Anatomy, Medial Antebrachial Cutaneous Nerve

There have been several reported variations in the anatomy of the medial antebrachial cutaneous nerve as well as its branching pattern. There are cases where the nerve itself arises from the inferior trunk of the brachial plexus instead of the medial cord.[7] The posterior branch is highly variable as reports have described anastomosis between it and the ulnar nerve as well as its palmar cutaneous branch, the medial brachial cutaneous nerve, and the posterior antebrachial cutaneous nerve.[2] There is another variation in which the described four brachial branches of the medial antebrachial cutaneous nerve emerging before the separation into anterior and posterior branches. These branches travel to the medial, distal region of the upper arm, which is an area normally innervated by the medial brachial cutaneous nerve.[2]

Understanding the anatomy of the medial antebrachial cutaneous nerve is important in transplant surgery using forearm flaps as donor tissue. Recipient tissues for such flaps have included the mouth, penis, and hands. Thus, successful sensory recovery for these areas relies on knowledge of the cutaneous innervation of the donor tissue.[1] One such example is the forearm free flap phalloplasty. This surgical technique is used in transgender surgeries to create a neophallus. The flap involved in this procedure contains the skin of the anterior forearm and much of the surrounding tissue, including the medial and lateral cutaneous nerves of the forearm.[8] The medial antebrachial cutaneous nerve itself can also be used in surgical grafts and gets frequently used in brachial plexus reconstructions.[9] 

Posterior branches of the medial antebrachial cutaneous nerve cross the ulnar nerve, normally 2 cm distal to the medial epicondyle, and are therefore at risk of damage during ulnar nerve releases at the elbow to treat cubital tunnel syndrome. Complications of damage to the medial antebrachial cutaneous nerve in such procedures include hyperesthesia and hyperalgesia, as well as painful neuromas.[10][11] The anterior branch of the medial antebrachial cutaneous nerve is also important surgically as it is used as the “cable graft” in the repair of peripheral nerves such as the digital nerve.[12] Knowledge of the anatomy of the medial antebrachial cutaneous nerve plays a significant role in several vascular surgeries involving the upper arm. Examples of these surgeries include arteriovenous fistula formation between the brachial artery and basilic vein as well as the brachial artery and vein, arteriovenous fistula steal syndrome surgery, thrombectomies, and embolectomies of the brachial artery.[13]

Knowledge of the anatomy of the medial antebrachial cutaneous nerve is vital clinically as the nerve is prone to damage during various procedures such as venipunctures, therapeutic injections for elbow pain, and cubital tunnel releases.[2][14] Accidental damage to the nerve following such procedures has been found to result in painful paresthesias, dysesthesias, and numbness.[7] Snapping elbow refers to a condition where flexion and extension of the elbow causes a painful, popping sensation which at times can even be heard, seen, and palpated. This condition is most often the result of ulnar nerve dislocation over the medial epicondyle. There are reports, however, of patients who described a similar painful popping sensation of the elbow and were found to have a snapping of the medial antebrachial cutaneous nerve.[15][16] The medial antebrachial cutaneous nerve, along with many other nerves of the upper extremity, is prone to injury in athletes who perform repetitive throwing motions. Throwing motions damage these nerves by creating compression and traction, leading to various neuropathic syndromes.[17] Rare causes of damage to the medial antebrachial cutaneous nerve include subcutaneous lipomas, laceration, and neuritis caused by tuberculoid leprosy.[7]