Micromyoclonic seizures of sleep.

A patient with primary generalized epilepsy had convulsive seizures refractory to anticonvulsant therapy. Several waking EEGs failed to show paroxysmal activity, but a sleep recording revealed polyspike EEG discharges associated with individual electromyographic discharges localized to the chin. The discharges occurred with a 90- to 100-minute period during the night. An increased frequency and duration of the EEG discharges on the last night of recording preceded a marked increase in the number of convulsions the following day.