Abstract
Analysis of optokinetic nystagmus has been one of the most important means to examining the function of the vestibulo-oculomotor system. Especially in Japan, it has been used as a means to analyze the function of the brainstem.
We investigated directional preponderance of optokinetic nystagmus in supratentorial lesions especially unilateral lesions in the cerebral hemisphere. This subject has been nearly neglected as an object of the investigation of the vestibular system. We examined 30 cases of unilateral lesions in the cerebral hemisphere, about which it was confirmed in all the cases by CT-Scanning that these lesions have no mass effect which might affect the function of the adjacent brain. These patients were also confirmed as having no spontaneous nystagmus. They consisted of 11 cases of cerebral thromboses, 9 cerebral emboli, 6 cerebral hemorrhages and 4 cerebral contusions.
As a result, 27 cases showed directional preponderance of optokinetic nystagmus to the ipsilateral side, while none showed the nystagmus to the contralateral side. Three patients had no directional preponderance. Some patient showed marked inhibition of optokinetic nystagmus of the contralateral side. They could hardly be differentiated from those with the pontine lesions which usually develops marked inhibition of optokinetic nystagmus in the contralateral side.
