Phenotypic analysis of juvenile myoclonic epilepsy in Indian families

Objectives - Phenotypic analysis of juvenile myoclonic epilepsy (JME) is presented to document the variations in disease expression. Material and methods - Information on seizure type and frequency, seizure precipitating factors, electro-encephalographic (EEG) data, response to antiepileptic drugs (AEDs) and family history was collected on 500 Indian probands and 61 relatives with JME. Results - The overall clinical features, EEG characteristics, and familial occurrence were similar to other reports. JME probands and relatives having absences (56 of 561, 10%), those with only myoclonic jerks (MJ) or MJ with one generalized tonic-clonic seizure (GTCS) in remission without treatment (five of 561, 1%) and those who required valproic acid (VPA) and another AED for seizure control (19 of 561, 3%) are examples of differential disease expression within JME. Seizures among those having photoparoxysmal response (PPR) on EEG responded very well to VPA alone while those with all three seizure types (MJ, GTCS and absences) were poor responders. Conclusions - Recognition of clinical 'subtypes' among JME could have therapeutic implications and help improve JME phenotypic characterization for molecular studies.