Radial Nerve

Question 1

What are the nerve roots?

Answer 1

Nerve roots: C5-T1.

Question 2

What are the sensory functions?

Answer 2

Innervates most of the skin of the posterior side of forearm, and the dorsal surface of the lateral side of the palm, and lateral three and a half digits.

Question 3

What are the motor functions?

Answer 3

Innervates the triceps brachii (extends at the elbow), and the majority of the extensor muscles in the forearm (extends the wrist and fingers and supinates the forearm).

Question 4

What is the anatomical course?

Answer 4

• continuation of the posterior cord of the brachial plexus. It therefore contains fibres from nerve roots C5 – T1.
• It exits the axilla inferiorly (via the triangular interval), and supplies branches to the long and medial heads of the triceps brachii.
• The radial nerve then descends down the arm, travelling in a shallow depression within the surface of the humerus known as the radial groove.
• As it descends, the radial nerve wraps around the humerus laterally, and supplies a branch to the lateral head of the triceps brachii. During much of its course within the upper arm, it is accompanied by the deep branch of the brachial artery.
• To enter the forearm, the radial nerve moves anteriorly over the lateral epicondyle of the humerus, through the cubital fossa. The nerve then terminates by dividing into two branches:

Deep branch (motor) – innervates most of the muscles in the posterior compartment of the forearm.

Superficial branch (sensory) – contributes to the cutaneous innervation of the hand and fingers.