The Ulnar Nerve

Abstract

The ulnar nerve represents the direct continuation of the medial cord of the brachial plexus, and is the largest of its terminal branches. It carries nerve fibers from vertebral levels C-8 and T-1, with frequent contributions from C-7. From its origin in the axilla, the ulnar nerve passes into the arm distally, where it continues medial to the brachial artery. At approximately the level of insertion of the coracobrachialis muscle, the nerve courses posteriorly and passes through the medial intermuscular septum. Beyond this point, the nerve occupies a groove or tunnel in the medial head of the triceps muscle. It continues distally to pass through a gap formed by the medial epicondyle of the humerus and the olecranon process of the ulna. Local investments of deep fascia approximates the ulnar nerve to the medial head of the triceps in this region.