FAMILIAL TEMPORAL-LOBE EPILEPSY - A COMMON DISORDER IDENTIFIED IN TWINS

We describe a new syndrome of familial temporal lobe epilepsy in 38 in dividuals from 13 unrelated white families. The disorder was first ide ntified in 5 concordant monozygotic twin pairs as part of a large-scal e twin study of epilepsy. When idiopathic partial epilepsy syndromes w ere excluded, the 5 pairs accounted for 23% of monozygotic pairs with partial epilepsies, and 38% of monozygotic pairs with partial epilepsy and no known etiology. Seizure onset for twin and nontwin subjects us ually occurred during adolescence or early adult life. Seizure types w ere simple partial seizures with psychic or autonomic symptoms, infreq uent complex partial seizures, and rare secondarily generalized seizur es. Electroencephalograms revealed sparse focal temporal interictal ep ileptiform discharges in 22% of subjects. Magnetic resonance images ap peared normal. Nine affected family members (24%) had not been diagnos ed prior to the study. Pedigree analysis suggested autosomal dominant inheritance with age-dependent penetrance. The estimated segregation r atio was 0.3, indicating an overall penetrance of 60% assuming autosom al dominant inheritance. The mild and often subtle nature of the sympt oms in some family members may account for lack of prior recognition o f this common familial partial epilepsy. This disorder has similaritie s to the El mouse, a genetic model of temporal lobe epilepsy with a ma jor gene on mouse chromosome 9, which is homologous with a region on h uman chromosome 3.