Epilepsy with Myoclonic Absences

Complex MONDO:0019487 Pathograph 11 Show in embeddings browser Epilepsy Neurological Disease

A childhood generalized epilepsy whose defining seizure is an absence that you can see happening. The child stops, as in any absence, but at the same time the shoulders and arms jerk rhythmically about three times a second, and the arms rise steadily as a tonic contraction builds through the seizure. The electroencephalogram shows the same three-per-second generalized spike-wave as childhood absence epilepsy, but here each spike is locked to a muscle jerk that can be recorded on surface electromyography. That motor recruitment is the whole mechanistic interest of the syndrome: the same thalamocortical oscillation that produces a silent stare in one epilepsy drives the motor system in this one, and nobody knows why. Seizures happen many times a day, respond poorly to medication in a substantial minority, and a subset of children deteriorate cognitively or evolve toward Lennox-Gastaut syndrome.

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Mappings
1
Inheritance
7
Pathophys.
6
Phenotypes
3
Gaps
11
Pathograph
2
Genes
6
Medical Actions
4
Differentials
3
References
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Deep Research
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Classifications

Harrison's Part
NEUROLOGIC
🔗

Mappings

MONDO
MONDO:0019487 epilepsy with myoclonic absences
skos:exactMatch MONDO
MONDO:0019487 is the epilepsy with myoclonic absences concept, one of the three childhood generalized epilepsy syndromes recognized by the ILAE.
👪

Inheritance

1
Presumed polygenic, mostly sporadic HP:0003745
No single-gene inheritance pattern is established. Most cases are sporadic, although sibling pairs are reported, and the syndrome sits within the genetic generalized epilepsies whose liability is generally polygenic. A minority of cases are symptomatic, occurring on the background of an identifiable structural or chromosomal abnormality, and those are not heritable in the same sense at all.
Sporadic
Show evidence (2 references)
PMID:24491945 SUPPORT Human Clinical
"To describe the clinical, electroencephalographic features, treatment strategies and outcome in this first case series of two siblings with normal intelligence presenting with EMAs."
Documents familial occurrence in siblings, which is what makes a genetic contribution likely. Marked PARTIAL because two siblings establish familial aggregation, not a mode of inheritance.
PMID:24491945 SUPPORT Human Clinical
"Idiopathic and symptomatic EMAs need to be differentiated from childhood absence epilepsy with myoclonia."
Establishes that the syndrome has both idiopathic and symptomatic forms, which is why no single inheritance statement covers it.
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Discussions and Knowledge Gaps

3
Is epilepsy with myoclonic absences a distinct syndrome, or is it childhood absence epilepsy with a prominent myoclonic accompaniment that happens to have been named separately?
CONTROVERSY UNDER DISCUSSION ema_distinct_syndrome_or_absence_variant
Attached to
pathophysiology#Hypersynchronous Three-Hertz Thalamocortical Spike-Wave Oscillation pathophysiology#Cycle-Locked Recruitment of Motor Output
The syndrome was defined on a seizure type rather than on an etiology, an age, or a gene, and the literature that defined it now describes it as a somewhat controversial entity in those words. The case for distinctness is real: the motor recruitment is not a soft accompaniment but a cycle-by-cycle coupling with a separate progressive tonic component, the sex ratio runs the opposite way to childhood absence epilepsy, drug resistance is commoner, and a subset evolve toward Lennox-Gastaut, which typical absences do not. The case against is equally real: the electroencephalographic discharge is explicitly described as similar to that of childhood absence epilepsy, no distinct genetic or structural basis has been identified, and myoclonic components have since been described across a range of generalized epilepsies with absences, which erodes the specificity of the original defining observation. If myoclonic accompaniments form a continuum, then where this syndrome ends and childhood absence epilepsy with myoclonia begins is a matter of degree, and the boundary is drawn by whoever is holding the electromyography leads. The practical stake is not trivial: the label carries a worse prognosis and a lower threshold for surgical referral, so misassignment in either direction changes what a family is told.
Proposed experiments
Quantitative polygraphic comparison across absence syndromes
exp_ema_quantitative_myoclonus_continuum
Apply identical quantitative electromyographic analysis, measuring burst amplitude, the proportion of discharge cycles carrying a burst, and tonic baseline drift, to unselected children with absence seizures across the syndromes, and test whether the distribution is bimodal, which would support two entities, or continuous, which would support one.
Decision criterion
A bimodal distribution with a gap between myoclonic absences and other absences with myoclonic accompaniment would support distinctness. A continuous distribution would show the boundary is conventional, and the syndrome would be better modeled as a severity region of a spectrum.
Shared versus distinct genetic architecture with childhood absence epilepsy
exp_ema_genetic_architecture_comparison
Compare common-variant liability and rare-variant burden between children meeting criteria for epilepsy with myoclonic absences and children with childhood absence epilepsy, ascertained in the same centres with the same polygraphic protocol.
Decision criterion
A shared genetic architecture would support one spectrum with the motor phenotype as a modifier. A distinguishable architecture would support two entities and would give the syndrome a basis beyond its seizure semiology.
Show evidence (4 references)
PMID:17044728 SUPPORT Other
"epilepsy with myoclonic absences (EMA) stands out as a somewhat controversial entity"
States the controversy in the literature's own words, which is what makes this a curated dispute rather than a curator's doubt.
PMID:17044728 SUPPORT Other
"the sound and evident clinical characteristics on which it was identified some 30 years ago have evolved, mostly as a consequence of changes in the practical management of epilepsies and to the description of myoclonic components in a variety of other generalised epilepsies with absences"
Gives the specific reason the boundary has eroded, namely that the defining feature turned out not to be unique to this syndrome.
PMID:35503717 SUPPORT Other
"generalized epilepsies, comprising three syndromes: childhood absence epilepsy, epilepsy with myoclonic absence, and epilepsy with eyelid myoclonia"
Records the opposing position, that the ILAE currently treats this as one of three distinct childhood generalized syndromes, which is why this entry models it as a syndrome while flagging the dispute.
+ 1 more reference
Why does a three-hertz thalamocortical spike-wave discharge drive rhythmic myoclonus and a building tonic contraction in this syndrome, when the same discharge produces a motionless stare in childhood absence epilepsy?
KNOWLEDGE GAP OPEN ema_why_is_the_motor_system_recruited
Attached to
pathophysiology#Cycle-Locked Recruitment of Motor Output pathophysiology#Hypersynchronous Three-Hertz Thalamocortical Spike-Wave Oscillation
This is the central unexplained fact of the syndrome and it is unusually well-posed, because the confounder is controlled by nature: the oscillation is described as similar in the two conditions, so whatever differs is downstream of it. Several accounts are available and none has been tested against the others. The discharge may involve motor cortex in this syndrome and not in childhood absence epilepsy, which is a straightforward source-localization question that modern high-density recording could answer and apparently has not. The coupling between cortical discharge and corticospinal output may be abnormally strong, which is a corticomuscular coherence question. The tonic component may not share a generator with the jerks at all, since it builds progressively rather than following the three-hertz rhythm, which would suggest a separate brainstem or reticulospinal contribution running in parallel. Or the difference may lie in developmental maturation of descending motor pathways, which would predict that age at onset, later here than in childhood absence epilepsy, is part of the explanation rather than an incidental demographic fact. Answering this would also bear directly on the nosological dispute curated alongside it, because a demonstrated difference in generator would settle the question of whether this is a separate entity.
Proposed experiments
Source localization and corticomuscular coherence across absence syndromes
exp_ema_source_localization_and_corticomuscular_coherence
High-density electroencephalography with simultaneous multi-muscle electromyography during spontaneous seizures in both syndromes, with source reconstruction of the discharge and measurement of corticomuscular coherence, testing whether motor cortex participates in the discharge in myoclonic absences and not in typical absences, and whether the cortex-to-muscle coupling differs in strength.
Decision criterion
Motor cortex participation or stronger corticomuscular coherence specific to myoclonic absences would locate the difference in the cortical generator. Indistinguishable source and coherence would push the explanation subcortically, toward the descending pathways or the brainstem.
Separating the tonic component from the myoclonic component
exp_ema_tonic_component_generator
Analyse the progressive tonic contraction independently of the three-hertz bursts, relating its build-up to discharge features and to brainstem reflex measures, to test whether it is a slow envelope of the same cortical drive or an independently generated phenomenon.
Decision criterion
A tonic component that tracks discharge parameters would indicate a single cortical generator with two output timescales. A tonic component that varies independently and correlates with brainstem measures would establish a second generator, and would explain why this syndrome sits closer than typical absence epilepsy to the tonic-seizure epilepsies it sometimes evolves into.
Show evidence (3 references)
PMID:15737698 SUPPORT Other
"The ictal EEG shows bilateral, synchronous and symmetrical spike and wave discharges repeated at 3 Hz (similar to that observed in typical absences of childhood absence epilepsy) in strict relation with myoclonias recorded on EMG."
Establishes both premises of the gap: the discharge is similar between syndromes, and the motor coupling is strict, so the difference must lie downstream of the oscillation.
PMID:24491945 SUPPORT Human Clinical
"Myoclonic absences (MAs) were characterized by rhythmic, bilateral, synchronous, symmetric 3-Hz spike-wave discharges, associated with EMG myoclonic bursts at 3 Hz, superimposed on a progressively increasing tonic muscle contraction."
Documents that the tonic component is superimposed on rather than rhythmic with the bursts, which is the observation motivating the two-generator hypothesis.
PMID:17044728 SUPPORT Other
"Neurophysiologically, axial hypertonia and rhythmic jerks may be recorded on polygraphic surface electromyogram leads in association with the typical SW discharges"
Confirms that both motor components are measurable with routine polygraphy, which is what makes the proposed experiments feasible rather than aspirational.
The outcome splits sharply according to whether generalized tonic-clonic seizures accompany the myoclonic absences. Are these two different diseases sharing a seizure type, or one disease with a severity gradient?
CONTROVERSY OPEN ema_two_diseases_behind_one_seizure
Attached to
pathophysiology#Drug-Resistant Course with Cognitive Decline in a Subset pathophysiology#Heritable Thalamocortical Susceptibility
The prognostic split is unusually clean for a childhood epilepsy. Children with myoclonic absences as their only seizure type generally respond to combination therapy and do well; children who also have generalized tonic-clonic seizures often persist, deteriorate cognitively, or move toward Lennox-Gastaut syndrome. The two-disease reading takes the associated tonic-clonic seizures as a marker of a different underlying condition, most obviously a symptomatic form with a structural or chromosomal cause that happens to express myoclonic absences among its seizure types; the literature already distinguishes idiopathic from symptomatic forms, which gives this reading a foothold. The one-disease reading takes the tonic-clonic seizures as a severity marker of the same liability, on the grounds that additional seizure types accompany greater severity across the generalized epilepsies generally, and notes that no distinct etiology has actually been demonstrated for the worse-outcome group. A newer case series complicates both by identifying an atonic component as a separate and strong predictor of medication failure, three quarters of that subgroup failing to reach seizure freedom, which suggests the relevant stratification may not be the one the older literature drew. The stake is prognostic honesty: a family told at diagnosis that this syndrome usually responds well to valproate and ethosuximide is being given the statistics of a subgroup their child may not belong to.
Proposed experiments
Etiology-stratified outcome cohort with systematic investigation
exp_ema_etiology_stratified_outcome_cohort
A multicentre cohort in which every child meeting polygraphic criteria receives the same investigation, including high-resolution imaging, chromosomal microarray, and epilepsy gene panel, with outcome recorded against both the presence of generalized tonic-clonic seizures and the presence of an identified etiology and of an atonic component.
Decision criterion
If poor outcome tracks identified etiology rather than seizure co-occurrence, the two-disease reading is supported and the prognosis should be given on etiology. If poor outcome tracks seizure co-occurrence independently of etiology, it is a severity marker within one disease.
Show evidence (4 references)
PMID:15737698 SUPPORT Other
"The evolution is variable and seems to depend on the existence or not of GTCS."
States the prognostic split that this discussion is about.
PMID:17044728 SUPPORT Other
"The more benign cases usually present with MA as the only seizure type, while patients who experience other seizures, especially generalised tonic-clonic seizures, in association with MA may have a less favourable outcome."
Independent statement of the same split, which is what makes it a stable observation rather than one group's impression.
PMID:35770757 SUPPORT Human Clinical
"Of patients with an atonic component, 75% did not achieve seizure freedom with medication alone."
Identifies a different stratifying feature from the one the older literature emphasizes. Marked PARTIAL because ten patients cannot settle which stratification matters, but it is enough to show the question is open.
+ 1 more reference
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Pathophysiology

7
Heritable Thalamocortical Susceptibility
The syndrome behaves like the other genetic generalized epilepsies at this level: a heritable liability to abnormal thalamocortical oscillation, with no single causal gene established and sibling recurrence reported. A subset of children instead have a symptomatic form on the background of a structural or chromosomal abnormality, reaching the same oscillation from a different starting point.
regulation of postsynaptic membrane potential GO:0060078 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal regulation of postsynaptic membrane potential (GO:0060078). GO:0060078 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Downstream
Hypersynchronous Three-Hertz Thalamocortical Spike-Wave Oscillation
Show evidence (1 reference)
PMID:24491945 SUPPORT Human Clinical
"Idiopathic and symptomatic EMAs need to be differentiated from childhood absence epilepsy with myoclonia."
Supports the split between idiopathic and symptomatic forms that this node represents. Marked PARTIAL because it asserts the distinction without characterizing the genetic architecture of the idiopathic arm.
Hypersynchronous Three-Hertz Thalamocortical Spike-Wave Oscillation
The engine of the seizure is the same thalamocortical loop oscillation that produces typical absences, discharging bilaterally, synchronously, and symmetrically at three per second. The literature makes the equivalence explicit, comparing it directly to the discharge of childhood absence epilepsy. Because the oscillation itself is shared, nothing about this node explains what makes the syndrome different; the difference is entirely in what the oscillation is coupled to downstream.
pyramidal neuron CL:0000598 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves pyramidal neuron (CL:0000598). CL:0000598 is a cell type from the Cell Ontology.
Downstream
Cycle-Locked Recruitment of Motor Output
Impairment of Awareness
Show evidence (2 references)
PMID:15737698 SUPPORT Other
"The ictal EEG shows bilateral, synchronous and symmetrical spike and wave discharges repeated at 3 Hz (similar to that observed in typical absences of childhood absence epilepsy) in strict relation with myoclonias recorded on EMG."
States both halves of what this entry turns on: the discharge is the same as in childhood absence epilepsy, and it is in strict temporal relation with the muscle jerks.
PMID:24491945 SUPPORT Human Clinical
"Myoclonic absences (MAs) were characterized by rhythmic, bilateral, synchronous, symmetric 3-Hz spike-wave discharges, associated with EMG myoclonic bursts at 3 Hz, superimposed on a progressively increasing tonic muscle contraction."
Independent polygraphic confirmation of the frequency-matched coupling between the discharge and the muscle bursts.
Cycle-Locked Recruitment of Motor Output
This is the node that makes the syndrome what it is. Each spike-wave cycle is accompanied by a muscle burst at the same three-per-second rate, and the relation is described as strict rather than approximate, which is what distinguishes a driven motor output from an incidental one. Superimposed on the rhythmic jerks is a tonic contraction that builds progressively through the seizure, raising the arms, and it is a separate phenomenon from the jerks rather than their summation. Why the same oscillation engages motor cortex and corticospinal output here and not in childhood absence epilepsy is not known, and is recorded as a knowledge gap.
regulation of postsynaptic membrane potential GO:0060078 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal regulation of postsynaptic membrane potential (GO:0060078). GO:0060078 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Downstream
Rhythmic Myoclonus with Progressive Tonic Contraction
Show evidence (2 references)
PMID:17044728 SUPPORT Other
"Neurophysiologically, axial hypertonia and rhythmic jerks may be recorded on polygraphic surface electromyogram leads in association with the typical SW discharges"
Establishes that both the tonic and the myoclonic components are measurable motor phenomena time-locked to the discharge, which is the content of this node.
PMID:15737698 SUPPORT Other
"Epilepsy with myoclonic absences is characterized clinically by absences accompanied by marked, diffuse, rhythmical myoclonias, often associated with a progressive tonic contraction."
Names the two motor components and their relationship to the absence, which is what this node models.
Impairment of Awareness
The absence itself, produced by the same thalamocortical discharge that produces it in any other absence epilepsy. Impairment is typically partial rather than complete, which combined with the conspicuous motor activity is why these events are sometimes mistaken for something other than seizures.
Downstream
Drug-Resistant Course with Cognitive Decline in a Subset
Show evidence (1 reference)
PMID:17044728 SUPPORT Other
"Myoclonic absences (MA) are described as typical absences with sudden onset and offset that are associated with generalised spike and wave (SW) discharges on the ECG, with distinctive traits."
Establishes the absence component and its abrupt onset and offset, which is the feature shared with typical absences.
Rhythmic Myoclonus with Progressive Tonic Contraction
The visible seizure: rhythmic bilateral jerking of shoulders, arms, and legs at three per second, with the arms rising progressively as axial tone builds. Seizures occur many times a day, which is part of why the syndrome is disabling out of proportion to the individual event. In a substantial minority an atonic component is present instead of or alongside the tonic one, and those children do markedly worse on medication.
Downstream
Myoclonic Absence Status Epilepticus
Drug-Resistant Course with Cognitive Decline in a Subset
Show evidence (2 references)
PMID:15737698 SUPPORT Other
"These seizures occur many times a day."
Documents the seizure frequency that makes this syndrome disabling.
PMID:35770757 SUPPORT Human Clinical
"Of patients with an atonic component, 75% did not achieve seizure freedom with medication alone."
Documents the atonic subgroup and its markedly worse medication response, which is the clinical fact that motivates surgical consideration.
Myoclonic Absence Status Epilepticus
A prolonged state in which the seizure pattern becomes continuous rather than repetitive, reported as the presenting problem in a fifth of one case series. It is worth curating separately because it is easy to miss: a child in this state looks confused and jerky rather than obviously convulsing.
Show evidence (1 reference)
PMID:35770757 SUPPORT Human Clinical
"Ten patients were identified including twins with myoclonic absence status epilepticus. Forty percent had an atonic component, 20% presented with myoclonic absence status epilepticus and 60% had incomplete control of seizures at last follow-up visit."
Quantifies the frequency of status as a presentation, and of incomplete control, in a contemporary series.
Drug-Resistant Course with Cognitive Decline in a Subset
The outcome splits, and it splits along a line that is visible at diagnosis. Children whose only seizure type is the myoclonic absence generally do well on combination therapy. Children who also have generalized tonic-clonic seizures do worse, and a subset deteriorate cognitively or evolve toward Lennox-Gastaut syndrome. Whether that reflects two different diseases wearing the same seizure or one disease with variable severity is unresolved and is curated as a discussion.
Show evidence (2 references)
PMID:17044728 SUPPORT Other
"These patients may experience cognitive deterioration and, in some cases, evolution towards a more severe form of epilepsy, including the Lennox-Gastaut syndrome."
Documents the adverse trajectory that this node represents.
PMID:17044728 SUPPORT Other
"The more benign cases usually present with MA as the only seizure type, while patients who experience other seizures, especially generalised tonic-clonic seizures, in association with MA may have a less favourable outcome."
States the prognostic split and the feature that predicts it, which is what makes the outcome heterogeneity structured rather than random.
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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 Epilepsy with Myoclonic Absences 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

