Ulnar Nerve

Abstract

The ulnar nerve (C7, C8, and T1) is one of the main branches of the medial cord of the brachial plexus in the axilla. It courses medial to the axillary artery and then posterior to the brachial artery . It enters the posterior compartment of the arm dorsal to the medial intermuscular septum and then the medial epicondyle . It enters the forearm between the two heads of flexor carpi ulnaris (when the ulnar head is present) , to course between it, and the flexor digitorum profundus , medial to the ulnar artery . The first branches arise in the forearm supplying flexor carpi ulnaris and the medial half of flexor digitorum profundus. It enters Guyon’s canal at the wrist, lateral to the pisiform bone. It gives off a superficial branch that supplies the palmaris brevis and the palmar aspect of the medial one and half fingers as well as the medial aspect of the palm and a deep motor branch that supplies the hypothenar muscles: abductor digiti minimi , flexor digiti minimi , and opponens digiti minimi . It also supplies the medial 2 lumbricals, the interossei , the adductor pollicis , as well as part of the flexor pollicis brevis . The dorsal cutaneous branch arises in the lower forearm to supply the dorsum of the medial one and half fingers as well as the medial aspect of the dorsum of the hand. Another palmar cutaneous branch may arise just proximal to Guyon’s canal and supply the ulnar aspect of the palm proximally.