A comparison of the regularity of involuntary muscle contractions in vascular chorea with that in Huntington's chorea, hemiballism and parkinsonian tremor.

We compared the regularity of involuntary muscle contractions in patients with Huntington's disease, vascular chorea, hemiballism and parkinsonian tremor to clarify the nature of phasic involuntary movements caused by lesions in the basal ganglia. Rectified and smoothed electromyograms (EMGs) in involuntary contractions of the predominantly affected muscles were analyzed. After detecting the muscle whose EMG waves showed the most regular rhythm, the frequency, coefficients of variation of interval, amplitude and rise time of the successive EMG waves were compared. The regularity of the intervals of the EMG waves in vascular chorea was significantly greater than that in Huntington's chorea, and some patients with vascular chorea showed a regular rhythm the degree of which approximated that of parkinsonian tremor. The regularity of the intervals of the EMG waves in hemiballism was greater than that in Huntington's chorea, but lower than that in vascular chorea. The regularities of interval, amplitude and rise time all showed the same ordering across the patient groups. The high regularity of muscle contraction intervals in vascular chorea and hemiballism may arise from neural circuits that are abnormally activated as well as those producing tremor.