[West syndrome associated with epileptic negative myoclonus]

We report a 10-month-old girl who had brief epileptic negative myoclonus during the course of West syndrome. She began to have epileptic spasms in series at the age of 8 months. Video-electroencephalograph (EEG) monitoring revealed that she also had brief epileptic negative myoclonus when she was 10 months old. Brief atonia of limbs occurred in isolation or in a cluster during drowsiness or sleep. The ictal EEG exhibited diffuse polyspikes and waves or diffuse high-voltage slow waves that were overlapped by low-voltage fast waves. 3 to 4 hundred milliseconds of silent periods were observed in the bilateral deltoid electromyograms, which correspond to the EEG patterns. The occurrence of other types of seizures, partial seizures in particular, accompanied by epileptic spasms has been fully investigated. This is the first case report of a patient with West syndrome whose coexisting epileptic negative myoclonus was confirmed by a silent electromyogram pattern.