Upper limb and brachial plexus: 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

Sample item

A cyclist develops weakness of finger spreading and numbness of the little finger and the ulnar half of the ring finger after prolonged handlebar pressure at the wrist, but sensation over the dorsum of the ulnar hand is normal. Why is dorsal sensation spared?

AThe median nerve supplies the dorsum of the ulnar handBThe dorsal cutaneous branch leaves the ulnar nerve in the forearm, proximal to the wristCThe dorsal branch arises from the radial nerve at the wristDThe palmar branch is the only branch of the ulnar nerve

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

The answer and the reasoning

B. The dorsal cutaneous branch leaves the ulnar nerve in the forearm, proximal to the wrist

In Guyon canal compression, the lesion is distal to the origin of the dorsal cutaneous branch, which arises about 5 cm above the wrist. Hence the dorsum of the hand and the palmar cutaneous branch territory are spared.

Option by option

A. The median nerve supplies the dorsum of the ulnar hand
The median nerve supplies dorsum only over the distal phalanges of the lateral fingers.
B. The dorsal cutaneous branch leaves the ulnar nerve in the forearm, proximal to the wrist (correct)
Correct. The dorsal cutaneous branch leaves in the forearm and bypasses the canal.
C. The dorsal branch arises from the radial nerve at the wrist
The dorsal ulnar territory is supplied by the ulnar dorsal branch, not the radial nerve.
D. The palmar branch is the only branch of the ulnar nerve
The ulnar nerve has dorsal, palmar, superficial and deep branches, not a single one.

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 B, The dorsal cutaneous branch leaves the ulnar nerve in the forearm, proximal to the wrist. In Guyon canal compression, the lesion is distal to the origin of the dorsal cutaneous branch, which arises about 5 cm above the wrist.

Why is "The median nerve supplies the dorsum of the ulnar hand" not the answer?

The median nerve supplies dorsum only over the distal phalanges of the lateral fingers.

Why is "The dorsal branch arises from the radial nerve at the wrist" not the answer?

The dorsal ulnar territory is supplied by the ulnar dorsal branch, not the radial nerve.

Why is "The palmar branch is the only branch of the ulnar nerve" not the answer?

The ulnar nerve has dorsal, palmar, superficial and deep branches, not a single one.

What concept does this question test?

It tests Upper limb and brachial plexus in Anatomy. Hence the dorsum of the hand and the palmar cutaneous branch territory are spared.

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?

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.