Palmar branch of ulnar nerve

At a glance

English

Palmar branch of ulnar nerve

Latin (TA2)

Ramus palmaris nervi ulnaris

System

Nerve

Region

Upper limb

Side

Paired, left and right

About the palmar branch of ulnar nerve

Also called the palmar cutaneous branch, this is a slender sensory twig of the ulnar nerve. It leaves the ulnar nerve in the forearm, commonly around its middle or lower part and a few centimetres above the wrist, near the point where the parent nerve also gives its dorsal branch. It runs down on the front of the ulnar artery, often sending fine filaments to the wall of that vessel, and pierces the deep fascia just above the wrist.

From there it ends in the skin over the ulnar side of the wrist and the hypothenar eminence, the fleshy mound at the base of the little finger. At its lower end it connects with the palmar branch of the median nerve, and above it may link with the anterior branch of the medial cutaneous nerve of the forearm. Its territory is small and varies a good deal, and it overlaps with these neighbours.

Some descriptions use the term differently. In older texts the phrase palmar branch sometimes refers to the whole ulnar nerve where it continues across the wrist into the palm, lateral to the pisiform and medial to and slightly behind the ulnar artery, before dividing into its superficial and deep branches. Most modern accounts instead regard the superficial and deep branches as the ulnar nerve's own end branches, and keep the name palmar branch for this small cutaneous nerve.

Because it leaves the ulnar nerve above the wrist and runs superficial to the flexor retinaculum and Guyon's canal, the palmar branch is usually spared when the ulnar nerve is squeezed in that canal. A patient with compression at the wrist may therefore keep feeling over the hypothenar skin while the little and ring fingers are numb, which helps place the lesion. The branch can be cut in incisions on the ulnar side of the palm, such as those for carpal tunnel release, causing a sore, sensitive scar.

Course and supply

Arises from

Arises from the ulnar nerve in the forearm, a few centimetres above the wrist.

Ends in

Pierces the deep fascia above the wrist and ends in the skin over the hypothenar eminence, joining the palmar branch of the median nerve.

Supplies

Purely sensory: supplies the skin of the ulnar side of the wrist and the hypothenar part of the palm, with fine twigs to the ulnar artery.