Neuroanatomy: midbrain: practice question

A Anatomy 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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Anatomy · Neuroanatomy: midbrain

Sample item

A posterior communicating artery aneurysm causes a dilated pupil with ptosis and a 'down and out' eye. Which nerve is compressed?

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

The answer and the reasoning

B. Oculomotor nerve

Parasympathetic fibres lie superficially on CN III and are vulnerable to compressive aneurysms. CN III palsy leaves lateral rectus and superior oblique unopposed.

Option by option

  • A. Trochlear nerve

    CN IV palsy causes vertical diplopia, especially on looking down.

  • B. Oculomotor nerve (correct)

    Correct. CN III palsy produces the pupil and eye-position pattern described.

  • C. Abducens nerve

    CN VI palsy causes inability to abduct the eye.

  • D. Optic nerve

    Optic nerve compression affects vision and afferent pupillary responses, not eye position.

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.

More Anatomy questions

Questions about this Anatomy question

What is the answer to this Anatomy question?

The best answer is B, Oculomotor nerve. Parasympathetic fibres lie superficially on CN III and are vulnerable to compressive aneurysms.

Why is "Trochlear nerve" not the answer?

CN IV palsy causes vertical diplopia, especially on looking down.

Why is "Abducens nerve" not the answer?

CN VI palsy causes inability to abduct the eye.

Why is "Optic nerve" not the answer?

Optic nerve compression affects vision and afferent pupillary responses, not eye position.

What concept does this question test?

It tests Neuroanatomy: midbrain in Anatomy. CN III palsy leaves lateral rectus and superior oblique unopposed.

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 Neuroanatomy: midbrain?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy 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.