Upper limb and brachial plexus: interscalene block: 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: interscalene block

Sample item

A patient develops shortness of breath and a raised hemidiaphragm on the same side after an interscalene brachial plexus block for shoulder surgery. Which nerve has been blocked?

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

The answer and the reasoning

A. Phrenic nerve

The phrenic nerve runs on the front of scalenus anterior, close to the roots of the plexus between scalenus anterior and medius. Local anaesthetic spreads to it and causes ipsilateral diaphragmatic paralysis. Winging of the scapula from the long thoracic nerve would not cause dyspnoea.

Option by option

  • A. Phrenic nerve (correct)

    Correct. Spread to the phrenic nerve on scalenus anterior paralyses the hemidiaphragm.

  • B. Suprascapular nerve

    Suprascapular nerve block weakens the supraspinatus and infraspinatus, not breathing.

  • C. Vagus nerve

    The vagus lies in the carotid sheath, away from the interscalene groove.

  • D. Long thoracic nerve

    Long thoracic nerve block weakens serratus anterior and winges the scapula without a raised diaphragm.

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, Phrenic nerve. The phrenic nerve runs on the front of scalenus anterior, close to the roots of the plexus between scalenus anterior and medius.

Why is "Suprascapular nerve" not the answer?

Suprascapular nerve block weakens the supraspinatus and infraspinatus, not breathing.

Why is "Vagus nerve" not the answer?

The vagus lies in the carotid sheath, away from the interscalene groove.

Why is "Long thoracic nerve" not the answer?

Long thoracic nerve block weakens serratus anterior and winges the scapula without a raised diaphragm.

What concept does this question test?

It tests Upper limb and brachial plexus: interscalene block in Anatomy. Local anaesthetic spreads to it and causes ipsilateral diaphragmatic paralysis. Winging of the scapula from the long thoracic nerve would not cause dyspnoea.

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 Upper limb and brachial plexus: interscalene block?

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.