true
  description: >
    Epileptic spasms beginning in infancy, often occurring in clusters, are the
    cardinal clinical seizure type of IESS.
  phenotype_term:
    preferred_term: Infantile spasms
    term:
      id: HP:0012469
      label: Infantile spasms
  evidence:
  - reference: ORPHA:697160
    reference_title: "Infantile epileptic spasms syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0012469 | Infantile spasms | Very frequent (99-80%)"
    explanation: Orphanet records infantile spasms as very frequent in IESS.
- name: Epileptic spasms
  category: Clinical
  frequency: VERY_FREQUENT
  diagnostic: true
  description: >
    Epileptic spasms are the defining seizure semiology of IESS: sudden, brief,
    symmetric flexor, extensor, or mixed flexor-extensor contractions of the
    neck, trunk, and extremities, characteristically occurring in clusters. In
    the 2022 ILAE nosology, epileptic spasms are the mandatory seizure type,
    whereas hypsarrhythmia is supportive but not required.
  phenotype_term:
    preferred_term: Epileptic spasm
    term:
      id: HP:0011097
      label: Epileptic spasm
  evidence:
  - reference: PMID:38540325
    reference_title: "Genetic Advancements in Infantile Epileptic Spasms Syndrome and Opportunities for Precision Medicine."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >
      Infantile epileptic spasms syndrome (IESS) is a devastating developmental epileptic encephalopathy (DEE) consisting of epileptic spasms, as well as one or both of developmental regression or stagnation and hypsarrhythmia on EEG.
    explanation: Defines epileptic spasms as the mandatory seizure type of IESS, with developmental regression/stagnation and hypsarrhythmia as the associated (not both-required) features.
- name: Hypsarrhythmia
  category: Diagnostic
  frequency: VERY_FREQUENT
  diagnostic: true
  description: >
    Hypsarrhythmia or a modified/similar epileptiform EEG pattern is the
    characteristic interictal EEG abnormality supporting IESS diagnosis.
  phenotype_term:
    preferred_term: Hypsarrhythmia
    term:
      id: HP:0002521
      label: Hypsarrhythmia
  electrophysiology:
    electrophysiology_modality: EEG
    ictal_state: INTERICTAL
  evidence:
  - reference: ORPHA:697160
    reference_title: "Infantile epileptic spasms syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0002521 | Hypsarrhythmia | Very frequent (99-80%)"
    explanation: Orphanet records hypsarrhythmia as very frequent in IESS.
  - reference: PMID:27838190
    reference_title: "Safety and effectiveness of hormonal treatment versus hormonal treatment with vigabatrin for infantile spasms (ICISS): a randomised, multicentre, open-label trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "clinical diagnosis of infantile spasms and a hypsarrhythmic (or similar) EEG"
    explanation: ICISS trial used hypsarrhythmic or similar EEG as part of the electroclinical inclusion criteria.
- name: Developmental regression
  category: Clinical
  frequency: VERY_FREQUENT
  diagnostic: true
  description: >
    Loss or stagnation of developmental skills is a core West syndrome feature
    and a major contributor to long-term disability.
  phenotype_term:
    preferred_term: Developmental regression
    term:
      id: HP:0002376
      label: Developmental regression
  evidence:
  - reference: ORPHA:697160
    reference_title: "Infantile epileptic spasms syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0002376 | Developmental regression | Very frequent (99-80%)"
    explanation: Orphanet records developmental regression as very frequent in IESS.
  - reference: PMID:37736852
    reference_title: "Treatment modalities for infantile spasms: current considerations and evolving strategies in clinical practice."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "concomitant hypsarrhythmia on electroencephalogram (EEG) and developmental regression"
    explanation: Review includes developmental regression in the West syndrome triad.
- name: Myoclonus
  category: Clinical
  frequency: VERY_FREQUENT
  description: >
    Myoclonic or spasm-like motor events are part of the IESS seizure
    presentation and overlap clinically with epileptic spasms.
  phenotype_term:
    preferred_term: Myoclonus
    term:
      id: HP:0001336
      label: Myoclonus
  evidence:
  - reference: ORPHA:697160
    reference_title: "Infantile epileptic spasms syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0001336 | Myoclonus | Very frequent (99-80%)"
    explanation: Orphanet records myoclonus as very frequent in IESS.
- name: Global developmental delay
  category: Clinical
  description: >
    Developmental impairment commonly persists beyond the acute spasm period,
    especially when etiology is structural or symptomatic and treatment is
    delayed.
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:35503712
    reference_title: "ILAE classification and definition of epilepsy syndromes with onset in neonates and infants: Position statement by the ILAE Task Force on Nosology and Definitions."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "developmental impairment related to both the underlying etiology independent of epileptiform activity and the epileptic encephalopathy"
    explanation: ILAE statement supports developmental impairment as intrinsic to developmental and epileptic encephalopathy syndromes.
  - reference: PMID:39029407
    reference_title: "Epidemiology and outcome of infantile spasms in Denmark in 1996-2019."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "severe neurodevelopmental outcome was seen in 44.2 %"
    explanation: National cohort documents severe neurodevelopmental outcome in a large fraction of children with IESS.
- name: Cutaneous signs of underlying etiology
  category: Clinical
  frequency: FREQUENT
  description: >
    Skin abnormalities may be present when IESS is caused by a neurocutaneous or
    syndromic genetic etiology; they should be interpreted as etiologic clues
    rather than as defining spasm semiology.
  phenotype_term:
    preferred_term: Abnormal skin morphology
    term:
      id: HP:0011121
      label: Abnormal skin morphology
  evidence:
  - reference: ORPHA:697160
    reference_title: "Infantile epileptic spasms syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HP:0011121 | Abnormal skin morphology | Frequent (79-30%)"
    explanation: Orphanet records abnormal skin morphology as frequent for the IESS spectrum.
diagnosis:
- name: Video EEG and electroclinical syndrome diagnosis
  description: >
    Diagnosis is based on recognizing the spasm semiology together with EEG
    evidence of hypsarrhythmia or a similar epileptiform pattern; video-EEG is
    used to confirm events and assess electroclinical response.
  diagnosis_term:
    preferred_term: electroencephalography
    term:
      id: NCIT:C38054
      label: Electroencephalography
  evidence:
  - reference: PMID:27838190
    reference_title: "Safety and effectiveness of hormonal treatment versus hormonal treatment with vigabatrin for infantile spasms (ICISS): a randomised, multicentre, open-label trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >
      enrolled infants who had a clinical diagnosis of infantile spasms and a hypsarrhythmic (or similar) EEG no more than 7 days before enrolment.
    explanation: Trial criteria demonstrate the diagnostic pairing of clinical spasms with a hypsarrhythmic or similar EEG pattern.
- name: Etiologic evaluation with neuroimaging and genetic testing
  description: >
    After electroclinical diagnosis, evaluation should seek an underlying
    structural, metabolic, or genetic cause using neuroimaging, metabolic
    assessment, and genetic testing as clinically appropriate.
  diagnosis_term:
    preferred_term: genetic testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  evidence:
  - reference: PMID:35503712
    reference_title: "ILAE classification and definition of epilepsy syndromes with onset in neonates and infants: Position statement by the ILAE Task Force on Nosology and Definitions."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "For each syndrome, we report epidemiology, clinical course, seizure types, electroencephalography (EEG), neuroimaging, genetics, and differential diagnosis."
    explanation: ILAE syndrome framework includes EEG, neuroimaging, genetics, and differential diagnosis for infant epilepsy syndromes.
  - reference: PMID:35503712
    reference_title: "ILAE classification and definition of epilepsy syndromes with onset in neonates and infants: Position statement by the ILAE Task Force on Nosology and Definitions."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Guidance is given on the criteria for syndrome diagnosis in resource-limited regions where laboratory confirmation, including EEG, MRI, and genetic testing, might not be available."
    explanation: ILAE notes EEG, MRI, and genetic testing as usual confirmatory resources for syndrome diagnosis and etiologic evaluation.
treatments:
- name: Hormonal therapy with ACTH or high-dose prednisolone
  description: >
    ACTH, tetracosactide, or high-dose prednisolone are first-line hormonal
    therapies for IESS, aiming for rapid cessation of spasms and EEG
    improvement. A leading mechanistic hypothesis for hormonal efficacy is the
    stress/corticotropin-releasing-hormone (CRH) model, in which CRH acts as an
    endogenous convulsant in the immature brain and ACTH suppresses CRH through
    negative feedback; this remains a hypothesis supported chiefly by animal
    models.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: corticotropin
      term:
        id: CHEBI:3892
        label: corticotropin
    - preferred_term: prednisolone
      term:
        id: CHEBI:8378
        label: prednisolone
  target_phenotypes:
  - preferred_term: Infantile spasms
    term:
      id: HP:0012469
      label: Infantile spasms
  - preferred_term: Hypsarrhythmia
    term:
      id: HP:0002521
      label: Hypsarrhythmia
  target_mechanisms:
  - target: Developing brain epileptic network hyperexcitability
    treatment_effect: MODULATES
    description: Hormonal therapy reduces the epileptic network activity that produces spasms and hypsarrhythmia.
  evidence:
  - reference: PMID:35765990
    reference_title: "Treatment of children with infantile spasms: A network meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Treatments including ACTH and high dose prednisolone are more effective in achieving electroclinical and clinical remissions for infantile spasms."
    explanation: Network meta-analysis supports ACTH and high-dose prednisolone as effective first-line therapies.
  - reference: PMID:31903560
    reference_title: "Prednisolone/prednisone as adrenocorticotropic hormone alternative for infantile spasms: a meta-analysis of randomized controlled trials."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Prednisolone/prednisone elicits a similar electroclinical response as ACTH for infantile spasms"
    explanation: RCT meta-analysis supports prednisolone/prednisone as an ACTH alternative for electroclinical response.
  - reference: PMID:29105055
    reference_title: "The impact of hypsarrhythmia on infantile spasms treatment response: Observational cohort study from the National Infantile Spasms Consortium."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >
      First-line treatment with standard therapy was by far the most important variable in determining likelihood of response to treatment of infantile spasms with or without hypsarrhythmia.
    explanation: National Infantile Spasms Consortium cohort shows that using standard first-line therapy (hormonal therapy or vigabatrin) is the strongest determinant of treatment response.
  - reference: PMID:23312951
    reference_title: "Basic mechanisms of catastrophic epilepsy--overview from animal models."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >
      The stress theory of spasms yielded the corticotropin releasing hormone (CRH)-induced model, which showed the higher proconvulsant potency of CRH in developing rats, although only limbic seizures were observed.
    explanation: The CRH/stress animal model provides the mechanistic rationale for hormonal (ACTH) therapy; graded PARTIAL because the model reproduces only limbic (not classic flexion) seizures.
- name: Vigabatrin
  description: >
    Vigabatrin is an antiseizure medication used for IESS, especially when
    tuberous sclerosis complex is the underlying cause; it increases brain GABA
    concentrations but requires visual-field toxicity risk management.
  treatment_term:
    preferred_term: anticonvulsant agent therapy
    term:
      id: NCIT:C64172
      label: Anticonvulsant Therapy
    therapeutic_agent:
    - preferred_term: vigabatrin
      term:
        id: CHEBI:63638
        label: vigabatrin
  target_phenotypes:
  - preferred_term: Infantile spasms
    term:
      id: HP:0012469
      label: Infantile spasms
  target_mechanisms:
  - target: Developing brain epileptic network hyperexcitability
    treatment_effect: MODULATES
    description: Vigabatrin increases inhibitory GABA tone and reduces epileptic spasm frequency.
  evidence:
  - reference: PMID:22364326
    reference_title: "Vigabatrin monotherapy for infantile spasms."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical studies have shown that vigabatrin is superior to placebo in decreasing the frequency of infantile spasms."
    explanation: Review summarizes clinical trial evidence for vigabatrin reducing infantile spasms.
  - reference: PMID:22364326
    reference_title: "Vigabatrin monotherapy for infantile spasms."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In tuberous sclerosis, vigabatrin may be considered the first-line treatment for IS."
    explanation: Supports the specific first-line role of vigabatrin in TSC-associated IESS.
  - reference: PMID:22364326
    reference_title: "Vigabatrin monotherapy for infantile spasms."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The mode of action is increasing concentrations of the inhibitory neurotransmitter GABA in the brain."
    explanation: Provides the mechanism rationale for vigabatrin modulation of epileptic network activity.
  - reference: PMID:33180985
    reference_title: "Prevention of Epilepsy in Infants with Tuberous Sclerosis Complex in the EPISTOP Trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >
      drug-resistant epilepsy (OR = 0.23, p = 0.022), and infantile spasms (OR = 0, p < 0.001). No adverse events related to preventive treatment were noted.
    explanation: The EPISTOP trial shows that preemptive vigabatrin, started on epileptiform EEG before clinical seizures in TSC infants, abolished infantile spasms and reduced drug-resistant epilepsy without related adverse events.
- name: Combination hormonal therapy plus vigabatrin
  description: >
    Combined hormonal therapy with vigabatrin can be used as initial therapy to
    increase early spasm cessation compared with hormonal therapy alone.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: corticotropin
      term:
        id: CHEBI:3892
        label: corticotropin
    - preferred_term: prednisolone
      term:
        id: CHEBI:8378
        label: prednisolone
    - preferred_term: vigabatrin
      term:
        id: CHEBI:63638
        label: vigabatrin
  target_phenotypes:
  - preferred_term: Infantile spasms
    term:
      id: HP:0012469
      label: Infantile spasms
  evidence:
  - reference: PMID:27838190
    reference_title: "Safety and effectiveness of hormonal treatment versus hormonal treatment with vigabatrin for infantile spasms (ICISS): a randomised, multicentre, open-label trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >
      Between days 14 and 42 inclusive no spasms were witnessed in 133 (72%) of 186 patients on hormonal therapy with vigabatrin compared with 108 (57%) of 191 patients on hormonal therapy alone
    explanation: ICISS randomized trial shows higher early spasm cessation with combination hormonal therapy plus vigabatrin.
  - reference: PMID:27838190
    reference_title: "Safety and effectiveness of hormonal treatment versus hormonal treatment with vigabatrin for infantile spasms (ICISS): a randomised, multicentre, open-label trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hormonal therapy with vigabatrin is significantly more effective at stopping infantile spasms than hormonal therapy alone."
    explanation: ICISS interpretation directly supports combination therapy efficacy.
- name: mTOR inhibitor therapy (everolimus)
  description: >
    Everolimus is an mTOR inhibitor used as mechanism-matched precision therapy
    for tuberous sclerosis complex-associated epilepsy, targeting the mTORC1
    hyperactivation that underlies TSC. It is an adjunctive option for
    treatment-resistant TSC seizures rather than a first-line therapy for
    infantile spasms.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: everolimus
      term:
        id: CHEBI:68478
        label: everolimus
  target_mechanisms:
  - target: mTOR pathway hyperactivation
    treatment_effect: INHIBITS
    description: Everolimus inhibits mTORC1, the hyperactivated node driving TSC-associated epileptogenesis.
  evidence:
  - reference: PMID:27613521
    reference_title: "Adjunctive everolimus therapy for treatment-resistant focal-onset seizures associated with tuberous sclerosis (EXIST-3): a phase 3, randomised, double-blind, placebo-controlled study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Everolimus, a mammalian target of rapamycin (mTOR) inhibitor, has been used for various benign tumours associated with tuberous sclerosis complex."
    explanation: Identifies everolimus as an mTOR inhibitor used in tuberous sclerosis complex, the prototypical mTORopathy cause of infantile spasms.
  - reference: PMID:27613521
    reference_title: "Adjunctive everolimus therapy for treatment-resistant focal-onset seizures associated with tuberous sclerosis (EXIST-3): a phase 3, randomised, double-blind, placebo-controlled study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Adjunctive everolimus treatment significantly reduced seizure frequency with a tolerable safety profile compared with placebo in patients with tuberous sclerosis complex and treatment-resistant seizures."
    explanation: Phase 3 RCT shows adjunctive everolimus reduces seizures in TSC, supporting mechanism-matched mTOR-inhibitor therapy for the TSC-associated etiologic class.
- name: Genetic counseling
  description: >
    Genetic counseling is indicated when IESS has an inherited or de novo
    genetic etiology, because the spectrum includes autosomal dominant,
    autosomal recessive, and X-linked genetic causes.
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: ORPHA:697160
    reference_title: "Infantile epileptic spasms syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Autosomal dominant"
    explanation: Orphanet's genetic inheritance assertions support counseling for recurrence-risk assessment.
clinical_trials:
- name: NCT04302116
  phase: NOT_APPLICABLE
  status: RECRUITING
  description: >
    Randomized trial comparing vigabatrin plus high-dose prednisolone
    combination therapy with vigabatrin alone for infantile spasms.
  target_phenotypes:
  - preferred_term: Infantile spasms
    term:
      id: HP:0012469
      label: Infantile spasms
  - preferred_term: Hypsarrhythmia
    term:
      id: HP:0002521
      label: Hypsarrhythmia
  evidence:
  - reference: clinicaltrials:NCT04302116
    reference_title: "Efficacy of Vigabatrin With High Dose Prednisolone Combination Therapy Versus Vigabatrin Alone for Infantile Spasm: a Randomized Trial"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "this study is aimed to compare the efficacy of vigabatrin with high dose prednisolone combination therapy and vigabatrin alone."
    explanation: ClinicalTrials.gov record describes the active randomized comparison of combination therapy versus vigabatrin alone.
- name: NCT04289467
  phase: PHASE_II
  status: RECRUITING
  description: >
    Phase II trial of fenfluramine for refractory infantile spasms that have
    not responded to vigabatrin and ACTH.
  target_phenotypes:
  - preferred_term: Refractory infantile spasms
    term:
      id: HP:0012469
      label: Infantile spasms
  evidence:
  - reference: clinicaltrials:NCT04289467
    reference_title: "A Phase II Study of Fenfluramine for Treatment of Refractory Infantile Spasms"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "children with refractory infantile spasms (also called epileptic spasms or West syndrome) will be treated with fenfluramine"
    explanation: ClinicalTrials.gov record describes fenfluramine evaluation for refractory infantile spasms.
notes: >
  Orphanet also lists the generic root term HP:0000707 Abnormality of the
  nervous system for ORPHA:697160. This entry does not model that root term as
  a separate phenotype because the more specific IESS neurologic phenotypes are
  represented directly.
references: []
discussions:
- discussion_id: gap_iess_final_common_pathway_convergence
  prompt: >-
    By what shared developmental mechanism do etiologically diverse insults
    (tuberous sclerosis and other mTORopathies, hypoxic-ischemic injury, trisomy
    21, and monogenic developmental and epileptic encephalopathies) converge on
    the SAME age-dependent electroclinical syndrome of epileptic spasms and
    hypsarrhythmia?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Heterogeneous developmental brain etiologies
  - pathophysiology#Developing brain epileptic network hyperexcitability
  rationale: >-
    IESS is defined precisely by this convergence: structural, metabolic, and
    genetic causes producing an indistinguishable spasms/hypsarrhythmia
    phenotype within a narrow infantile window. The entry currently models the
    convergence descriptively (diverse etiologies -> abnormal epileptic network
    activity) but the physiological hub that unifies them is unresolved.
    Candidate convergent nodes proposed in the literature include CRH/stress-axis
    hyperactivity, a mistimed GABA developmental switch (NKCC1/KCC2 imbalance),
    and brainstem/cortical dysmaturation. Identifying the shared hub matters
    because it would define the syndrome mechanistically rather than by list of
    causes, and could reveal an etiology-agnostic therapeutic target.
  evidence:
  - reference: PMID:39029407
    reference_title: "Epidemiology and outcome of infantile spasms in Denmark in 1996-2019."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Aetiology was prenatal (40.3 %), perinatal (10.5 %), postnatal (3.7 %), with unknown timing (10.2 %) or with unknown aetiology (33.5 %).
    explanation: >-
      Documents the etiologic heterogeneity that nonetheless converges on one
      electroclinical syndrome, framing the open convergence question.
  - reference: PMID:38540325
    reference_title: "Genetic Advancements in Infantile Epileptic Spasms Syndrome and Opportunities for Precision Medicine."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      some of the most commonly reported genetic aetiologies include trisomy 21 and pathogenic variants in genes such as TSC1, TSC2, CDKL5, ARX, KCNQ2, STXBP1 and SCN2A.
    explanation: >-
      Illustrates the mechanistically diverse genetic causes (transcription
      factor, ion channel, synaptic, mTOR-pathway) that all produce IESS,
      underscoring the unresolved final common pathway.
  proposed_experiments:
  - experiment_id: exp_iess_convergent_hub_crossetiology_profiling
    name: Cross-etiology convergent-hub profiling in IESS models
    description: >-
      Assemble a panel of distinct IESS etiologic models (e.g., TSC/mTOR,
      ARX interneuronopathy, and an acquired hypoxic-ischemic model) and test
      whether they share a common physiological signature at the proposed
      convergence hubs (CRH/stress-axis tone, NKCC1/KCC2 ratio and GABA reversal
      potential, and brainstem-cortical network maturation) during the
      spasm-susceptible developmental window.
    experiment_type:
      preferred_term: cross-model convergent-pathway profiling experiment
    readouts:
    - name: Chloride-handling and GABA-switch readout
      target: pathophysiology#Developing brain epileptic network hyperexcitability
      biological_processes:
      - preferred_term: GABA signaling
        term:
          id: GO:0007214
          label: gamma-aminobutyric acid signaling pathway
        modifier: DYSREGULATED
      assays:
      - preferred_term: gramicidin perforated-patch recording
      direction: POSITIVE
    controls:
    - name: Age-matched wild-type
      description: Littermate controls profiled in the same developmental window.
    decision_criterion: >-
      A convergence hub is supported if mechanistically distinct etiologic
      models share the same abnormality at that node (e.g., a common shift in
      GABA reversal potential or CRH tone) that is absent in age-matched
      controls; divergent signatures argue against a single unifying mechanism.
    would_support:
    - pathophysiology#Developing brain epileptic network hyperexcitability
    - pathophysiology#Heterogeneous developmental brain etiologies

