To the Editor: A 27-year-old woman was admitted to the hospital for a one-month history of worsening nausea, vomiting, anorexia, weakness, vertigo, and blurry vision with hypokalemia and ketosis three months after a Roux-en-Y gastric bypass. The patient had no immediate postoperative complications and adhered to over-the-counter multivitamin supplementation as prescribed by her surgeon. During her three-month postoperative visit, the patient reported increasing nausea and vomiting and was diagnosed with dumping syndrome. She was instructed to avoid complex starches; however, her symptoms continued to worsen during the next month despite strict dietary adherence. After admission to the hospital, the patient's anorexia and emesis improved with intravenous fluids and proton pump inhibitors; however, fatigue, vertigo, and blurry vision persisted.

A neurologic examination showed horizontal jerk nystagmus on lateral gaze bilaterally and ataxia. The patient's thiamine (vitamin B₁) levels were low. Magnetic resonance imaging of the brain did not show any abnormalities. The patient was diagnosed with Wernicke encephalopathy because of the reported symptoms in the context of a recent bariatric operation, despite the negative imaging results. The patient was immediately treated with intravenous thiamine to prevent irreversible complications and subsequently improved within 12 hours. The patient continued to receive 500 mg of intravenous thiamine every eight hours for three days with full resolution of nystagmus, ataxia, nausea, vomiting, and fatigue. The patient was discharged on a fortified vitamin regimen based on the American Society for Metabolic and Bariatric Surgery guidelines.¹

Nutritional deficiency is a common complication of bariatric surgery. Rare and potentially fatal vitamin-deficient states such as Wernicke encephalopathy can occur even when vitamin supplementation protocols are followed.^2,3 Wernicke encephalopathy is an acute neuropsychiatric syndrome caused by thiamine deficiency with a classic triad of nystagmus and ophthalmoplegia, mental status changes, and ataxia.⁴ It occurs more commonly in patients who abuse alcohol but can also be present in patients who have had gastrointestinal surgeries.¹ Initial symptoms of thiamine deficiency, including nausea and vomiting, are nonspecific, which increases the risk of progression to Wernicke encephalopathy in patients who have had bariatric surgery and are initially misdiagnosed.³

This example illustrates the potential for severe, irreversible consequences of thiamine deficiency in patients after Roux-en-Y gastric bypass. Adequate postoperative vitamin supplementation and recognition of the complex presentation and subtle physical examination findings in the diagnosis and treatment of Wernicke encephalopathy are essential.

The authors acknowledge Erika Walker for her contributions to this letter and continuous mentorship.

The views expressed in this letter are those of the authors and do not reflect the official policy of the Department of the Army, Department of the Navy, U.S. Air Force, Public Health Service, Department of Defense, or the U.S. government.