A Case of Wernicke Encephalopathy with Primary Position Upbeat Nystagmus.

A 32-year-old man with Wernicke encephalopathy due to malnutrition is reported. The patient showed primary position upbeating nystagmus (PPUN) with severe ataxia and lateral gaze nystagmus. Neurootological examinations showed bilateral canal paresis, saccadic pursuit and disturbance of optokinetic responses. ABR revealed a prolongation of the I-III interwave interval, although his pure-tone audiogram was normal. Brain MRI demonstrated symmetrical high intensity areas on T2-weighted images in the periventricular regions of the third ventricle. MRI is a useful tool for the diagnosis of Wernicke encephalopathy in the early stages. After thiamine therapy, PPUN and ataxia gradually, but incompletely recovered, although lateral gaze nystagmus and the high intensity areas on MRI disappeared. These observations suggest that brainstem-cerebellar lesions contributed to the clinical manifestations of this case.