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Posterior Cutaneous Nerve of the Arm

nervus cutaneus brachii posterior

The posterior cutaneous nerve of the arm is a branch of the radial nerve given off in the axilla before the radial nerve enters the radial groove. It emerges through the medial head of the triceps and supplies a strip of skin over the posterior arm from the axilla to the elbow. It is the first sensory branch of the radial nerve and is separate from the lower lateral cutaneous nerve of the arm and the posterior cutaneous nerve of the forearm.

Region: Upper Arm

Clinical Relevance

Clinical Notes

This nerve provides useful localising information in radial nerve injuries: preserved posterior arm sensation indicates that a radial nerve injury is at or distal to the radial groove (the spiral groove), since this branch has already been given off. Loss of posterior arm sensation with radial palsy indicates a lesion proximal to the spiral groove in the axilla or near the lateral cord of the brachial plexus. The nerve is occasionally used as an electrode placement landmark in EMG studies assessing radial nerve function.

Pathology

Common Injuries & Conditions

Axillary Radial Nerve Injury Localisation

Preserved sensation in the posterior arm with radial nerve palsy localises the lesion to the spiral groove or more distally, sparing this branch given off in the axilla; absent posterior arm sensation indicates a more proximal axillary injury with a different surgical and prognostic implication.