Fig. 1.

A shows the surface electromyographic (EMG) pattern from a normal voluntary ballistic movement of wrist flexion. The subject was instructed to perform the wrist extension as quick and as brief as possible. In B, there is a myoclonus surface EMG wrist extension discharge from a patient with multifocal action myoclonus. Despite the fact that the normal ballistic movement was performed as brief as possible, note that there is still a more gradual build-up of activity when compared to the involuntary myoclonus EMG discharge. Modified from (Caviness, 1996).