CORTICAL MYOCLONUS IN LEVODOPA-RESPONSIVE PARKINSONISM

We observed myoclonic movements of the fingers and wrists in two patie nts with a levodopa-responsive parkinsonian syndrome most consistent w ith Parkinson's disease. These patients were studied with electrophysi ological techniques. Brief (<50 ms) myoclonic electromyographic discha rges showed a time-locked relationship to a focal premovement electroe ncephalographic potential. Somatosensory evoked potentials were not en larged and long-latency reflexes were not grossly exaggerated. This pa ttern of electrophysiological findings can be distinguished from those previously found in other parkinsonian syndromes. These results provi de evidence for a cortical origin of the myoclonus seen in these patie nts.