Ulnar nerve

Dr Rishabh Verma and Dr Henry Knipe ◉ ◈ et al.

The ulnar nerve is one of the terminal branches of the brachial plexus and has motor and sensory supply to the forearm and hand.

In the arm, the ulnar nerve runs medial to the axillary artery and subsequently the brachial artery on the coracobrachialis muscle in the anterior compartment. The nerve passes to the posterior compartment through the medial intermuscular septum distally running with the superior ulnar collateral artery. Further on, it runs between medial head of triceps brachii muscle and the medial intermuscular septum to pass posterior to the medial humeral epicondyle in the superficial condylar groove (cubital tunnel).

Forearm

The ulnar nerve enters the forearm from the arm via the two heads of flexor carpi ulnaris (FCU) muscle. It subsequently lies superficial to flexor digitorum profundus and deep to FCU and medial to the ulnar artery. At the wrist, the ulnar nerve runs lateral to the tendon of FCU.

Hand

The ulnar nerve enters the hand superficial to the flexor retinaculum and inside Guyon's canal. Then it divides into its terminal branches at the level of the pisiform bone.

Prior to passing the flexor retinaculum at the wrist, the ulnar nerve gives off the dorsal cutaneous branch.

Branches

Terminal branches

palmar cutaneous branch
branch to palmaris brevis
superficial terminal branch
deep terminal branch

Supply

The ulnar nerve has both sensory and motor supply:

motor
- flexor carpi ulnaris, flexor digitorum profundus (medial half)
- hypothenar muscles
- 3^rd and 4^th lumbricals, interossei muscles,
- flexor pollicis brevis (deep head), adductor pollicis
- palmaris brevis
sensory
- articular innervation to elbow, wrist, carpal and phalangeal joints
- cutaneous innervation to ulnar aspect of the hand, 5^th finger, medial 4^thfinger

Related pathology

Quiz questions

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