- discussion_id: gap_iess_rodent_model_human_fidelity
  prompt: >-
    Do rodent models of infantile spasms (ARX interneuronopathy mice and the
    CRH/stress model) faithfully reproduce the human syndrome, given that these
    models generate spasm-like or limbic events but do not clearly reproduce
    human hypsarrhythmia or the human developmental timing window?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Developing brain epileptic network hyperexcitability
  rationale: >-
    The mechanistic case for the excitation-inhibition (ARX interneuronopathy)
    and stress/CRH arms rests largely on rodent models, yet their fidelity to
    human IESS is uncertain. The CRH model produces only limbic seizures rather
    than the classic epileptic (flexion) spasms, and no rodent model
    convincingly reproduces the human hypsarrhythmic EEG signature or the
    tightly age-restricted human window. This is a HUMAN_MODEL_MISMATCH rather
    than a plain knowledge gap: model-system evidence EXISTS, but its
    translational validity is the open question. Resolving it matters because
    the CRH model is the principal mechanistic rationale offered for hormonal
    (ACTH) therapy, and the ARX model underpins the interneuronopathy account of
    the syndrome.
  evidence:
  - reference: PMID:23312951
    reference_title: "Basic mechanisms of catastrophic epilepsy--overview from animal models."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      The stress theory of spasms yielded the corticotropin releasing hormone (CRH)-induced model, which showed the higher proconvulsant potency of CRH in developing rats, although only limbic seizures were observed.
    explanation: >-
      Explicitly notes that the CRH model reproduces only limbic (not classic
      flexion) seizures, the core of the model-to-human mismatch.
  - reference: PMID:23312951
    reference_title: "Basic mechanisms of catastrophic epilepsy--overview from animal models."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      two genetic mouse models of interneuronopathies with infantile spasms due to loss of function of the aristaless X-linked homeobox-related gene (ARX).
    explanation: >-
      Identifies the ARX interneuronopathy mouse models whose fidelity to human
      hypsarrhythmia and the human developmental window remains to be
      established.
  proposed_experiments:
  - experiment_id: exp_iess_model_eeg_phenotype_concordance
    name: Model-to-human EEG and developmental-window concordance study
    description: >-
      Systematically compare long-term video-EEG from ARX and CRH rodent models
      against human IESS, scoring for a hypsarrhythmia-equivalent interictal
      pattern, epileptic-spasm (rather than limbic-seizure) semiology, and the
      developmental timing of onset and offset relative to human infancy.
    experiment_type:
      preferred_term: cross-species electroclinical concordance experiment
    readouts:
    - name: Hypsarrhythmia-equivalent EEG signature
      target: pathophysiology#Developing brain epileptic network hyperexcitability
      biological_processes:
      - preferred_term: trans-synaptic signaling
        term:
          id: GO:0099537
          label: trans-synaptic signaling
        modifier: ABNORMAL
      assays:
      - preferred_term: continuous video-EEG recording
      direction: POSITIVE
    controls:
    - name: Age-matched non-epileptic animals
      description: Littermate controls recorded across the equivalent developmental window.
    decision_criterion: >-
      Model fidelity is supported only if a model reproduces a
      hypsarrhythmia-equivalent interictal EEG pattern together with genuine
      epileptic-spasm semiology within a developmentally restricted window
      analogous to human infancy; absence of the hypsarrhythmic signature keeps
      the mechanistic inference model-limited.
    would_support:
    - pathophysiology#Developing brain epileptic network hyperexcitability

