Focal reflex epilepsy with myoclonus; electrophysiological investigation and therapeutic implications.

A middle-aged man suffering from myoclonic jerks of the right arm and leg and occasional grand mal seizures was investigated electrophysiologically. The EEG showed a left central spike focus which could be activated by any stimulus which distorted the biceps, triceps or brachioradialis muscles but skin stimulation was ineffective. Electrical nerve stimulation subthreshold to the alpha motoneurone fibres evoked cortical spikes and myoclonic jerks. The evidence supports the hypothesis that the myoclonus was triggered by muscle spindle afferent fibres (Ia) which projected to an epileptogenic focus in the sensori-motor area. A marked improvement of symptoms was achieved by a combination of baclophen and dipropylacetate.