Radial nerve
Branches · C5 C6 C7 C8 T1
The largest branch of the plexus. Runs in the spiral groove against the humeral shaft, then divides into a deep motor branch (the posterior interosseous nerve) and a superficial sensory branch.
Traced from the start
Detail
- Motor
- Triceps brachii and anconeus. Brachioradialis and extensor carpi radialis longus. Supinator, and the extensor compartment of the forearm via the posterior interosseous nerve
- Sensory
- Posterior arm and forearm, and the dorsum of the lateral three and a half digits as far as the proximal interphalangeal joints — including the anatomical snuffbox. The dorsal skin over the distal phalanges and nail beds is median (ulnar for the medial one and a half digits)
When it goes wrong
Midshaft humeral fracture involving the spiral groove
Wrist drop with weak finger extension and numbness over the snuffbox. Triceps is spared, because its branches leave above the groove.
Crutch palsy — compression in the axilla by a crutch
As above, but triceps is also weak and the triceps reflex is depressed, because the lesion is proximal to its branches. Beware the eponym: the arm draped over a chair back in a drunken sleep — Saturday night palsy — compresses the nerve at the spiral groove instead, so the triceps is spared.
Posterior interosseous nerve entrapment at the arcade of Frohse
Finger drop with no sensory loss, and the wrist deviates radially on extension because extensor carpi radialis longus is spared.
Practise this structure
1 question in the bank tagged Radial Nerve.