Comparison of optokinetic nystagmus elicited by full versus partial visual field stimulation: diagnostic implications

Optokinetic nystagmus (OKN) testing is one method to determine central vestibular dysfunction. OKN may be elicited by partial visual field stimulation with a light bar (OKN-ENG) or by full visual field stimulation with rotating stripes in a rotational chair test booth (OKN-RVT). OKN-ENG and OKN-RVT were elicited in 36 healthy subjects and 48 patients with known peripheral or central vestibular disorders. Abnormal test results suggested central pathology in 29 of 36 healthy subjects with OKN-ENG versus 1 of 36 with OKN-RVT. Twenty-eight of 33 patients with peripheral pathology demonstrated abnormal OKN-ENG findings, whereas 4 of 33 had abnormal OKN-RVT results. Thirteen of 15 patients with central vestibular disorders had abnormal OKN-ENG, whereas 7 of 15 had abnormal OKN-RVT. Sensitivity and specificity of OKN-ENG were 86.7% and 17.4% versus 46.7% and 92.7%, respectively, for OKN-RVT. These findings were statistically significant (P < 0.00001). OKN elicited by full visual field stimulation (OKN-RVT) is a more accurate indicator of central disease than OKN elicited by partial visual field stimulation (OKN-ENG). The use of OKN-ENG to identify central vestibular dysfunction is questionable.