Substance use: osmotic demyelination after sodium correction: practice question

A Psychiatry 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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Psychiatry · Substance use: osmotic demyelination after sodium correction

Sample item

A malnourished chronic drinker is admitted with a serum sodium of 106 mmol/L, and the level is corrected to 128 mmol/L within 24 hours. Four days later he develops dysarthria, dysphagia and flaccid quadriparesis, and becomes unable to move anything except his eyes. What is the most likely diagnosis?

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

The answer and the reasoning

B. Central pontine myelinolysis

Rapid correction of chronic hyponatraemia in alcoholics and the malnourished causes osmotic demyelination, classically of the basis pontis. It produces a delayed quadriparesis, pseudobulbar signs and a locked-in state, and prevention depends on limiting correction to a slow rate.

Option by option

  • A. Wernicke encephalopathy

    Wernicke encephalopathy presents with confusion, ophthalmoplegia and ataxia, and is not linked to sodium correction.

  • B. Central pontine myelinolysis (correct)

    Correct. Delayed quadriparesis with preserved eye movements after rapid sodium correction is typical of pontine demyelination.

  • C. Hepatic encephalopathy

    Hepatic encephalopathy causes fluctuating consciousness and asterixis, not a locked-in state following sodium correction.

  • D. Marchiafava-Bignami disease

    Marchiafava-Bignami disease involves corpus callosum demyelination in malnourished drinkers and is not tied to sodium correction.

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 Psychiatry question

What is the answer to this Psychiatry question?

The best answer is B, Central pontine myelinolysis. Rapid correction of chronic hyponatraemia in alcoholics and the malnourished causes osmotic demyelination, classically of the basis pontis.

Why is "Wernicke encephalopathy" not the answer?

Wernicke encephalopathy presents with confusion, ophthalmoplegia and ataxia, and is not linked to sodium correction.

Why is "Hepatic encephalopathy" not the answer?

Hepatic encephalopathy causes fluctuating consciousness and asterixis, not a locked-in state following sodium correction.

Why is "Marchiafava-Bignami disease" not the answer?

Marchiafava-Bignami disease involves corpus callosum demyelination in malnourished drinkers and is not tied to sodium correction.

What concept does this question test?

It tests Substance use: osmotic demyelination after sodium correction in Psychiatry. It produces a delayed quadriparesis, pseudobulbar signs and a locked-in state, and prevention depends on limiting correction to a slow rate.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Substance use: osmotic demyelination after sodium correction?

Learn each diagnosis by its core features and its first-line treatment. Then use the flashcards and the other Psychiatry 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.