Hand: Allen test and palmar arches: 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 · Hand: Allen test and palmar arches

Sample item

Before radial artery cannulation, an anaesthetist compresses both radial and ulnar arteries while the patient clenches the fist, then opens the hand and releases the ulnar artery only. The palm remains pale for more than 10 seconds. What does this indicate?

AAdequate collateral circulation, so cannulation is safeBInadequate ulnar supply to the hand through the superficial palmar archCCompression of the median nerve in the carpal tunnelDObstruction of the radial artery at the wrist

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

The answer and the reasoning

B. Inadequate ulnar supply to the hand through the superficial palmar arch

The superficial palmar arch is formed mainly by the ulnar artery and is completed by the superficial palmar branch of the radial artery. When only the ulnar artery is released, persistent pallor shows that the ulnar artery or arch cannot perfuse the hand, so the radial artery should not be used. Rapid flushing in under 5 to 10 seconds is a normal result.

Option by option

A. Adequate collateral circulation, so cannulation is safe
Persistent pallor is the opposite of adequate collateral flow, which produces quick flushing.
B. Inadequate ulnar supply to the hand through the superficial palmar arch (correct)
Correct. Persistent pallor shows that the ulnar supply through the arch is inadequate.
C. Compression of the median nerve in the carpal tunnel
The test assesses arteries and does not test the median nerve.
D. Obstruction of the radial artery at the wrist
The radial artery is still compressed in this step, so the test is not assessing it.

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, Inadequate ulnar supply to the hand through the superficial palmar arch. The superficial palmar arch is formed mainly by the ulnar artery and is completed by the superficial palmar branch of the radial artery.

Why is "Adequate collateral circulation, so cannulation is safe" not the answer?

Persistent pallor is the opposite of adequate collateral flow, which produces quick flushing.

Why is "Compression of the median nerve in the carpal tunnel" not the answer?

The test assesses arteries and does not test the median nerve.

Why is "Obstruction of the radial artery at the wrist" not the answer?

The radial artery is still compressed in this step, so the test is not assessing it.

What concept does this question test?

It tests Hand: Allen test and palmar arches in Anatomy. When only the ulnar artery is released, persistent pallor shows that the ulnar artery or arch cannot perfuse the hand, so the radial artery should not be used. Rapid flushing in under 5 to 10 seconds is a normal result.

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 Hand: Allen test and palmar arches?

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.