Movements not involved in posture are abnormal in Parkinson's disease.

We have studied movements of the top joint of the thumb in a group of patients with Parkinson's disease. Even when movements were performed with the proximal phalanx of the thumb clamped, and with the forearm fully supported, movement time was prolonged and multiple bursts of EMG activity were present in the flexor pollicis longus. An abnormality of such movements performed with complete external postural support suggests that disease of the basal ganglia affect all movements, not just those involved in posture.