Inhibition of forearm EMG by palatal myoclonus.

The forearm electromyogram (EMG), pharyngeal EMG, and wrist tremor were recorded simultaneously from a 74-year-old woman with the syndrome of palatal myoclonus and progressive ataxia. Her wrist tremor had the characteristics of enhanced physiologic tremor. The enhancement of her tremor was attributable to 50- to 80-ms silent periods in the forearm EMG that followed the 1.9-Hz bursts of palatal myoclonus by 50 to 60 ms. This observation and those of previous authors support the notion that rhythmic olivocerebellar discharges can cause tremorogenic excitation and inhibition of postural EMG activity in the upper extremities.