Dissociated nystagmus as a common sign of ocular motor disorders in HIV-infected patients.

In order to determine if ocular motor disturbances due to brainstem and cerebellar dysfunction provide a frequent and early marker for HIV infection of the brain, neurological examination was performed in 133 HIV-infected persons who were consecutively admitted to our hospital. In 22 patients (17%) we found no other reason for cerebellar or pontomesencephalic signs than HIV encephalopathy. Ocular motor disorders accounted for the most frequent signs of cerebellar and pontomesencephalic dysfunction. Ocular motor disorders mainly consisted of dissociated nystagmus (n = 12), gaze-evoked nystagmus (n = 10) and impaired smooth pursuit (n = 6). Cerebellar ataxic gait and dysmetria were present in 3 patients. Since dissociated nystagmus was the primary ocular motor disorder, we assume that the medial longitudinal fasciculus may be a predilected circumscribed area for HIV infection of the brain. We suppose that cerebellar and pontomesencephalic disorders may be an early marker for HIV encephalopathy because they were the only neurological signs found in 12 patients.