Superficial Branch of the Radial Nerve
Definition
The superficial branch of the radial nerve (superficial radial nerve) is the sensory terminal branch of the radial nerve. It is a purely cutaneous nerve.
Also called: superficial terminal branch of the radial nerve.
Origin
Arises from the radial nerve in the cubital fossa, just below the level of the lateral epicondyle of the humerus — at the same point as the posterior interosseous nerve.
Course
| Segment | Description |
|---|---|
| Upper third of forearm | Runs down the front of the forearm, widely separated from the radial artery — lies lateral to the artery |
| Middle third of forearm | Closely related to the radial artery — runs parallel to it on its lateral side |
| Lower third of forearm | Passes posteriorly under the tendon of brachioradialis (about 7 cm above the wrist) |
| Dorsum of wrist/hand | Divides into terminal digital branches on the dorsum of the hand |
Key landmark: The nerve passes beneath the brachioradialis tendon to reach the dorsum — this is a common point of entrapment (Wartenberg’s syndrome).
Cutaneous Distribution
The superficial radial nerve supplies:
- Lateral half of the dorsum of the hand
- Dorsal surface of the thumb (proximal phalanx)
- Dorsal surface of the index finger (proximal phalanx)
- Dorsal surface of the middle finger (lateral half, proximal phalanx)
Note: Only the proximal parts of the dorsal digit surfaces are supplied (up to the proximal interphalangeal joint level). The distal dorsum of these fingers is supplied by palmar digital branches of the median nerve (which wrap around).
The superficial radial nerve does not supply the little finger or medial half of the ring finger (those are supplied by the dorsal branch of the ulnar nerve).
Clinical Significance
- Injury to the superficial branch: Results in a small area of sensory loss over the dorsum of the first web space (root of the thumb) — the only consistent area of sensory loss
- The total area of numbness is often less than expected because of overlap from adjacent nerves (lateral cutaneous nerve of forearm, dorsal cutaneous branch of ulnar nerve)
- Wartenberg’s syndrome: Entrapment of the superficial radial nerve under the brachioradialis tendon at the wrist — causes pain, numbness, and paraesthesia over the dorsum of the thumb and first web space; may mimic de Quervain’s tenosynovitis
- The nerve is at risk during surgical approaches to the radial aspect of the wrist and during venous cannulation of the dorsum of the hand