Superficial branch of radial nerve

At a glance

English

Superficial branch of radial nerve

Latin (TA2)

Ramus superficialis nervi radialis

System

Nerve

Region

Upper limb

Side

Paired, left and right

About the superficial branch of radial nerve

One of the two terminal branches into which the radial nerve divides in front of the lateral epicondyle of the humerus, the superficial branch is entirely sensory. From the elbow it runs down the front of the lateral forearm, under cover of brachioradialis, resting in turn on supinator, pronator teres and flexor digitorum superficialis. Halfway down the forearm it lies just lateral to the radial artery.

Roughly 7 cm above the wrist the nerve leaves the artery and turns backwards beneath the tendon of brachioradialis. It pierces the deep fascia on the lateral side of the forearm and becomes subcutaneous, where it crosses over the tendons of the thumb muscles in the region of the anatomical snuffbox. Here it splits into a lateral and a medial part. The lateral part, which is smaller, serves the radial border and ball of the thumb and joins the lateral cutaneous nerve of the forearm. The medial part communicates with the lateral cutaneous nerve of the forearm above the wrist and on the dorsum of the hand with the ulnar nerve's dorsal branch.

The medial part then gives four dorsal digital nerves: one each to the thumb's ulnar border and the index finger's radial border, one to the facing sides of index and middle fingers, and one to the facing sides of middle and ring fingers, the last shared with the ulnar nerve. These supply the back of the lateral hand and the backs of the lateral three and a half digits as far as the middle phalanx; the skin over the end segments and nail beds belongs to the palmar digital nerves of the median nerve. The web space between thumb and index finger is its most reliable test area.

Lying just under the skin at the wrist, the nerve is easily squeezed or cut. Tight watch straps, bracelets or handcuffs can compress it, causing tingling and numbness on the back of the thumb and hand, a condition called Wartenberg's syndrome or cheiralgia paraesthetica. It can be confused with de Quervain's tenosynovitis of the thumb tendons nearby. The nerve can also be damaged by cannulas in the cephalic vein at the wrist and during operations on the thumb tendons or radius.

Course and supply

Arises from

One of the two terminal branches of the radial nerve, arising in front of the lateral epicondyle.

Ends in

Ends in lateral and medial branches and four dorsal digital nerves on the back of the thumb, index, middle and radial half of the ring finger.

Supplies

Purely sensory: supplies the radial half of the dorsal hand skin and the dorsal skin of the lateral three and a half digits up to the end segments.