Medial Antebrachial Cutaneous Nerve, Posterior View

Description

Running along the posteromedial aspect of the forearm, the medial antebrachial cutaneous nerve is traced as it emerges from the medial cord region of the brachial plexus and becomes superficial near the distal arm and elbow. From a posterior perspective, it courses inferiorly within the superficial fascia, closely related to the basilic vein on the medial side and skirting the medial intermuscular septum proximal to the medial epicondyle. Deep to it lie the ulnar nerve in the ulnar groove and the posterior compartment muscle mass, including triceps brachii proximally and the extensor carpi ulnaris and flexor carpi ulnaris borders defining the ulnar side distally. The humerus, ulna, and radius provide fixed landmarks as the nerve fans into posterior ulnar forearm cutaneous branches. Posterior mapping of this nerve matters when sensory loss or dysesthesia localizes to the medial forearm but spares the ulnar digits, a pattern that helps separate medial antebrachial cutaneous neuropathy from ulnar neuropathy at the cubital tunnel. Venipuncture, basilic vein cannulation, and medial elbow surgical approaches can injure these superficial branches, producing painful neuroma or patchy hypesthesia along the ulnar forearm. Small nerve, common complaint. Educators can drop this figure into upper limb dissection labs to teach cutaneous territory versus named peripheral nerves, and authors will find it useful in chapters on brachial plexus branches, regional anesthesia, and iatrogenic nerve injury around the elbow. It also fits well in preoperative counseling materials for medial elbow and forearm procedures where postoperative numbness is discussed. Anatomical accuracy verified by SciePro's Medical Advisory Board.