- discussion_id: gap_iess_early_cessation_disease_modifying
  prompt: >-
    Is rapid cessation of spasms and hypsarrhythmia after first-line therapy
    itself disease-modifying for neurodevelopment, or is it mainly a marker of a
    milder underlying etiology that would have had a better developmental
    trajectory regardless?
  kind: OPEN_QUESTION
  status: OPEN
  attaches_to:
  - pathophysiology#Developmental and epileptic encephalopathy burden
  - treatments#Hormonal therapy with ACTH or high-dose prednisolone
  rationale: >-
    Observational data consistently associate shorter lead-time to effective
    treatment and early spasm control with better developmental outcome, which
    is often read as evidence that the epileptic encephalopathy itself drives
    developmental harm and that stopping it early rescues development. But
    because etiology strongly confounds both treatment response and baseline
    developmental potential, the association is equally compatible with early
    responders simply having milder underlying brain disease. Distinguishing a
    causal disease-modifying effect from a prognostic marker is decision-relevant:
    it determines whether aggressive early treatment escalation changes long-term
    outcome or only changes the seizure course.
  evidence:
  - reference: PMID:30236380
    reference_title: "Vigabatrin with hormonal treatment versus hormonal treatment alone (ICISS) for infantile spasms: 18-month outcomes of an open-label, randomised controlled trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Increasing lead-time to treatment was associated with lower VABS scores
    explanation: >-
      Establishes the lead-time-to-treatment association with developmental
      outcome that motivates, but does not by itself resolve, the
      disease-modifying-versus-marker question.
  - reference: PMID:30236380
    reference_title: "Vigabatrin with hormonal treatment versus hormonal treatment alone (ICISS) for infantile spasms: 18-month outcomes of an open-label, randomised controlled trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Initial control of spasms between days 14 and 42 of treatment was associated with higher mean VABS scores at 18 months
    explanation: >-
      Shows the early-cessation/outcome association whose causal versus
      prognostic interpretation is the open question.
  proposed_experiments:
  - experiment_id: exp_iess_etiology_stratified_leadtime_analysis
    name: Etiology-stratified lead-time and outcome analysis
    description: >-
      Using a prospective IESS cohort with uniform etiologic workup, test
      whether the association between early electroclinical response and
      developmental outcome persists WITHIN etiologic strata (e.g., within TSC,
      within trisomy 21, within unknown-etiology cases) and after adjustment for
      baseline development, rather than being explained by etiology differences
      between fast and slow responders.
    experiment_type:
      preferred_term: etiology-stratified prospective cohort analysis
    readouts:
    - name: Developmental outcome within etiologic strata
      target: pathophysiology#Developmental and epileptic encephalopathy burden
      assays:
      - preferred_term: standardized developmental assessment
      direction: POSITIVE
    controls:
    - name: Etiology-matched slow/non-responders
      description: >-
        Within each etiologic stratum, compare early responders against
        matched slow or non-responders.
    decision_criterion: >-
      A disease-modifying effect is supported if earlier spasm cessation
      predicts better developmental outcome WITHIN etiologic strata and after
      baseline-development adjustment; if the association collapses once etiology
      and baseline are controlled, early cessation is better interpreted as a
      prognostic marker.
    would_support:
    - pathophysiology#Developmental and epileptic encephalopathy burden
datasets:
- accession: geo:GSE215362
  title: Dual developmental effects of ARX poly-alanine mutations in human cortical excitatory and inhibitory neurons
  description: Infantile spasms (IS), a severe childhood epilepsy with an incidence of 1.6–4.5 per 10,000 live births, often lead to lifelong intellectual disability. Up to 5% of affected males carry mutations in the Aristaless-related homeobox (ARX) gene. The lack of human-specific models for developmental epilepsy limits progress, making organoids a promising alternative. We use human cortical (CO) and ganglionic eminence organoids (GEO) to model poly-alanine expansion (PAE) mutations in ARX. PAE mutations increase cortical progenitor proliferation and accelerate early cortical development.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: BULK_RNA_SEQ
  sample_count: 24
  publication: PMID:41422506
  notes: Identified by GEO DataSets index search for Infantile Spasms (scripts/discover_datasets.py); accession and metadata verified against NCBI E-utilities on 2026-07-31. Title, sample count, and organism are GEO's own values.
- accession: geo:GSE84585
  title: Remodeling of synaptic transmission genomic fabrics in the hypothalamic arcuate nucleus of a rat female model of infantile spasms
  description: We profiled the whole transcriptomes of female rat hypothalamic arcuate nuclei to determine the remodeling of the genomic fabrics responsible for the glutamatergic, GABAergic, dopaminergic, cholinergic and serotonergic transmission in epilepsy and recovery following different treatments. The rats were prenatally exposed (G15) to betamethasone (or just saline for control) followed by repeated adiministration of N-Methyl-D-Aspartic acid (NMDA) on postnatal days 12, 13 and 15 which triggered infantile spasms.
  organism:
    preferred_term: rat
    term:
      id: NCBITaxon:10116
      label: Rattus norvegicus
  data_type: MICROARRAY
  sample_count: 20
  publication: PMID:29636502
  notes: Identified by GEO DataSets index search for Infantile Spasms (scripts/discover_datasets.py); accession and metadata verified against NCBI E-utilities on 2026-07-31. Title, sample count, and organism are GEO's own values.
📚

