The Question
A 48-year-old woman with a history of Roux-en-Y gastric bypass 5 years ago presents to the emergency department with 3 weeks of progressive gait instability and confusion. Her husband reports that she has become increasingly apathetic and forgetful. For the past two months, she has had nausea and poor oral intake, and has been inconsistent with her prescribed nutritional supplements. On examination, she is lethargic and oriented only to person. Temperature is 37.1°C (98.8°F), blood pressure is 118/76 mmHg, heart rate is 88/min, and respirations are 16/min. Neurologic examination reveals bilateral horizontal nystagmus on lateral gaze and bilateral abducens palsy. She has a wide-based, ataxic gait and is unable to perform tandem walking. Laboratory studies show a hemoglobin of 11.2 g/dL with a mean corpuscular volume (MCV) of 105 fL. Serum electrolytes, creatinine, and liver enzymes are within normal limits. Which of the following is the most appropriate immediate intervention?
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A
Explanation
High-Yield Pearl: In patients with suspected Wernicke encephalopathy (the triad of encephalopathy, oculomotor dysfunction, and gait ataxia), intravenous thiamine must be administered emergently before any glucose-containing fluids to prevent precipitating irreversible neurologic injury.
Detailed Reasoning: This patient's presentation is classic for Wernicke encephalopathy (WE), a neurologic emergency resulting from severe thiamine (vitamin B1) deficiency. Her history of Roux-en-Y gastric bypass is a significant risk factor for malabsorption and subsequent micronutrient deficiencies. The clinical triad of encephalopathy (confusion, apathy), oculomotor dysfunction (nystagmus, abducens palsy), and gait ataxia is highly suggestive of the diagnosis. The most critical step is the immediate administration of high-dose parenteral thiamine. Delaying treatment to await diagnostic confirmation, such as with an MRI, can lead to irreversible brain damage or death. Administering glucose-containing fluids (like 5% dextrose) before thiamine is contraindicated as it can deplete the remaining thiamine stores by increasing its metabolic demand, thereby acutely worsening the encephalopathy. While an MRI can show characteristic findings like mamillary body enhancement, it should not precede treatment. A lumbar puncture is not indicated as the primary diagnosis is metabolic, not infectious or inflammatory. Although vitamin B12 deficiency (suggested by the macrocytic anemia) is also common after gastric bypass and can cause neurologic symptoms, the acute presentation with the classic triad makes WE the most urgent diagnosis to treat.
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