A 38-year-old hospitalized woman is evaluated for new-onset confusion. The patient has a prolonged history of Crohn disease and was admitted 2 days ago due to worsening abdominal pain, nausea, and watery diarrhea. She tested positive for Clostridioides (formerly Clostridium) difficile infection and is receiving oral vancomycin and intravenous fluids. Her gastrointestinal symptoms have been improving, but since yesterday the patient has been incoherent, disoriented, and unsteady. She has no other medical conditions but has had small bowel resections due to stricture and fistula in the past and has lost 10 kg (22 lbs) over the past 6 months. The patient does not use tobacco, alcohol, or illicit drugs. Temperature is 36.6 C (98 F), blood pressure is 120/70 mm Hg, and pulse is 92/min with no orthostatic changes. BMI is 19.5 kg/m². On examination, she is not oriented to time or place. Pupils are equal and reactive to light. Abduction of the right eye is limited and elicits bilateral horizontal nystagmus. Motor strength and deep tendon reflexes are normal throughout. Finger-to-nose and heel-to-shin testing are normal, but the gait is wide based. Which of the following is the most likely cause of this patient's neurologic symptoms?

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11ec25c8_d15b_4836_bc81_a1e9f218886b_MD0003_00 This patient with Crohn disease had multiple small bowel resections complicated by significant weight loss, a finding that suggests malnutrition. She developed altered mental status, a lateral-gaze palsy (eg, limited eye abduction) with horizontal nystagmus, and a wide-based gait after receiving intravenous fluids, which raises concern for Wernicke encephalopathy (WE). WE is a neurologic complication of thiamine deficiency; it classically manifests as the triad of ataxia, encephalopathy (eg, lethargy, disorientation), and oculomotor dysfunction (eg, nystagmus, gaze palsies). It is usually associated with long-standing alcohol abuse; however, WE can be associated with any form of chronic malnourishment (eg, short-gut syndrome, anorexia). Iatrogenic WE can be precipitated in malnourished patients by the administration of dextrose (which this patient likely received as a maintenance fluid), which depletes the last remaining stores of thiamine, a vitamin cofactor for enzymes involved in glucose metabolism. There are no diagnostic laboratory studies to confirm WE; therefore, intravenous thiamine supplementation should be promptly administered if the diagnosis is suspected. Korsakoff syndrome, a late-stage complication of WE, is characterized by significant retrograde and anterograde amnesia, often with confabulation. Up to 80% of patients with alcohol use disorder who have WE develop Korsakoff syndrome; however, it occurs less frequently in WE patients who are nonabusers. (Choice A) Immune-mediated demyelination occurs in a variety of diseases, including Guillain-Barré syndrome (GBS) and multiple sclerosis. GBS typically causes a rapidly progressive, ascending paralysis with hyporeflexia, and multiple sclerosis causes neurologic deficits (eg, diplopia, focal weakness, bowel/bladder dysfunction) disseminated in time and space. Altered mentation is rare and occurs subacutely with severe disease. (Choice B) Medication-induced delirium is common with anticholinergics, benzodiazepines, or opiate medications, but is not expected with vancomycin. Although delirium is associated with confusion and disorientation, focal neurologic deficits are unexpected. (Choice C) Bacterial or fungal meningoencephalitis can cause focal neurologic deficits and altered mentation, but they are typically associated with fever, headache, and meningismus. (Choice E) Symptoms of vertebrobasilar artery occlusions are dependent on the area involved but often cause ataxia or altered mentation. However, diplopia, hemiparesis/paraparesis, or Wallenberg syndrome (loss of pain/temperature in the ipsilateral face and contralateral body) are common. In addition, cerebellar examinations (eg, finger-to-nose; heel to shin) are typically positive. Educational objective: Wernicke encephalopathy is a neurologic complication of thiamine deficiency; it classically manifests as the triad of ataxia, encephalopathy, and oculomotor dysfunction. It is usually associated with long-standing alcohol abuse; however, it may be caused by any disorder that causes chronic malnourishment (eg, short-gut syndrome). Treatment is with intravenous thiamine.

A 38-Year-Old Hospitalized Woman Is Evaluated for New-Onset Confusion