Upper limb and brachial plexus: lunate dislocation: 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 · Upper limb and brachial plexus: lunate dislocation

Sample item

After a fall on the outstretched hand, a man has wrist swelling, a lunate displaced anteriorly on lateral X-ray, and tingling in the thumb, index and middle fingers. Which structure is compressed?

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

The answer and the reasoning

B. Median nerve in the carpal tunnel

A volar lunate dislocation pushes the bone into the carpal tunnel, where it compresses the median nerve and gives acute carpal tunnel syndrome, with paraesthesia in the lateral three and a half digits.

Option by option

  • A. Superficial radial nerve

    This nerve is sensory to the dorsum of the thumb and is not in the carpal tunnel.

  • B. Median nerve in the carpal tunnel (correct)

    Correct. The displaced lunate enters the carpal tunnel and compresses the median nerve.

  • C. Ulnar nerve in Guyon canal

    Guyon canal lies on the ulnar side and its compression would affect the little finger.

  • D. Anterior interosseous nerve

    This nerve is purely motor and does not cause finger sensory loss.

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 Anatomy question

What is the answer to this Anatomy question?

The best answer is B, Median nerve in the carpal tunnel. A volar lunate dislocation pushes the bone into the carpal tunnel, where it compresses the median nerve and gives acute carpal tunnel syndrome, with paraesthesia in the lateral three and a half digits.

Why is "Superficial radial nerve" not the answer?

This nerve is sensory to the dorsum of the thumb and is not in the carpal tunnel.

Why is "Ulnar nerve in Guyon canal" not the answer?

Guyon canal lies on the ulnar side and its compression would affect the little finger.

Why is "Anterior interosseous nerve" not the answer?

This nerve is purely motor and does not cause finger sensory loss.

What concept does this question test?

It tests Upper limb and brachial plexus: lunate dislocation in Anatomy. The correct option holds because: Correct. The displaced lunate enters the carpal tunnel and compresses the median nerve.

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 Upper limb and brachial plexus: lunate dislocation?

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.