Head and neck: posterior triangle: 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 · Head and neck: posterior triangle

Sample item

A 30-year-old man has a lymph node biopsy from the posterior triangle of the neck. Afterwards he cannot shrug the right shoulder and the scapula looks slightly drooped. Which nerve was injured?

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

The answer and the reasoning

A. Spinal part of the accessory nerve (XI)

The spinal accessory nerve runs superficially across the posterior triangle, roughly at the midpoint of the posterior border of sternocleidomastoid (Erb's point), and supplies trapezius. Injury during node biopsy weakens shoulder shrugging and arm abduction above the horizontal and causes shoulder droop.

Option by option

  • A. Spinal part of the accessory nerve (XI) (correct)

    Correct. It lies subcutaneously in the posterior triangle and supplies trapezius.

  • B. Dorsal scapular nerve

    The dorsal scapular nerve supplies the rhomboids and levator scapulae and lies deep in the neck.

  • C. Long thoracic nerve

    The long thoracic nerve supplies serratus anterior, and its injury gives a winged scapula, not a drooped shoulder with weak shrugging.

  • D. Suprascapular nerve

    The suprascapular nerve supplies supraspinatus and infraspinatus, which are not responsible for shrugging.

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 A, Spinal part of the accessory nerve (XI). The spinal accessory nerve runs superficially across the posterior triangle, roughly at the midpoint of the posterior border of sternocleidomastoid (Erb's point), and supplies trapezius.

Why is "Dorsal scapular nerve" not the answer?

The dorsal scapular nerve supplies the rhomboids and levator scapulae and lies deep in the neck.

Why is "Long thoracic nerve" not the answer?

The long thoracic nerve supplies serratus anterior, and its injury gives a winged scapula, not a drooped shoulder with weak shrugging.

Why is "Suprascapular nerve" not the answer?

The suprascapular nerve supplies supraspinatus and infraspinatus, which are not responsible for shrugging.

What concept does this question test?

It tests Head and neck: posterior triangle in Anatomy. Injury during node biopsy weakens shoulder shrugging and arm abduction above the horizontal and causes shoulder droop.

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 Head and neck: posterior triangle?

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.