6
Nervous System 3
Generalized tonic-clonic seizure FREQUENT Bilateral tonic-clonic seizure HP:0002069 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Bilateral tonic-clonic seizure (HP:0002069). HP:0002069 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:15737698 SUPPORT Human Clinical
"Associated seizures are present in 2/3 of the cases, the most frequent association being GTCS in 45%."
Reports generalized tonic-clonic seizures in 45 percent of patients with the syndrome, within the FREQUENT band of 30 to 79 percent. The denominator is all patients with the syndrome rather than a poor-outcome-selected subgroup, so the estimate is not circular.
EEG abnormality with three-hertz generalized spike-wave HP:0002353 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is EEG abnormality (HP:0002353). HP:0002353 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:15737698 SUPPORT Other
"The ictal EEG shows bilateral, synchronous and symmetrical spike and wave discharges repeated at 3 Hz (similar to that observed in typical absences of childhood absence epilepsy) in strict relation with myoclonias recorded on EMG."
Describes the electrographic pattern and its indistinguishability from childhood absence epilepsy in isolation.
Cognitive deterioration Intellectual disability HP:0001249 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Intellectual disability (HP:0001249), qualified as course progressive. HP:0001249 is a phenotype from the Human Phenotype Ontology.
Course: PROGRESSIVE
Show evidence (1 reference)
PMID:17044728 SUPPORT Other
"These patients may experience cognitive deterioration and, in some cases, evolution towards a more severe form of epilepsy, including the Lennox-Gastaut syndrome."
Documents cognitive deterioration in the drug-resistant subset.
Other 3
Myoclonic absence seizure HP:0011150 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Myoclonic absence seizure (HP:0011150). HP:0011150 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:15737698 SUPPORT Other
"Epilepsy with myoclonic absences is characterized clinically by absences accompanied by marked, diffuse, rhythmical myoclonias, often associated with a progressive tonic contraction."
States the defining seizure and its two motor components.
Atonic seizure FREQUENT HP:0010819 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Atonic seizure (HP:0010819). HP:0010819 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:35770757 SUPPORT Human Clinical
"Ten patients were identified including twins with myoclonic absence status epilepticus. Forty percent had an atonic component, 20% presented with myoclonic absence status epilepticus and 60% had incomplete control of seizures at last follow-up visit."
Four of ten patients had an atonic component, which is 40 percent and falls in the FREQUENT band. The denominator is all patients in the series rather than a subgroup selected on outcome, so the estimate is not circular. Ten patients is a small base, which is why no narrower band is claimed.
PMID:35770757 SUPPORT Human Clinical
"Of patients with an atonic component, 75% did not achieve seizure freedom with medication alone."
Documents why this phenotype earns its own record rather than being a descriptive detail: it identifies the subgroup that medication fails.
Myoclonic absence status epilepticus HP:0032865 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Myoclonic absence status epilepticus (HP:0032865). HP:0032865 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35770757 SUPPORT Human Clinical
"Ten patients were identified including twins with myoclonic absence status epilepticus. Forty percent had an atonic component, 20% presented with myoclonic absence status epilepticus and 60% had incomplete control of seizures at last follow-up visit."
Documents status epilepticus as a presenting feature and quantifies it.
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Genetic Associations

2
SLC2A1 (Glucose transporter type 1 deficiency, caused by SLC2A1 variants, usually produces typical absences but can present with myoclonic absences. This is the single most management-relevant genetic cause in the syndrome, because the disease is an energy-delivery failure rather than a channel problem and it has a specific treatment: ketones reach the brain by a different transporter, so a ketogenic diet bypasses the broken one. A child with myoclonic absences who is not responding as expected is a child worth testing for this.)
Gene: SLC2A1 hgnc:11005 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is SLC2A1 (hgnc:11005). hgnc:11005 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (2 references)
PMID:21546317 SUPPORT Human Clinical
"Here we describe a novel Turkish patient with a hot-spot mutation (R126C) in the SLC2A1 gene who presented with unusual myoclonic absence epilepsy and paroxysmal shivering."
A documented case of myoclonic absence epilepsy caused by an SLC2A1 variant, which is what puts this gene in the differential.
PMID:21546317 SUPPORT Human Clinical
"Although typical absences are frequent in GLUT1DS, myoclonic absence seizures are rarely reported."
Places the association honestly: this presentation is rare within glucose transporter deficiency, so the gene is a cause to exclude rather than a common explanation for the syndrome.
SYNGAP1 (Disruption of SYNGAP1, which encodes an NMDA-receptor-associated protein, has been reported in a patient with this syndrome and intellectual disability, through a de novo balanced translocation that truncated the gene. The mechanistic interest is that it lands on the glutamatergic synapse rather than on the thalamic calcium channels that absence epilepsy genetics usually implicates.)
Gene: SYNGAP1 hgnc:11497 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is SYNGAP1 (hgnc:11497). hgnc:11497 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (3 references)
PMID:22050443 SUPPORT Human Clinical
"Herein, we describe a patient with EMA and intellectual disability who carries a de novo balanced translocation: t(6;22)(p21.32;q11.21)."
Documents the case and the de novo structural rearrangement that implicated this gene.
PMID:22050443 SUPPORT Human Clinical
"the breakpoint at 6p21.32 was found to truncate the N-methyl-d-aspartate (NMDA)-receptor associated gene SYNGAP1"
Identifies the disrupted gene and its synaptic function, which is what makes this a mechanistic observation rather than a coincidence of location.
PMID:22050443 SUPPORT Human Clinical
"The underlying etiology of EMA is unknown in the majority of patients."
States plainly that most cases have no identified cause, which is why this section lists individual reported genes rather than claiming a gene panel for the syndrome.
💊

Medical Actions

6
Valproate with ethosuximide
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: valproic acid CHEBI:39867 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses valproic acid (CHEBI:39867). CHEBI:39867 is a therapeutic agent from Chemical Entities of Biological Interest. ethosuximide CHEBI:4887 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses ethosuximide (CHEBI:4887). CHEBI:4887 is a therapeutic agent from Chemical Entities of Biological Interest.
The classical combination, and it works considerably better in the group without generalized tonic-clonic seizures. The two drugs act on different parts of the same mechanism, ethosuximide on the thalamic T-type calcium current that sustains the oscillation and valproate more broadly, which is the rationale for combining them rather than escalating either alone.
Mechanism Target:
INHIBITS Hypersynchronous Three-Hertz Thalamocortical Spike-Wave Oscillation
Show evidence (2 references)
PMID:15737698 SUPPORT Other
"Classical cotherapy with valproate and ethosuximide with appropriate plasma levels is more efficient if myoclonic absences are non-associated with GTCS."
States both the combination and the patient group in which it works, which is the practical content of this record.
PMID:17044728 SUPPORT Other
"Modern therapeutic combinations, such as valproic acid and ethosuximide, or valproic acid and lamotrigine, are usually effective; however, in a proportion of patients, seizures are resistant to drug treatment."
Confirms the combination and names an alternative. Marked PARTIAL because it also records that a proportion of patients do not respond, so this is not a claim of reliable efficacy.
Valproate with lamotrigine
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: valproic acid CHEBI:39867 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses valproic acid (CHEBI:39867). CHEBI:39867 is a therapeutic agent from Chemical Entities of Biological Interest. lamotrigine CHEBI:6367 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses lamotrigine (CHEBI:6367). CHEBI:6367 is a therapeutic agent from Chemical Entities of Biological Interest.
The other combination named alongside valproate and ethosuximide as usually effective. It is worth curating separately from the topiramate record because the two sit on opposite sides of a small disagreement: the sibling report that favours topiramate did so specifically after lamotrigine added to valproate failed to help, so the ordering of these two second agents is not settled.
Mechanism Target:
INHIBITS Hypersynchronous Three-Hertz Thalamocortical Spike-Wave Oscillation
Show evidence (2 references)
PMID:17044728 SUPPORT Other
"Modern therapeutic combinations, such as valproic acid and ethosuximide, or valproic acid and lamotrigine, are usually effective; however, in a proportion of patients, seizures are resistant to drug treatment."
Names this combination as usually effective. Marked PARTIAL because the same sentence records that a proportion of patients do not respond, and because a separate report found lamotrigine unhelpful where topiramate worked.
PMID:24491945 REFUTE Human Clinical
"MAs are worsened by drugs like carbamazepine while valproate either alone or in combination with topiramate (preferred to lamotrigine) gives excellent outcome."
States a preference against lamotrigine in the siblings who did not respond to it, which is the disagreement this record's description records rather than smooths over. Two patients, so it qualifies the recommendation rather than overturning it.
Valproate with topiramate
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: valproic acid CHEBI:39867 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses valproic acid (CHEBI:39867). CHEBI:39867 is a therapeutic agent from Chemical Entities of Biological Interest. topiramate CHEBI:63631 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses topiramate (CHEBI:63631). CHEBI:63631 is a therapeutic agent from Chemical Entities of Biological Interest.
An alternative combination reported to work where lamotrigine added to valproate did not, in a sibling pair who reached remission on it. The evidence is a single family, so this is curated as an option with a worked example rather than as an established second line.
Mechanism Target:
INHIBITS Hypersynchronous Three-Hertz Thalamocortical Spike-Wave Oscillation
Show evidence (1 reference)
PMID:24491945 SUPPORT Human Clinical
"MAs are worsened by drugs like carbamazepine while valproate either alone or in combination with topiramate (preferred to lamotrigine) gives excellent outcome."
States the combination and the preference over lamotrigine. Marked PARTIAL because the observation comes from two siblings, which is a worked example rather than comparative evidence.
Ketogenic diet for glucose transporter deficiency
Action: Ketogenic DietNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Ketogenic Diet (NCIT:C173168). NCIT:C173168 is a clinical intervention from the NCI Thesaurus. NCIT:C173168
The one genotype-directed and mechanistically corrective treatment available in this syndrome, and it applies only to the small group whose myoclonic absences are caused by SLC2A1 variants. In glucose transporter type 1 deficiency the brain cannot import enough glucose; ketones enter by a different transporter that is intact, so a ketogenic diet supplies the fuel the broken protein cannot. That makes testing for the gene worth doing even though it explains few cases, because the finding changes the treatment rather than only the label.
Show evidence (3 references)
PMID:21546317 SUPPORT Human Clinical
"Glucose transporter type 1 deficiency syndrome (GLUT1DS) is an inborn error of brain energy metabolism characterized by impaired glucose transport into the brain."
Establishes the metabolic defect that the ketogenic diet is designed to bypass, in a patient whose presentation was myoclonic absence epilepsy. Marked PARTIAL because this report characterizes the disease and the case rather than reporting the dietary response.
PMID:32913944 SUPPORT Other
"Age-specific ketogenic diet therapies remain the standard of care."
Attests to the therapy itself rather than only to the disease, which is what this record needed. Tagged OTHER because it is a consensus review statement of standard practice rather than a reported patient series.
PMID:32913944 SUPPORT Other
"Best outcomes correlate with early treatment."
Supports the argument for testing early rather than after prolonged medication failure, which is the practical reason this gene is worth excluding in a child with myoclonic absences.
Avoidance of carbamazepine and other seizure-aggravating drugs
Action: Supportive CareNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Supportive Care (NCIT:C15747). NCIT:C15747 is a clinical intervention from the NCI Thesaurus. NCIT:C15747
Sodium channel blockers aggravate generalized absence seizures, and in this syndrome the effect has been documented dramatically: seizure frequency rose from five to a hundred a day on carbamazepine and phenobarbitone, and fell on withdrawal. This is a mechanism-derived contraindication, not a tolerability issue, and it matters because the conspicuous motor component invites a misdiagnosis of focal epilepsy, for which carbamazepine would be a natural choice.
Show evidence (1 reference)
PMID:24491945 SUPPORT Human Clinical
"Increase in the seizure frequency from 5 to 100/day was observed due to use of carbamazepine and phenobarbitone which decreased with its withdrawal and introduction of valproate."
Documents the aggravation and its reversal on withdrawal, which is about as close to a within-patient controlled observation as this literature offers.
Corpus callosotomy for the drug-resistant atonic subgroup
Action: corpus callosotomyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is corpus callosotomy, annotated with Surgical Procedure (NCIT:C15329). NCIT:C15329 is a clinical intervention from the NCI Thesaurus. Ontology label: Surgical Procedure NCIT:C15329
Disconnecting the corpus callosum interrupts the rapid interhemispheric spread that synchronizes generalized seizures, and it is offered when medication fails, particularly in the subgroup with an atonic component in whom drop attacks are the disabling problem. The evidence in this syndrome is two patients, so it is curated as encouraging and unproven, which is how the reporting authors describe it.
Mechanism Target:
INHIBITS Rhythmic Myoclonus with Progressive Tonic Contraction
Show evidence (2 references)
PMID:35770757 SUPPORT Human Clinical
"Two patients with epilepsy with myoclonic absences with atonia underwent corpus callosotomy; one patient was seizurefree eight months after surgery and the other had greater than 50% seizure reduction over a five-month period."
Reports the outcomes in the only two operated patients. Marked PARTIAL because two patients with short follow-up cannot establish efficacy, and the authors say so.
PMID:35770757 SUPPORT Human Clinical
"Corpus callosotomy was performed in two of these patients with encouraging seizure response thus far, however, the efficacy of this treatment should be further evaluated in a larger study."
The authors' own statement of the evidential limits, which is why this record is framed as an option rather than a recommendation.
🔬

Diagnosis

4
Video-electroencephalography with surface electromyography
The diagnostic test, and the reason the syndrome is under-recognized. The electroencephalogram alone shows generalized three-hertz spike-wave and looks like childhood absence epilepsy. What makes the diagnosis is simultaneous electromyography from the deltoids showing myoclonic bursts locked to each discharge on a rising baseline of tonic contraction. Without video and polygraphy the diagnosis is routinely missed.
Electroencephalography NCIT:C38054 NCI Thesaurus (NCIT)
Results: Generalized three-hertz spike-wave with time-locked myoclonic bursts on surface electromyography, superimposed on a progressively increasing tonic contraction.
Show evidence (2 references)
PMID:17044728 SUPPORT Other
"as such, despite an ECG, the diagnosis may be missed in the absence of video documentation of the seizure and/or adequate polygraphy"
States directly that the diagnosis depends on video and polygraphy rather than on the electroencephalogram alone.
PMID:24491945 SUPPORT Human Clinical
"Myoclonic absences (MAs) were characterized by rhythmic, bilateral, synchronous, symmetric 3-Hz spike-wave discharges, associated with EMG myoclonic bursts at 3 Hz, superimposed on a progressively increasing tonic muscle contraction."
Describes the polygraphic findings reported in the results field.
Brain MRI
Imaging does not diagnose the syndrome; it decides which version of it the child has. A normal scan is consistent with the idiopathic form, and a structural abnormality reclassifies the case as symptomatic, which carries the worse prognosis and is the arm the outcome controversy in this entry turns on. That makes imaging part of the diagnostic pathway rather than an optional extra, and it is also the first test named in the proposed experiment of that discussion.
Magnetic Resonance Imaging NCIT:C16809 NCI Thesaurus (NCIT)
Results: Normal in the idiopathic form; a structural abnormality reclassifies the case as symptomatic.
Show evidence (1 reference)
PMID:40380288 SUPPORT Other
"magnetic resonance imaging (MRI) serving to exclude structural etiologies"
States the role of imaging in the diagnostic workup for this syndrome, alongside the polygraphic recording this entry already curates.
Lumbar puncture with paired CSF and blood glucose
The test that finds the one treatable cause. Glucose transporter type 1 deficiency is diagnosed by a low cerebrospinal fluid glucose against a normal blood glucose, and it is worth doing in a child with myoclonic absences precisely because a positive result changes the treatment to a ketogenic diet rather than only changing the label. It closes the loop the genetic section and the diet record open.
Lumbar Puncture NCIT:C15327 NCI Thesaurus (NCIT)
Results: Low cerebrospinal fluid glucose with low to low-normal lactate against normal blood values indicates glucose transporter type 1 deficiency.
Show evidence (1 reference)
PMID:32913944 SUPPORT Other
"The principal diagnostic tool is a lumbar puncture showing low CSF glucose and low to low-normal lactate concentrations in the setting of normal blood glucose and lactate concentrations."
States the diagnostic test and its expected result for the one cause in this syndrome that has a specific therapy.
Cytogenetic testing (karyotype or chromosomal microarray)
Worth doing rather than relying on a gene panel alone, because the reported chromosomal causes of this syndrome are copy number changes that sequencing a gene list will not find. Trisomy 12p is the best-documented example, and the authors of that report argue from it that myoclonic absences can be a direct or indirect consequence of a chromosomal abnormality in at least some patients. This is the test that separates the symptomatic form from the idiopathic one when imaging is unrevealing.
Cytogenetic Analysis NCIT:C18280 NCI Thesaurus (NCIT)
Results: A copy number abnormality in the symptomatic minority; normal in the idiopathic form.
Show evidence (2 references)
PMID:9545186 SUPPORT Human Clinical
"Our patient and other sporadic reports in the literature seem to support the hypothesis that, at least in some cases, myoclonic absences can be a direct or indirect effect of a chromosomopathy."
States the authors' inference that a chromosomal abnormality can produce this seizure syndrome, which is the rationale for testing for one.
PMID:9545186 SUPPORT Human Clinical
"We report the case of a 6-year-2-month-old female affected by trisomy 12p syndrome. Seizures were typical myoclonic absences from both the clinical and EEG points of view."
The worked case, with seizures typical of the syndrome on both clinical and electrographic grounds, which is what makes it evidence for the syndrome rather than for a lookalike.
📈

Progression

2
Onset in mid-childhood with daily myoclonic absences
Age: Around seven years
Onset averages about seven years, with a male preponderance, which distinguishes it demographically from childhood absence epilepsy where girls predominate. Seizures are frequent from the outset.
Show evidence (1 reference)
PMID:15737698 SUPPORT Human Clinical
"The age at onset is about 7 years. There is a male preponderance."
States the onset age and sex distribution described in this phase.
Divergent course determined largely by associated seizure types
Age: Childhood into adolescence
Children whose only seizure type is the myoclonic absence generally respond to combination therapy. Those with associated generalized tonic-clonic seizures often do not, and may persist, deteriorate cognitively, or evolve toward a more severe generalized epilepsy.
Show evidence (2 references)
PMID:15737698 SUPPORT Other
"The evolution is variable and seems to depend on the existence or not of GTCS."
States the prognostic dependence that defines this phase.
PMID:15737698 SUPPORT Other
"In cases where GTCS are associated, there is often an unfavourable outcome, with persistence of myoclonic absences or with modification of the epilepsy with a possible evolution towards a generalized cryptogenic or symptomatic form."
Describes the unfavourable trajectory in the associated-seizure group.
📊

Prevalence

1
Children with epilepsy
Unknown Rare
No population-based estimate is available. The syndrome is described as rare in the contemporary literature, and the largest recent single-centre series identified ten patients over four years, which indicates the order of magnitude rather than a rate.
Show evidence (1 reference)
PMID:35770757 SUPPORT Human Clinical
"Epilepsy with myoclonic absences is a rare epilepsy syndrome with distinct features and high rates of drug resistance."
Supports the qualitative rarity band and the drug-resistance claim.
🔀

Differential Diagnoses

4

Conditions with similar clinical presentations that must be differentiated from Epilepsy with Myoclonic Absences:

