JAW MOVEMENT DYSFUNCTION RELATED TO PARKINSONS-DISEASE AND PARTIALLY MODIFIED BY LEVODOPA

Objectives-To test the hypotheses that Parkinson's disease can differe ntially produce deficits in voluntary and rhythmic jaw movements, whic h involve different neuronal circuits, and that levodopa treatment imp roves specific components of the motor deficit. Methods-Patients with idiopathic Parkinson's disease and control subjects were tested on a s eries of jaw motor tasks that included simple voluntary movement, isom etric clenching, and natural and paced rhythmic movements. Jaw movemen ts were measured by changes in electromagnetic fields and EMG activity . Patients with Parkinson's disease with fluctuations in motor respons es to levodopa were tested while off and on. Results-During the off st ate, patients with Parkinson's disease were significantly worse than t he control subjects on most tasks. The deficits included a decrease in amplitude and velocity during jaw opening and closing, aberrant patte rns and low amplitude of EMG activity during clenching, and low vertic al amplitude and prolonged durations of occlusion during rhythmic move ments. No decrements were found in the amplitude of voluntary lateral jaw movements or the frequency of rhythmic movements. During the on st ate, improvements occurred in the patterns and level of EMG activity d uring clenching and in the vertical amplitude and duration of occlusio n during rhythmic movements, although a significant decrement occurred in the lateral excursion of the jaw. Conclusions Parkinson's disease affects the central programming of functionally related muscles involv ed in voluntary and rhythmic jaw movements and levodopa replacement in fluences only certain aspects of jaw movement, most likely those requi ring sensory feedback.