A 22-year-old woman is brought to the emergency department by her boyfriend after an episode of syncope. The patient says she feels "fine" and wants to go home. She has no prior medical conditions and takes no medications. Her boyfriend states that she is in good health and that she exercises every day, sometimes even "too much" because she wants to be in great shape. The patient has smoked a pack of cigarettes daily for 2 years but does not use alcohol. She smokes marijuana at least twice a week.
Temperature is 36.7 C (98 F) , blood pressure is 100/70 mm Hg, pulse is 114/min, and respirations are 16/min. BMI is 17 kg/m². Physical examination shows dry mucous membranes and normal jugular venous pressure with no thyromegaly. The lungs are clear on auscultation and heart sounds are normal. The abdomen is soft and nontender. Neurologic examination is within normal limits.
Laboratory results are as follows:
Urine pregnancy test results are negative. In the emergency department, 50% dextrose is administered and normal saline infusion is begun. Two hours later, the patient experiences sudden-onset double vision. On repeat examination, she appears mildly lethargic and there is lateral gaze palsy on the right side.
Which of the following is the most likely cause of this patient's vision disturbance?

Question

A 22-year-old woman is brought to the emergency department by her boyfriend after an episode of syncope. The patient says she feels "fine" and wants to go home. She has no prior medical conditions and takes no medications. Her boyfriend states that she is in good health and that she exercises every day, sometimes even "too much" because she wants to be in great shape. The patient has smoked a pack of cigarettes daily for 2 years but does not use alcohol. She smokes marijuana at least twice a week.
Temperature is 36.7 C (98 F) , blood pressure is 100/70 mm Hg, pulse is 114/min, and respirations are 16/min. BMI is 17 kg/m². Physical examination shows dry mucous membranes and normal jugular venous pressure with no thyromegaly. The lungs are clear on auscultation and heart sounds are normal. The abdomen is soft and nontender. Neurologic examination is within normal limits.
Laboratory results are as follows:

Urine pregnancy test results are negative. In the emergency department, 50% dextrose is administered and normal saline infusion is begun. Two hours later, the patient experiences sudden-onset double vision. On repeat examination, she appears mildly lethargic and there is lateral gaze palsy on the right side.
Which of the following is the most likely cause of this patient's vision disturbance?

Quizplus · Accepted Answer

11ec193a_965e_b7b7_853d_153c65b0cacc_MD0002_00 This underweight woman with multiple electrolyte disturbances, hypoglycemia, and an anion gap metabolic acidosis with urine ketones has evidence of severe malnourishment, likely from anorexia nervosa. She developed double vision with lateral gaze palsy and lethargy after an infusion of dextrose-containing solution, raising concern for Wernicke encephalopathy (WE). WE is a neurologic complication of thiamine deficiency; it classically manifests as the triad of ataxia, encephalopathy (eg, lethargy), and oculomotor dysfunction (eg, nystagmus, gaze palsies), although all 3 signs often do not present together. It is usually associated with long-standing alcohol abuse; however, WE may be caused by any disorder causing chronic malnourishment (eg, anorexia nervosa, hyperemesis gravidarum, post-bariatric surgery). Iatrogenic WE can be precipitated in malnourished patients by the administration of dextrose, which depletes the last remaining stores of thiamine (a cofactor for enzymes involved in glucose metabolism). Most physicians are aware of the need to give thiamine with dextrose in patients with chronic alcohol use; however, there is less awareness regarding thiamine administration with dextrose for other at-risk populations. (Choice A) Magnesium deficiency may cause hypokalemia and vertical nystagmus, but severe deficiency also typically causes hypocalcemia, involuntary movements, seizures, and arrhythmias. It is unlikely to cause a gaze palsy. (Choice B) Marijuana toxicity usually presents with acute mood and thought disturbances in addition to red eyes, tachycardia, elevated blood pressure, and dry mouth. However, it does not usually cause vision disturbances or nystagmus. (Choice C) Refeeding syndrome occurs in a chronically malnourished patient and may cause hypokalemia; however, it also leads to severe hypophosphatemia and causes congestive heart failure, edema, seizures, and rhabdomyolysis. Although this patient is at risk for development of refeeding syndrome, gaze palsies would be unlikely. (Choice D) Starvation (or fasting) ketoacidosis is a normal response to fasting and is commonly seen in patients who are malnourished or even on low-carbohydrate diets. Although this patient does have starvation ketoacidosis, fasting ketosis itself would not cause visual changes. Educational objective: Wernicke encephalopathy (WE) is due to thiamine deficiency and can occur in patients with chronic alcohol use or chronic malnutrition (eg, anorexia nervosa, hyperemesis gravidarum, post-gastric bypass surgery). Iatrogenic WE can be prevented by administering intravenous thiamine before or concurrently with dextrose. __________ References: Wernicke's encephalopathy in non-alcoholics. An autopsy study. (http://www.ncbi.nlm.nih.gov/pubmed/2723677) Wernicke's encephalopathy presenting with upbeating nystagmus. (http://www.ncbi.nlm.nih.gov/pubmed/12217687) Wernicke encephalopathy in nonalcoholic patients. (http://www.ncbi.nlm.nih.gov/pubmed/11863078)

A 22-Year-Old Woman Is Brought to the Emergency Department by Her