Channel-gating kinetics are changed. Sodium channel inactivation is slower, with longer depolarization and increased neuronal excitability. This sodium channel underlies the action potentials in sustained burst firing. Phenytoin, carbamazepine, and valproic acid work through use-dependent blockade of this sodium channel. Onset is usually age 10 to 20.
Myoclonic jerks occur most often in the morning.
EEG shows generalized atypical polyspike and wave. Valproic acid is effective in most patients. The epilepsy is usually lifelong. Linkage studies have suggested linkage to chromosome 6p or 15q. Childhood absence epilepsy Some cases have been mapped to 8q.