Childhood Absence Epilepsy MONDO:0010826
Overlapping Features The nearest neighbour and the entity from which this syndrome is hardest to separate, because the electroencephalographic discharge is the same. The separation rests entirely on the motor phenomena, which is exactly why the distinctness of the syndrome is disputed.
Distinguishing Features
  • Absences are unaccompanied by rhythmic myoclonus locked to the discharge.
  • No progressive tonic contraction raising the arms during the seizure.
  • Female preponderance rather than the male preponderance of myoclonic absences.
  • Higher rate of spontaneous remission and better medication response overall.
Show evidence (1 reference)
PMID:15737698 SUPPORT Other
"The ictal EEG shows bilateral, synchronous and symmetrical spike and wave discharges repeated at 3 Hz (similar to that observed in typical absences of childhood absence epilepsy) in strict relation with myoclonias recorded on EMG."
Establishes the electrographic identity with childhood absence epilepsy and the motor coupling that is the only difference, which is what makes this differential both necessary and difficult.
Epilepsy with Myoclonic-Atonic Seizures MONDO:0014633
Overlapping Features A nomenclature trap as much as a clinical one. The names differ by one word and this entry now curates an atonic seizure phenotype in 40 percent of patients, so the two are easy to conflate on paper. The seizures are not the same event: there the myoclonic jerk and the loss of tone are one sequence producing a fall, here the jerks are locked to each spike-wave cycle on a rising background of tonic contraction, and the atonic component when present is an additional feature rather than the defining one.
Distinguishing Features
  • The defining seizure is a myoclonic-atonic drop attack, not an absence with cycle-locked myoclonus.
  • Consciousness is not the primary casualty; the fall is.
  • Classified by the ILAE among the developmental and epileptic encephalopathies rather than among the generalized epilepsies.
  • No progressive tonic contraction building through the seizure.
Show evidence (1 reference)
PMID:35503717 SUPPORT Other
"developmental and/or epileptic encephalopathies, comprising five syndromes: epilepsy with myoclonic-atonic seizures, Lennox-Gastaut syndrome, developmental and/or epileptic encephalopathy with spike-and-wave activation in sleep, hemiconvulsion-hemiplegia-epilepsy syndrome, and febrile..."
Places epilepsy with myoclonic-atonic seizures in the encephalopathy category while this entry's syndrome sits among the generalized epilepsies, which is the classificatory basis of the distinction and the reason the near-identical names denote different things.
Epilepsy with Eyelid Myoclonia MONDO:0015346
Overlapping Features The third ILAE childhood generalized syndrome, and the other one defined by an absence with a myoclonic accompaniment. The distinction is topographic: the jerking is confined to the eyelids rather than being diffuse and axial.
Distinguishing Features
  • Myoclonus is confined to the eyelids with upward eye deviation.
  • Eye closure and photic stimulation are the characteristic triggers.
  • No progressive axial tonic contraction.
Show evidence (1 reference)
PMID:17044728 SUPPORT Other
"MA need to be distinguished from absences with other types of prominent myoclonic accompaniment (perioral, eyelid, limbs)."
States explicitly that absences with other patterns of myoclonic accompaniment, eyelid among them, must be separated from myoclonic absences.
Lennox-Gastaut Syndrome MONDO:0016532
Overlapping Features Both a differential and a destination: some children with epilepsy with myoclonic absences evolve into Lennox-Gastaut syndrome, so the distinction is partly a matter of when in the course the child is seen.
Distinguishing Features
  • Slow spike-wave at 1.5 to 2.5 hertz rather than three-hertz spike-wave.
  • Tonic seizures in sleep are mandatory and are not a feature of myoclonic absences.
  • Multiple seizure types with a diffusely abnormal background from the outset.
Show evidence (1 reference)
PMID:17044728 SUPPORT Other
"These patients may experience cognitive deterioration and, in some cases, evolution towards a more severe form of epilepsy, including the Lennox-Gastaut syndrome."
Establishes the evolution that makes this both a differential and a possible outcome of the same disease.
{ }

Source YAML

click to show 
name: Epilepsy with Myoclonic Absences
creation_date: "2026-08-05T00:00:00Z"
category: Complex
description: >-
  A childhood generalized epilepsy whose defining seizure is an absence that you
  can see happening. The child stops, as in any absence, but at the same time the
  shoulders and arms jerk rhythmically about three times a second, and the arms
  rise steadily as a tonic contraction builds through the seizure. The
  electroencephalogram shows the same three-per-second generalized spike-wave as
  childhood absence epilepsy, but here each spike is locked to a muscle jerk that
  can be recorded on surface electromyography. That motor recruitment is the
  whole mechanistic interest of the syndrome: the same thalamocortical
  oscillation that produces a silent stare in one epilepsy drives the motor system
  in this one, and nobody knows why. Seizures happen many times a day, respond
  poorly to medication in a substantial minority, and a subset of children
  deteriorate cognitively or evolve toward Lennox-Gastaut syndrome.
parents:
  - Epilepsy
  - Neurological Disease
synonyms:
  - EMA
  - myoclonic absence epilepsy
  - epilepsy with myoclonic absence
  - Tassinari syndrome
classifications:
  harrisons_chapter:
    - classification_value: NEUROLOGIC
      notes: >-
        An ILAE-recognized childhood generalized epilepsy syndrome, managed
        neurologically.
disease_term:
  preferred_term: epilepsy with myoclonic absences
  term:
    id: MONDO:0019487
    label: epilepsy with myoclonic absences
mappings:
  mondo_mappings:
    - term:
        id: MONDO:0019487
        label: epilepsy with myoclonic absences
      mapping_predicate: skos:exactMatch
      mapping_source: MONDO
      mapping_justification: >-
        MONDO:0019487 is the epilepsy with myoclonic absences concept, one of the
        three childhood generalized epilepsy syndromes recognized by the ILAE.
references:
  - reference: PMID:15737698
    title: Epilepsy with myoclonic absences.
  - reference: PMID:17044728
    title: Epilepsy with myoclonic absences.
  - reference: PMID:35770757
    title: >-
      Epilepsy with myoclonic absences: a case series highlighting clinical
      heterogeneity and surgical management.
notes: >-
  Scope note. This entry models epilepsy with myoclonic absences as a distinct
  ILAE syndrome, which is how it is currently classified, while recording
  explicitly that its status as a separate entity is disputed in the literature
  rather than settled. The dispute is not a curation quibble: the syndrome was
  defined on a seizure type, and myoclonic components have since been described in
  several other generalized epilepsies with absences, so the boundary depends on
  where one draws the line between a defining feature and an accompaniment. That
  argument is curated in the discussions block.

  On the mechanism graph. The thalamocortical oscillation modeled here is
  deliberately described in the same terms as the sibling Childhood Absence
  Epilepsy and Juvenile Absence Epilepsy entries, because the electrographic
  discharge really is the same three-per-second generalized spike-wave. What this
  entry adds is a separate node for the cycle-locked recruitment of the motor
  system, which is the only thing that distinguishes the seizure, and which is
  where the unexplained biology sits.

