Wernicke's encephalopathy presenting with upbeating nystagmus.

The case of a 49-year-old woman with Wernicke's encephalopathy is described, in which primary position upbeating nystagmus was the chief ocular sign. Although there was no history of excessive alcohol consumption, Wernicke's encephalopathy was diagnosed on a background of anorexia nervosa. The diagnosis was supported by the patient's symptomatic and clinical recovery following thiamine therapy.