Comparison of the tonic stretch reflex in athetotic patients during rest and voluntary activity

SUMMARY An electromyographic technique was used to record the tonic stretch reflex (TSR) responses to passive sinusoidal stretching of biceps brachii muscle in athetotic patients. The TSR transmission characteristics measured while the patient was in a relaxed state were compared with those measured while the patient was voluntarily active. The resting TSR and action TSR were found to differ markedly. Sensitivity, pattern, duration, and timing of the TSR responses were all changed during voluntary activity. The results suggest that the TSR in athetosis is functionally reorganized by supraspinal influences during voluntary activity. It is proposed that athetoid move-ments and action tremor may be a manifestation of abnormal action TSR caused by faulty supra-spinal control during activity. Athetosis has been described as a manifestation of fluctuating rigido-spasticity (Narabayashi, Nagahata, Nagao, and Shimazu, 1965). They described a neurophysiological analysis based primarily on electromyography. The limb was passively moved while the electromyogra