References & Deep Research

Deep Research

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1. Disease Information
claude-opus-4-8[1m] 12 citations 2026-07-10T17:31:57.093100

1. Disease Information

Overview. Infantile spasms (IS) is an age-specific epileptic encephalopathy of infancy classically defined by a triad of (1) epileptic/infantile spasms, (2) a characteristic chaotic interictal EEG pattern called hypsarrhythmia, and (3) developmental arrest or regression. When all three are present the condition has historically been called West syndrome, first described by William James West in 1841 in his own son. The 2022 ILAE nosology renamed and broadened the entity to Infantile Epileptic Spasms Syndrome (IESS), which requires epileptic spasms but does not require hypsarrhythmia, recognizing that spasms and developmental impairment can occur with atypical or absent hypsarrhythmia (According to PubMed — Zuberi et al., Epilepsia 2022, PMID 35503712, DOI; Pavone et al., Neurol Sci 2020, PMID 32827285, DOI).

The 2020 comprehensive review states the classical definition directly: "the classical triad of (1) infantile spasms; (2) hypsarrhythmia, and (3) developmental arrest or regression as 'West syndrome'" and notes it is "currently regarded as a spectrum of disorders: the so-called infantile spasm syndrome (ISs), in association with other causal factors, including structural, infectious, metabolic, syndromic, and immunologic events, all acting on a genetic predisposing background" (PMID 32827285, DOI).

