Clinical Significance of the Optokinetic Nystagmus Abnormality

Chung, Woon Kyo; Lee, Won Sang; Choi, Mu Seong

Abstract

Optokinetic nystagmus(OKN) is commonly employed in the assessment of central vestibular lesion. Asymmetry in the OKN has been found in lesions ipsilateral to the direction of the slow phase in parietal lobe, in brain stem, and in the cerebellum. Asymmetry of the OKN may also occur in peripheral vestibular lesions due to spontaneous nystagmus, and this may explain why even enhanced velocities of OKN are sometimes met in these patients. The ocular abnormality as congenital strabismus, extraocular paresis, and congenital nystagmus can cause abnormalities of optokinetic nystagmus. We investigated the clinical significance of OKN test and spontaneous nystagmus for differentiation of peripheral and central vestibular disorder. In this study, we recorded the optokinetic nystagmus by the electronystagmography. We divided the optokinetic response from normal to type III according to direction of the nystagmus and difference of(Rt-Lt) Vmean. At the result, all of the vestibuloneuronitis who had the optokinetic abnormality showed type I OKN abnormality with spontaneous nystagmus. Type II and type III OKN abnormality always appeared in central vertigo patients. Type I OKN abnormality could be seen in peripheral and central vertigo patient. But half of the central vertigo patients who had type I OKN abnormality did not have spontaneous nystagmus. We could not correlated OKN abnormality with specific location of central nervous system.