Perioperative Nerve Injury — FRCA Final MCQ

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ModerateAnaesthetic Equipment & SafetyPerioperative Nerve InjuryFRCA Final

A 55-year-old woman undergoes mastectomy and axillary clearance under general anaesthesia without a regional block. The operative-side arm is abducted to 90° on an arm board throughout surgery. In recovery, she cannot extend the wrist or the metacarpophalangeal joints. Elbow extension is preserved, but sensation is reduced over the dorsal first web space. Which nerve is most likely to have been injured?

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Correct answer: C — Radial nerve

The correct answer is C, the radial nerve. It supplies the wrist and finger extensors, so injury causes loss of wrist and metacarpophalangeal extension. Sensory loss over the dorsal first web space is also characteristic. Preserved triceps function suggests that the lesion is distal to the branches supplying triceps, compatible with compression of the radial nerve around the humerus during positioning. Median nerve injury primarily impairs thumb opposition and median-innervated flexors; ulnar injury causes intrinsic hand weakness and sensory loss in the little finger and ulnar half of the ring finger. Musculocutaneous injury weakens elbow flexion and alters lateral forearm sensation. Long thoracic nerve injury causes serratus anterior weakness and scapular winging, not wrist drop.

Reference: Cambridge University Hospitals NHS Foundation Trust. Peripheral nerve injuries of the upper limb – surgical repair, section ‘Common postures and functional difficulties’, 2024. https://www.cuh.nhs.uk/patient-information/peripheral-nerve-injuries-of-the-upper-limb-surgical-repair/