Palatal Myoclonus Associated With Abnormal Ocular and Extremity Movements

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Abstract
The electroencephalogram, electromyogram, and electro-oculogram were recorded during wakefulness and sleep from two patients with palatal myoclonus. The myoclonus of branchial muscles was persistently present and irregularly varied around a fixed frequency. Its amplitude varied directly with the amplitude of background EMG activity both during wakefulness and in sleep. The complex abnormal ocular movements occurred at the same frequency as the branchial myoclonus. They disappeared during sleep to return during desynchronized sleep following a rapid eye movement. Voluntary extremity movements provoked in them a rhythmical myoclonus of identical frequency to the simultaneously recorded branchial myoclonus. These observations suggest that voluntary or involuntary muscle activity is necessary for the expression of palatal myoclonus and that the abnormal branchial muscle, ocular, and extremity movements are caused by a common pathophysiologic mechanism.