Palmar branch of median nerve
Ramus palmaris nervi mediani
A cutaneous branch of the median nerve that leaves it above the wrist and crosses over the flexor retinaculum to the palm.
At a glance
- English
- Palmar branch of median nerve
- Latin (TA2)
- Ramus palmaris nervi mediani
- System
- Nerve
- Region
- Upper limb
- Side
- Paired, left and right
About the palmar branch of median nerve
Also known as the palmar cutaneous branch, the median nerve's palmar branch is a small sensory nerve given off in the lower forearm, a few centimetres above the wrist crease. It leaves the radial side of the parent nerve and runs down between the tendons of palmaris longus and flexor carpi radialis, often in its own small fascial channel close to the flexor carpi radialis sheath.
Rather than following the median nerve into the carpal tunnel, the branch stays superficial. It pierces the deep fascia at the wrist, near the palmar carpal ligament, and crosses in front of the flexor retinaculum. In the palm it divides into lateral and medial branches. The lateral branch serves the skin of the thenar eminence and is linked to the anterior branch of the lateral cutaneous nerve of the forearm. The medial branch serves the central palm and is linked to the palmar branch of the ulnar nerve.
The territory is therefore the radial and central part of the palm, bounded laterally by the radial nerve and medially by the ulnar nerve. The branch has no motor fibres. Its distribution explains why the skin of the palm itself is supplied differently from the palmar surface of the fingers, which belongs to the digital branches of the median nerve that pass through the tunnel.
The course of this branch above the retinaculum is the key to an important clinical sign. In carpal tunnel syndrome the median nerve is squeezed inside the tunnel, causing numbness and tingling in the thumb, index, middle and part of the ring finger, but feeling over the thenar eminence and central palm is usually normal because the palmar branch is untouched. Numbness of the palm suggests that the median nerve is damaged higher up. Surgeons open the carpal tunnel through an incision placed to avoid this branch, since cutting it can leave a painful scar or a tender neuroma.
Course and supply
- Arises from
- Arises from the radial side of the median nerve in the distal forearm, a few centimetres above the wrist.
- Ends in
- Passes superficial to the flexor retinaculum and ends in lateral and medial branches to the skin of the palm.
- Supplies
- Purely sensory: supplies the skin over the thenar eminence and the central palm.
Anthromica
See the palmar branch of median nerve where it really sits, with every layer of the body around it.
- Every layer, one body. Peel from muscle to bone, nerve, vessel and organ, and turn it any way.
- English and Latin. Every structure named the way your exam names it.
- Quiz until it sticks. Short drills on the structures you keep missing.
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