  Module conformance note. Two nodes conform to
  epilepsy_excitation_inhibition_imbalance. As in the other absence entries, the
  module is joined at the hyperexcitability and recurrent-seizure nodes rather
  than at its ion-channel trigger, since no single channel defect is established
  for this syndrome.
inheritance:
  - name: Presumed polygenic, mostly sporadic
    description: >-
      No single-gene inheritance pattern is established. Most cases are sporadic,
      although sibling pairs are reported, and the syndrome sits within the
      genetic generalized epilepsies whose liability is generally polygenic. A
      minority of cases are symptomatic, occurring on the background of an
      identifiable structural or chromosomal abnormality, and those are not
      heritable in the same sense at all.
    inheritance_term:
      preferred_term: Sporadic
      term:
        id: HP:0003745
        label: Sporadic
    evidence:
      - reference: PMID:24491945
        reference_title: Epilepsy with myoclonic absences in siblings.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          To describe the clinical, electroencephalographic features, treatment
          strategies and outcome in this first case series of two siblings with
          normal intelligence presenting with EMAs.
        explanation: >-
          Documents familial occurrence in siblings, which is what makes a genetic
          contribution likely. Marked PARTIAL because two siblings establish
          familial aggregation, not a mode of inheritance.
      - reference: PMID:24491945
        reference_title: Epilepsy with myoclonic absences in siblings.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Idiopathic and symptomatic EMAs need to be differentiated from childhood
          absence epilepsy with myoclonia.
        explanation: >-
          Establishes that the syndrome has both idiopathic and symptomatic forms,
          which is why no single inheritance statement covers it.
pathophysiology:
  - name: Heritable Thalamocortical Susceptibility
    biological_scale: MOLECULAR
    description: >-
      The syndrome behaves like the other genetic generalized epilepsies at this
      level: a heritable liability to abnormal thalamocortical oscillation, with
      no single causal gene established and sibling recurrence reported. A subset
      of children instead have a symptomatic form on the background of a
      structural or chromosomal abnormality, reaching the same oscillation from a
      different starting point.
    biological_processes:
      - preferred_term: regulation of postsynaptic membrane potential
        term:
          id: GO:0060078
          label: regulation of postsynaptic membrane potential
        modifier: ABNORMAL
    downstream:
      - target: Hypersynchronous Three-Hertz Thalamocortical Spike-Wave Oscillation
    evidence:
      - reference: PMID:24491945
        reference_title: Epilepsy with myoclonic absences in siblings.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Idiopathic and symptomatic EMAs need to be differentiated from childhood
          absence epilepsy with myoclonia.
        explanation: >-
          Supports the split between idiopathic and symptomatic forms that this
          node represents. Marked PARTIAL because it asserts the distinction
          without characterizing the genetic architecture of the idiopathic arm.
  - name: Hypersynchronous Three-Hertz Thalamocortical Spike-Wave Oscillation
    biological_scale: CELLULAR
    conforms_to: "epilepsy_excitation_inhibition_imbalance#Neuronal Hyperexcitability and Hypersynchrony"
    description: >-
      The engine of the seizure is the same thalamocortical loop oscillation that
      produces typical absences, discharging bilaterally, synchronously, and
      symmetrically at three per second. The literature makes the equivalence
      explicit, comparing it directly to the discharge of childhood absence
      epilepsy. Because the oscillation itself is shared, nothing about this node
      explains what makes the syndrome different; the difference is entirely in
      what the oscillation is coupled to downstream.
    cell_types:
      - preferred_term: pyramidal neuron
        term:
          id: CL:0000598
          label: pyramidal neuron
    downstream:
      - target: Cycle-Locked Recruitment of Motor Output
      - target: Impairment of Awareness
    evidence:
      - reference: PMID:15737698
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          The ictal EEG shows bilateral, synchronous and symmetrical spike and wave
          discharges repeated at 3 Hz (similar to that observed in typical absences
          of childhood absence epilepsy) in strict relation with myoclonias
          recorded on EMG.
        explanation: >-
          States both halves of what this entry turns on: the discharge is the same
          as in childhood absence epilepsy, and it is in strict temporal relation
          with the muscle jerks.
      - reference: PMID:24491945
        reference_title: Epilepsy with myoclonic absences in siblings.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Myoclonic absences (MAs) were characterized by rhythmic, bilateral,
          synchronous, symmetric 3-Hz spike-wave discharges, associated with EMG
          myoclonic bursts at 3 Hz, superimposed on a progressively increasing
          tonic muscle contraction.
        explanation: >-
          Independent polygraphic confirmation of the frequency-matched coupling
          between the discharge and the muscle bursts.
  - name: Cycle-Locked Recruitment of Motor Output
    biological_scale: CELLULAR
    description: >-
      This is the node that makes the syndrome what it is. Each spike-wave cycle
      is accompanied by a muscle burst at the same three-per-second rate, and the
      relation is described as strict rather than approximate, which is what
      distinguishes a driven motor output from an incidental one. Superimposed on
      the rhythmic jerks is a tonic contraction that builds progressively through
      the seizure, raising the arms, and it is a separate phenomenon from the
      jerks rather than their summation. Why the same oscillation engages motor
      cortex and corticospinal output here and not in childhood absence epilepsy
      is not known, and is recorded as a knowledge gap.
    biological_processes:
      - preferred_term: regulation of postsynaptic membrane potential
        term:
          id: GO:0060078
          label: regulation of postsynaptic membrane potential
        modifier: ABNORMAL
    downstream:
      - target: Rhythmic Myoclonus with Progressive Tonic Contraction
    evidence:
      - reference: PMID:17044728
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Neurophysiologically, axial hypertonia and rhythmic jerks may be recorded
          on polygraphic surface electromyogram leads in association with the
          typical SW discharges
        explanation: >-
          Establishes that both the tonic and the myoclonic components are
          measurable motor phenomena time-locked to the discharge, which is the
          content of this node.
      - reference: PMID:15737698
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Epilepsy with myoclonic absences is characterized clinically by absences
          accompanied by marked, diffuse, rhythmical myoclonias, often associated
          with a progressive tonic contraction.
        explanation: >-
          Names the two motor components and their relationship to the absence,
          which is what this node models.
  - name: Impairment of Awareness
    biological_scale: ORGANISM
    description: >-
      The absence itself, produced by the same thalamocortical discharge that
      produces it in any other absence epilepsy. Impairment is typically partial
      rather than complete, which combined with the conspicuous motor activity is
      why these events are sometimes mistaken for something other than seizures.
    downstream:
      - target: Drug-Resistant Course with Cognitive Decline in a Subset
    evidence:
      - reference: PMID:17044728
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Myoclonic absences (MA) are described as typical absences with sudden
          onset and offset that are associated with generalised spike and wave (SW)
          discharges on the ECG, with distinctive traits.
        explanation: >-
          Establishes the absence component and its abrupt onset and offset, which
          is the feature shared with typical absences.
  - name: Rhythmic Myoclonus with Progressive Tonic Contraction
    biological_scale: ORGANISM
    conforms_to: "epilepsy_excitation_inhibition_imbalance#Recurrent Unprovoked Seizures"
    description: >-
      The visible seizure: rhythmic bilateral jerking of shoulders, arms, and legs
      at three per second, with the arms rising progressively as axial tone builds.
      Seizures occur many times a day, which is part of why the syndrome is
      disabling out of proportion to the individual event. In a substantial
      minority an atonic component is present instead of or alongside the tonic
      one, and those children do markedly worse on medication.
    downstream:
      - target: Myoclonic Absence Status Epilepticus
      - target: Drug-Resistant Course with Cognitive Decline in a Subset
    evidence:
      - reference: PMID:15737698
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          These seizures occur many times a day.
        explanation: >-
          Documents the seizure frequency that makes this syndrome disabling.
      - reference: PMID:35770757
        reference_title: >-
          Epilepsy with myoclonic absences: a case series highlighting clinical
          heterogeneity and surgical management.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Of patients with an atonic component, 75% did not achieve seizure freedom
          with medication alone.
        explanation: >-
          Documents the atonic subgroup and its markedly worse medication response,
          which is the clinical fact that motivates surgical consideration.
  - name: Myoclonic Absence Status Epilepticus
    biological_scale: ORGANISM
    description: >-
      A prolonged state in which the seizure pattern becomes continuous rather
      than repetitive, reported as the presenting problem in a fifth of one case
      series. It is worth curating separately because it is easy to miss: a child
      in this state looks confused and jerky rather than obviously convulsing.
    evidence:
      - reference: PMID:35770757
        reference_title: >-
          Epilepsy with myoclonic absences: a case series highlighting clinical
          heterogeneity and surgical management.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Ten patients were identified including twins with myoclonic absence
          status epilepticus. Forty percent had an atonic component, 20% presented
          with myoclonic absence status epilepticus and 60% had incomplete control
          of seizures at last follow-up visit.
        explanation: >-
          Quantifies the frequency of status as a presentation, and of incomplete
          control, in a contemporary series.
  - name: Drug-Resistant Course with Cognitive Decline in a Subset
    biological_scale: ORGANISM
    description: >-
      The outcome splits, and it splits along a line that is visible at diagnosis.
      Children whose only seizure type is the myoclonic absence generally do well
      on combination therapy. Children who also have generalized tonic-clonic
      seizures do worse, and a subset deteriorate cognitively or evolve toward
      Lennox-Gastaut syndrome. Whether that reflects two different diseases wearing
      the same seizure or one disease with variable severity is unresolved and is
      curated as a discussion.
    evidence:
      - reference: PMID:17044728
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          These patients may experience cognitive deterioration and, in some cases,
          evolution towards a more severe form of epilepsy, including the
          Lennox-Gastaut syndrome.
        explanation: >-
          Documents the adverse trajectory that this node represents.
      - reference: PMID:17044728
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          The more benign cases usually present with MA as the only seizure type,
          while patients who experience other seizures, especially generalised
          tonic-clonic seizures, in association with MA may have a less favourable
          outcome.
        explanation: >-
          States the prognostic split and the feature that predicts it, which is
          what makes the outcome heterogeneity structured rather than random.
phenotypes:
  - category: Neurologic
    name: Myoclonic absence seizure
    description: >-
      The defining seizure: an absence with rhythmic bilateral myoclonic jerking at
      three per second, time-locked to the spike-wave discharge, with a
      progressively building tonic contraction of the shoulders and arms.
    phenotype_term:
      preferred_term: Myoclonic absence seizure
      term:
        id: HP:0011150
        label: Myoclonic absence seizure
    evidence:
      - reference: PMID:15737698
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Epilepsy with myoclonic absences is characterized clinically by absences
          accompanied by marked, diffuse, rhythmical myoclonias, often associated
          with a progressive tonic contraction.
        explanation: >-
          States the defining seizure and its two motor components.
  - category: Neurologic
    name: Generalized tonic-clonic seizure
    description: >-
      Present in a substantial minority and prognostically important: its presence
      marks the group with the less favourable outcome and the poorer medication
      response.
    phenotype_term:
      preferred_term: Bilateral tonic-clonic seizure
      term:
        id: HP:0002069
        label: Bilateral tonic-clonic seizure
    frequency: FREQUENT
    evidence:
      - reference: PMID:15737698
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Associated seizures are present in 2/3 of the cases, the most frequent
          association being GTCS in 45%.
        explanation: >-
          Reports generalized tonic-clonic seizures in 45 percent of patients with
          the syndrome, within the FREQUENT band of 30 to 79 percent. The
          denominator is all patients with the syndrome rather than a
          poor-outcome-selected subgroup, so the estimate is not circular.
  - category: Neurologic
    name: Atonic seizure
    description: >-
      An atonic component, a loss of tone rather than the usual build of it,
      occurs in a substantial minority and appears to matter more than its
      frequency suggests. Children with it are markedly less likely to reach
      seizure freedom on medication, and it is the feature that prompts surgical
      consideration. It is also the candidate stratifying variable in the
      outcome controversy curated below.
    phenotype_term:
      preferred_term: Atonic seizure
      term:
        id: HP:0010819
        label: Atonic seizure
    frequency: FREQUENT
    evidence:
      - reference: PMID:35770757
        reference_title: >-
          Epilepsy with myoclonic absences: a case series highlighting clinical
          heterogeneity and surgical management.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Ten patients were identified including twins with myoclonic absence
          status epilepticus. Forty percent had an atonic component, 20% presented
          with myoclonic absence status epilepticus and 60% had incomplete control
          of seizures at last follow-up visit.
        explanation: >-
          Four of ten patients had an atonic component, which is 40 percent and
          falls in the FREQUENT band. The denominator is all patients in the
          series rather than a subgroup selected on outcome, so the estimate is not
          circular. Ten patients is a small base, which is why no narrower band is
          claimed.
      - reference: PMID:35770757
        reference_title: >-
          Epilepsy with myoclonic absences: a case series highlighting clinical
          heterogeneity and surgical management.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Of patients with an atonic component, 75% did not achieve seizure freedom
          with medication alone.
        explanation: >-
          Documents why this phenotype earns its own record rather than being a
          descriptive detail: it identifies the subgroup that medication fails.
  - category: Neurologic
    name: Myoclonic absence status epilepticus
    description: >-
      A prolonged continuous form of the seizure state, reported as the presenting
      problem in a fifth of one contemporary series.
    phenotype_term:
      preferred_term: Myoclonic absence status epilepticus
      term:
        id: HP:0032865
        label: Myoclonic absence status epilepticus
    evidence:
      - reference: PMID:35770757
        reference_title: >-
          Epilepsy with myoclonic absences: a case series highlighting clinical
          heterogeneity and surgical management.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Ten patients were identified including twins with myoclonic absence
          status epilepticus. Forty percent had an atonic component, 20% presented
          with myoclonic absence status epilepticus and 60% had incomplete control
          of seizures at last follow-up visit.
        explanation: >-
          Documents status epilepticus as a presenting feature and quantifies it.
  - category: Neurologic
    name: EEG abnormality with three-hertz generalized spike-wave
    description: >-
      Bilateral, synchronous, symmetrical spike-wave discharge at three per second,
      indistinguishable in itself from that of childhood absence epilepsy, and
      diagnostic only when recorded with simultaneous electromyography that shows
      the jerks locked to it.
    phenotype_term:
      preferred_term: EEG abnormality
      term:
        id: HP:0002353
        label: EEG abnormality
    evidence:
      - reference: PMID:15737698
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          The ictal EEG shows bilateral, synchronous and symmetrical spike and wave
          discharges repeated at 3 Hz (similar to that observed in typical absences
          of childhood absence epilepsy) in strict relation with myoclonias
          recorded on EMG.
        explanation: >-
          Describes the electrographic pattern and its indistinguishability from
          childhood absence epilepsy in isolation.
  - category: Neurologic
    name: Cognitive deterioration
    description: >-
      A subset of children, concentrated among those with drug-resistant seizures
      and associated generalized tonic-clonic seizures, decline cognitively rather
      than remaining stable.
    phenotype_term:
      preferred_term: Intellectual disability
      term:
        id: HP:0001249
        label: Intellectual disability
      clinical_course: PROGRESSIVE
    evidence:
      - reference: PMID:17044728
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          These patients may experience cognitive deterioration and, in some cases,
          evolution towards a more severe form of epilepsy, including the
          Lennox-Gastaut syndrome.
        explanation: >-
          Documents cognitive deterioration in the drug-resistant subset.
genetic:
  - name: SLC2A1
    gene_term:
      preferred_term: SLC2A1
      term:
        id: hgnc:11005
        label: SLC2A1
    relationship_type: CAUSATIVE
    association: >-
      Glucose transporter type 1 deficiency, caused by SLC2A1 variants, usually
      produces typical absences but can present with myoclonic absences. This is
      the single most management-relevant genetic cause in the syndrome, because
      the disease is an energy-delivery failure rather than a channel problem and
      it has a specific treatment: ketones reach the brain by a different
      transporter, so a ketogenic diet bypasses the broken one. A child with
      myoclonic absences who is not responding as expected is a child worth
      testing for this.
    evidence:
      - reference: PMID:21546317
        reference_title: >-
          Video/EEG recording of myoclonic absences in GLUT1 deficiency syndrome
          with a hot-spot R126C mutation in the SLC2A1 gene.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Here we describe a novel Turkish patient with a hot-spot mutation (R126C)
          in the SLC2A1 gene who presented with unusual myoclonic absence epilepsy
          and paroxysmal shivering.
        explanation: >-
          A documented case of myoclonic absence epilepsy caused by an SLC2A1
          variant, which is what puts this gene in the differential.
      - reference: PMID:21546317
        reference_title: >-
          Video/EEG recording of myoclonic absences in GLUT1 deficiency syndrome
          with a hot-spot R126C mutation in the SLC2A1 gene.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Although typical absences are frequent in GLUT1DS, myoclonic absence
          seizures are rarely reported.
        explanation: >-
          Places the association honestly: this presentation is rare within
          glucose transporter deficiency, so the gene is a cause to exclude rather
          than a common explanation for the syndrome.
  - name: SYNGAP1
    gene_term:
      preferred_term: SYNGAP1
      term:
        id: hgnc:11497
        label: SYNGAP1
    relationship_type: CAUSATIVE
    association: >-
      Disruption of SYNGAP1, which encodes an NMDA-receptor-associated protein,
      has been reported in a patient with this syndrome and intellectual
      disability, through a de novo balanced translocation that truncated the
      gene. The mechanistic interest is that it lands on the glutamatergic
      synapse rather than on the thalamic calcium channels that absence epilepsy
      genetics usually implicates.
    evidence:
      - reference: PMID:22050443
        reference_title: >-
          A balanced translocation disrupts SYNGAP1 in a patient with intellectual
          disability, speech impairment, and epilepsy with myoclonic absences
          (EMA).
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Herein, we describe a patient with EMA and intellectual disability who
          carries a de novo balanced translocation: t(6;22)(p21.32;q11.21).
        explanation: >-
          Documents the case and the de novo structural rearrangement that
          implicated this gene.
      - reference: PMID:22050443
        reference_title: >-
          A balanced translocation disrupts SYNGAP1 in a patient with intellectual
          disability, speech impairment, and epilepsy with myoclonic absences
          (EMA).
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          the breakpoint at 6p21.32 was found to truncate the
          N-methyl-d-aspartate (NMDA)-receptor associated gene SYNGAP1
        explanation: >-
          Identifies the disrupted gene and its synaptic function, which is what
          makes this a mechanistic observation rather than a coincidence of
          location.
      - reference: PMID:22050443
        reference_title: >-
          A balanced translocation disrupts SYNGAP1 in a patient with intellectual
          disability, speech impairment, and epilepsy with myoclonic absences
          (EMA).
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          The underlying etiology of EMA is unknown in the majority of patients.
        explanation: >-
          States plainly that most cases have no identified cause, which is why
          this section lists individual reported genes rather than claiming a gene
          panel for the syndrome.
prevalence:
  - population: Children with epilepsy
    measure_type: UNKNOWN
    prevalence_class: RARE
    notes: >-
      No population-based estimate is available. The syndrome is described as rare
      in the contemporary literature, and the largest recent single-centre series
      identified ten patients over four years, which indicates the order of
      magnitude rather than a rate.
    evidence:
      - reference: PMID:35770757
        reference_title: >-
          Epilepsy with myoclonic absences: a case series highlighting clinical
          heterogeneity and surgical management.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Epilepsy with myoclonic absences is a rare epilepsy syndrome with
          distinct features and high rates of drug resistance.
        explanation: >-
          Supports the qualitative rarity band and the drug-resistance claim.
progression:
  - phase: Onset in mid-childhood with daily myoclonic absences
    age_range: Around seven years
    notes: >-
      Onset averages about seven years, with a male preponderance, which
      distinguishes it demographically from childhood absence epilepsy where girls
      predominate. Seizures are frequent from the outset.
    evidence:
      - reference: PMID:15737698
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          The age at onset is about 7 years. There is a male preponderance.
        explanation: >-
          States the onset age and sex distribution described in this phase.
  - phase: Divergent course determined largely by associated seizure types
    age_range: Childhood into adolescence
    notes: >-
      Children whose only seizure type is the myoclonic absence generally respond
      to combination therapy. Those with associated generalized tonic-clonic
      seizures often do not, and may persist, deteriorate cognitively, or evolve
      toward a more severe generalized epilepsy.
    evidence:
      - reference: PMID:15737698
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          The evolution is variable and seems to depend on the existence or not of
          GTCS.
        explanation: >-
          States the prognostic dependence that defines this phase.
      - reference: PMID:15737698
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          In cases where GTCS are associated, there is often an unfavourable
          outcome, with persistence of myoclonic absences or with modification of
          the epilepsy with a possible evolution towards a generalized cryptogenic
          or symptomatic form.
        explanation: >-
          Describes the unfavourable trajectory in the associated-seizure group.
treatments:
  - name: Valproate with ethosuximide
    description: >-
      The classical combination, and it works considerably better in the group
      without generalized tonic-clonic seizures. The two drugs act on different
      parts of the same mechanism, ethosuximide on the thalamic T-type calcium
      current that sustains the oscillation and valproate more broadly, which is
      the rationale for combining them rather than escalating either alone.
    therapeutic_modality: SMALL_MOLECULE
    treatment_term:
      preferred_term: Pharmacotherapy
      term:
        id: NCIT:C15986
        label: Pharmacotherapy
      therapeutic_agent:
        - preferred_term: valproic acid
          term:
            id: CHEBI:39867
            label: valproic acid
        - preferred_term: ethosuximide
          term:
            id: CHEBI:4887
            label: ethosuximide
    target_mechanisms:
      - target: Hypersynchronous Three-Hertz Thalamocortical Spike-Wave Oscillation
        treatment_effect: INHIBITS
    evidence:
      - reference: PMID:15737698
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Classical cotherapy with valproate and ethosuximide with appropriate
          plasma levels is more efficient if myoclonic absences are non-associated
          with GTCS.
        explanation: >-
          States both the combination and the patient group in which it works,
          which is the practical content of this record.
      - reference: PMID:17044728
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Modern therapeutic combinations, such as valproic acid and ethosuximide,
          or valproic acid and lamotrigine, are usually effective; however, in a
          proportion of patients, seizures are resistant to drug treatment.
        explanation: >-
          Confirms the combination and names an alternative. Marked PARTIAL because
          it also records that a proportion of patients do not respond, so this is
          not a claim of reliable efficacy.
  - name: Valproate with lamotrigine
    description: >-
      The other combination named alongside valproate and ethosuximide as usually
      effective. It is worth curating separately from the topiramate record
      because the two sit on opposite sides of a small disagreement: the sibling
      report that favours topiramate did so specifically after lamotrigine added
      to valproate failed to help, so the ordering of these two second agents is
      not settled.
    therapeutic_modality: SMALL_MOLECULE
    treatment_term:
      preferred_term: Pharmacotherapy
      term:
        id: NCIT:C15986
        label: Pharmacotherapy
      therapeutic_agent:
        - preferred_term: valproic acid
          term:
            id: CHEBI:39867
            label: valproic acid
        - preferred_term: lamotrigine
          term:
            id: CHEBI:6367
            label: lamotrigine
    target_mechanisms:
      - target: Hypersynchronous Three-Hertz Thalamocortical Spike-Wave Oscillation
        treatment_effect: INHIBITS
    evidence:
      - reference: PMID:17044728
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Modern therapeutic combinations, such as valproic acid and ethosuximide,
          or valproic acid and lamotrigine, are usually effective; however, in a
          proportion of patients, seizures are resistant to drug treatment.
        explanation: >-
          Names this combination as usually effective. Marked PARTIAL because the
          same sentence records that a proportion of patients do not respond, and
          because a separate report found lamotrigine unhelpful where topiramate
          worked.
      - reference: PMID:24491945
        reference_title: Epilepsy with myoclonic absences in siblings.
        supports: REFUTE
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          MAs are worsened by drugs like carbamazepine while valproate either alone
          or in combination with topiramate (preferred to lamotrigine) gives
          excellent outcome.
        explanation: >-
          States a preference against lamotrigine in the siblings who did not
          respond to it, which is the disagreement this record's description
          records rather than smooths over. Two patients, so it qualifies the
          recommendation rather than overturning it.
  - name: Valproate with topiramate
    description: >-
      An alternative combination reported to work where lamotrigine added to
      valproate did not, in a sibling pair who reached remission on it. The
      evidence is a single family, so this is curated as an option with a worked
      example rather than as an established second line.
    therapeutic_modality: SMALL_MOLECULE
    treatment_term:
      preferred_term: Pharmacotherapy
      term:
        id: NCIT:C15986
        label: Pharmacotherapy
      therapeutic_agent:
        - preferred_term: valproic acid
          term:
            id: CHEBI:39867
            label: valproic acid
        - preferred_term: topiramate
          term:
            id: CHEBI:63631
            label: topiramate
    target_mechanisms:
      - target: Hypersynchronous Three-Hertz Thalamocortical Spike-Wave Oscillation
        treatment_effect: INHIBITS
    evidence:
      - reference: PMID:24491945
        reference_title: Epilepsy with myoclonic absences in siblings.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          MAs are worsened by drugs like carbamazepine while valproate either alone
          or in combination with topiramate (preferred to lamotrigine) gives
          excellent outcome.
        explanation: >-
          States the combination and the preference over lamotrigine. Marked
          PARTIAL because the observation comes from two siblings, which is a worked
          example rather than comparative evidence.
  - name: Ketogenic diet for glucose transporter deficiency
    description: >-
      The one genotype-directed and mechanistically corrective treatment available
      in this syndrome, and it applies only to the small group whose myoclonic
      absences are caused by SLC2A1 variants. In glucose transporter type 1
      deficiency the brain cannot import enough glucose; ketones enter by a
      different transporter that is intact, so a ketogenic diet supplies the fuel
      the broken protein cannot. That makes testing for the gene worth doing even
      though it explains few cases, because the finding changes the treatment
      rather than only the label.
    therapeutic_modality: BEHAVIORAL
    treatment_term:
      preferred_term: Ketogenic Diet
      term:
        id: NCIT:C173168
        label: Ketogenic Diet
    evidence:
      - reference: PMID:21546317
        reference_title: >-
          Video/EEG recording of myoclonic absences in GLUT1 deficiency syndrome
          with a hot-spot R126C mutation in the SLC2A1 gene.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Glucose transporter type 1 deficiency syndrome (GLUT1DS) is an inborn
          error of brain energy metabolism characterized by impaired glucose
          transport into the brain.
        explanation: >-
          Establishes the metabolic defect that the ketogenic diet is designed to
          bypass, in a patient whose presentation was myoclonic absence epilepsy.
          Marked PARTIAL because this report characterizes the disease and the case
          rather than reporting the dietary response.
      - reference: PMID:32913944
        reference_title: >-
          Glut1 Deficiency Syndrome (Glut1DS): State of the art in 2020 and
          recommendations of the international Glut1DS study group.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Age-specific ketogenic diet therapies remain the standard of care.
        explanation: >-
          Attests to the therapy itself rather than only to the disease, which is
          what this record needed. Tagged OTHER because it is a consensus review
          statement of standard practice rather than a reported patient series.
      - reference: PMID:32913944
        reference_title: >-
          Glut1 Deficiency Syndrome (Glut1DS): State of the art in 2020 and
          recommendations of the international Glut1DS study group.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Best outcomes correlate with early treatment.
        explanation: >-
          Supports the argument for testing early rather than after prolonged
          medication failure, which is the practical reason this gene is worth
          excluding in a child with myoclonic absences.
  - name: Avoidance of carbamazepine and other seizure-aggravating drugs
    description: >-
      Sodium channel blockers aggravate generalized absence seizures, and in this
      syndrome the effect has been documented dramatically: seizure frequency rose
      from five to a hundred a day on carbamazepine and phenobarbitone, and fell on
      withdrawal. This is a mechanism-derived contraindication, not a tolerability
      issue, and it matters because the conspicuous motor component invites a
      misdiagnosis of focal epilepsy, for which carbamazepine would be a natural
      choice.
    therapeutic_modality: BEHAVIORAL
    treatment_term:
      preferred_term: Supportive Care
      term:
        id: NCIT:C15747
        label: Supportive Care
    evidence:
      - reference: PMID:24491945
        reference_title: Epilepsy with myoclonic absences in siblings.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Increase in the seizure frequency from 5 to 100/day was observed due to
          use of carbamazepine and phenobarbitone which decreased with its
          withdrawal and introduction of valproate.
        explanation: >-
          Documents the aggravation and its reversal on withdrawal, which is about
          as close to a within-patient controlled observation as this literature
          offers.
  - name: Corpus callosotomy for the drug-resistant atonic subgroup
    description: >-
      Disconnecting the corpus callosum interrupts the rapid interhemispheric
      spread that synchronizes generalized seizures, and it is offered when
      medication fails, particularly in the subgroup with an atonic component in
      whom drop attacks are the disabling problem. The evidence in this syndrome is
      two patients, so it is curated as encouraging and unproven, which is how the
      reporting authors describe it.
    therapeutic_modality: SURGERY
    treatment_term:
      preferred_term: corpus callosotomy
      term:
        id: NCIT:C15329
        label: Surgical Procedure
    target_mechanisms:
      - target: Rhythmic Myoclonus with Progressive Tonic Contraction
        treatment_effect: INHIBITS
    evidence:
      - reference: PMID:35770757
        reference_title: >-
          Epilepsy with myoclonic absences: a case series highlighting clinical
          heterogeneity and surgical management.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Two patients with epilepsy with myoclonic absences with atonia underwent
          corpus callosotomy; one patient was seizurefree eight months after
          surgery and the other had greater than 50% seizure reduction over a
          five-month period.
        explanation: >-
          Reports the outcomes in the only two operated patients. Marked PARTIAL
          because two patients with short follow-up cannot establish efficacy, and
          the authors say so.
      - reference: PMID:35770757
        reference_title: >-
          Epilepsy with myoclonic absences: a case series highlighting clinical
          heterogeneity and surgical management.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Corpus callosotomy was performed in two of these patients with
          encouraging seizure response thus far, however, the efficacy of this
          treatment should be further evaluated in a larger study.
        explanation: >-
          The authors' own statement of the evidential limits, which is why this
          record is framed as an option rather than a recommendation.
diagnosis:
  - name: Video-electroencephalography with surface electromyography
    description: >-
      The diagnostic test, and the reason the syndrome is under-recognized. The
      electroencephalogram alone shows generalized three-hertz spike-wave and
      looks like childhood absence epilepsy. What makes the diagnosis is
      simultaneous electromyography from the deltoids showing myoclonic bursts
      locked to each discharge on a rising baseline of tonic contraction. Without
      video and polygraphy the diagnosis is routinely missed.
    diagnosis_term:
      preferred_term: Electroencephalography
      term:
        id: NCIT:C38054
        label: Electroencephalography
    results: >-
      Generalized three-hertz spike-wave with time-locked myoclonic bursts on
      surface electromyography, superimposed on a progressively increasing tonic
      contraction.
    evidence:
      - reference: PMID:17044728
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          as such, despite an ECG, the diagnosis may be missed in the absence of
          video documentation of the seizure and/or adequate polygraphy
        explanation: >-
          States directly that the diagnosis depends on video and polygraphy rather
          than on the electroencephalogram alone.
      - reference: PMID:24491945
        reference_title: Epilepsy with myoclonic absences in siblings.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Myoclonic absences (MAs) were characterized by rhythmic, bilateral,
          synchronous, symmetric 3-Hz spike-wave discharges, associated with EMG
          myoclonic bursts at 3 Hz, superimposed on a progressively increasing
          tonic muscle contraction.
        explanation: >-
          Describes the polygraphic findings reported in the results field.
  - name: Brain MRI
    description: >-
      Imaging does not diagnose the syndrome; it decides which version of it the
      child has. A normal scan is consistent with the idiopathic form, and a
      structural abnormality reclassifies the case as symptomatic, which carries
      the worse prognosis and is the arm the outcome controversy in this entry
      turns on. That makes imaging part of the diagnostic pathway rather than an
      optional extra, and it is also the first test named in the proposed
      experiment of that discussion.
    diagnosis_term:
      preferred_term: Magnetic Resonance Imaging
      term:
        id: NCIT:C16809
        label: Magnetic Resonance Imaging
    results: >-
      Normal in the idiopathic form; a structural abnormality reclassifies the
      case as symptomatic.
    evidence:
      - reference: PMID:40380288
        reference_title: Research progress on epilepsy with myoclonic absence.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          magnetic resonance imaging (MRI) serving to exclude structural
          etiologies
        explanation: >-
          States the role of imaging in the diagnostic workup for this syndrome,
          alongside the polygraphic recording this entry already curates.
  - name: Lumbar puncture with paired CSF and blood glucose
    description: >-
      The test that finds the one treatable cause. Glucose transporter type 1
      deficiency is diagnosed by a low cerebrospinal fluid glucose against a
      normal blood glucose, and it is worth doing in a child with myoclonic
      absences precisely because a positive result changes the treatment to a
      ketogenic diet rather than only changing the label. It closes the loop the
      genetic section and the diet record open.
    diagnosis_term:
      preferred_term: Lumbar Puncture
      term:
        id: NCIT:C15327
        label: Lumbar Puncture
    results: >-
      Low cerebrospinal fluid glucose with low to low-normal lactate against
      normal blood values indicates glucose transporter type 1 deficiency.
    evidence:
      - reference: PMID:32913944
        reference_title: >-
          Glut1 Deficiency Syndrome (Glut1DS): State of the art in 2020 and
          recommendations of the international Glut1DS study group.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          The principal diagnostic tool is a lumbar puncture showing low CSF
          glucose and low to low-normal lactate concentrations in the setting of
          normal blood glucose and lactate concentrations.
        explanation: >-
          States the diagnostic test and its expected result for the one cause in
          this syndrome that has a specific therapy.
  - name: Cytogenetic testing (karyotype or chromosomal microarray)
    description: >-
      Worth doing rather than relying on a gene panel alone, because the reported
      chromosomal causes of this syndrome are copy number changes that sequencing
      a gene list will not find. Trisomy 12p is the best-documented example, and
      the authors of that report argue from it that myoclonic absences can be a
      direct or indirect consequence of a chromosomal abnormality in at least some
      patients. This is the test that separates the symptomatic form from the
      idiopathic one when imaging is unrevealing.
    diagnosis_term:
      preferred_term: Cytogenetic Analysis
      term:
        id: NCIT:C18280
        label: Cytogenetic Analysis
    results: >-
      A copy number abnormality in the symptomatic minority; normal in the
      idiopathic form.
    evidence:
      - reference: PMID:9545186
        reference_title: Trisomy 12p and epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Our patient and other sporadic reports in the literature seem to support
          the hypothesis that, at least in some cases, myoclonic absences can be a
          direct or indirect effect of a chromosomopathy.
        explanation: >-
          States the authors' inference that a chromosomal abnormality can produce
          this seizure syndrome, which is the rationale for testing for one.
      - reference: PMID:9545186
        reference_title: Trisomy 12p and epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          We report the case of a 6-year-2-month-old female affected by trisomy 12p
          syndrome. Seizures were typical myoclonic absences from both the clinical
          and EEG points of view.
        explanation: >-
          The worked case, with seizures typical of the syndrome on both clinical
          and electrographic grounds, which is what makes it evidence for the
          syndrome rather than for a lookalike.
differential_diagnoses:
  - name: Childhood Absence Epilepsy
    disease_term:
      preferred_term: childhood absence epilepsy
      term:
        id: MONDO:0010826
        label: childhood absence epilepsy
    description: >-
      The nearest neighbour and the entity from which this syndrome is hardest to
      separate, because the electroencephalographic discharge is the same. The
      separation rests entirely on the motor phenomena, which is exactly why the
      distinctness of the syndrome is disputed.
    distinguishing_features:
      - Absences are unaccompanied by rhythmic myoclonus locked to the discharge.
      - No progressive tonic contraction raising the arms during the seizure.
      - Female preponderance rather than the male preponderance of myoclonic absences.
      - Higher rate of spontaneous remission and better medication response overall.
    evidence:
      - reference: PMID:15737698
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          The ictal EEG shows bilateral, synchronous and symmetrical spike and wave
          discharges repeated at 3 Hz (similar to that observed in typical absences
          of childhood absence epilepsy) in strict relation with myoclonias
          recorded on EMG.
        explanation: >-
          Establishes the electrographic identity with childhood absence epilepsy
          and the motor coupling that is the only difference, which is what makes
          this differential both necessary and difficult.
  - name: Epilepsy with Myoclonic-Atonic Seizures
    disease_term:
      preferred_term: epilepsy with myoclonic atonic seizures
      term:
        id: MONDO:0014633
        label: epilepsy with myoclonic atonic seizures
    description: >-
      A nomenclature trap as much as a clinical one. The names differ by one word
      and this entry now curates an atonic seizure phenotype in 40 percent of
      patients, so the two are easy to conflate on paper. The seizures are not the
      same event: there the myoclonic jerk and the loss of tone are one sequence
      producing a fall, here the jerks are locked to each spike-wave cycle on a
      rising background of tonic contraction, and the atonic component when present
      is an additional feature rather than the defining one.
    distinguishing_features:
      - The defining seizure is a myoclonic-atonic drop attack, not an absence with cycle-locked myoclonus.
      - Consciousness is not the primary casualty; the fall is.
      - Classified by the ILAE among the developmental and epileptic encephalopathies rather than among the generalized epilepsies.
      - No progressive tonic contraction building through the seizure.
    evidence:
      - reference: PMID:35503717
        reference_title: >-
          International League Against Epilepsy classification and definition of
          epilepsy syndromes with onset in childhood: Position paper by the ILAE
          Task Force on Nosology and Definitions.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          developmental and/or epileptic encephalopathies, comprising five
          syndromes: epilepsy with myoclonic-atonic seizures, Lennox-Gastaut
          syndrome, developmental and/or epileptic encephalopathy with
          spike-and-wave activation in sleep, hemiconvulsion-hemiplegia-epilepsy
          syndrome, and febrile infection-related epilepsy syndrome.
        explanation: >-
          Places epilepsy with myoclonic-atonic seizures in the encephalopathy
          category while this entry's syndrome sits among the generalized
          epilepsies, which is the classificatory basis of the distinction and the
          reason the near-identical names denote different things.
  - name: Epilepsy with Eyelid Myoclonia
    disease_term:
      preferred_term: epilepsy with eyelid myoclonia
      term:
        id: MONDO:0015346
        label: epilepsy with eyelid myoclonia
    description: >-
      The third ILAE childhood generalized syndrome, and the other one defined by
      an absence with a myoclonic accompaniment. The distinction is topographic:
      the jerking is confined to the eyelids rather than being diffuse and axial.
    distinguishing_features:
      - Myoclonus is confined to the eyelids with upward eye deviation.
      - Eye closure and photic stimulation are the characteristic triggers.
      - No progressive axial tonic contraction.
    evidence:
      - reference: PMID:17044728
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          MA need to be distinguished from absences with other types of prominent
          myoclonic accompaniment (perioral, eyelid, limbs).
        explanation: >-
          States explicitly that absences with other patterns of myoclonic
          accompaniment, eyelid among them, must be separated from myoclonic
          absences.
  - name: Lennox-Gastaut Syndrome
    disease_term:
      preferred_term: Lennox-Gastaut syndrome
      term:
        id: MONDO:0016532
        label: Lennox-Gastaut syndrome
    description: >-
      Both a differential and a destination: some children with epilepsy with
      myoclonic absences evolve into Lennox-Gastaut syndrome, so the distinction is
      partly a matter of when in the course the child is seen.
    distinguishing_features:
      - Slow spike-wave at 1.5 to 2.5 hertz rather than three-hertz spike-wave.
      - Tonic seizures in sleep are mandatory and are not a feature of myoclonic absences.
      - Multiple seizure types with a diffusely abnormal background from the outset.
    evidence:
      - reference: PMID:17044728
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          These patients may experience cognitive deterioration and, in some cases,
          evolution towards a more severe form of epilepsy, including the
          Lennox-Gastaut syndrome.
        explanation: >-
          Establishes the evolution that makes this both a differential and a
          possible outcome of the same disease.
discussions:
  - discussion_id: ema_distinct_syndrome_or_absence_variant
    kind: CONTROVERSY
    status: UNDER_DISCUSSION
    prompt: >-
      Is epilepsy with myoclonic absences a distinct syndrome, or is it childhood
      absence epilepsy with a prominent myoclonic accompaniment that happens to
      have been named separately?
    attaches_to:
      - pathophysiology#Hypersynchronous Three-Hertz Thalamocortical Spike-Wave Oscillation
      - pathophysiology#Cycle-Locked Recruitment of Motor Output
    rationale: >-
      The syndrome was defined on a seizure type rather than on an etiology, an
      age, or a gene, and the literature that defined it now describes it as a
      somewhat controversial entity in those words. The case for distinctness is
      real: the motor recruitment is not a soft accompaniment but a
      cycle-by-cycle coupling with a separate progressive tonic component, the sex
      ratio runs the opposite way to childhood absence epilepsy, drug resistance is
      commoner, and a subset evolve toward Lennox-Gastaut, which typical absences
      do not. The case against is equally real: the electroencephalographic
      discharge is explicitly described as similar to that of childhood absence
      epilepsy, no distinct genetic or structural basis has been identified, and
      myoclonic components have since been described across a range of generalized
      epilepsies with absences, which erodes the specificity of the original
      defining observation. If myoclonic accompaniments form a continuum, then
      where this syndrome ends and childhood absence epilepsy with myoclonia begins
      is a matter of degree, and the boundary is drawn by whoever is holding the
      electromyography leads. The practical stake is not trivial: the label carries
      a worse prognosis and a lower threshold for surgical referral, so
      misassignment in either direction changes what a family is told.
    proposed_experiments:
      - experiment_id: exp_ema_quantitative_myoclonus_continuum
        name: Quantitative polygraphic comparison across absence syndromes
        description: >-
          Apply identical quantitative electromyographic analysis, measuring burst
          amplitude, the proportion of discharge cycles carrying a burst, and tonic
          baseline drift, to unselected children with absence seizures across the
          syndromes, and test whether the distribution is bimodal, which would
          support two entities, or continuous, which would support one.
        decision_criterion: >-
          A bimodal distribution with a gap between myoclonic absences and other
          absences with myoclonic accompaniment would support distinctness. A
          continuous distribution would show the boundary is conventional, and the
          syndrome would be better modeled as a severity region of a spectrum.
      - experiment_id: exp_ema_genetic_architecture_comparison
        name: Shared versus distinct genetic architecture with childhood absence epilepsy
        description: >-
          Compare common-variant liability and rare-variant burden between children
          meeting criteria for epilepsy with myoclonic absences and children with
          childhood absence epilepsy, ascertained in the same centres with the same
          polygraphic protocol.
        decision_criterion: >-
          A shared genetic architecture would support one spectrum with the motor
          phenotype as a modifier. A distinguishable architecture would support two
          entities and would give the syndrome a basis beyond its seizure
          semiology.
    evidence:
      - reference: PMID:17044728
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          epilepsy with myoclonic absences (EMA) stands out as a somewhat
          controversial entity
        explanation: >-
          States the controversy in the literature's own words, which is what makes
          this a curated dispute rather than a curator's doubt.
      - reference: PMID:17044728
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          the sound and evident clinical characteristics on which it was identified
          some 30 years ago have evolved, mostly as a consequence of changes in the
          practical management of epilepsies and to the description of myoclonic
          components in a variety of other generalised epilepsies with absences
        explanation: >-
          Gives the specific reason the boundary has eroded, namely that the
          defining feature turned out not to be unique to this syndrome.
      - reference: PMID:35503717
        reference_title: >-
          International League Against Epilepsy classification and definition of
          epilepsy syndromes with onset in childhood: Position paper by the ILAE
          Task Force on Nosology and Definitions.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          generalized epilepsies, comprising three syndromes: childhood absence
          epilepsy, epilepsy with myoclonic absence, and epilepsy with eyelid
          myoclonia
        explanation: >-
          Records the opposing position, that the ILAE currently treats this as one
          of three distinct childhood generalized syndromes, which is why this entry
          models it as a syndrome while flagging the dispute.
      - reference: PMID:15737698
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          The ictal EEG shows bilateral, synchronous and symmetrical spike and wave
          discharges repeated at 3 Hz (similar to that observed in typical absences
          of childhood absence epilepsy) in strict relation with myoclonias
          recorded on EMG.
        explanation: >-
          Supports the lumping side by asserting electrographic similarity, and the
          splitting side by asserting strict motor coupling. Marked PARTIAL because
          it cuts both ways.
  - discussion_id: ema_why_is_the_motor_system_recruited
    kind: KNOWLEDGE_GAP
    status: OPEN
    prompt: >-
      Why does a three-hertz thalamocortical spike-wave discharge drive rhythmic
      myoclonus and a building tonic contraction in this syndrome, when the same
      discharge produces a motionless stare in childhood absence epilepsy?
    attaches_to:
      - pathophysiology#Cycle-Locked Recruitment of Motor Output
      - pathophysiology#Hypersynchronous Three-Hertz Thalamocortical Spike-Wave Oscillation
    rationale: >-
      This is the central unexplained fact of the syndrome and it is unusually
      well-posed, because the confounder is controlled by nature: the oscillation
      is described as similar in the two conditions, so whatever differs is
      downstream of it. Several accounts are available and none has been tested
      against the others. The discharge may involve motor cortex in this syndrome
      and not in childhood absence epilepsy, which is a straightforward
      source-localization question that modern high-density recording could answer
      and apparently has not. The coupling between cortical discharge and
      corticospinal output may be abnormally strong, which is a corticomuscular
      coherence question. The tonic component may not share a generator with the
      jerks at all, since it builds progressively rather than following the
      three-hertz rhythm, which would suggest a separate brainstem or
      reticulospinal contribution running in parallel. Or the difference may lie in
      developmental maturation of descending motor pathways, which would predict
      that age at onset, later here than in childhood absence epilepsy, is part of
      the explanation rather than an incidental demographic fact. Answering this
      would also bear directly on the nosological dispute curated alongside it,
      because a demonstrated difference in generator would settle the question of
      whether this is a separate entity.
    proposed_experiments:
      - experiment_id: exp_ema_source_localization_and_corticomuscular_coherence
        name: Source localization and corticomuscular coherence across absence syndromes
        description: >-
          High-density electroencephalography with simultaneous multi-muscle
          electromyography during spontaneous seizures in both syndromes, with
          source reconstruction of the discharge and measurement of
          corticomuscular coherence, testing whether motor cortex participates in
          the discharge in myoclonic absences and not in typical absences, and
          whether the cortex-to-muscle coupling differs in strength.
        decision_criterion: >-
          Motor cortex participation or stronger corticomuscular coherence specific
          to myoclonic absences would locate the difference in the cortical
          generator. Indistinguishable source and coherence would push the
          explanation subcortically, toward the descending pathways or the
          brainstem.
      - experiment_id: exp_ema_tonic_component_generator
        name: Separating the tonic component from the myoclonic component
        description: >-
          Analyse the progressive tonic contraction independently of the
          three-hertz bursts, relating its build-up to discharge features and to
          brainstem reflex measures, to test whether it is a slow envelope of the
          same cortical drive or an independently generated phenomenon.
        decision_criterion: >-
          A tonic component that tracks discharge parameters would indicate a
          single cortical generator with two output timescales. A tonic component
          that varies independently and correlates with brainstem measures would
          establish a second generator, and would explain why this syndrome sits
          closer than typical absence epilepsy to the tonic-seizure epilepsies it
          sometimes evolves into.
    evidence:
      - reference: PMID:15737698
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          The ictal EEG shows bilateral, synchronous and symmetrical spike and wave
          discharges repeated at 3 Hz (similar to that observed in typical absences
          of childhood absence epilepsy) in strict relation with myoclonias
          recorded on EMG.
        explanation: >-
          Establishes both premises of the gap: the discharge is similar between
          syndromes, and the motor coupling is strict, so the difference must lie
          downstream of the oscillation.
      - reference: PMID:24491945
        reference_title: Epilepsy with myoclonic absences in siblings.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Myoclonic absences (MAs) were characterized by rhythmic, bilateral,
          synchronous, symmetric 3-Hz spike-wave discharges, associated with EMG
          myoclonic bursts at 3 Hz, superimposed on a progressively increasing
          tonic muscle contraction.
        explanation: >-
          Documents that the tonic component is superimposed on rather than
          rhythmic with the bursts, which is the observation motivating the
          two-generator hypothesis.
      - reference: PMID:17044728
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Neurophysiologically, axial hypertonia and rhythmic jerks may be recorded
          on polygraphic surface electromyogram leads in association with the
          typical SW discharges
        explanation: >-
          Confirms that both motor components are measurable with routine
          polygraphy, which is what makes the proposed experiments feasible rather
          than aspirational.
  - discussion_id: ema_two_diseases_behind_one_seizure
    kind: CONTROVERSY
    status: OPEN
    prompt: >-
      The outcome splits sharply according to whether generalized tonic-clonic
      seizures accompany the myoclonic absences. Are these two different diseases
      sharing a seizure type, or one disease with a severity gradient?
    attaches_to:
      - pathophysiology#Drug-Resistant Course with Cognitive Decline in a Subset
      - pathophysiology#Heritable Thalamocortical Susceptibility
    rationale: >-
      The prognostic split is unusually clean for a childhood epilepsy. Children
      with myoclonic absences as their only seizure type generally respond to
      combination therapy and do well; children who also have generalized
      tonic-clonic seizures often persist, deteriorate cognitively, or move toward
      Lennox-Gastaut syndrome. The two-disease reading takes the associated
      tonic-clonic seizures as a marker of a different underlying condition, most
      obviously a symptomatic form with a structural or chromosomal cause that
      happens to express myoclonic absences among its seizure types; the literature
      already distinguishes idiopathic from symptomatic forms, which gives this
      reading a foothold. The one-disease reading takes the tonic-clonic seizures
      as a severity marker of the same liability, on the grounds that additional
      seizure types accompany greater severity across the generalized epilepsies
      generally, and notes that no distinct etiology has actually been demonstrated
      for the worse-outcome group. A newer case series complicates both by
      identifying an atonic component as a separate and strong predictor of
      medication failure, three quarters of that subgroup failing to reach seizure
      freedom, which suggests the relevant stratification may not be the one the
      older literature drew. The stake is prognostic honesty: a family told at
      diagnosis that this syndrome usually responds well to valproate and
      ethosuximide is being given the statistics of a subgroup their child may not
      belong to.
    proposed_experiments:
      - experiment_id: exp_ema_etiology_stratified_outcome_cohort
        name: Etiology-stratified outcome cohort with systematic investigation
        description: >-
          A multicentre cohort in which every child meeting polygraphic criteria
          receives the same investigation, including high-resolution imaging,
          chromosomal microarray, and epilepsy gene panel, with outcome recorded
          against both the presence of generalized tonic-clonic seizures and the
          presence of an identified etiology and of an atonic component.
        decision_criterion: >-
          If poor outcome tracks identified etiology rather than seizure
          co-occurrence, the two-disease reading is supported and the prognosis
          should be given on etiology. If poor outcome tracks seizure co-occurrence
          independently of etiology, it is a severity marker within one disease.
    evidence:
      - reference: PMID:15737698
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          The evolution is variable and seems to depend on the existence or not of
          GTCS.
        explanation: >-
          States the prognostic split that this discussion is about.
      - reference: PMID:17044728
        reference_title: Epilepsy with myoclonic absences.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          The more benign cases usually present with MA as the only seizure type,
          while patients who experience other seizures, especially generalised
          tonic-clonic seizures, in association with MA may have a less favourable
          outcome.
        explanation: >-
          Independent statement of the same split, which is what makes it a stable
          observation rather than one group's impression.
      - reference: PMID:35770757
        reference_title: >-
          Epilepsy with myoclonic absences: a case series highlighting clinical
          heterogeneity and surgical management.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Of patients with an atonic component, 75% did not achieve seizure freedom
          with medication alone.
        explanation: >-
          Identifies a different stratifying feature from the one the older
          literature emphasizes. Marked PARTIAL because ten patients cannot settle
          which stratification matters, but it is enough to show the question is
          open.
      - reference: PMID:24491945
        reference_title: Epilepsy with myoclonic absences in siblings.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Idiopathic and symptomatic EMAs need to be differentiated from childhood
          absence epilepsy with myoclonia.
        explanation: >-
          Establishes that an idiopathic and a symptomatic form are already
          recognized, which is the foothold for the two-disease reading.
📚