Key identifiers. - MONDO: MONDO:0018097 (infantile spasms / West syndrome) — verified via OLS. - HPO (phenotype): HP:0012469 Infantile spasms; HP:0011097 Epileptic spasm. - OMIM: No single OMIM number for the syndrome overall; genetically defined forms use "Developmental and epileptic encephalopathy" (DEE) series entries. The X-linked ARX-related form maps to OMIM 308350 (EIEE1/DEE1); many others in the DEE series (e.g., CDKL5, STXBP1, SPTAN1). - ICD-10: G40.4 (other generalized epilepsy and epileptic syndromes; West syndrome). ICD-11: 8A62 (Infantile epileptic spasms syndrome / epileptic spasms). - MeSH: D013036 "Spasms, Infantile" (UMLS CUI C0037769, "West syndrome"). - Orphanet: ORPHA:3451 (West syndrome). - NBO: NBO:0000734 infantile spasm.

Data derivation. Aggregate disease-level resources (OMIM, Orphanet, ILAE syndrome definitions) plus multicenter prospective cohorts (National Infantile Spasms Consortium; ICISS trial). Individual-patient/EHR-derived data exist chiefly through registries and consortium cohorts rather than routine EHR mining.

Synonyms: West syndrome; infantile spasms; epileptic spasms; infantile epileptic spasms syndrome (IESS, the current ILAE term); "salaam attacks/seizures" (historical, from the flexor posture); jackknife/flexion spasms; generalized flexion epilepsy (historical, Gibbs). Note the ILAE distinction: infantile spasms denotes onset <1 year in the classic window; epileptic spasms is the seizure semiology term, which can occur beyond infancy.

2. Etiology

IESS is etiologically heterogeneous — a final common phenotype reached by many upstream insults acting on the developing brain during a critical window (typically 3–12 months). The most useful etiologic framework is the ILAE structural/genetic/metabolic/infectious/immune/unknown scheme.

Distribution of causes. The 2024 genetics review summarizes: "broadly, 60% of cases are thought to be structural, metabolic or infectious in nature, with the remainder genetic or of unknown cause" (Snyder et al., Genes 2024, PMID 38540325, DOI). Historically ~60–70% are "symptomatic" (identifiable cause) and ~30–40% "cryptogenic/unknown," though modern genetic testing steadily shrinks the unknown fraction.

Structural causes: - Tuberous sclerosis complex (TSC) — the single most recognizable cause (~10–25% of symptomatic IS). TSC affects "approximately 1 per 6000–10,000 individuals" and "the pediatric neurologist is often responsible for making the initial diagnosis when the affected individual presents with infantile spasms or another early-onset epilepsy syndrome" (Islam, Semin Pediatr Neurol 2021, PMID 33892851, DOI). - Malformations of cortical development — focal cortical dysplasia (FCD type II), hemimegalencephaly, lissencephaly, polymicrogyria. In a surgical IESS cohort, "a genetic diagnosis was achieved in 47 children (80% of cohort)," with germline variants in 46% and brain somatic (mosaic) variants in 36%, and mTOR-pathway/SLC35A2-related MOGHE being major causes (Coleman et al., Brain Commun 2025, PMID 39926610, DOI). - Hypoxic-ischemic encephalopathy (HIE), perinatal stroke, periventricular leukomalacia, intracranial hemorrhage, CNS infection sequelae, trauma.

Metabolic causes: pyridoxine (vitamin B6)-dependent epilepsy (ALDH7A1), pyridoxal-5′-phosphate deficiency (PNPO), biotinidase deficiency, PKU (untreated), mitochondrial disorders, nonketotic hyperglycinemia, Menkes disease, congenital disorders of glycosylation, glucose transporter-1 (GLUT1/SLC2A1) deficiency.

Infectious causes: congenital CMV (most common infectious cause), congenital Zika, rubella, toxoplasmosis, herpes, bacterial meningitis/encephalitis sequelae.

Risk factors: prematurity, perinatal asphyxia, low birth weight, structural brain injury, family history of TSC or a monogenic DEE, chromosomal syndromes (esp. Down syndrome). Male predominance is modest (~55–60% male).

Protective factors: In TSC specifically, preemptive/preventive antiseizure treatment is protective. The EPISTOP trial showed vigabatrin started on the basis of epileptiform EEG (before clinical seizures) "reduced the risk of clinical seizures (OR = 0.21, p = 0.032), drug-resistant epilepsy (OR = 0.23, p = 0.022), and infantile spasms (OR = 0, p < 0.001)" (Kotulska et al., Ann Neurol 2021, PMID 33180985, DOI). No robust dietary/lifestyle protective factors are established for non-TSC IS. There are no well-validated protective germline variants.

Gene–environment interaction. The prevailing model is a genetic predisposing background on which structural/metabolic/infectious insults act (PMID 32827285). Somatic mosaicism (a "genetic" lesion confined to brain arising during development) is itself a gene×developmental-timing interaction, and a "two-hit" germline+somatic mechanism was documented in the surgical cohort (PMID 39926610).

3. Phenotypes

Core seizure phenotype — epileptic/infantile spasms (HP:0011097 / HP:0012469): sudden, brief (0.5–2 s) symmetric contractions, typically flexor, extensor, or mixed flexor-extensor, characteristically occurring in clusters (dozens to hundreds/day), often on awakening. Onset 3–12 months (peak 4–7 months). Frequency: near-universal by definition.

Hypsarrhythmia (EEG sign; ~82% of cohort): The National Infantile Spasms Consortium found "Eighty-two percent of patients had hypsarrhythmia, but this was not associated with gender, mean age, preexisting developmental delay or epilepsy, etiology, or response to first-line therapy" (Demarest et al., Epilepsia 2017, PMID 29105055, DOI). Suggested term: HP:0002521 Hypsarrhythmia.

Developmental impairment / regression (HP:0001263 Global developmental delay; HP:0002376 Developmental regression): developmental arrest or regression (loss of social smile, visual attention, motor milestones) is a defining feature; long-term intellectual disability is frequent.

Associated/downstream phenotypes: - Intellectual disability (HP:0001249) — majority; often moderate-severe. - Autism spectrum features (HP:0000717) — elevated risk, esp. TSC. - Evolution to other epilepsies, notably Lennox-Gastaut syndrome and focal epilepsy (HP:0002123 Generalized myoclonic seizures; HP:0002133 Status epilepticus in some). - Visual inattention/cortical visual impairment (HP:0100704 / HP:0000618). - Microcephaly (HP:0000252) when secondary to structural/genetic cause. - Hypotonia (HP:0001252).

Severity & course: Severe by definition; developmentally the trajectory strongly depends on etiology and lead time to effective treatment (see §8, §11). Cryptogenic/unknown-cause cases with normal pre-onset development and rapid response have the best cognitive outcomes.

Quality-of-life impact: Profound — combined seizure burden plus developmental/behavioral disability imposes very high caregiver burden and lifelong dependency in many. (Disease-specific validated QoL data are limited; ICISS used the Vineland Adaptive Behaviour Scales as the developmental outcome — see §11.)

4. Genetic / Molecular Information

Scale of genetic contribution. "Over 28 copy number variants and 70 single gene pathogenic variants related to IESS have been discovered to date," with commonly reported etiologies including trisomy 21 and single-gene variants (Snyder et al., PMID 38540325, DOI).

Major causal genes (gene symbol / HGNC / mechanism): - TSC1 (HGNC:12362) & TSC2 (HGNC:12363) — loss of function → mTORC1 hyperactivation (mTORopathy). TSC2 more severe. (PMID 33892851) - ARX (HGNC:18060; Xp21.3; OMIM 308350) — X-linked interneuronopathy; polyalanine expansions and LoF; classic monogenic IS model. - CDKL5 (HGNC:11411; X-linked) — DEE with early spasms. - STXBP1 (HGNC:11444) — synaptic vesicle release; haploinsufficiency. - SPTAN1, GRIN1, GRIN2B, SCN1A, SCN2A, SCN8A, KCNQ2, STK39, DNM1, GABRB3, FOXG1, MEF2C, CDKL5, SLC35A2, MTOR, AKT3, PIK3CA, DEPDC5, TSC1/2 (structural/mosaic mTOR pathway). SLC35A2 somatic variants define MOGHE (mild malformation of cortical development with oligodendroglial hyperplasia). - Chromosomal: Trisomy 21 (Down syndrome; strongest chromosomal association), 1p36 deletion, Miller-Dieker (17p13.3, PAFAH1B1/LIS1), 15q duplication, Pallister-Killian.

