Abstracts

Idiopathic Generalized Epilepsy (IGE) is generally thought of as common and relatively benign. We examined the Nova Scotia Childhood Epilepsy Cohort to better understand the frequency of IGE syndromes and their outcome. All children in Nova Scotia who developed epilepsy (two or more unprovoked seizures) between 1977-85 were identified from a central EEG reading facility for the entire Province (population [sim]850,000). Cases were followed by chart review, telephone or in person 5-20 years later. Children were included if their first two seizures occurred before age 16 years.
IGE was diagnosed when the first seizure type was absence, generalized tonic-clonic or myoclonic and the child had normal intelligence, normal neurologic examination and no alternative cause. All initial EEGs showed normal background and spontaneous or provoked (hyperventilation, photic stimulation) bursts of generalized spike-wave.
Remission was defined as seizure free and no longer receiving daily anti-epileptic medication at the end of follow [ndash]up. The entire NS cohort included 692 patients. At the time of diagnosis, there were 140 with IGE; therefore, IGE accounts for 20% of all incidence cases[italic] of [/italic]childhood epilepsy. Among the 140 with IGE, syndromes were Childhood Absence Epilepsy (CAE) (n=81, 58%), Juvenile Absence Epilepsy (n=12, 9%), Juvenile Myoclonic Epilepsy (JME) (n=14, 10%), benign myoclonic epilepsy of infancy (n=1), IGE not otherwise defined (n=32, 23%). The overall long term remission rate for all IGE was 55% (75/140). The remission rates by syndrome were CAE (65%), Juvenile Absence (60%), JME (14%) and IGE not otherwise defined (44%). We note that 15% of those presenting with CAE evolved over time to meet all the criteria for JME. For those with IGE otherwise not defined, the long term remission rate for those with onset [le]10 years was 71% (10/14) compared 22% (4/18) for those with onset [gt]10 years (p=0.01). At the time of diagnosis, IGE accounts for only one-fifth of all childhood epilepsy and is made up from a relatively uncommon group of syndromes. Childhood Absence Epilepsy represents the majority of IGE cases. About one-quarter do not fit into a clearly defined IGE syndrome at diagnosis. Long term remission occurs in 55% of IGE with varying rates depending on the IGE syndrome. The most favorable remission rate appears to be for IGE, otherwise not defined, provided that the epilepsy begins before age 10 years.