Unknown. If strict criteria apply (generalized tonic-clonic seizures (GTCS) only), this may be very small (0.9% of idiopathic generalized epilepsies (IGEs)) but others give a prevalence of 13% to 15% among IGEs.

Age at onset
6 to 47 years (peak 16 to 17 years); 80% have their first GTCS in the second decade of life.

Males (55%) slightly predominate, probably because of alcohol exposure and sleep habits.

Neurological and mental state

Genetically determined. Linkage to EJM1 locus for GTCS on awakening but not with GTCS at other times.

Clinical manifestations
All patients suffer from GTCS. Only IGE with GTCS on awakening has been extensively studied, with GTCS occurring within 1 to 2 hours after awakening from sleep. GTCS may also occur during relaxation or leisure.

Overall, GTCS occur on awakening (17% to 53% of patients), diffusely while awake (23% to 36%) or during sleep (27% to 44%) or randomly (13% to 26%).

Seizure-precipitating factors
Sleep deprivation, fatigue, and excessive alcohol consumption.

Inter-ictal EEG
Usually normal background, with generalized discharges of spike/multiple spike waves in half of patients with GTCS only and 70% of those with additional mild absences or myoclonic jerks. Focal EEG abnormalities, in the absence of generalized discharges, are rare. 13% show EEG photosensitivity.

Ictal EEG
Myoclonic jerks and mainly brief phantom absences are revealed with video-EEG during generalized discharges of spike/multiple spike waves.

IGE with GTCS on awakening is probably lifelong with high (83%) incidence of relapse on withdrawal of treatment. Characteristically, the intervals between seizures become shorter with time, the precipitating factors less obvious, and GTCS may become more random (diurnal and nocturnal), either as a result of the evolution of the disease or drug-induced modifications.

Differential diagnosis
Mainly from other IGEs, which share the same propensity to GTCS on awakening. Symptomatic and focal epileptic seizures with secondarily GTCS which may also occur, predominantly on awakening.

Management options*
Avoidance of seizure precipitants.

For GTCS only, valproate, lamotrigine, levetiracetam, phenobarbital, topiramate, carbamazepine, phenytoin or oxcarbazepine can be considered. AEDs in italics are not recommended if patients also have absences or myoclonic jerks.

*Expert opinion, please check FDA-approved indications and prescribing information

This page was adapted from:

The educational kit on epilepsies: The epileptic syndromes By C. P. Panayiotopoulos Originally published by MEDICINAE 21 Cave Street, Oxford OX4 1BA
First published 2006 and reprinted in 2007

Authored By: 
C. P. Panayiotopoulos MD, PhD, FRCP
Authored Date: 
Reviewed By: 
Steven C. Schachter MD
Sunday, June 1, 2008