Median nerve: anterior interosseous branch: 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 · Median nerve: anterior interosseous branch

Sample item

After a forearm injury a 30-year-old woman cannot make a circle with the thumb and index finger. Instead she pinches with the flat of the fingertips, and the distal joints of the thumb and index finger stay extended. Sensation in the hand is normal. Which nerve is affected?

ADeep branch of the ulnar nerveBPosterior interosseous nerveCRecurrent (thenar) branch of the median nerveDAnterior interosseous nerve

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

The answer and the reasoning

D. Anterior interosseous nerve

The anterior interosseous nerve arises from the median nerve in the forearm and supplies flexor pollicis longus, the lateral half of flexor digitorum profundus and pronator quadratus. Loss of these muscles abolishes flexion of the thumb interphalangeal and index distal interphalangeal joints (the OK sign fails). It carries no cutaneous fibres, so sensation is spared.

Option by option

A. Deep branch of the ulnar nerve
The deep ulnar branch supplies the interossei and adductor pollicis and would affect finger spread and key pinch.
B. Posterior interosseous nerve
The posterior interosseous nerve supplies the extensors and would cause finger drop.
C. Recurrent (thenar) branch of the median nerve
The recurrent branch supplies the thenar muscles and would affect thumb abduction and opposition, not distal joint flexion.
D. Anterior interosseous nerve (correct)
Correct. A purely motor branch to the deep flexors of the thumb and index finger explains the pinch posture.

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.

Questions about this Anatomy question

What is the answer to this Anatomy question?

The best answer is D, Anterior interosseous nerve. The anterior interosseous nerve arises from the median nerve in the forearm and supplies flexor pollicis longus, the lateral half of flexor digitorum profundus and pronator quadratus.

Why is "Deep branch of the ulnar nerve" not the answer?

The deep ulnar branch supplies the interossei and adductor pollicis and would affect finger spread and key pinch.

Why is "Posterior interosseous nerve" not the answer?

The posterior interosseous nerve supplies the extensors and would cause finger drop.

Why is "Recurrent (thenar) branch of the median nerve" not the answer?

The recurrent branch supplies the thenar muscles and would affect thumb abduction and opposition, not distal joint flexion.

What concept does this question test?

It tests Median nerve: anterior interosseous branch in Anatomy. Loss of these muscles abolishes flexion of the thumb interphalangeal and index distal interphalangeal joints (the OK sign fails). It carries no cutaneous fibres, so sensation is spared.

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 Median nerve: anterior interosseous branch?

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.