References & Deep Research

References

3
PMID:15737698
Epilepsy with myoclonic absences.
No top-level findings curated for this source.
PMID:17044728
Epilepsy with myoclonic absences.
No top-level findings curated for this source.
PMID:35770757
Epilepsy with myoclonic absences: a case series highlighting clinical heterogeneity and surgical management.
No top-level findings curated for this source.

Deep Research

1
Claude Code ▸
Epilepsy with Myoclonic Absences — Research Report
claude-haiku-4-5-20251001, claude-opus-5[1m] 34 citations 2026-08-05T15:21:36.314167

Epilepsy with Myoclonic Absences — Research Report

(a.k.a. Tassinari syndrome, EMA. MONDO:0019487)

sup. Quick framing before the wall of text: this one is a weird little disease. Most absence epilepsies are a brain that briefly goes quiet — the lights flicker, the kid stares, it's over. EMA is a brain that goes quiet and starts drumming at the same time. Same 3-beats-per-second rhythm you see in ordinary childhood absence, but here that rhythm leaks out into the muscles and you can literally watch it: the arms ratchet upward, jerk by jerk, in lockstep with the brainwave. It's the one absence syndrome where the electrical signature is visible from across the room.

That "leak into the motor system" is basically the whole mechanistic story, and it's also the biggest open question in the field.

One caveat up front, stated plainly: EMA is rare enough that there is no large prospective cohort anywhere. Everything below rests on case series of 7–12 patients, a handful of single-case genetic reports, and one 2017 imaging study with two subjects. I've flagged sample sizes throughout because they matter a lot here. Anything I couldn't verify against a real abstract or ontology lookup, I've marked as unverified rather than smoothing it over.

1. Disease Information

What it is

EMA is a rare, childhood-onset generalized epilepsy syndrome whose defining seizure is the myoclonic absence — an impairment-of-awareness spell with rhythmic bilateral jerking of the shoulders and arms, superimposed on a slowly building tonic pull that ratchets the arms up and outward.

MONDO's definition (sourced from Orphanet:86911), verified via local OAK lookup:

"A rare childhood-onset epilepsy characterized by sudden onset, short lasting absence associated with rhythmical myoclonia of head and shoulders."

Historically, Tassinari and colleagues described the seizure type in 1969–70 (PMID:4985251, Rev Neurol Paris; PMID:4194033, Electroencephalogr Clin Neurophysiol — "Studies on spike and wave discharges in man. II. Clinical and EEG aspects of myoclonic absences"), and Tassinari named the syndrome in 1985. Hence "Tassinari syndrome."

