Electromechanical characteristics of tardive dyskinesia.

Fifty patients with mild-to-moderate tardive dyskinesia (TD), who were devoid of other clinically apparent movement abnormalities, and 70 neurologically normal controls were assessed with a battery of instruments developed to measure and analyze the hyperkinetic movements of TD directly, objectively, and noninvasively. The electro-mechanical features that most consistently characterized and differentiated the TD group were a greater variability of all movements, increased energy in the 1-2 Hz frequency band in hand and foot movements, and a marked increase in movements during distracting tasks. This instrumentation promises to be useful in quantitating abnormal involuntary movements, in prospectively following individual patients to scan for small deviations from an instrument-established baseline, and in examining patients with combined movement abnormalities.