Early-onset childhood absence epilepsy: is it a distinct entity?

Childhood absence epilepsy (CAE) typically starts between four and seven years of age. Onset before three years is rare and has not been previously reported from North America. We retrospectively reviewed the electroencephalography laboratory database and paediatric neurology clinic records (from January 2000 to June 2009) at our institution in order to identify patients with absence seizures beginning before age three. Information was collected for age, gender, neurodevelopment, antiepileptic drugs (AEDs) used, seizure control, follow-up, and side effects. Of 12 patients identified, mean age at onset was 20.5 months (range: 11 months to two years; follow-up: six months to 11 years). Seven of 12 patients had normal neurodevelopment and five had speech delay. Four patients were seizure-free without AEDs, three were seizure-free with a single AED, and five still had seizures with multiple AEDs. Three patients had recurrences after medication withdrawal. Other previously published series have identified better seizure control than that reported here, however, 16% of the 130 patients so far documented are reported to have poorly controlled epilepsy, indicating that early-onset CAE is not a homogeneous condition. The debate as to whether early-onset CAE is a distinct epilepsy syndrome therefore continues. We believe that early-onset CAE may be a distinct epilepsy syndrome, with some features that overlap with those of typical CAE, as well as unique distinguishing features. Large prospective multicentric studies would be necessary to definitely resolve this matter.