Corpus: Medial brachial cutaneous nerve

The nerve is the smallest branch of the brachial plexus, originating from its medial cord. Initially, it passes through the axilla, where it is located posteriorly and then medially to the axillary vein. Here, it forms anastomoses with the intercostobrachial nerve from the 2nd and 3rd intercostal nerves, potentially creating a small plexus in the armpit. Further distally, the medial brachial cutaneous nerve accompanies the brachial artery to about the midpoint of the upper arm, where it pierces the fascia and spreads in the subcutaneous tissue of the medial and dorsal lower third of the upper arm to the elbow.

The medial brachial cutaneous nerve (Nervus cutaneus brachii medialis) provides sensory innervation to a strip-like skin area of the lower dorsal and medial thirds of the upper arm and parts of the skin over the elbow.

Isolated lesions of the medial brachial cutaneous nerve are rare but may occur during axillary lymphadenectomy surgery. The result can be hypoesthesia and paresthesia in its area of innervation. However, anastomosis with the intercostobrachial nerve prevents complete sensory loss. Diseases of the breast (e.g., breast cancer) and intercostal neuralgia can cause pain in the innervation area of the medial brachial cutaneous nerve through the anastomosis with the intercostobrachial nerve.