EMG analysis of patients with cerebellar deficits.

EMGs from biceps and triceps were recorded during stereotyped elbow flexion tasks performed by 20 patients fulfilling clinical criteria for 'cerebellar deficits' and the data were compared with previously established normal standards. In a fast flexion task, 15 of 18 patients showed prolongation of the initial biceps and/or triceps components, and it is suggested that this abnormality might be an elemental feature of dysmetria. Ten of 14 patients showed the normal pattern of smooth flexion indicating that, with cerebellar deficits, smooth movements are better preserved than fast movements. The timing of the cessation of triceps activity before the initiation of biceps activity in an alternating movement was abnormal in 12 of 16 patients; this abnormality might be an elemental feature of dysdiadochokinesia.