Neurology: cavernous sinus thrombosis: practice question

A General 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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General Medicine · Neurology: cavernous sinus thrombosis

Sample item

A 30-year-old with a facial furuncle develops fever, unilateral periorbital oedema, proptosis, chemosis and ptosis, followed by diplopia, and soon the other eye is affected. Which cranial nerve is usually first to be affected?

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

The answer and the reasoning

B. Abducens nerve

The abducens nerve runs freely within the lumen of the cavernous sinus, lateral to the internal carotid artery, so it is the first to be involved in thrombosis. The oculomotor, trochlear and trigeminal branches lie in the lateral wall. Bilateral spread occurs through the intercavernous sinuses.

Option by option

  • A. Trochlear nerve

    The trochlear nerve also lies in the lateral wall.

  • B. Abducens nerve (correct)

    Correct. The abducens nerve lies within the sinus, so it is affected earliest.

  • C. Oculomotor nerve

    The oculomotor nerve lies in the lateral wall and is affected later.

  • D. Ophthalmic division of the trigeminal nerve

    The ophthalmic division runs in the lateral wall and is involved later.

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 General Medicine question

What is the answer to this General Medicine question?

The best answer is B, Abducens nerve. The abducens nerve runs freely within the lumen of the cavernous sinus, lateral to the internal carotid artery, so it is the first to be involved in thrombosis.

Why is "Trochlear nerve" not the answer?

The trochlear nerve also lies in the lateral wall.

Why is "Oculomotor nerve" not the answer?

The oculomotor nerve lies in the lateral wall and is affected later.

Why is "Ophthalmic division of the trigeminal nerve" not the answer?

The ophthalmic division runs in the lateral wall and is involved later.

What concept does this question test?

It tests Neurology: cavernous sinus thrombosis in General Medicine. The oculomotor, trochlear and trigeminal branches lie in the lateral wall. Bilateral spread occurs through the intercavernous sinuses.

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 Neurology: cavernous sinus thrombosis?

For each disease know the classic presentation, the best test, and the first-line treatment. Then use the flashcards and the other General 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.