Variant classes: missense, nonsense, frameshift, splice-site, CNVs/deletions, polyalanine tract expansions (ARX), and brain-restricted somatic mosaic variants (mTOR pathway, SLC35A2). Classification per ACMG/AMP; deposited in ClinVar/DECIPHER.

Somatic vs germline. Landmark finding in surgical IESS: "Germline pathogenic variants were identified in 27/59 (46%)… Pathogenic brain somatic variants were identified in 21/59 (36%)… Somatic mosaicism was a major cause of focal cortical dysplasia type II/hemimegalencephaly (81%) and mild malformation of cortical development with oligodendroglial hyperplasia (100%)" (Coleman et al., PMID 39926610, DOI).

Functional consequences: convergent themes — (i) mTOR pathway hyperactivation (TSC1/2, DEPDC5, MTOR, PIK3CA, AKT3); (ii) GABAergic interneuron dysfunction / interneuronopathy (ARX); (iii) synaptic/ion-channel dysfunction (STXBP1, SCN, KCNQ2, GRIN).

Epigenetics / modifiers: SLC35A2 (glycosylation) and MOGHE illustrate a distinct mechanistic class. Formal modifier-gene and methylation data are limited; the diverse genetic background is itself thought to modify penetrance of structural insults (PMID 32827285).

Diagnostic yield. Trio exome/genome and CMA give the highest yields; up to 80% in structurally-defined surgical cohorts (PMID 39926610), lower (~30–40%) in unselected IS.

5. Environmental Information

  • Perinatal/environmental insults: hypoxia-ischemia, prematurity, perinatal stroke, hypoglycemia, kernicterus, trauma, CNS infection.
  • Infectious agents: congenital CMV (NCBITaxon:10359) is the leading infectious cause; also congenital Zika virus (NCBITaxon:64320), rubella, Toxoplasma gondii, HSV, and bacterial meningitis sequelae.
  • Toxins/lifestyle: No established causal lifestyle exposure. Historically, IS was linked to whole-cell pertussis vaccine, but controlled studies attribute this to coincidental timing (onset window coincides with immunization schedule), not causation. Vitamin B6 (pyridoxine) dependency/deficiency is a treatable metabolic mimic to exclude.

6. Mechanism / Pathophysiology

IS is a developmental-window disorder: diverse insults converge on age-specific network dysfunction during a period of rapid synaptogenesis, myelination, and GABAergic maturation. No single unifying mechanism explains all cases; several complementary models are supported by animal work.

Molecular pathways: - mTOR (mechanistic target of rapamycin) hyperactivation — the best-defined pathway (TSC1/2 → mTORC1 disinhibition). "the identification of the responsible genes and gene products forming the mechanistic target of rapamycin complex… has inspired the search for targeted interventions" (PMID 33892851). Suggested GO: GO:0032008 positive regulation of TOR signaling; GO:0038202 TORC1 signaling. - Stress axis / CRH hypothesis — corticotropin-releasing hormone as an endogenous convulsant in the immature brain, motivating ACTH/steroid efficacy. The CRH model "showed the higher proconvulsant potency of CRH in developing rats" (Galanopoulou, Brain Dev 2013, PMID 23312951, DOI). Proposed mechanism for ACTH: suppression of CRH via negative feedback and melanocortin receptor signaling. GO: GO:0051458 corticotropin secretion. - GABAergic interneuronopathy (ARX) — impaired tangential migration/function of cortical interneurons → excitation–inhibition imbalance. GABA also explains vigabatrin efficacy (irreversible GABA-transaminase inhibitor → ↑GABA). GO: GO:0021853 cerebral cortex GABAergic interneuron migration; CHEBI: GABA CHEBI:16865. - Cortical–subcortical (brainstem) network dysfunction — disruption of cortical–brainstem communication implicated in the spasm generator (PMID 23312951).

Cellular processes / cell types: - Cortical GABAergic interneurons (CL:0000617 GABAergic neuron) — dysfunction/interneuronopathy. - Cortical excitatory pyramidal neurons (CL:0000598 pyramidal neuron). - Dysmorphic neurons / balloon cells in FCD II/TSC tubers (mTOR-driven). - Oligodendroglial hyperplasia in MOGHE (SLC35A2). - Neuroinflammation and abnormal neuronal migration/proliferation contribute (PMID 23312951).

Causal chain (representative, mTOR/structural): genetic or somatic mTOR-activating lesion → abnormal cortical cytoarchitecture (tubers/dysplasia, dysmorphic neurons) → aberrant excitatory–inhibitory network with immature-brain-specific hyperexcitability → epileptic spasms + hypsarrhythmia during the critical developmental window → epileptic encephalopathy disrupting normal development → developmental arrest/regression and later epilepsy (LGS/focal).

Causal chain (stress/CRH model): brain insult → dysregulated CRH/HPA-axis signaling in immature limbic/brainstem circuits → age-specific spasm generation → ACTH/steroid feedback suppresses CRH → clinical response (PMID 23312951).

Anatomical/subcellular: cerebral cortex (UBERON:0000956), brainstem, subcortical structures; subcellular convergence on the lysosome/mTORC1 signaling hub, synaptic vesicle machinery, and ion channels.

7. Anatomical Structures Affected

  • Primary organ: brain (UBERON:0000955) — cerebral cortex (UBERON:0000956), often with subcortical/brainstem network involvement.
  • Body system: central nervous system (UBERON:0001017).
  • Tissue/cell level: cortical gray matter; GABAergic interneurons (CL:0000617), pyramidal neurons (CL:0000598), dysmorphic neurons/balloon cells (mTORopathy), oligodendrocytes (CL:0000128; MOGHE).
  • Subcellular: mTORC1 signaling complex (lysosomal surface; GO CC GO:0031931 TORC1 complex), synapse (GO:0045202), plasma-membrane ion channels.
  • Localization/lateralization: generalized network dysfunction (bilateral hypsarrhythmia) but frequently arises from a focal/lateralized structural lesion (unilateral FCD, hemimegalencephaly) — a key point because focal lesions are surgically treatable. Asymmetric hypsarrhythmia suggests an underlying focal lesion.

8. Temporal Development

  • Onset: infancy, typically 3–12 months (peak 4–7 months); onset >2 years is atypical. Onset pattern: subacute emergence of spasm clusters, often initially mistaken for colic, startle, or reflux — contributing to diagnostic delay.
  • Course/progression: an epileptic encephalopathy — the epileptic activity itself contributes to developmental deterioration beyond the underlying etiology (ILAE DEE concept; PMID 35503712). Spasms/hypsarrhythmia often self-resolve by age 3–5 years but frequently evolve into other epilepsies (Lennox-Gastaut syndrome, focal epilepsy).
  • Critical period / lead time. Time to effective treatment is prognostically decisive. In ICISS 18-month follow-up: "Increasing lead-time to treatment was associated with lower VABS scores… and worse epilepsy outcomes (p=0.023)," and "Initial control of spasms between days 14 and 42 of treatment was associated with higher mean VABS scores at 18 months (79.1 vs 63.2… p<0.001)" (O'Callaghan et al., Lancet Child Adolesc Health 2018, PMID 30236380, DOI). Smartphone video capture shortened lead time: video-captured cases were "diagnosed and started treatment 17 days earlier" with "a 25% greater response to initial standard treatment" (Rao et al., J Pediatr 2023, PMID 36931494, DOI).
  • Remission: treatment-induced (hormonal/vigabatrin) is the goal; spontaneous remission of spasms occurs but with poor developmental outcome if untreated.

9. Inheritance and Population

Epidemiology. Incidence approximately 2–5 per 10,000 live births (roughly 0.25–0.42 per 1,000); prevalence in childhood on the order of 1.5–2 per 10,000. IS accounts for a large share of epilepsy with onset in the first year. (Orphanet ORPHA:3451; PMID 32827285.)

Inheritance patterns (etiology-dependent): - Autosomal dominant: TSC1/TSC2 (though ~2/3 of TSC are de novo), STXBP1, many DEE genes (usually de novo dominant). - X-linked: ARX (males affected; OMIM 308350), CDKL5. - Autosomal recessive: several metabolic causes (ALDH7A1, PNPO, biotinidase). - Chromosomal/sporadic: trisomy 21, CNVs — usually de novo. - Mosaic/somatic: brain-restricted mTOR/SLC35A2 variants (not heritable, not in blood). - Multifactorial: structural-acquired cases on a genetic background.