The 2025 review by Tang et al. (PMID:40380288) states verbatim:

"Epilepsy with myoclonic absence (EMA) is a rare childhood-onset generalized epilepsy syndrome characterized by myoclonic absence seizures. First discovered by Tassinari et al. in 1969, EMA has been extensively studied by researchers from all over the world."

Identifiers (OAK-verified against local sqlite:obo:mondo)

Resource ID
MONDO MONDO:0019487 — epilepsy with myoclonic absences
Orphanet ORPHA:86911
MedGen 140741
UMLS C0393703
SNOMED CT 230422001
GARD 0019087
NANDO 1200589
ICD-11 foundation 274380122

MONDO parentage: is_a MONDO:0005395 (movement disorder) and is_a MONDO:0800498 (childhood-onset genetic generalized epilepsy syndrome). That dual parentage is actually a nice bit of curation — it encodes the "absence + movement" hybrid nature.

Not available / flagged: there is no dedicated OMIM entry for EMA as a syndrome. It's a clinically-defined electroclinical syndrome, not a Mendelian gene-disease pair, so OMIM entries only exist for the individual gene disorders that can present as EMA (SYNGAP1, SETD1B, SLC2A1, GLUD1, CREBBP). I could not verify a specific ICD-10 code from an authoritative source in this session — do not populate ICD-10 from memory; Orphanet's mapping page was behind a bot check.

Synonyms

  • Epilepsy with myoclonic absences (EMA) — preferred
  • Myoclonic absence epilepsy (MAE — careful, this abbreviation collides with myoclonic-astatic epilepsy / Doose syndrome; a real named-entity-confusion trap)
  • Tassinari syndrome
  • MONDO records "EMA" EXACT

Data provenance

Aggregated disease-level, entirely. There is no EHR-derived or registry-derived population data for EMA that I could find — the evidence base is single-center retrospective chart reviews plus case reports. No OMOP/OHDSI phenotype algorithm exists for it.

2. Etiology

The honest summary

Tang et al. 2025 (PMID:40380288), verbatim:

"Overall, the etiology of EMA remains unclear and appears to be heterogeneous, categorized into idiopathic, symptomatic and cryptogenic forms."

Think of EMA less as a disease with a cause and more as a final common pathway — a particular way a child's thalamocortical circuit can misfire, reachable from many different genetic starting points. Like a fever: lots of upstream causes, one recognizable downstream output.

Roughly one-third of cases are idiopathic (myoclonic absences only, normal MRI, normal EEG background, better outcome); two-thirds are symptomatic or have additional seizure types (Tang 2025).

Genetic risk factors

Family history of epilepsy in 20–25% of EMA patients (Tang 2025). In the Videira 2023 series (PMID:36893512), only 2/7 had a positive family history. Sibling cases exist (Cherian 2014, PMID:24491945, "Epilepsy with myoclonic absences in siblings"), which points at a heritable component without a clean Mendelian pattern.

Single-gene and chromosomal findings reported in EMA — each of these is a case report or small series, not an established gene-disease association:

Lesion Evidence PMID
SYNGAP1 truncation by de novo balanced translocation t(6;22)(p21.32;q11.21) Klitten 2011, n=1 22050443
SETD1B de novo missense c.386T>G p.(Val129Gly) Hiraide 2019, n=1 (+1 prior) 31440728
SLC2A1 (GLUT1DS), R126C hot-spot Gökben 2011, n=1 21546317
GLUD1 (glutamate dehydrogenase), gain-of-function, HI/HA syndrome Bahi-Buisson 2008, n=4 family members 18321734
CREBBP pathogenic variant (Rubinstein-Taybi) Matsubara 2025, n=1 40451035
Trisomy 12p Elia 1998, n=1 9545186
2q13 recurrent microdeletion (BUB1, ACOXL, BCL2L11, ANAPC1, MERTK, TMEM87B, FBLN7, ZC3H8, ZC3H6) Ogawa 2023, n=1 36796225
15q11.2 microdeletion (maternal), with Angelman-like notched delta on EEG Chin 2026 42434914
Inverted duplication chromosome 15 Elia, cited in Tang 2025 — (secondary)
FOXP1, MBD5 cited in Tang 2025 via Frydson — (secondary)

Key verbatim quotes:

Klitten 2011 (PMID:22050443):

"the breakpoint at 6p21.32 was found to truncate the N-methyl-d-aspartate (NMDA)-receptor associated gene SYNGAP1... This finding, together with our report, suggests that dysfunction of SYNGAP1 contributes to the development of generalized epilepsy, including EMA."

Hiraide 2019 (PMID:31440728):

"Therefore, this report supports the indication that SETD1B may be a causative gene for neurodevelopmental disorders and suggests that epilepsy with myoclonic absences may be a characteristic feature of SETD1B-related disorders."

Gökben 2011 (PMID:21546317):

"Although typical absences are frequent in GLUT1DS, myoclonic absence seizures are rarely reported. Here we describe a novel Turkish patient with a hot-spot mutation (R126C) in the SLC2A1 gene who presented with unusual myoclonic absence epilepsy and paroxysmal shivering."

Bahi-Buisson 2008 (PMID:18321734):

"The mother, brother and both sisters had myoclonic absence seizures, but only the mother and one sister had the complete HI/HA pattern."

The broader genetic landscape of absence epilepsies (Balestrini et al., Epilepsia 2026, doi:10.1111/epi.18655) identifies SLC2A1, SLC6A1, SYNGAP1, CHD2, SCN1A as the most frequent monogenic causes across absence-featuring epilepsies, with CACNA1A also implicated. That paper reports hyperventilation as a precipitant across CACNA1A, GABRA2, GABRG2, SETD1B, SLC2A1, SLC6A1, and SYNGAP1 variants, and notes atypical absences were most common with SYNGAP1 (n=9).

Environmental / acquired risk factors

Tang 2025:

"Symptomatic EMA is associated with factors including prematurity, perinatal damage, consanguineous marriage, and congenital hemiparesis."

Older literature (via MedLink secondary summary, unverified against primary source) puts etiological factors in ~35% of cases: prematurity, perinatal damage, consanguinity, congenital hemiparesis, chromosomal anomalies.

Sex is a genuine risk factor: male predominance ~70% (Tang 2025; epilepsydiagnosis.org). Though note the cohorts disagree — Zanzmera 2016 was 50% male, Videira 2023 was 7/7 male, Hu 2025 was 7:4. Small-n noise.

Seizure precipitants (not disease-risk factors, but seizure-trigger factors — worth keeping distinct): - Hyperventilation - Awakening - Intermittent photic stimulation: 14% of myoclonic absences are IPS-inducible (Tang 2025)

Protective factors

Not available. No protective genetic variants or lifestyle protective factors have been reported for EMA. Given the rarity, no GWAS exists.

Gene–environment interactions

Largely not available. The one real example: in GLUT1 deficiency, the environmental variable is dietary — fasting and carbohydrate state modulate seizures, and the ketogenic diet is directly therapeutic because it bypasses the broken glucose transporter. That's a genuine G×E axis (SLC2A1 genotype × dietary substrate), and it's actionable.

3. Phenotypes

The core seizure — myoclonic absence

HP:0011150 — Myoclonic absence seizure (OAK-verified). This is mandatory for the diagnosis under ILAE 2022.

What it looks like, per Tang 2025:

"The severity of impaired consciousness is usually milder than that in childhood absence epilepsy (CAE), however, the seizure duration (ranging from 8–60 s) exceeds that of CAE"

"The tonic element affecting both shoulders is often present in myoclonus, leading to rigid abduction and elevation of the upper limbs"

"Rhythmic myoclonic seizures primarily affect the shoulder and limb muscles with rare eyelid involvement"

The mechanical picture: the jerks are the fast beat, the tonic contraction is a slow steady pull underneath, and because the jerks ride on top of a rising tonic baseline, the arms climb upward in a ratcheting staircase over the course of the seizure. Like a socket wrench — each click advances and holds.

Videira 2023 (PMID:36893512, n=7): "All patients had seizures with impairment of awareness accompanied by bilateral rhythmic myoclonus of the proximal segments of the upper limbs, followed by arm abduction," asymmetrical in 4/7, duration 4–60 s, all with ≥2 seizures/day.

Hu 2025 (PMID:40414191, n=11): 4/11 (36.36%) had asymmetrical features.

Frequency: multiple daily, "ranging from several to dozens" per day (Tang 2025), abrupt onset and offset.

Phenotype HPO term (verified) Frequency Onset Course Notes
Myoclonic absence seizure HP:0011150 100% (definitional) childhood recurrent/daily mandatory for dx
Generalized tonic-clonic seizure HP:0002069 Bilateral tonic-clonic seizure ~45% (Bureau 2005); 42% (Zanzmera 2016) after MA onset recurrent key prognostic marker
Atonic seizure HP:0010819 40% had atonic component (Carter 2022, n=10) childhood recurrent drives drug resistance
Generalized myoclonic seizure HP:0002123 present in subset childhood recurrent Hu 2025
Typical absence seizure HP:0011147 subset childhood recurrent
Myoclonic absence status epilepticus HP:0032865 20% (Carter 2022, n=10) childhood episodic incl. a twin pair
Intellectual disability HP:0001249 ~70% eventually (epilepsydiagnosis.org); 20/28 in Tassinari follow-up variable progressive in subset
Delayed speech and language development HP:0000750 3/6 drug-resistant patients (Hu 2025) pre- or post-onset
Developmental regression HP:0002376 7/15 initially-normal patients (Tassinari series) after onset progressive
ADHD HP:0007018 subset childhood chronic Tang 2025
Autism HP:0000717 subset (SETD1B, 2q13, SYNGAP1 cases) childhood stable
EEG with spike-wave complexes (2.5–3.5 Hz) HP:0010848 ~82% (Zanzmera 2016) — — ictal + interictal
EEG with generalized epileptiform discharges HP:0011198 high — —
EEG with photoparoxysmal response HP:0010852 14% IPS-inducible — — Tang 2025
EEG with hyperventilation-induced generalized epileptiform discharges HP:0011184 common — —
Childhood onset HP:0011463 — — — onset descriptor

Cognitive trajectory — the part that actually hurts

Tang 2025, summarizing Tassinari's follow-up of 28 patients:

"13 exhibited intellectual impairment before or at MA onset, while 15 initially showed normal intelligence—of these, 8 remained normal throughout the evolution but 7 developed significant mental deterioration during disease progression. Overall, 20 patients (including 13 with pre-existing and 7 with acquired impairment) ultimately exhibited cognitive deficits, presenting a markedly different neurodevelopmental trajectory compared to childhood absence epilepsy."

And the sting in the tail:

"Although seizures may gradually diminish over time, the accompanying cognitive deficits frequently persist, and complete functional recovery is rarely achieved."

"In most children with drug-resistant EMA, the severity of cognitive decline is proportional to the duration of intractable epilepsy."

That last one is the clinically actionable claim in the whole report: time-with-uncontrolled-seizures appears to be the dose. It argues for aggressive early control. It's also an observational correlation from a small series and could easily be confounded by severity — worth curating as a hypothesis, not a fact.

Unusual presentations worth knowing

Complex gestural automatisms — Myers & Scheffer 2018 (PMID:29325826):

"complex gestural automatisms were often observed; in one case, a boy undid his seatbelt and attempted to exit a moving vehicle... Complex automatisms have not been described in myoclonic absence seizures. This generalized seizure type can be confused with focal seizures when these ictal behaviours occur."

Focal seizures in EMA: Çetin 2016, PMID:27596001, "A rare finding in epilepsy with myoclonic absences: focal seizure."

Quality of life

Not available as measured data. No EQ-5D, SF-36, PROMIS, or QOLCE data specific to EMA exists that I could find. Impact is inferable from the seizure burden (dozens daily) plus the cognitive/behavioral comorbidity load, but nobody has measured it. This is a real gap.

4. Genetic / Molecular Information

Causal genes

There is no single causal gene. What exists is a set of genes in which individual patients have presented with an EMA phenotype. Curate these as relationship_type: CAUSATIVE only for the specific reported cases, and consider SUSCEPTIBILITY/MODIFIER framing for the syndrome as a whole.

Gene HGNC Protein / function Variant reported Mechanism PMID
SYNGAP1 hgnc:11497* Synaptic Ras-GTPase-activating protein 1; NMDA-receptor-associated postsynaptic regulator de novo balanced translocation t(6;22)(p21.32;q11.21), truncating haploinsufficiency / LoF 22050443
SETD1B hgnc:29187* Histone H3 lysine 4 methyltransferase component de novo c.386T>G p.(Val129Gly), missense LoF, epigenetic dysregulation 31440728
SLC2A1 hgnc:11005* GLUT1, blood-brain-barrier glucose transporter R126C (hot-spot), missense LoF, impaired brain glucose supply 21546317
GLUD1 hgnc:4335* Glutamate dehydrogenase dominantly inherited activating variant gain of function 18321734
CREBBP hgnc:2348* CREB-binding protein, histone acetyltransferase pathogenic variant (Rubinstein-Taybi) LoF 40451035

* HGNC IDs above are from memory and were NOT verified with OAK in this session. Verify each with just validate-terms before committing any of them to a KB entry. Note this repo uses lowercase hgnc:.

Mechanistic notes per gene

SYNGAP1 — sits in the postsynaptic density and acts as a brake on Ras signaling downstream of NMDA receptors. Lose one copy and excitatory synapses mature too early and too strong. Relevant GO: GO:0098989 (NMDA selective glutamate receptor signaling pathway), GO:0050803 (regulation of synapse structure or activity). Note Klitten's framing that "Two-thirds of the patients described so far also have generalized epilepsy."

SETD1B — writes the H3K4 methyl mark, an activating chromatin tag. Relevant GO molecular function: GO:0042800 (histone H3K4 methyltransferase activity). Careful: GO:0051568 "histone H3-K4 methylation" is obsolete in current GO — don't use it.

SLC2A1 / GLUT1 — Tang 2025 describes it as "mainly expressed in endothelial cells and astrocytes of the blood-brain barrier, facilitates glucose transport across the blood-brain barrier into astrocytes to provide energy for the brain." Relevant GO: GO:1904659 (D-glucose transmembrane transport), GO:0098708 (D-glucose import across plasma membrane), GO:0006006 (glucose metabolic process). All OAK-verified. Diagnostic corollary: low CSF glucose / low CSF:blood glucose ratio, and it's treatable with ketogenic diet — this is the one genotype where finding it changes management immediately.

GLUD1 / GDH — a gain-of-function, which is unusual in this list. Tang 2025 describes it as "Enhanced glutamate dehydrogenase's function, increasing oxidative deamination of glutamate and elevating levels of α-ketoglutaric acid and ammonia." Chronic hyperammonemia plus recurrent hypoglycemia plus depleted brain glutamate → a plausible triple hit on cortical excitability. Note this family was also photosensitive, which is a phenotype marker worth tracking.

Variant classification / allele frequency / somatic vs germline

  • All reported variants are germline, mostly de novo. GLUD1 was dominantly inherited through a family.
  • ACMG classification: individually reported as pathogenic/likely pathogenic in their source papers; I did not query ClinVar directly this session, so treat per-variant classifications as unverified.
  • Allele frequencies: not available. These are private/de novo variants; gnomAD frequencies would be zero or absent. Not a meaningful field here.

Modifier genes

Not available. No modifier gene has been identified for EMA.

Epigenetic information

Indirect but real: SETD1B (H3K4 methyltransferase) and CREBBP (histone acetyltransferase) are both chromatin writers, and 15q11.2 / inv dup(15) sits in an imprinted region with maternal-origin effects. So chromatin-level regulation shows up three separate ways in this small gene list, which is suggestive. No direct methylome study of EMA patients exists (no ENCODE/Roadmap/DiseaseMeth data specific to EMA).

Chromosomal abnormalities

Genuinely a recurring theme — Elia 1998 (PMID:9545186) argued this explicitly:

"Our patient and other sporadic reports in the literature seem to support the hypothesis that, at least in some cases, myoclonic absences can be a direct or indirect effect of a chromosomopathy."

Reported: trisomy 12p; 2q13 recurrent microdeletion; maternal 15q11.2 microdeletion; inverted duplication of chromosome 15. Practical implication: chromosomal microarray belongs in the EMA workup, not just a gene panel.

5. Environmental Information

  • Environmental toxins / radiation / occupational exposure: not applicable / not reported.
  • Infectious agents: not applicable. EMA is not infection-triggered.
  • Perinatal factors: prematurity and perinatal brain injury are reported as antecedents in symptomatic EMA (Tang 2025). These are the closest thing to an environmental exposure in this disease.
  • Consanguinity: reported as an associated factor (Tang 2025), which is really a genetic-architecture signal (recessive burden) wearing an environmental costume.
  • Lifestyle: the only lifestyle variable with mechanistic weight is diet, and only in the GLUT1-deficiency subgroup, where carbohydrate/ketone state directly modulates brain fuel supply.
  • Iatrogenic aggravation — this is environmental in the practical sense and it matters: several antiseizure drugs worsen EMA. Tang 2025: "Carbamazepine, phenytoin, vigabatrin, gabapentin, and tiagabine should be avoided due to their potential to exacerbate seizures." Levetiracetam aggravation of absence seizures is also documented (Auvin 2011, PMID:21680209) — which is awkward, because levetiracetam is also listed as a second-line option. Genuine tension in the literature; curate both directions.

6. Mechanism / Pathophysiology

The causal chain, as best anyone knows it

Here's the story in plain terms. There's a three-way loop in the brain — cortex talks to thalamus, thalamus talks back to cortex, and a thin shell of inhibitory cells called the thalamic reticular nucleus wraps around the thalamus and gates the whole conversation. Normally that loop does useful rhythmic things (it's the machinery behind sleep spindles). In absence epilepsy it slips into a pathological resonance and starts ringing at 3 cycles per second, and consciousness drops out while it rings.

Tang 2025, verbatim:

"Previous experimental studies have confirmed that the activation of a neural loop—including the cerebral cortex, thalamic reticular nucleus and thalamus—produces the 3 Hz spike-slow wave in absence seizures."

Then EMA does the extra thing. The central unsolved question, stated by Tang 2025:

"A key unresolved question is why motor symptoms (e.g., myoclonus) are prominent in EMA but absent in typical absence epilepsy."

Their proposed model:

"Given these observations, it is plausible that in EMA, the 3 Hz spike-waves generated by the thalamocortical loop likely excessively drive the motor cortex, especially the precentral gyrus, leading to simultaneous occurrence of myoclonus."

So: same oscillator, but the motor strip is unusually strongly coupled into it, and each cycle of the oscillation discharges down the corticospinal tract as a jerk. The 3 Hz rhythm stops being purely an internal brain event and becomes a motor command.

The one piece of direct human evidence

Ikeda et al. 2018 (PMID:28823645), ictal SPECT with 99mTc-ECD in two patients (ages 4 and 8):

  • Patient 1: increased perfusion in "perirolandic areas, thalamus, caudate nucleus, and precuneus"; decreased in frontal and orbitofrontal regions
  • Patient 2: increased in "thalamus, putamen, and globus pallidus"; decreased precuneus

Conclusion, verbatim:

"in addition to the thalamus and basal ganglia, the perirolandic cortical motor area is involved in MAs"

That's the empirical anchor for the motor-cortex-recruitment model. n=2. Please curate it with that caveat attached — it is a suggestive finding, not a demonstrated mechanism.

Proposed causal chain for a pathograph

Upstream → downstream:

  1. Genetic or chromosomal lesion (MOLECULAR) — SYNGAP1/SETD1B/SLC2A1/GLUD1 LoF or GoF, or a CNV. Sets the excitability baseline.
  2. Altered synaptic excitation/inhibition balance (MOLECULAR/CELLULAR) — GO:0007268 chemical synaptic transmission, GO:0060080 inhibitory postsynaptic potential, GO:0007214 GABA signaling pathway, GO:0070588 calcium ion transmembrane transport (T-type Ca²⁺ currents in thalamic relay cells are the classic absence substrate).
  3. Thalamocortical loop enters hypersynchronous 3 Hz resonance (TISSUE) — cortex UBERON:0016529, thalamus UBERON:0001897, thalamic reticular nucleus UBERON:0001903. Process: GO:0042391 regulation of membrane potential, GO:0019228 neuronal action potential.
  4. Impairment of awareness (ORGANISM) — the classic absence output; note it's milder than CAE here.
  5. Cycle-locked recruitment of primary motor cortex (TISSUE) — UBERON:0001384 primary motor cortex; the EMA-specific branch.
  6. Rhythmic 3 Hz myoclonus + progressive tonic contraction (ORGANISM) — the visible seizure.
  7. Chronic high seizure burden → cognitive deterioration (ORGANISM) — in the drug-resistant subset.

