Prevalence
<1% in children (9.3% in adults) with typical absences.

Age at onset
2 to 13 years (median 10 years).

Sex
Females (~80%) predominate.

Neurological and mental state
Normal.

Etiology
Half of patients have first-degree relatives and mainly siblings with idiopathic generalized epilepsy (IGE) and absences.

Clinical manifestations
Typical absence seizures with perioral myoclonia are the defining symptom. Perioral myoclonia consists of rhythmic protrusion of the lips, twitching of the corners of the mouth, or jaw jerking. Impairment of consciousness varies from severe to mild. The absences last 2 to 9 sec (median 4 sec), with varying frequency from many times per day, 1 to 2 per week, or rarer.

All patients suffer from generalized tonic-clonic seizures (GTCS), starting before, soon after, or exceptionally many years after the absences. GTCS are usually infrequent and are often heralded by clusters of absences or absence status.

Absence status epilepticus is very common (57%) and frequently ends with GTCS.

Seizure-precipitating factors
Absences are nearly invariably provoked by hyperventilation.

Inter-ictal EEG
Normal background, with frequent (<1 sec) generalized discharges of 3 to 7 Hz spike/multiple spike waves that are usually asymmetrical. Focal abnormalities, including single spikes, spike-wave complexes, or slow waves, are common.

Ictal EEG
Generalized discharges of 3 to 4 Hz spikes/multiple spike waves with frequent irregularities in terms of the number of spikes, fluctuations in spike amplitude, and fragmentations.

Prognosis
Seizures are often resistant to medication, unremitting, and possibly lifelong.

Differential diagnosis
Focal motor seizures because of (1) the prominent motor features of perioral myoclonic absences often reported as unilateral and (2) inter-ictal focal EEG abnormalities.

Perioral myoclonia may rarely occur in absence seizures of other IGEs.

Other syndromes of IGE with absences such as epilepsy with myoclonic absences, childhood absence epilepsy, juvenile absence epilepsy, or IGE with phantom absences, depending on age at onset.

Management options*
Treatment is with valproate alone or combined with ethosuximide, lamotrigine, or clonazepam. Levetiracetam may be effective because of its anti-myoclonic and probable anti-absence properties.

Absence status epilepticus, for which most patients are aware, should be terminated with self-administered benzodiazepines.

Contraindicated drugs include vigabatrin#, tiagabine, carbamazepine and gabapentin.

*Expert opinion, please check FDA-approved indications and prescribing information
#Not approved by the FDA

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
I<
Authored Date: 
01/2006
Reviewed By: 
Steven C. Schachter MD
on: 
Sunday, June 1, 2008