Acute up-beating nystagmus in a pregnant woman with hyperemesis gravidarum

Purpose To describe a case of sudden onset of nystagmus in a pregnant patient with hyperemesis gravidarum. Observations Sixteen days after onset of persistent nausea and uncontrollable vomiting, a 12 week pregnant woman presented up-beating nystagmus, mild memory impairment and reduced sensitivity in the lower limbs. Laboratory tests presented thiamine deficiency and magnetic resonance imaging showed bilateral medial thalami and midbrain lesions. Because of suspected Wernicke's encephalopathy, the patient was treated with thiamine replacement and significant improvement of symptoms took place. Conclusions and importance Uncontrollable vomiting can lead to malabsorption of vitamin B1 causing acute onset of nystagmus.