Radial Nerve | Notion

Continuation of posterior cord of the brachial plexus (root values C5 to T1)

Path

In the axilla: lies posterior to the axillary artery on subscapularis, latissimus dorsi and teres major.
Enters the arm between the brachial artery and the long head of triceps (medial to humerus).
Spirals around the posterior surface of the humerus in the groove for the radial nerve.
At the distal third of the lateral border of the humerus it then pierces the intermuscular septum and descends in front of the lateral epicondyle.
At the lateral epicondyle it lies deeply between brachialis and brachioradialis where it then divides into a superficial and deep terminal branch.
Deep branch crosses the supinator to become the posterior interosseous nerve.

Image sourced from Wikipedia

In the image above the relationships of the radial nerve can be appreciated

Regions innervated

| Motor (main nerve) | • Triceps • Anconeus • Brachioradialis • Extensor carpi radialis | | --- | --- | | Motor (posterior interosseous branch) | • Supinator • Extensor carpi ulnaris • Extensor digitorum • Extensor indicis • Extensor digiti minimi • Extensor pollicis longus and brevis • Abductor pollicis longus | | Sensory | The area of skin supplying the proximal phalanges on the dorsal aspect of the hand is supplied by the radial nerve (this does not apply to the little finger and part of the ring finger) |

Muscular innervation and effect of denervation

Anatomical location	Muscle affected	Effect of paralysis
Shoulder	Long head of triceps	Minor effects on shoulder stability in abduction
Arm	Triceps	Loss of elbow extension
Forearm	SupinatorBrachioradialisExtensor carpi radialis longus and brevis	Weakening of supination of prone hand and elbow flexion in mid prone position

Patterns of damage

wrist drop
sensory loss to small area between the dorsal aspect of the 1st and 2nd metacarpals

Axillary damage