We report a case of an acute incomitant esotropia with Wernike's encephalopathy.

A 64-year-old male visited our hospital because of diplopia lasting a week. He was a chronic alcoholic drinking two bottles of makgeolli daily and eating little for a month. He showed -2 underaction of bilateral lateral rectus muscles and 45 prism diopters of esotropia at the primary position at the first visit. He had ataxia and mild cognitive impairment. There were high signal intensities in the periaqueductal area and mammillary bodies in the brain fluid attenuated inversion recovery magnetic resonance image. He was diagnosed with Wernike's encephalopathy clinically and was immediately treated with intravenous thiamine. He showed -0.5 underaction of bilateral lateral muscles and 8 prism diopters of esotropia at the primary position 3 days after thiamine treatment.

Wernicke's encephalopathy is a medical emergency. If diagnosis and treatment are delayed, patients may have neurological sequelae that can lead to death. Esotropia and diplopia can be the presenting manifestations in Wernike's syndrome without other symptoms. In taking patient histories, physicians should ask about alcohol consumption and low food intake because of the possibility of acute incomitant esotropia associated with Wernicke's encephalopathy.