Penetrance/expressivity: highly variable; TSC shows near-complete penetrance but markedly variable expressivity (PMID 33892851). No genetic anticipation (except insofar as ARX polyalanine tracts). Germline mosaicism documented for TSC (recurrence risk counseling implication). Consanguinity increases recessive metabolic causes. Carrier frequency relevant for recessive metabolic forms.

Demographics: slight male predominance (~55–60%). No strong ethnic predilection overall; specific founder variants exist for particular metabolic genes in isolated populations. Geographic variation in etiology (e.g., higher perinatal-injury and infectious causes in resource-limited settings; PMID 35503712 gives guidance for resource-limited diagnosis).

10. Diagnostics

Cornerstone: EEG demonstrating hypsarrhythmia (high-amplitude, chaotic, asynchronous slow waves with multifocal spikes) — best captured on sleep/overnight or video-EEG, as hypsarrhythmia may be present only in sleep. Ictal EEG during a spasm shows the electrodecremental response. Note IESS can be diagnosed without hypsarrhythmia (PMID 35503712, 29105055).

Home video is increasingly a first diagnostic step — smartphone capture significantly shortens time to EEG, diagnosis, and treatment (Rao et al., PMID 36931494, DOI).

Neuroimaging: brain MRI (structural cause in a large fraction — tubers, FCD, HIE, malformation); may require repeat/high-resolution MRI. PET/SPECT for surgical localization of subtle lesions.

Etiologic workup: - Genetic testing: chromosomal microarray (CMA), trio whole-exome/whole-genome sequencing (highest yield), targeted epilepsy gene panels; testing of resected brain tissue for somatic/mosaic variants when blood is negative and a lesion is resected (PMID 39926610). - Metabolic screen: plasma/CSF amino acids, urine organic acids, lactate, ammonia, biotinidase, and a pyridoxine (B6) / pyridoxal-5′-phosphate trial to exclude treatable vitamin-responsive epilepsies; CSF glucose (GLUT1). - Infection: congenital CMV (urine/saliva PCR, dried blood spot), TORCH. - TSC evaluation: skin exam (Wood's lamp), echocardiogram, renal imaging, TSC1/TSC2 sequencing.

Diagnostic criteria: ILAE 2022 IESS definition (mandatory features, cautionary alerts, exclusionary features tabulated) (PMID 35503712).

Differential diagnosis: benign myoclonus of early infancy, benign infantile sleep myoclonus, Sandifer syndrome/GERD, colic, startle/hyperekplexia, tonic seizures, other early DEEs (Ohtahara syndrome, EIMFS).

11. Outcome / Prognosis

Overall. Guarded. IESS is "a devastating developmental epileptic encephalopathy" (PMID 38540325) with high rates of long-term intellectual disability, ongoing epilepsy, and autism. Prognosis is dominated by (1) etiology and (2) speed/effectiveness of spasm control.

Developmental outcome quantified. In ICISS at 18 months, mean VABS composite ~73; crucially, achieving early spasm cessation raised mean VABS from 63.2 to 79.1 (p<0.001), and freedom from seizures at 18 months was far more common in early responders (PMID 30236380, DOI).

Evolution: many progress to Lennox-Gastaut syndrome or drug-resistant focal epilepsy. Mortality is elevated relative to the general pediatric population, driven mainly by the underlying etiology and refractory epilepsy (including SUDEP risk).

Prognostic factors (better outcome): unknown/cryptogenic etiology with normal pre-onset development; short lead time to treatment; rapid and sustained response; absence of hypsarrhythmia relapse. (Worse: identified severe structural/genetic etiology, pre-existing developmental delay, long lead time, relapse.)

12. Treatment

First-line standard therapies (the NISC cohort showed first-line standard therapy is by far the strongest determinant of response — vigabatrin OR 5.2, prednisolone OR 8.0, ACTH OR 10.2; PMID 29105055, DOI):

  1. Hormonal therapy — ACTH (adrenocorticotropic hormone / tetracosactide/cosyntropin depot) or oral corticosteroids (high-dose prednisolone). MAXO: MAXO:0000058/pharmacotherapy NCIT:C15986; agents — corticotropin, prednisolone (CHEBI:8382).
  2. Vigabatrin (irreversible GABA-transaminase inhibitor; ↑GABA) — drug of choice for TSC-associated IS, and effective generally. Risk: irreversible peripheral visual-field constriction/retinal toxicity requiring monitoring. Vigabatrin CHEBI:63638.

Combination therapy. ICISS demonstrated hormonal + vigabatrin > hormonal alone for early spasm cessation: "no spasms were witnessed in 133 (72%) of 186 patients on hormonal therapy with vigabatrin compared with 108 (57%) of 191 patients on hormonal therapy alone (difference 15.0%… p=0.002)" (O'Callaghan et al., Lancet Neurol 2017, PMID 27838190, DOI). However, the developmental advantage did not persist at 18 months (mean VABS 73.9 vs 72.7, p=0.55) (PMID 30236380).

Comparative efficacy (meta-analysis). "There was no significant difference in the effectiveness of oral corticosteroids and ACTH… Low-dose ACTH had similar effectiveness… but conferred a lower risk of AEs… ACTH was more beneficial in controlling spasms than vigabatrin (RR = 1.31…) for patients without tuberous sclerosis complex" (Guang et al., Front Neurol 2022, PMID 35222241, DOI).

Other/second-line: ketogenic diet (MAXO: MAXO:0000010 dietary intervention / ketogenic diet); topiramate, zonisamide, valproate, pyridoxine (for B6-responsive forms), sulthiame. Epilepsy surgery — resection of a focal structural lesion (FCD, tuber, hemimegalencephaly → hemispherectomy) can be curative in lesional/mosaic cases (PMID 39926610). MAXO: surgical procedure MAXO:0000004.

Precision/targeted therapy: mTOR inhibitors (everolimus, sirolimus) for TSC-related epilepsy (mechanism-matched to mTORC1 hyperactivation); emerging gene-directed approaches for monogenic DEEs (PMID 38540325, 33892851). Everolimus (CHEBI:68478).

Treatment strategy: rapid diagnosis → prompt first-line standard therapy (hormonal ± vigabatrin; vigabatrin-first in TSC) → early EEG reassessment for response → escalate to ketogenic diet, alternative ASMs, or surgery/precision therapy if refractory. Speed matters (§8, §11).

13. Prevention

  • Primary/preemptive prevention in TSC: the standout evidence — EPISTOP preventive vigabatrin (started on epileptiform EEG before clinical seizures) reduced clinical seizures, drug-resistant epilepsy, and abolished infantile spasms (OR = 0, p < 0.001) with no related adverse events (Kotulska et al., PMID 33180985, DOI). This has driven surveillance-EEG protocols in infants with known TSC.
  • Secondary prevention (early detection): caregiver and pediatrician education (recognizing spasm clusters, home video), rapid-access EEG pathways to shorten lead time and improve outcomes (PMID 36931494, 30236380).
  • Etiology-directed: newborn screening for treatable metabolic causes (biotinidase, PKU); congenital-infection prevention (CMV hygiene counseling, rubella vaccination).
  • Genetic counseling: for TSC and monogenic DEEs — recurrence-risk assessment including germline mosaicism; prenatal/preimplantation options where a familial variant is known.
  • Tertiary prevention: aggressive spasm control to limit encephalopathic developmental damage; developmental surveillance and early intervention.

14. Other Species / Natural Disease

Naturally occurring West syndrome/IESS as such is essentially a human developmental syndrome; there is no well-characterized spontaneous animal equivalent. The relevant cross-species work is in model organisms (§15). Conserved disease genes (TSC1/TSC2, ARX, mTOR pathway) have clear orthologs in mouse, rat, and zebrafish (NCBITaxon: mouse 10090, rat 10116, zebrafish 7955), enabling comparative study of mTORopathy and interneuronopathy mechanisms.

