Superficial branch of ulnar nerve

At a glance

English

Superficial branch of ulnar nerve

Latin (TA2)

Ramus superficialis nervi ulnaris

System

Nerve

Region

Upper limb

Side

Paired, left and right

About the superficial branch of ulnar nerve

The ulnar nerve enters the hand in the ulnar canal (Guyon's canal), passing in front of the flexor retinaculum on the lateral side of the pisiform and medial to the ulnar artery. Within or just beyond the canal it divides into its two terminal branches: a deep branch, which is motor and sinks into the hypothenar muscles, and a superficial branch, which stays near the surface of the palm.

The superficial branch lies under palmaris brevis and the palmar fascia, beside the ulnar artery. It first gives a small motor twig to palmaris brevis, the thin sheet of muscle in the skin over the hypothenar eminence. It then divides into a proper palmar digital nerve, which runs along the ulnar side of the little finger, and a common palmar digital nerve, which heads for the web between the ring and little fingers. That common nerve divides into two proper digital nerves for their adjacent sides and usually sends a communicating branch to the nearest common digital nerve of the median nerve. In the fingers its digital branches follow the same plan as the median nerve's.

The branch therefore carries feeling from the palmar skin of the little finger and the ulnar half of the ring finger, together with the backs of their end segments and nail beds. The skin of the hypothenar part of the palm itself comes mainly from the palmar branch of the ulnar nerve, given off in the forearm.

Compression in the ulnar canal, from a ganglion, a fracture of the hook of the hamate, or long periods of pressure on the heel of the hand as in cycling, can affect the superficial branch, the deep branch or both. When the superficial branch is involved, the little finger and half the ring finger go numb on the palmar side while the back of the hand keeps normal feeling. Pure involvement of the superficial branch causes no weakness except of palmaris brevis, which is hard to test, so a sensory loss without wasting points to this branch.

Course and supply

Arises from

One of the two terminal branches of the ulnar nerve, given off in or just beyond the ulnar canal at the wrist.

Ends in

Ends as a proper palmar digital nerve to the ulnar side of the little finger and a common palmar digital nerve to the fourth web space.

Supplies

Motor to palmaris brevis; sensory to the palmar skin of the little finger and ulnar half of the ring finger and to their dorsal tips and nail beds.