Toxicology: Wernicke's encephalopathy: practice question

A Forensic Medicine question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Forensic Medicine · Toxicology: Wernicke's encephalopathy

Sample item

A chronic alcoholic is brought with confusion, nystagmus and ataxia. A nurse prepares to start a dextrose infusion. Which drug must be given first?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Thiamine

Wernicke's encephalopathy is due to thiamine deficiency and features confusion, ophthalmoplegia or nystagmus, and ataxia. Glucose given before thiamine can precipitate or worsen it, because thiamine is a cofactor for carbohydrate metabolism. Thiamine is therefore given before or with the dextrose.

Option by option

  • A. Folic acid

    Folic acid is given in alcoholic macrocytic anaemia but does not treat this syndrome.

  • B. Cyanocobalamin

    Cyanocobalamin treats vitamin B12 deficiency, not Wernicke's encephalopathy.

  • C. Thiamine (correct)

    Correct. Thiamine is needed to metabolise the glucose load safely and to treat the encephalopathy.

  • D. Pyridoxine

    Pyridoxine is the antidote for isoniazid-induced seizures.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Forensic Medicine question

What is the answer to this Forensic Medicine question?

The best answer is C, Thiamine. Wernicke's encephalopathy is due to thiamine deficiency and features confusion, ophthalmoplegia or nystagmus, and ataxia.

Why is "Folic acid" not the answer?

Folic acid is given in alcoholic macrocytic anaemia but does not treat this syndrome.

Why is "Cyanocobalamin" not the answer?

Cyanocobalamin treats vitamin B12 deficiency, not Wernicke's encephalopathy.

Why is "Pyridoxine" not the answer?

Pyridoxine is the antidote for isoniazid-induced seizures.

What concept does this question test?

It tests Toxicology: Wernicke's encephalopathy in Forensic Medicine. Glucose given before thiamine can precipitate or worsen it, because thiamine is a cofactor for carbohydrate metabolism. Thiamine is therefore given before or with the dextrose.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Toxicology: Wernicke's encephalopathy?

Learn postmortem changes with their timelines, and toxicology as poison, sign, test and antidote. Then use the flashcards and the other Forensic Medicine questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.