[Monozygotic twins with centrotemporal spikes on the electroencephalogram--differences in clinical manifestations and the effect of valproate therapy].

Monozygotic twin sisters who had almost identical electroencephalographic abnormalities, but different clinical features and different response of this abnormalities to valproate at the age of 6 years are described. One twin was admitted to the hospital because of numerous brief myotonic seizures of sudden onset with corresponding abnormalities in the electroencephalogram. The seizures disappeared completely and the electroencephalogram became normal within a week of treatment with valproate. The other twin never had any seizures. However, her electroencephalogram repeatedly showed impressive abnormalities and the therapy with valproate had no substantial effect on these abnormalities. We believe this twins to be a suitable model for studying the inheritance of epilepsy and electroencephalographic abnormalities, as well as for studying the action of antiepileptic drugs. At this moment, it is not possible to offer any reasonable explanation for the normalization of the electroencephalographic abnormality during valproate treatment in the clinically affected twin, while the electroencephalogram remained abnormal in the clinically unaffected twin.