Abstracts

Rationale: Absence epilepsy is an idiopathic generalized epilepsy syndrome defined by episodes of unresponsiveness, accompanied by bilaterally synchronous 3 Hz spike and wave discharges on EEG. Childhood absence epilepsy (CAE) typically starts between 4-7 years. The onset of absence epilepsy before the age of 3 years is rare and has not been previously reported from North America to the best of our knowledge. Optimal treatment and prognosis for this age group is not well known. The aim of this study is to assess the clinical relevance of early onset absence epilepsy and to characterize seizure frequency, treatment and outcome in a subset of patients with this diagnosis. Methods: A retrospective chart review was performed. The EEG database from St Christopher’s Hospital for Children from January 2000 to June 2009 was reviewed to identify patients with absence epilepsy that began below the age of three years. Absence seizures were defined as paroxysmal episodes of staring with concomitant 3Hz spike and wave electrographically on a normal EEG background. Patients had no other seizure types. The following clinical data were collected: age, sex, neurodevelopment, antiepileptic drugs (AEDs) used, seizure control and side effects. Results: There were a total of 11 patients identified; 7 boys and 4 girls. The mean age of seizure onset was 19.9 months (11 months-2 yrs) with mean age at diagnosis of 3.2 years (16 months-7 yrs). AEDs used were ethosuximide in 10 patients, valproate in 6, levetiracetam in 3, and lamotrigine and topiramate each in 1 patient. Follow-up ranged from 6 months to 9 years (mean 3.7 years) Of the 11 patients, one child is currently seizure free and off medication after treatment with ethosuximide for two years. One patient is not on any medication as per the parent’s request after an initial allergic reaction to ethosuximide. Nine patients are currently on medication. Three of them are currently seizure free on a single AED. Two of the three were successfully controlled and treated with a single AED. They were weaned off AEDs after being seizure free for two years. Both had seizure recurrence within two to three months of cessation of treatment. Six patients continue to show clinical and/or EEG evidence of absence seizures, despite being on therapeutic doses of multiple AEDs used either as monotherapy or combination. No patients have developed any other seizure types on follow-up. Neurodevelopment has been normal in 6 patients, 4 patients have mild speech delay and one has moderate language delay. Conclusions: Early onset absence epilepsy appears to be an entity different from typical childhood absence epilepsy. Early onset absence seizures may be difficult to treat and sometimes require the use of multiple AEDs. We propose that early onset absence epilepsy be recognized as a distinct idiopathic generalized epilepsy (IGE) syndrome in the International League Against Epilepsy (ILAE) classification