Vertical optokinetic nystagmus.

Abstract

Among 6377 investigations for optokinetic nystagmus the authors found 97 patients with abnormal vertical optokinetic nystagmus and normal horizontal optokinetic nystagmus. This is 10 % of the approx. 1000 patients with manifest organic lesion of the central nervous system. In 30 the vertical optokinetic nystagmus was abnormal in one direction, in 67 cases in both. Abnormality of the vertical optokinetic nystagmus in both directions was found in unilateral cerebral lesions, unilateral brain-stem lesions, and in more diffuse lesions of the central nervous system. Total absence of vertical optokinetic nystagmus was observed in only 7 patients, 5 of whom had vertical gaze paralysis, 4 of them due to pseudobulbar paralysis. Abnormality of the vertical optokinetic nystagmus in both directions in cases with definitely unilateral signs from the cerebrum or mesencephalon indicates that both vertical gaze centres have to function simultaneously to elicit normal optokinetic nystagmus. This is also confirmed by the fact that the severity of the abnormal vertical optokinetic nystagmus is greatest in lesions high in the mesencephalon, where the paths for vertical optokinetic nystagmus assemble in the two vertical gaze centres. Abnormality of the vertical optokinetic nystagmus as an isolated finding is interpreted as a sign of organic disease in the central nervous system and should lead to further special investigations for a more detailed diagnosis.