Idiopathic Generalized Epilepsies

What You'll Learn

Four IGE syndromes (ILAE 2022): CAE, JAE, JME, GTCA — all share generalized spike-wave (2.5–5.5 Hz), normal exam, normal MRI, presumed genetic etiology
Only CAE is self-limited (65–80% remission); JAE, JME, and GTCA all require lifelong ASM therapy
JME is the most common IGE: classic triad of morning myoclonus (100%), GTC (80–95%), and absences (15–40%); relapse >80–90% on ASM withdrawal
AVOID Na channel blockers (CBZ, OXC, PHT) in ALL IGEs — they worsen absence, myoclonic, and atonic seizures
VPA is the most effective ASM across all IGEs but is teratogenic; LEV is first-line in women of childbearing potential
Jeavons syndrome: eyelid myoclonia on eye closure, nearly 100% photosensitive, drug-resistant in 40–50%
Absence status epilepticus: prolonged confusion in IGE patients; treat with IV benzodiazepines; triggered by ASM noncompliance or inappropriate ASM changes

HighYield Pearls

CAE = ethosuximide first-line: Glauser NEJM 2010 (CAE trial) showed ETX = VPA > LTG for freedom from treatment failure, and ETX has the best attentional profile — pick ETX for pure absence with no GTC
Ethosuximide does NOT cover GTC: never use ETX monotherapy in JAE or JME (GTC in ~80–95%) — pick VPA, LEV, or LTG instead
VPA is teratogenic — pick LEV first-line in women of childbearing potential (SANAD II); VPA stays the most effective ASM in IGE for men
AVOID Na-channel blockers in IGE: CBZ, OXC, PHT, GBP, PGB, TGB, VGB worsen absence and myoclonic seizures — the most common cause of "drug-resistant" JME is misdiagnosis as focal epilepsy → CBZ/OXC prescribed → worse seizures
AVOID LTG in prominent myoclonus: lamotrigine may paradoxically worsen myoclonic jerks in JME and eyelid myoclonia in Jeavons — broad-spectrum does NOT mean myoclonus-safe
Morning myoclonic jerks + GTC in a teenager = JME: ask about "dropping cereal/toothbrush in the morning"; sleep deprivation and alcohol are the dominant triggers; lifelong therapy (>80–90% relapse off ASM)
Eye-closure–induced eyelid jerking + near-100% photosensitivity in a young girl = Jeavons syndrome; self-induced seizures are epileptic, not behavioral — AVOID LTG, use VPA/LEV/clonazepam
Only CAE is self-limited (65–80% remit by adolescence); JAE, JME, and GTCA all require lifelong ASM — do not attempt withdrawal in JME
Consider GLUT1 deficiency (SLC2A1) in atypical/early-onset absence (<4 yrs), microcephaly, paroxysmal exertional dyskinesia, or movement disorder — check CSF:serum glucose ratio <0.45 and start ketogenic diet (disease-modifying)
Prolonged confusion in an IGE patient after ASM noncompliance or a switch to a Na-channel blocker = absence status epilepticus — emergent EEG and IV benzodiazepines are both diagnostic and therapeutic

🔍 Quick ReferenceEEG · Clinical · Treatment / pharmacology

EEG signs

Regular 3-Hz generalized spike-and-wave activated by hyperventilation → CAE
Generalized 3.5–4.5 Hz spike-and-wave (faster than CAE) → JAE
Irregular 3.5–6 Hz polyspike-and-wave, often on awakening → JME
Photoparoxysmal response on intermittent photic stimulation → JME or Jeavons
Generalized polyspike-wave within 0.5–2 sec of eye closure → Jeavons syndrome
Focal/frontal-appearing discharges in a teen with morning jerks → JME (NOT focal epilepsy — do not give CBZ)
Slow (<2.5 Hz) spike-and-wave on an abnormal background → Lennox-Gastaut (atypical absence), NOT IGE

Clinical signs

School-age child with multiple daily brief blank stares + eyelid flutter or oral automatisms → CAE
Teen presenting with first GTC + prior history of "spaced-out spells" → JAE
Morning myoclonic jerks ("dropping the toothbrush / spilling cereal") + GTC after sleep deprivation → JME
GTC on awakening triggered by sleep deprivation or alcohol, no myoclonus/absences → GTCA
Eyelid jerks with upward eye deviation triggered by eye closure in a young girl + photosensitivity → Jeavons syndrome
Seizures triggered by TV / video games / patterned stimuli ("Pokémon stroboscope") → photosensitive IGE (JME, Jeavons)
Normal neuro exam + normal MRI + family history of epilepsy → IGE hallmark