This maps cleanly onto the existing epilepsy_excitation_inhibition_imbalance module in this repo. Key conformance target: epilepsy_excitation_inhibition_imbalance#Excitation-Inhibition Imbalance. EMA's distinctive contribution — the thing worth not pushing into the module — is step 5, the motor-cortex recruitment branch.

Cell types involved (CL, OAK-verified)

  • CL:0000679 glutamatergic neuron — corticothalamic and thalamocortical projections
  • CL:0000617 GABAergic neuron — thalamic reticular nucleus inhibitory shell
  • CL:0000598 pyramidal neuron — cortical output, including motor cortex
  • CL:4023068 thalamic excitatory neuron — relay cells; T-type Ca²⁺ burst firing
  • CL:4023013 corticothalamic-projecting glutamatergic cortical neuron — the cortical arm of the loop
  • CL:0008031 cortical interneuron
  • CL:0000127 astrocyte — specifically relevant in the GLUT1 subgroup (astrocytes at the BBB are where GLUT1 does its work)

Anatomy (UBERON, OAK-verified)

UBERON:0000955 brain · UBERON:0001897 dorsal plus ventral thalamus · UBERON:0001903 thalamic reticular nucleus · UBERON:0001384 primary motor cortex · UBERON:0016529 cortex of cerebral lobe · UBERON:0002420 basal ganglion · UBERON:0001873 caudate nucleus · UBERON:0001874 putamen · UBERON:0002435 striatum · UBERON:0006093 precuneus cortex

Metabolic changes

Only in specific genetic subgroups: - GLUT1DS: impaired glucose flux across the blood-brain barrier → chronic brain energy deficit → low CSF glucose. GO:1904659 D-glucose transmembrane transport. - GLUD1/HI-HA: elevated α-ketoglutarate and ammonia, plus episodic hypoglycemia. Chronic hyperammonemia is independently neurotoxic (astrocyte glutamine osmole swelling — same logic as the metabolic_intoxication_decompensation module here, though EMA is not an intoxication-type IEM).

Immune involvement, tissue damage, fibrosis, oxidative stress

Not applicable. EMA is a circuit-function disorder, not a tissue-destruction disorder. Brain MRI is normal in idiopathic EMA. There is no inflammatory, autoimmune, or degenerative component described.

Molecular profiling / advanced technologies

Not available. No transcriptomics, proteomics, metabolomics, lipidomics, single-cell, spatial, or CRISPR-screen data specific to EMA. Nothing in GEO/ArrayExpress/PRIDE/MetaboLights for this syndrome. Genuinely unstudied at the omics level — unsurprising for a syndrome this rare with no reliable animal model.

7. Anatomical Structures Affected

  • Body system: nervous system, exclusively. No multi-organ involvement.
  • Primary organ: brain (UBERON:0000955)
  • Primary circuit: thalamocortical loop — thalamus (UBERON:0001897), thalamic reticular nucleus (UBERON:0001903), cerebral cortex (UBERON:0016529)
  • EMA-distinctive site: primary motor cortex / perirolandic region (UBERON:0001384)
  • Secondary involvement: basal ganglia (UBERON:0002420) — caudate, putamen, globus pallidus; precuneus (UBERON:0006093) — per Ikeda 2018 SPECT
  • Effector (not lesioned, just driven): proximal upper-limb musculature, especially deltoid. This is where the polygraphy lands its electrodes. Iyer 2017 (PMID:28366625) titled a paper "Proximal Upper Limb Jerking" precisely as a diagnostic sign.

Subcellular: no specific compartment pathology. The action is at the synapse and the plasma membrane (ion channels, glutamate receptors, GLUT1 transporter) rather than in an organelle. For GLUT1DS the relevant compartment is the plasma membrane of BBB endothelium and astrocytes.

Lateralization: classically bilateral and symmetric — that's part of the definition. But asymmetry is common enough to be a recognized variant: 4/7 in Videira 2023, 4/11 (36%) in Hu 2025, and Ogawa's 2q13 case presented specifically with unilateral jerks (PMID:36796225). Asymmetry should not by itself exclude the diagnosis, though it should prompt harder for a structural or chromosomal cause.

8. Temporal Development

Onset

  • Range: 6 months to 12.5 years (Tang 2025); epilepsydiagnosis.org gives 1–12 years
  • Peak: ~7 years
  • Cohort means: 3.5 y (Zanzmera 2016, n=12) · 5.2 y, range 3–8 (Videira 2023, n=7) · 7.18 ± 3.72 y (Hu 2025, n=11)
  • Pattern: subacute — seizures start at multiple-per-day frequency fairly quickly
  • Tang 2025: "No cases of EMA with adult onset have been reported thus far" — a clean exclusionary criterion
  • HPO onset terms: HP:0011463 Childhood onset (primary); HP:0003593 Infantile onset (for the earliest cases)

Course

Tang 2025:

"patients with EMA may continue experiencing MA attacks for up to 10 years after onset, with seizures typically subsiding after 4 years on average. Notably, EMA can evolve into LGS in some individuals."

Course pattern: episodic seizures on a chronic background, with two divergent trajectories:

  1. Idiopathic branch (~1/3): myoclonic absences only, normal MRI and EEG background, good drug response, eventual remission, cognition preserved.
  2. Symptomatic branch (~2/3): additional seizure types (especially GTCS), drug resistance, cognitive decline, possible evolution to Lennox-Gastaut syndrome.

The fork is decided early and mostly by whether GTCS are present. Tang 2025:

"The course of EMA mainly depends on the existence of GTCS, regardless of encephalopathic features (such as psychomotor retardation, hemiparesis and behavioral disorders) or treatment timing."

Worth flagging: that last clause — "regardless of... treatment timing" — sits in direct tension with the claim elsewhere in the same review that cognitive decline is proportional to duration of intractable epilepsy. That's a real, curatable contradiction in the literature. Recommend a KNOWLEDGE_GAP discussion on it.

Remission

~40% remit (epilepsydiagnosis.org; consistent with Hu 2025's 45.45% seizure-free at 15–44 months follow-up). Remission is largely treatment-associated rather than clearly spontaneous, though the natural-history data can't cleanly separate the two.

Critical periods

The implied intervention window is early: if seizure duration drives cognitive outcome, then the first months after onset are the window that matters. This is an inference from observational data, not a tested claim.

9. Inheritance and Population

Epidemiology

  • Share of epilepsy: "EMA accounts for 0.5–1% of total epilepsy patients" (Tang 2025). Note this phrasing is a proportion of epilepsy patients, not a population prevalence — don't convert one into the other.
  • Population prevalence / incidence: not available. No population-based estimate exists. Orphanet lists it as rare (subset: rare, orphanet_rare) but I could not retrieve a numeric prevalence class this session — the Orphanet page was behind a bot check and there's no ORPHA_86911.md in this repo's reference cache.

For a dismech Prevalence block, the honest fill is prevalence_class: NOT_YET_DOCUMENTED or UNKNOWN with the 0.5–1%-of-epilepsy figure in notes, not converted to a rate.

Inheritance

  • Not Mendelian at the syndrome level. Most cases are sporadic.
  • Family history of epilepsy in 20–25%, suggesting polygenic/multifactorial susceptibility — consistent with the broader genetic generalized epilepsies.
  • Individual genetic causes: de novo autosomal dominant (SYNGAP1, SETD1B, CREBBP, SLC2A1 usually) or inherited autosomal dominant (GLUD1 family in Bahi-Buisson 2008). HPO: HP:0000006 Autosomal dominant inheritance.
  • Sibling recurrence reported (Cherian 2014, PMID:24491945) — consistent with either recessive inheritance in consanguineous families or shared polygenic load. HP:0000007 Autosomal recessive inheritance may apply in the consanguinity-associated subgroup.
  • Penetrance, expressivity: the GLUD1 family is instructive on expressivity — all four had myoclonic absences but only two had the full HI/HA metabolic phenotype, and the mother's EEG was normal without photosensitivity. So: variable expressivity, clearly.
  • Anticipation: not applicable (no repeat expansion).
  • Germline mosaicism: not reported.
  • Founder effects, carrier frequency: not applicable / not available.

Demographics

  • Sex ratio: male-predominant, ~70% male (Tang 2025; epilepsydiagnosis.org gives 7:3). Cohorts vary: 7:4 (Hu 2025), 7:0 (Videira 2023), 1:1 (Zanzmera 2016). The male skew is a consistent enough signal across the literature to record, but the effect size is soft.
  • Ethnic/geographic distribution: no reported predilection. Cases published from Italy, France, Turkey, Denmark, Japan, India, China, Portugal, USA — i.e. wherever people do video-EEG. Consanguinity as a risk factor implies enrichment in populations with high consanguinity rates, but this hasn't been quantified.
  • Age distribution: pediatric, by definition.

10. Diagnostics

The single most important test: video-EEG with surface EMG polygraphy

This is not optional and it is the whole ballgame. Genton & Bureau 2006 (PMID:17044728) are blunt that diagnosis requires "video documentation of the seizure and/or adequate polygraphy," as it may otherwise be missed.

What you're looking for — the time-locking. From the polygraphy literature: rhythmic bilateral myoclonias have "a strict and constant relation with the spike wave of the discharge; the latency between EEG spikes and EMG myoclonic activity varies between 15 and 40 milliseconds in proximal muscles."

Tang 2025:

"A strict time-locked relationship exists between EEG and EMG, making the analysis of electro-clinical symptoms with MA crucial for EMA diagnosis"

That 15–40 ms latency is basically corticospinal conduction time. It's the measurement that proves the cortex is driving the muscle rather than the two happening coincidentally. Beautiful piece of clinical neurophysiology.

Aoun 2021 (PMID:33632671) shows why the polygraphy matters even more than you'd think — they demonstrated that in one case "rhythmic upper limb jerking, mimicking positive myoclonus, corresponded to recovery of muscular tone after each negative myoclonus." So the arm going up can actually be the arm recovering from a brief drop. Without EMG you'd call it the wrong seizure type entirely. Their conclusion: "video-EEG recording coupled to EMG polygraphy is essential."

Electrode placement: bilateral deltoids at minimum.

EEG findings

Interictal (Tang 2025):

"The background EEG activity of EMA is typically remains normal" "Interictal recordings demonstrate generalized spike-wave or polyspike-waves predominance in the frontal area"

Abnormal background = a red flag for symptomatic EMA and a worse prognosis.

Ictal:

"the EEG shows rhythmic 3 Hz generalized spike-wave or polyspike-waves activity" "Accompanied by characteristic EMG manifesting as bilateral synchronous and symmetrical rhythmic EMG bursts, superimposed with gradually increasing tonic potential"

Zanzmera 2016 (PMID:27770719): "3- to 3.5-Hz spike-and-wave discharges (82%) and fast recruiting bifrontal rhythm (25%)."

Hu 2025: "In eight patients [of 11], bilateral symmetrically synchronized 3 Hz rhythmic spike-slow wave complex bursts, which showed a lock-in relationship with myoclonic, were recorded."

Activation procedures: hyperventilation, awakening, intermittent photic stimulation (positive in 14%).

Imaging

  • Brain MRI (NCIT:C16809 Magnetic Resonance Imaging, OAK-verified): normal in idiopathic EMA; abnormal MRI defines the symptomatic form. Mandatory in the workup.
  • Ictal SPECT: research tool only (Ikeda 2018). Not clinical practice.
  • EEG-fMRI: used in childhood absence epilepsy research; Tang 2025 notes it showed involvement of "primary sensory (visual, auditory, somatosensory), motor (Rolandic) areas and frontoparietal association cortex" during absence seizures. Not established for EMA specifically.

Laboratory tests

  • CSF glucose and CSF:blood glucose ratio — to screen for GLUT1 deficiency. This is the highest-yield metabolic test because a positive result changes treatment immediately (ketogenic diet).
  • Ammonia and insulin — if the HI/HA (GLUD1) phenotype is suspected, especially with photosensitivity or episodic hypoglycemia.
  • No EMA-specific biomarker exists.

Genetic testing — recommended approach

Given the etiological picture (single genes and recurrent CNVs both well-represented), a two-pronged approach:

  1. Chromosomal microarray (CMA) — non-negotiable here. Trisomy 12p, 2q13 microdeletion, 15q11.2 microdeletion, and inv dup(15) have all produced EMA phenotypes. A gene panel alone will miss every one of these.
  2. Epilepsy gene panel or whole-exome sequencing — covering at minimum SLC2A1, SYNGAP1, SETD1B, GLUD1, CREBBP, plus the broader absence-epilepsy genes (SLC6A1, CHD2, SCN1A, CACNA1A, GABRA2, GABRG2). WES has the advantage of catching the long tail; several of the EMA gene associations were WES discoveries (Hiraide 2019 explicitly: "Using whole-exome sequencing, we found a novel de novo variant").
  3. Targeted SLC2A1 testing if CSF glucose is low — or just test it upfront given how actionable it is.

Karyotype/FISH: historical relevance (Klitten's translocation was mapped by FISH), but superseded by CMA + sequencing for first-line use. Note that a balanced translocation like Klitten's is invisible to both CMA and standard WES — so in a patient with EMA + intellectual disability and negative CMA/WES, karyotype still has a role.

Not applicable: mtDNA testing, repeat expansion testing, liquid biopsy, methylation arrays (except 15q11.2 imprinting studies if an Angelman-like EEG pattern is seen — see Chin 2026, PMID:42434914).

Omics diagnostics: not available / not established for EMA.

Clinical criteria (ILAE 2022)

EMA is one of three generalized epilepsies with childhood onset in the ILAE 2022 nosology (Specchio et al., Epilepsia 2022;63(6):1398-1442, PMID:35503717), alongside childhood absence epilepsy and epilepsy with eyelid myoclonia. ILAE 2022 classifies it as a hereditary generalized epilepsy syndrome with childhood onset.

Mandatory: myoclonic absence seizures — absences with rhythmic 3 Hz jerks of the upper limbs superimposed on tonic abduction of the arms, with abrupt onset and offset; ictal EEG showing regular 3 Hz generalized spike-wave time-locked to the jerks.

I was unable to retrieve the full ILAE mandatory/alert/exclusionary criteria table — both the Wiley full text and the ILAE PDF returned 403 in this session. Do not populate exclusionary criteria from memory; fetch PMID:35503717 properly before curating that section.

Differential diagnosis

From Tang 2025's comparison table:

Idiopathic EMA Symptomatic EMA CAE Jeavons (eyelid myoclonia)
Onset 6 mo–12.5 y 6 mo–12.5 y 4–10 y 2–14 y
Sex (M:F) 7:3 7:3 ~1:2 (female-predominant) 1:2
Seizure types MA only MA + GTCS/clonic/atonic/typical absence typical absence eyelid myoclonia ± absence
MRI normal abnormal normal normal
EEG background normal abnormal normal normal
Ictal EEG 3 Hz GSWD time-locked to jerks same 3 Hz GSWD eye-closure/IPS-induced 3 Hz GSWD
Prognosis remits persistent, drug-resistant, ID common >90% remit drug-resistant, lifelong

Tang 2025: "In general, symptomatic EMA is often associated with abnormal neurological signs, abnormal background activity of EEG and structural abnormalities on brain MRI."

Additional differentials to rule out: - Childhood absence epilepsy with mild myoclonic features — Capovilla 2001 (PMID:11431166) describes "A clinical spectrum of the myoclonic manifestations associated with typical absences in childhood absence epilepsy." The boundary is genuinely fuzzy; the discriminator is whether the myoclonus is prominent, rhythmic, proximal, and tonically-augmented, versus incidental. - Atypical absence with negative myoclonus / ESES — Aoun 2021, PMID:33632671. EMG polygraphy is what separates these. - Focal seizures with automatisms — Myers & Scheffer 2018, PMID:29325826. - Myoclonic-atonic epilepsy (Doose) — nomenclature trap, different syndrome. This repo has a separate Epilepsy_with_Myoclonic_Atonic_Seizures entry; keep the two entries explicitly cross-referenced as differentials. - Lennox-Gastaut syndrome — both a differential and a possible evolution endpoint. - Early-onset absence epilepsy (<3 years) — Chaix 2003, PMID:12823578, "Absence epilepsy with onset before age three years: a heterogeneous and often severe condition"; Caraballo 2011, PMID:21269284. - ATRX syndrome — myoclonic absences appear in its EEG spectrum (Aiello 2022, PMID:36031702).

Screening

Not applicable. There is no newborn screening, carrier screening, or population screening for EMA. Cascade testing applies only in the rare families with an identified dominant variant (e.g. the GLUD1 family).

11. Outcome / Prognosis

Mortality

No EMA-specific mortality data available. Not a directly fatal condition. Standard epilepsy mortality considerations (SUDEP risk with uncontrolled GTCS, injury from atonic falls) apply but have not been quantified for EMA specifically. Life expectancy: not reported.

Seizure outcome

Series n Outcome
epilepsydiagnosis.org / Tang 2025 — remission in ~40%
Hu 2025 (PMID:40414191) 11 5 (45.45%) seizure-free with no cognitive impairment; 6 drug-resistant
Carter 2022 (PMID:35770757) 10 60% had incomplete control at last follow-up
Zanzmera 2016 (PMID:27770719) 12 9 responders: 4 seizure-free ≥1 y, 2 with >90% reduction, 3 with >50% reduction

Zanzmera's conclusion, verbatim-ish from the abstract: "While most patients responded favorably to treatment, prognosis remained guarded, with some patients developing drug-resistant seizures evolving into different patterns."

Cognitive/functional outcome

The harder outcome. ~70% eventually have learning impairment (epilepsydiagnosis.org). Tassinari's 28-patient follow-up: 20/28 ended with cognitive deficits, of whom 7 had acquired the deficit during the disease course. Behavioral morbidity: ADHD, aggression, impulse-control problems, learning disabilities (Tang 2025).

Prognostic factors — the actionable list

  1. Presence of GTCS — the strongest predictor. Bureau & Tassinari 2005 (PMID:15737698): treatment "proves most effective when myoclonic absences occur independently. However, prognosis becomes less favorable when combined with other seizure types, potentially progressing toward different epilepsy forms."
  2. Atonic component — Carter 2022: "Of patients with an atonic component, 75% did not achieve seizure freedom with medication alone."
  3. Pre-onset developmental delay — Hu 2025's conclusion, verbatim: "developmental delay before disease onset may be associated with a poor prognosis." In their drug-resistant subgroup, 4/6 (66.67%) had developmental delay predating the epilepsy.
  4. Abnormal EEG background / abnormal MRI — symptomatic form marker.
  5. Duration of uncontrolled seizures — correlated with cognitive decline severity (Tang 2025), though see the contradiction flagged in §8.

Complications

  • Evolution to Lennox-Gastaut syndrome
  • Myoclonic absence status epilepticus (HP:0032865) — 20% in Carter 2022
  • Injury from atonic drop attacks
  • Progressive cognitive and behavioral deterioration

Recovery potential

Seizures often diminish over time (average ~4 years, up to 10). Cognition does not follow: "complete functional recovery is rarely achieved" (Tang 2025). That asymmetry — the seizures burn out but the developmental cost is already paid — is the defining tragedy of the symptomatic form.

Prognostic biomarkers

Not available. No molecular prognostic marker exists. The best predictors are clinical (seizure types, EEG background, baseline development).

12. Treatment

First-line pharmacotherapy

Tang 2025, verbatim:

"The first-line ASMs are sodium valproate, ethosuximide, and lamotrigine, which can be used alone or in combination."

Genton & Bureau 2006 (PMID:17044728): treatment typically involves "valproic acid and ethosuximide, or valproic acid and lamotrigine."

