A 52-year-old man with a 20-year history of alcohol use disorder presents to the emergency department with acute confusion, ataxia, and horizontal nystagmus. He has not eaten for 3 days. An EEG is performed and shows the pattern marked **B** in the diagram. Which of the following is the most appropriate immediate management?

Question

Accepted Answer

C. Intravenous thiamine 500 mg three times daily before any glucose-containing fluids. ## Why "Intravenous thiamine 500 mg three times daily before any glucose-containing fluids" is right

The EEG pattern marked **B** — diffuse symmetric theta-delta slowing with loss of posterior dominant alpha rhythm — reflects the non-specific but characteristic metabolic encephalopathy of Wernicke encephalopathy (WE). This pattern, combined with the clinical triad of encephalopathy, oculomotor dysfunction (horizontal nystagmus), and gait ataxia in a malnourished alcoholic patient, is diagnostic of acute thiamine deficiency. The critical teaching point from Harrison's is that thiamine MUST be administered intravenously at high dose (500 mg three times daily) BEFORE any glucose-containing IV fluids, because glucose metabolism consumes thiamine and can precipitate or worsen WE in deficient patients. This is a medical emergency with 17–20% mortality if untreated and progression to irreversible Korsakoff syndrome in up to 80% of survivors.

## Why each distractor is wrong

- **Intravenous dextrose 50% followed by thiamine supplementation**: This is the classic error. Giving glucose before thiamine in a thiamine-deficient patient will worsen or precipitate Wernicke encephalopathy. Thiamine must come first.
- **Oral thiamine 100 mg daily with standard IV fluids**: Oral thiamine is inadequate in acute WE; IV replacement at 500 mg three times daily is required. Standard IV fluids (often dextrose-containing) without prior thiamine repletion will cause harm.
- **Magnesium sulfate alone pending MRI confirmation of mammillary body involvement**: While magnesium repletion is essential (thiamine-dependent enzymes require Mg²⁺ as cofactor), it is NOT a substitute for thiamine. Waiting for MRI confirmation delays life-saving treatment in a medical emergency.

**High-Yield:** In any malnourished or alcoholic patient with altered mental status, give IV thiamine BEFORE glucose — this single rule prevents irreversible brain damage and death.

[cite: Harrison's Principles of Internal Medicine 21e — Nutritional Deficiencies]

Answer

A. Intravenous dextrose 50% followed by thiamine supplementation

Answer

B. Magnesium sulfate alone pending MRI confirmation of mammillary body involvement

Answer

D. Oral thiamine 100 mg daily with standard IV fluids

Explanation

Why "Intravenous thiamine 500 mg three times daily before any glucose-containing fluids" is right

Why each distractor is wrong

Practice similar questions