Treatment / pharmacology pearls

Ethosuximide → first-line for pure absence (CAE) per Glauser NEJM 2010 — absence only, no GTC coverage
Valproate → most effective ASM across all IGEs (SANAD II) but teratogenic — avoid in women of childbearing potential
Levetiracetam → first-line in women of childbearing potential with JME/JAE/GTCA
Lamotrigine → may worsen myoclonus — use cautiously in JME and Jeavons
Carbamazepine / oxcarbazepine / phenytoin → worsen absence and myoclonus — AVOID in all IGEs
Vigabatrin, gabapentin, pregabalin, tiagabine → worsen absence/myoclonus — AVOID in IGE
Sleep deprivation + alcohol → classic JME triggers; lifestyle counseling is core therapy
Lifelong therapy with >80–90% relapse on withdrawal → JME
IV benzodiazepines → absence status epilepticus (rapid resolution, diagnostic + therapeutic)

Terminology: IGE vs GGE (ILAE 2022)

Per ILAE 2022 (Hirsch et al.), IGE = the four electroclinical syndromes (CAE, JAE, JME, GTCA); GGE is the broader category that also includes generalized epilepsies of presumed genetic etiology not meeting any specific IGE syndrome. All IGEs are GGEs, but not all GGEs are IGEs.

Childhood Absence Epilepsy (CAE)

Clinical Features

Onset: 4–10 years; peak 5–7 years; slight female predominance
Seizure semiology: Multiple daily absences (10–100+/day); brief (<10 seconds); abrupt onset and offset; no postictal phase
Behavioral arrest with staring; may have subtle automatisms (lip smacking, fumbling) or mild eyelid flutter
Often discovered when teachers report "daydreaming" or "inattention" in a school-age child
GTC seizures rare (<10%) — if present, consider reclassification (JAE or JME)
Normal neurological examination and (usually) normal baseline cognition

EEG

Regular 3 Hz generalized spike-and-wave on a normal background (classically 3.5 Hz at onset slowing to 2.5 Hz at offset)
Hyperventilation provokes absences in >80–90% — the key diagnostic provocation; failure of HV to provoke a typical absence in an untreated patient should prompt reconsideration of the diagnosis
PPR uncommon (5–15%)
Ictal pattern is identical to interictal pattern, just sustained

Differential / Mimics

Consider GLUT1 deficiency (SLC2A1) in atypical/early-onset/microcephalic cases — especially if absences begin before age 4, are paroxysmal-exertional, or are accompanied by movement disorder/microcephaly; check low CSF glucose (CSF:serum ratio <0.45); ketogenic diet is responsive and disease-modifying
Atypical absences (slower <2.5 Hz spike-wave, abnormal background) suggest a developmental and epileptic encephalopathy (e.g., Lennox-Gastaut), not CAE

Treatment

First-line: Ethosuximide (ETX) or valproate (VPA)
Glauser NEJM 2010 (childhood absence epilepsy trial): ETX = VPA > LTG for freedom from treatment failure in CAE without GTC; ETX preferred over VPA due to a better attentional/cognitive profile
LTG is a reasonable alternative but less efficacious in this trial
AVOID CBZ, OXC, PHT, VGB, GBP, TGB — all worsen absences

Prognosis

Self-limited — remission in 65–80% by adolescence
A minority evolve into JME (myoclonic jerks emerge in adolescence) or JAE (sporadic absences plus GTC)
Subtle attention/executive deficits may persist even after seizure remission

Juvenile Absence Epilepsy (JAE)

Clinical Features

Onset: 9–13 years (later than CAE, earlier than JME)
Absences: Sporadic — often less than daily; less frequent and typically longer than in CAE; consciousness more variably impaired
GTC seizures in ~80% — frequently the presenting event (a teen presenting with first GTC + history of prior "spaced-out spells" should raise suspicion for JAE)
Myoclonic jerks rare (~15–20%); if prominent, reclassify as JME
Normal exam, normal MRI, normal cognition

EEG

Generalized spike-wave at ~3.5–4 Hz (slightly faster than CAE) on a normal background
PPR in 15–25%
Hyperventilation may provoke but is less reliably activating than in CAE

Treatment

First-line: VPA, LTG, LEV
In women of childbearing potential, prefer LEV over VPA (see SANAD II); LTG is also a reasonable choice but watch for myoclonic worsening if JAE/JME overlap is suspected
ETX is NOT first-line because it does not cover GTC seizures, which occur in ~80%
AVOID Na channel blockers (CBZ, OXC, PHT), VGB, GBP, PGB, TGB

Prognosis

NOT self-limited — typically requires lifelong treatment
High relapse rate (>70–80%) on ASM withdrawal
Good seizure control with appropriate ASMs in most patients

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