Thorax: cervical rib: 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 · Thorax: cervical rib

Sample item

A 28-year-old woman has weakness and numbness along the medial forearm and hand, and a diminished radial pulse on abduction of the arm. A radiograph shows a rib arising from C7. Which neural structure is most commonly compressed?

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

The answer and the reasoning

C. Lower trunk of the brachial plexus (C8, T1)

A cervical rib narrows the thoracic outlet, and the subclavian artery and the lower trunk of the brachial plexus (C8, T1) arch over it. This gives ulnar-side sensory loss, intrinsic hand muscle wasting and vascular signs such as a reduced pulse. Upper trunk injury produces Erb palsy instead.

Option by option

  • A. Upper trunk of the brachial plexus (C5, C6)

    Upper trunk injury gives shoulder abduction weakness with lateral arm sensory loss and is not the thoracic outlet pattern.

  • B. Long thoracic nerve

    The long thoracic nerve arises from roots and is not related to the thoracic outlet syndrome.

  • C. Lower trunk of the brachial plexus (C8, T1) (correct)

    Correct. The lower trunk crosses the first rib or cervical rib and is the most vulnerable.

  • D. Phrenic nerve

    The phrenic nerve runs on the anterior scalene and is not typically compressed here.

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 C, Lower trunk of the brachial plexus (C8, T1). A cervical rib narrows the thoracic outlet, and the subclavian artery and the lower trunk of the brachial plexus (C8, T1) arch over it.

Why is "Upper trunk of the brachial plexus (C5, C6)" not the answer?

Upper trunk injury gives shoulder abduction weakness with lateral arm sensory loss and is not the thoracic outlet pattern.

Why is "Long thoracic nerve" not the answer?

The long thoracic nerve arises from roots and is not related to the thoracic outlet syndrome.

Why is "Phrenic nerve" not the answer?

The phrenic nerve runs on the anterior scalene and is not typically compressed here.

What concept does this question test?

It tests Thorax: cervical rib in Anatomy. This gives ulnar-side sensory loss, intrinsic hand muscle wasting and vascular signs such as a reduced pulse. Upper trunk injury produces Erb palsy instead.

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 Thorax: cervical rib?

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.