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Saturday Night Radial Nerve Palsy — SCE Neurology MCQ

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EasyPeripheral Neuropathy & NeuromuscularSaturday Night Radial Nerve PalsySCE Neurology

A 45-year-old man presents with right wrist drop. He fell asleep on a park bench with his arm draped over the back. He cannot extend the wrist or fingers. Sensation is reduced over the dorsal first web space. Elbow flexion (brachioradialis) is weak but triceps is normal. Where is the most likely site of nerve injury?

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Correct answer: B — Radial nerve at the spiral groove of the humerus

Saturday night palsy results from radial nerve compression at the spiral groove, where the nerve is vulnerable against the humerus. Triceps is spared (it is innervated proximal to the spiral groove), but brachioradialis and wrist/finger extensors are affected. Sensory loss in the superficial radial nerve territory (dorsal first web space) is present. A: Posterior cord injury would affect the axillary nerve too. C: PIN syndrome is purely motor (no sensory loss) and spares the wrist extensors (ECRL). D: C7 radiculopathy would affect the triceps. E: Axillary-level injury would affect the triceps.

Reference: Preston & Shapiro – Electromyography; ABN Peripheral Nerve Guidelines