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Medial Cutaneous Nerve of the Arm

nervus cutaneus brachii medialis

The medial cutaneous nerve of the arm (C8-T1) is the smallest branch of the medial cord of the brachial plexus. It runs medially through the axilla, pierces the deep fascia near the basilic vein at the mid-arm, and provides cutaneous innervation to the medial and posterior skin of the arm as far as the medial epicondyle. It frequently communicates with the intercostobrachial nerve (T2).

Region: Upper Arm

Clinical Relevance

Clinical Notes

This nerve is most commonly injured during axillary lymph node dissection for breast cancer, where its transection causes a patch of numbness on the medial upper arm described by patients as a sleeve-like sensory loss. It is also at risk during surgical approaches to the medial brachial structures. Distinguishing its territory from the intercostobrachial nerve is achieved by the more distal and posterior distribution of the medial cutaneous nerve.

Pathology

Common Injuries & Conditions

Axillary Dissection Injury

Iatrogenic transection during breast cancer axillary node clearance produces medial arm numbness, often permanent, which patients find more distressing than expected and which may be accompanied by a painful neuroma at the axillary scar.