Phrenic nerve block during interscalene anaesthesia — FRCA Primary MCQ

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HardAnatomyPhrenic nerve block during interscalene anaesthesiaFRCA Primary

After an interscalene block, a patient has ipsilateral hemidiaphragm paresis and mild dyspnoea. Which nerve is most likely affected?

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Correct answer: D — Phrenic nerve

The best answer is “Phrenic nerve”. The phrenic nerve runs on the anterior surface of scalenus anterior and is commonly affected by interscalene local-anaesthetic spread, causing ipsilateral hemidiaphragm paresis. The other nerves can be vulnerable in the neck or shoulder region but do not explain this characteristic diaphragmatic finding.

Reference: RCoA, Primary FRCA Syllabus: https://rcoa.ac.uk/sites/default/files/documents/2026-01/Primary-FRCA-Syllabus.pdf