Myoclonus Epilepsy in Two Families–Clinical and Electrographic Studies

Abstract

Summary: Clinical and electrographic findings are described in two unrelated families with myoclonus. Both families had consanguineous marriage in the parents. Family A resembled progressive myoclonus epilepsy of Unverricht and Lundborg. In family B the illness was mild, mental function was normal and infrequent grand mal seizures affected one member only; the illness did not resemble hereditary essential myoclonus, familial myoclonus with ataxia or progressive myoclonus epilepsy (PME).The diurnal EEG, in affected members of family A, resembled the changes described in PME. In contrast, affected members of family B showed normal alpha rhythms accompanied by numerous epileptic discharges. Some affected members of both families showed eye closure triggered generalised epileptic discharges.Overnight poly graphic recordings in the probands of the two families showed preservation of normal nocturnal sleep cycles and marked attenuation of myoclonus in sleep. However, the epileptic discharges, though decreased in sleep, were most prominent during REM sleep in the proband of family A and in deep sleep (NREM 3 and 4 and REM) in the proband of family B.Two affected members from each family showed good control of their myoclonus on clonazepam; clinical improvement was accompanied by marked suppression of epileptic discharges.