15. Model Organisms

Multiple complementary rodent models exist, each capturing part of the phenotype (reviewed by Galanopoulou, Brain Dev 2013, PMID 23312951, DOI):

  • CRH-induced model — tests the stress hypothesis; CRH is more proconvulsant in developing rats, though it produces limbic (not classic flexion) seizures — a noted limitation.
  • NMDA model of "emprosthotonic" (flexion) seizures, plus prenatal betamethasone and prenatal stress variants.
  • γ-butyrolactone spasms in a Down syndrome (Ts65Dn) mouse model (trisomy 21 link).
  • Chronic models: the tetrodotoxin (TTX) model and the "multiple-hit" rat model (structural + chronic), which reproduce spasms plus chronic epileptic and cognitive deficits and are used for drug screening.
  • Genetic interneuronopathy models: ARX loss-of-function mice (polyalanine expansion / conditional knockouts) reproduce spasms via GABAergic interneuron dysfunction; TSC conditional knockouts model mTORopathy and respond to rapamycin.

The review frames these as testing distinct proposed mechanisms — "cortical or brainstem dysfunction, disruption of normal cortical-subcortical communications, genetic defects, inflammation, stress, developmental abnormalities" — and notes recent progress toward mechanism-based treatments (mTOR inhibition, carisbamate, etc.) (PMID 23312951).

Model utility & limitations: no single model reproduces the full human triad (spasms + hypsarrhythmia + developmental regression); hypsarrhythmia in particular is difficult to replicate. Models are strongest for testing etiology-specific mechanisms (mTOR, ARX/GABA, stress) and screening candidate therapies. Resources: MGI, RGD, ZFIN, IMPC/KOMP.

Summary of Key Ontology Term Suggestions

Domain Term ID
Disease infantile spasms / West syndrome MONDO:0018097
Phenotype Infantile spasms HP:0012469
Phenotype Epileptic spasm HP:0011097
Phenotype Hypsarrhythmia HP:0002521
Phenotype Global developmental delay HP:0001263
Phenotype Developmental regression HP:0002376
Phenotype Intellectual disability HP:0001249
Cell type GABAergic interneuron CL:0000617
Cell type Pyramidal neuron CL:0000598
Anatomy Cerebral cortex UBERON:0000956
Process TORC1 signaling GO:0038202
Chemical γ-aminobutyric acid (GABA) CHEBI:16865
Chemical Vigabatrin CHEBI:63638
Chemical Prednisolone CHEBI:8382
Chemical Everolimus CHEBI:68478
Treatment Pharmacotherapy NCIT:C15986
Treatment Dietary intervention (ketogenic) MAXO:0000010
Treatment Surgical procedure MAXO:0000004

(Ontology IDs for CHEBI/GO/CL/UBERON above should be re-verified against OAK before curation, per the dismech anti-hallucination SOP; MONDO:0018097 and the HP terms HP:0012469/HP:0011097 were confirmed via OLS during this research.)

Principal References (all retrieved from PubMed)

  1. Zuberi SM et al. ILAE classification and definition of epilepsy syndromes with onset in neonates and infants. Epilepsia. 2022;63(6):1349-1397. PMID 35503712. DOI
  2. Pavone P et al. West syndrome: a comprehensive review. Neurol Sci. 2020;41(12):3547-3562. PMID 32827285. DOI
  3. Snyder HE et al. Genetic Advancements in Infantile Epileptic Spasms Syndrome and Opportunities for Precision Medicine. Genes. 2024;15(3):266. PMID 38540325. DOI
  4. Islam MP. Tuberous Sclerosis Complex. Semin Pediatr Neurol. 2021;37:100875. PMID 33892851. DOI
  5. Coleman M et al. The genetic landscape and classification of infantile epileptic spasms syndrome requiring surgery due to suspected focal brain malformations. Brain Commun. 2025;7(1):fcaf034. PMID 39926610. DOI
  6. O'Callaghan FJK et al. Safety and effectiveness of hormonal treatment versus hormonal treatment with vigabatrin for infantile spasms (ICISS). Lancet Neurol. 2017;16(1):33-42. PMID 27838190. DOI
  7. O'Callaghan FJK et al. Vigabatrin with hormonal treatment versus hormonal treatment alone (ICISS): 18-month outcomes. Lancet Child Adolesc Health. 2018;2(10):715-725. PMID 30236380. DOI
  8. Guang S et al. Hormonal Therapy for Infantile Spasms: A Systematic Review and Meta-Analysis. Front Neurol. 2022;13:772333. PMID 35222241. DOI
  9. Demarest ST et al. The impact of hypsarrhythmia on infantile spasms treatment response (National Infantile Spasms Consortium). Epilepsia. 2017;58(12):2098-2103. PMID 29105055. DOI
  10. Kotulska K et al. Prevention of Epilepsy in Infants with Tuberous Sclerosis Complex in the EPISTOP Trial. Ann Neurol. 2021;89(2):304-314. PMID 33180985. DOI
  11. Galanopoulou AS. Basic mechanisms of catastrophic epilepsy — overview from animal models. Brain Dev. 2013;35(8):748-56. PMID 23312951. DOI
  12. Rao CK et al. The Effect of Smartphone Video on Lead Time to Diagnosis of Infantile Spasms. J Pediatr. 2023;258:113387. PMID 36931494. DOI

Curation notes for the dismech entry. (1) Model IESS as an etiologically heterogeneous DEE with a structural / genetic / metabolic / infectious / unknown etiology axis rather than a single mechanism. (2) The two strongest, most quotable causal chains for pathophysiology nodes are mTORopathy (TSC1/2 → mTORC1 → cortical dysplasia → spasms) and GABAergic interneuronopathy (ARX → interneuron dysfunction → E/I imbalance). (3) The lead-time-to-treatment → developmental-outcome relationship (PMID 30236380) is well-suited to a causal edge with strong human-clinical evidence. (4) Before committing any evidence item, run just fetch-reference PMID:<id> and just validate-references — the abstract quotes above are drawn verbatim from PubMed metadata but must pass the local snippet-substring check, and the CHEBI/GO/CL/UBERON IDs need OAK verification per the NEC/anti-hallucination SOP.

Infantile Spasms Deep Research Fallback ▸

Infantile Spasms Deep Research Fallback

Provider attempts

  • timeout 75s just research-disorder falcon Infantile_Spasms
  • Result: timed out with Recipe research-disorder was terminated by signal 15.
  • timeout 75s just research-disorder openai Infantile_Spasms
  • Result: timed out with Recipe research-disorder was terminated by signal 15.

No provider-generated research artifact was available within the bounded window.

Evidence-backed curation scope

The entry was curated from deterministic generated caches and primary/secondary biomedical sources:

  • Orphadata structured records:
  • ORPHA:697160 Infantile epileptic spasms syndrome, including inheritance, genes, phenotypes, and cross-references.
  • ORPHA:3451 West syndrome legacy exact mapping to MONDO:0018097.
  • PubMed caches:
  • PMID:35503712 ILAE classification and definition of epilepsy syndromes with onset in neonates and infants.
  • PMID:39029407 Danish national IESS epidemiology and outcome cohort.
  • PMID:27838190 ICISS randomized trial of hormonal therapy with or without vigabatrin.
  • PMID:16239177 UKISS randomized trial follow-up comparing hormone treatment and vigabatrin.
  • PMID:31903560 prednisolone/prednisone versus ACTH RCT meta-analysis.
  • PMID:35765990 network meta-analysis of first-line IESS treatments.
  • PMID:22364326 vigabatrin monotherapy review, including mechanism and TSC-specific first-line use.
  • PMID:37736852 current treatment-modality review and West syndrome triad wording.
  • ClinicalTrials.gov caches:
  • clinicaltrials:NCT04302116 vigabatrin plus high-dose prednisolone versus vigabatrin alone.
  • clinicaltrials:NCT04289467 fenfluramine for refractory infantile spasms.

Modeling notes

  • ORPHA:697160 lists the generic HPO root HP:0000707 Abnormality of the nervous system. It is intentionally documented in YAML notes rather than modeled as a phenotype because the entry includes more specific neurologic findings.
  • Treatment modeling emphasizes first-line hormonal therapy, vigabatrin, and combination therapy because these have cached RCT/meta-analysis support.
  • Refractory fenfluramine is represented as an active Phase II clinical trial rather than a standard treatment.