Spontaneous blinks of Parkinson's disease patients evaluated by EMG and EOG

In a study of spontaneous blinks, both electromyographic (EMG) activities from m. orbicularis oculi which is responsible for initiating closure of the eyelid and electro-oculogram (EOG) of vertical direction to the movement of the eyelid were measured in ten patients with Parkinson's disease and in thirty normal subjects. The aim of this study was to evaluate the generative mechanism of the spontaneous blinks by comparison of both the EMG and the EOG waveforms in the patients with Parkinson's disease and those in the normal subjects. The mean duration and the amplitude of both the EMG and the EOG were evaluated by the averaging of ten waveforms for the spontaneous blinks. The time lag between the onset of the generation of the EMG and the onset of the EOG signal was analyzed. The mean duration of the EMG and the mean amplitude of both the EMG and the EOG in the patients with Parkinson's disease were shorter and smaller than those in the normal subjects by the significant level of 1%, respectively. There was no difference of the time lag between the subject groups. These results suggest that the function of m. orbicularis oculi for the spontaneous blinks is reduced in patients with Parkinson's disease, because the motoneurones of the facial nucleus innervating the m. orbicularis oculi becomes hypoactive due to abnormal output of basal ganglia.