Phrenic Nerve — FRCA Primary MCQ
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Correct answer: A — C3, C4 and C5
Explanation lettering: D = shown as A · A = shown as B · B = shown as C · C = shown as D
The correct answer is D. The phrenic nerve is formed from the anterior rami of C3, C4 and C5, with C4 usually providing the principal contribution. It supplies the motor innervation of the ipsilateral hemidiaphragm. Its sensory fibres supply the fibrous pericardium, mediastinal pleura and the central diaphragmatic pleura and peritoneum. The traditional mnemonic is “C3, 4 and 5 keep the diaphragm alive.” Options A and E incorrectly shift the contribution caudally into roots associated predominantly with the brachial plexus; option B lies entirely within the lower cervical contribution to the brachial plexus. Option C incorrectly includes C2 and omits C5.
Reference: NHS Commissioning Board, Phrenic Nerve Pacing Policy – Spinal Cord Injury, section 1, 2013. https://www.england.nhs.uk/wp-content/uploads/2013/04/d13-p-a.pdf