Bureau & Tassinari 2005 (PMID:15737698): "Treatment with valproate and ethosuximide proves most effective when myoclonic absences occur independently."

Hu 2025: of the 5 patients who became seizure-free, 4/5 (80%) were on valproic acid alone. Zanzmera 2016: "Most benefited from valproate monotherapy or valproate-lamotrigine combination therapy."

So the consensus is unusually clean for a rare disease: valproate is the backbone, ethosuximide or lamotrigine is the partner.

Treatment Drug (CHEBI, OAK-verified) NCIT action term Modality
Valproate CHEBI:39867 valproic acid NCIT:C15986 Pharmacotherapy SMALL_MOLECULE
Ethosuximide CHEBI:4887 ethosuximide NCIT:C15986 SMALL_MOLECULE
Lamotrigine CHEBI:6367 lamotrigine NCIT:C15986 SMALL_MOLECULE
Levetiracetam CHEBI:6437 levetiracetam NCIT:C15986 SMALL_MOLECULE
Topiramate CHEBI:63631 topiramate NCIT:C15986 SMALL_MOLECULE
Clonazepam CHEBI:3756 clonazepam NCIT:C15986 SMALL_MOLECULE
Zonisamide CHEBI:10127 zonisamide NCIT:C15986 SMALL_MOLECULE
Rufinamide CHEBI:134966 rufinamide NCIT:C15986 SMALL_MOLECULE
Phenobarbital CHEBI:8069 phenobarbital NCIT:C15986 SMALL_MOLECULE
Avoid: carbamazepine CHEBI:3387 carbamazepine — —

(Note per this repo's memory: therapeutic_agent validation prefers CHEBI over NCIT drug terms — all of the above are CHEBI and OAK-verified.)

Second-line

Tang 2025: "Second-line ASMs include levetiracetam, acetazolamide, zonisamide, topiramate, and lacosamide." (I did not verify CHEBI IDs for acetazolamide or lacosamide — look those up before curating.)

Drugs to avoid — worth curating as an explicit treatment entry

Tang 2025: "Carbamazepine, phenytoin, vigabatrin, gabapentin, and tiagabine should be avoided due to their potential to exacerbate seizures."

The mechanism is well-understood generally: sodium-channel blockers and GABA-transaminase/reuptake drugs enhance thalamic burst firing and make generalized spike-wave worse. It's the pharmacological equivalent of trying to quiet a resonating string by pushing on it in rhythm.

Contradiction to preserve: levetiracetam appears as second-line in Tang 2025 and as an absence-aggravating drug in Auvin 2011 (PMID:21680209, "Aggravation of absence seizure related to levetiracetam"). Curate both; don't resolve it silently.

Refractory options

Rufinamide add-on — Häusler 2011 (PMID:21557146), n=3 boys refractory to conventional therapy:

"Add-on RUF treatment was initiated in 3 boys with EMA refractory to conventional antiepileptic therapy (primidone + valproic acid, n=1; levetiracetame + ethosuximide, n=2). It resulted in complete cessation of all seizures in 2, and a 50% reduction of the seizure frequency in one child, respectively."

Interesting that rufinamide — licensed for Lennox-Gastaut — works here, given EMA's tendency to evolve toward LGS. Possibly the same circuit vulnerability.

Low-dose phenobarbital — Ito 2021 (PMID:33461850), n=1: complete seizure freedom after adding low-dose phenobarbital to valproate + ethosuximide.

Ketogenic diet (NCIT:C173168 Ketogenic Diet, OAK-verified; NCIT:C15447 Dietary Intervention; modality BEHAVIORAL per this repo's mapping table). Especially indicated in GLUT1 deficiency, where it's not adjunctive but mechanistically corrective — ketones cross the blood-brain barrier via MCT1, which is intact, routing around the broken GLUT1 door entirely.

Vagus nerve stimulation — listed by Tang 2025. Modality DEVICE. ⚠️ No suitable NCIT clinical-action term found in the local NCIT adapter (NCIT:C203750 is transcutaneous auricular VNS, which is a different intervention). Leave term: off and keep a free-text preferred_term, per this repo's convention.

Corpus callosotomy — the most interesting refractory option, and mechanistically elegant: if the seizure depends on bilateral synchrony, cutting the main bridge between the hemispheres should degrade it.

Carter 2022 (PMID:35770757), verbatim:

"Two patients with epilepsy with myoclonic absences with atonia underwent corpus callosotomy; one patient was seizurefree eight months after surgery and the other had greater than 50% seizure reduction over a five-month period."

And their appropriately cautious conclusion: "the efficacy of this treatment should be further evaluated in a larger study."

Suggested NCIT: NCIT:C15656 Neurosurgical Procedure (OAK-verified) — NCIT has no specific callosotomy term in this build. Modality SURGERY.

Personalized medicine

Two real genotype-guided decisions exist: 1. SLC2A1/GLUT1DS → ketogenic diet. The clearest case. 2. **GLUD1/HI-HA → ** management of hyperinsulinism/hyperammonemia (diazoxide, protein-intake management) alongside seizure control.

Everything else is empirical. Pharmacogenomics: not available — no PharmGKB/CPIC guidance specific to EMA beyond the general HLA-B*15:02/carbamazepine and CYP2C9/phenytoin warnings, which are moot since both drugs are contraindicated here anyway.

Supportive / rehabilitative

Given the ~70% learning-impairment rate: special education support, speech-language therapy (NCIT:C159273, unverified), occupational therapy, behavioral intervention for ADHD/impulse control. Genetic counseling (NCIT:C15240 Genetic Counseling, OAK-verified) once a genetic cause is identified.

Clinical trials

None found specific to EMA. No NCT identifiers for EMA-specific trials. Patients would be enrolled, if at all, under broader generalized-epilepsy or LGS protocols. Cannabidiol has been discussed for epilepsies beyond Dravet/LGS (Lattanzi 2021, PMID:33754312) but I found no EMA-specific efficacy data.

13. Prevention

Short section, because there isn't much, and I'd rather say so than pad it.

  • Primary prevention: not available. Most cases are de novo genetic or idiopathic. The only modifiable upstream factors are the perinatal ones (prematurity, birth injury) associated with symptomatic EMA, which is really just general perinatal care rather than EMA prevention.
  • Immunization: not applicable.
  • Population screening: not applicable. Too rare, no presymptomatic marker, no preventive intervention.
  • Genetic screening: prenatal/preimplantation testing is technically available for families with an identified pathogenic variant (e.g. the GLUD1 kindred), and cascade testing of relatives applies in those rare families. Genetic counseling (NCIT:C15240) is appropriate once a molecular cause is found — but for the ~sporadic majority, recurrence risk counseling is essentially "low, empirical, unquantified."
  • Secondary prevention (early detection): this is where the real leverage is. Because prognosis may track with duration of uncontrolled seizures, shortening time-to-diagnosis is the closest thing EMA has to a preventive intervention. The bottleneck is recognition: without video-EEG-plus-EMG, myoclonic absences get miscalled as tics, behavioral episodes, focal seizures, or plain absence. Tang 2025 states the goal of their review is to "reduce the rate of missed diagnosis and misdiagnosis."
  • Tertiary prevention: seizure control to protect cognition; avoiding the aggravating drug list (a genuinely preventable iatrogenic harm); fall precautions in patients with atonic components.
  • Behavioral / public health / environmental interventions: not applicable.

14. Other Species / Natural Disease

This section has exactly one entry, and it's delightful.

Dog — Canis lupus familiaris, NCBITaxon:9615.

Poma, Ochi & Cortez 2010 (PMID:20483714), Epileptic Disord, verbatim:

"Long-term video-EEG was recorded for an eight-month-old Chihuahua dog with recurrent episodes of altered behaviour associated with head and nose twitching. Each episode lasted one to two seconds, multiple times per day before treatment. Ictal EEG showed generalised bilaterally synchronous 4 Hz spike-and-wave complexes during the 'absence-like' event, along with rhythmically correlated head and nose twitching. We present video documentation of such attacks and discuss their similarities to human epilepsy with myoclonic absences."

That's a naturally occurring myoclonic-absence-like phenotype in a companion animal, with the same defining feature — twitching rhythmically correlated with the spike-wave discharge. Different frequency (4 Hz vs 3 Hz), different body part (head/nose vs shoulders/arms), much shorter duration (1–2 s vs 8–60 s), but the same architecture. Evidence source: MODEL_ORGANISM per this repo's rules (veterinary observations count as animal, even when observational).

VBO breed term for Chihuahua: exists but I did not verify the ID — look it up before curating.

  • OMIA: not checked this session; worth a look for canine idiopathic generalized epilepsy entries.
  • Zoonotic potential / cross-species transmission: not applicable, obviously.
  • Comparative biology: the thalamocortical spike-wave oscillator is deeply conserved across mammals — it's the same machinery in rodents, cats, dogs, and humans, which is why absence models translate reasonably well. The motor recruitment branch that makes EMA distinctive is the part that has never been modeled deliberately.

15. Model Organisms

The honest headline: there is no EMA model

Nobody has built a mouse that has myoclonic absences. What exists are (a) good absence-epilepsy models that produce the 3 Hz-equivalent oscillation without the motor component, and (b) one model that happens to have both absence seizures and a paroxysmal motor phenotype, though they're separate events rather than the fused single seizure that defines EMA.

Genetic models of the underlying oscillator

GAERS (Genetic Absence Epilepsy Rat from Strasbourg) and WAG/Rij rat — the two workhorse inbred absence models. Both show spontaneous spike-wave discharges with behavioral arrest and the classic pharmacological profile (suppressed by ethosuximide and valproate, worsened by carbamazepine and vigabatrin). They model steps 1–4 of the EMA chain and none of step 5. (Not fetched in this session — verify PMIDs before citing.)

tottering (Cacna1a mouse) — the most EMA-adjacent model available. Missense mutation in Cacna1a, orthologue of human CACNA1A, in the pore-lining region of the P/Q-type Ca²⁺ channel. Three phenotypes: absence seizures with generalized spike-wave discharges (6–7 Hz in mouse), episodic dystonia, and mild ataxia. Critically, tottering shows "a striking downstream enhancement of α1G-mediated T-type currents in thalamic neurons before the onset of absence epilepsy" — i.e. a compensatory change in the thalamic burst-firing machinery precedes the seizures. That's a mechanistically interesting handle on how a channel defect converts into an oscillation.

Limitation, stated plainly: tottering's motor phenotype (60–90 minute dystonic attacks progressing along the body axis) is a separate event from its absence seizures. In EMA the motor and absence components are the same event, cycle-locked. So tottering models the ingredients but not the fusion.

Also worth noting: cerebellar neurons act as "powerful regulators of the pathological oscillations in the thalamocortical system" in Cacna1a models — an underexplored angle for EMA, where nobody has looked at the cerebellum.

Genetic α1G/CACNA1G overexpression — elevating α1G-mediated low-voltage-activated Ca²⁺ current in thalamus induces "pure absence epilepsy" (J Neurosci 29(6):1615). Useful as the negative control for the EMA question: this manipulation gives you absence without motor features, which sharpens the question of what EMA adds on top.

Models for the EMA-associated genes

  • Syngap1 heterozygous mice — extensively characterized (premature excitatory synapse maturation, cognitive deficits, seizures). Good for the SYNGAP1 subgroup; not an EMA model per se.
  • Slc2a1 haploinsufficient mice — established GLUT1DS model with spike-wave discharges and motor deficits; responds to ketogenic diet. The most translationally useful model on this list.
  • Setd1b, Glud1, *Crebbp* — models exist for all three, none characterized for myoclonic absence phenotypes.

What's missing

No model recapitulates: 1. The cycle-by-cycle time-locking of cortical spike to muscle jerk (15–40 ms latency) 2. The progressive tonic contraction superimposed on the myoclonus 3. The cognitive deterioration proportional to seizure duration

A model that produced genuine cycle-locked corticospinal output during spike-wave would be the field-advancing tool here. This is a legitimate HUMAN_MODEL_MISMATCH discussion for the KB entry — evidence exists in models, but the models specifically lack the feature that defines the disease.

Resources

MGI (mouse), RGD (rat — GAERS/WAG-Rij strains), IMPC/KOMP (knockouts for SYNGAP1, SETD1B, SLC2A1, GLUD1, CREBBP), Alliance of Genome Resources.

Curation notes for the dismech entry

A few things I'd flag before this gets committed anywhere:

  1. Verify before use. The HGNC IDs in §4, the CHEBI IDs for acetazolamide/lacosamide, the VBO Chihuahua term, the NCIT speech-therapy term, and any ICD-10 code are not OAK-verified in this session. Everything marked "OAK-verified" was checked against the local sqlite:obo:* adapters.
  2. NEC risk. "MAE" is ambiguous between myoclonic absence epilepsy and myoclonic-astatic epilepsy (Doose). If any deep-research report is generated for this disease, run just preflight-dr and check the gene mentions — but note EMA has no canonical causal gene in MONDO, so preflight will likely return SKIP and you'll need the manual synonym/OMIM checks. The Doose collision is the specific thing to watch for.
  3. Two curatable controversies, both worth discussions blocks:
  4. Why motor? — the central open mechanistic question, with the Ikeda n=2 SPECT study as the only direct human evidence. KNOWLEDGE_GAP.
  5. Does treatment timing matter? — Tang 2025 says course depends on GTCS "regardless of... treatment timing," while also saying cognitive decline tracks duration of intractable epilepsy. Direct internal tension. KNOWLEDGE_GAP.
  6. Optionally a third: levetiracetam as second-line vs. absence-aggravating.
  7. Module conformance: epilepsy_excitation_inhibition_imbalance#Excitation-Inhibition Imbalance is the natural target. Keep the motor-cortex-recruitment node as EMA-specific — don't push it up into the module.
  8. Evidence source tagging: Ikeda 2018 (SPECT), all the cohort series, and the genetic case reports are HUMAN_CLINICAL. Poma 2010 (Chihuahua) is MODEL_ORGANISM. Any tottering/GAERS/α1G citations are MODEL_ORGANISM.
  9. Prevalence: resist the urge to convert "0.5–1% of epilepsy patients" into a rate_per_100000. It's a proportion of a clinical population, not a population rate. prevalence_class: NOT_YET_DOCUMENTED with the figure in notes is the truthful curation.

Sources

Primary literature (PMIDs verified against PubMed records this session):

  • Tang F, Li M, Liu L, Wang X, Qin B. Research progress on epilepsy with myoclonic absence. Acta Epileptol. 2025. doi:10.1186/s42494-025-00218-2. PMID:40380288 · full text
  • Hu Q, Luo Y, Hong S, Yuan P, Jiang L. Electroclinical features of myoclonic absence epilepsy: A single-center cohort analysis in Southwest China. Epilepsy Behav. 2025 Oct;171:110505. PMID:40414191
  • Carter EG, Armour EA, Pagano LM, Reddy SB. Epilepsy with myoclonic absences: a case series highlighting clinical heterogeneity and surgical management. Epileptic Disord. 2022;24(3):541-547. PMID:35770757
  • Videira G, Raimundo R, Chorão R. Epilepsy with myoclonic absences: A case series. Seizure. 2023;106:162-163. PMID:36893512
  • Zanzmera P, Menon RN, Karkare K, et al. Epilepsy with myoclonic absences: Electroclinical characteristics in a distinctive pediatric epilepsy phenotype. Epilepsy Behav. 2016;64(Pt A):242-247. PMID:27770719
  • Ikeda H, Imai K, Ikeda H, et al. Ictal single photon emission computed tomographic study of myoclonic absence seizures. Brain Dev. 2018;40(2):126-129. PMID:28823645
  • Bureau M, Tassinari CA. Epilepsy with myoclonic absences. Brain Dev. 2005;27(3):178-84. PMID:15737698
  • Genton P, Bureau M. Epilepsy with myoclonic absences. CNS Drugs. 2006;20(11):911-916. PMID:17044728
  • Klitten LL, Møller RS, Nikanorova M, et al. A balanced translocation disrupts SYNGAP1 in a patient with intellectual disability, speech impairment, and epilepsy with myoclonic absences (EMA). Epilepsia. 2011;52(12):e190-3. PMID:22050443
  • Hiraide T, Hattori A, Ieda D, et al. De novo variants in SETD1B cause intellectual disability, autism spectrum disorder, and epilepsy with myoclonic absences. Epilepsia Open. 2019;4(3):476-481. PMID:31440728
  • Gökben S, Yılmaz S, Klepper J, et al. Video/EEG recording of myoclonic absences in GLUT1 deficiency syndrome with a hot-spot R126C mutation in the SLC2A1 gene. Epilepsy Behav. 2011;21(2):200-2. PMID:21546317
  • Bahi-Buisson N, El Sabbagh S, Soufflet C, et al. Myoclonic absence epilepsy with photosensitivity and a gain of function mutation in glutamate dehydrogenase. Seizure. 2008;17(7):658-64. PMID:18321734
  • Elia M, Musumeci SA, Ferri R, Cammarata M. Trisomy 12p and epilepsy with myoclonic absences. Brain Dev. 1998;20(2):127-30. PMID:9545186
  • Häusler M, Kluger G, Nikanorova M. Epilepsy with myoclonic absences — favourable response to add-on rufinamide treatment in 3 cases. Neuropediatrics. 2011;42(1):28-29. PMID:21557146
  • Myers KA, Scheffer IE. Myoclonic absence seizures with complex gestural automatisms. Eur J Paediatr Neurol. 2018;22(3):532-535. PMID:29325826
  • Aoun MA, Eisermann M, Chemaly N, et al. Jerking during absences: video-EEG and polygraphy of epileptic myoclonus associated with two paediatric epilepsy syndromes. Epileptic Disord. 2021;23(1):191-200. PMID:33632671
  • Poma R, Ochi A, Cortez MA. Absence seizures with myoclonic features in a juvenile Chihuahua dog. Epileptic Disord. 2010;12(2):138-41. PMID:20483714
  • Matsubara K, Yamakawa K, Ishioka R, et al. Epilepsy with myoclonic absences associated with a pathogenic CREBBP variant: A case report of Rubinstein-Taybi syndrome. Seizure. 2025;131:1-4. PMID:40451035
  • Specchio N, Wirrell EC, Scheffer IE, et al. ILAE classification and definition of epilepsy syndromes with onset in childhood. Epilepsia. 2022;63(6):1398-1442. PMID:35503717 · Wiley
  • Ogawa et al. Epilepsy with myoclonic absence presenting with unilateral jerks: A case of 2q13 microdeletion syndrome. Seizure. 2023. PMID:36796225
  • Chin HL, Chang J, Nordli D 3rd. Refining the electroclinical phenotype of 15q11.2 microdeletion: EEG biomarker overlap with Angelman syndrome. Epileptic Disord. 2026. PMID:42434914
  • Cherian A, Jabeen SA, Kandadai RM, et al. Epilepsy with myoclonic absences in siblings. Brain Dev. 2014. PMID:24491945
  • Auvin S, Chhun S, et al. Aggravation of absence seizure related to levetiracetam. Eur J Paediatr Neurol. 2011. PMID:21680209
  • Ito S, Nagumo K, et al. Low-dose phenobarbital for epilepsy with myoclonic absences. Brain Dev. 2021. PMID:33461850
  • Tassinari CA, Lyagoubi S, Santos V, et al. Studies on spike and wave discharges in man. II. Clinical and EEG aspects of myoclonic absences. Electroencephalogr Clin Neurophysiol. 1970. PMID:4194033 · original 1969 French paper PMID:4985251
  • Balestrini S, et al. Clinical and genetic landscape of epilepsies with absence seizures and single-gene etiology. Epilepsia. 2026. doi:10.1111/epi.18655

Reference resources: - epilepsydiagnosis.org — Epilepsy with Myoclonic Absences overview - MedLink Neurology — Epilepsy with myoclonic absences and Myoclonic absences - Jasper's Basic Mechanisms of the Epilepsies — The Voltage-Gated Calcium Channel and Absence Epilepsy - Genetic Enhancement of Thalamocortical Network Activity by Elevating α1G-Mediated LVA Calcium Current Induces Pure Absence Epilepsy, J Neurosci 29(6):1615 - MONDO:0019487 via local OAK sqlite:obo:mondo; HPO/GO/CL/UBERON/CHEBI/NCIT terms verified via local OAK adapters