A comparative electromyographic study of the reactions to passive movement in parkinsonism and in normal subjects

Abstract

Flexible bipolar electrodes were used to record motor unit potentials in the brachialis and triceps during passive movement in parkinsonian patients and in normal subjects at rest, with voluntary tension, and with tone increased by Suprarenin and by chilling. Because electrode movement tends to occur during passive movement, identification of motor units is often difficult. Nevertheless, records even suggestive of unit rotation are seen no more often in parkinsonism than among normal subjects; the rotating unit antoin-hibitory theory of parkinsonian rigidity is not supported. The variations of passive movement reaction in normal subjects are compared with those in parkinsonian rigidity and tremor, and the general similarities are discussed. It is suggested that a continuous, excessive net excitatory drive to the final common path a physiologically normal spinal cord-can account for the pathophysiological phenomena of parkinsonian hypertonus.