A 28-year-old woman presented to the emergency department with vertigo, confusion, and falls 2 weeks after a surgical abortion at 11 weeks of gestation. Her pregnancy had been complicated by persistent hyperemesis gravidarum. An examination revealed spontaneous upbeat nystagmus , gaze-evoked nystagmus , and gait ataxia. She had no ophthalmoplegia. Magnetic resonance imaging of the brain showed T₂ hyperintensities involving the periaqueductal white matter (Panel A, arrow) and bilateral thalami (Panel B, arrows). A diagnosis of Wernicke’s encephalopathy was made. Wernicke’s encephalopathy due to thiamine (vitamin B₁) deficiency can be a complication of hyperemesis gravidarum; it can also occur in the context of alcohol use, bariatric surgery, or malnutrition. If untreated, Wernicke’s encephalopathy can progress to coma or death. Eye-movement abnormalities reported in Wernicke’s encephalopathy include gaze-evoked nystagmus, spontaneous upbeat nystagmus, and horizontal or vertical ophthalmoplegia. Patients may also have a selective impairment of the horizontal vestibulo-ocular reflex that corrects rapidly after intravenous administration of thiamine. The patient received high-dose intravenous thiamine and had some alleviation of the eye-movement abnormalities and ataxia.