Radial Nerve

Question 1

Nerve Roots and Cord origin?

Answer 1

C5- T1

posterior cord

formed from posterior divisions of all three trunks

Question 2

Nerve course?

Answer 2

it passes behind the axillary artery and through the triangular interval to enter the posterior compartment of the arm

it then winds around the spiral groove of the humerus with the profunda brachii artery, between the heads of triceps muscle

it enters the antecubital fossa in front of the lateral epicondyle of the humerus, between the brachialis and brachioradialis muscles

Question 3

Whn it reaches the proximal forearm what does it branch into?

Answer 3

superficial branch (mainly sensory) – descends under brachioradialis muscle to end in the dorsum of the hand

deep branch (mainly motor) – pierces supinator muscle and descends along the posterior interosseous membrane with the posterior interosseous artery

Question 4

Sensory supply?

Answer 4

posterior arm and forearm

lateral ⅔ of dorsum of hand

proximal dorsal aspect of lateral 3½ fingers (thumb, index, middle and half of ring finger)

Question 5

What forearm muscles does it supply?

Answer 5

posterior compartment of forearm

brachioradialis – flexes elbow

anconeus – extends elbow, stabilises elbow joint

supinator – supinates forearm

extensor carpi radialis longus and brevis – extend and abduct wrist

extensor carpi ulnaris – extends and adducts wrist

extensor digitorum, extensor pollicis longus and brevis,
extensor indicis and extensor digiti minimi – extend thumb and fingers at MCPJs and IPJs

abductor pollicis longus – abducts thumb

Question 6

Some defects of nerve palsy?

Answer 6

SENSORY LOSS
numbness of skin over posterior arm, posterior forearm and radial distribution of dorsum of hand

MOTOR DEFICIT
paralysis of posterior compartment of arm – weak elbow extension
paralysis of posterior compartment of forearm – weak wrist extension, weak thumb extension and finger MCPJ extension
NB// finger IPJ extension is still possible due to intact nerve supply to the lumbrical muscles of the hand
absent triceps and supinator reflexes

DEFORMITY
wasting of triceps and posterior compartment of forearm
“WRIST DROP” deformity at rest and on attempted wrist extension – the patient cannot extend their wrist/fingers, resulting in unopposed wrist flexion. In the classical description of a radial nerve injury, the forearm is also pronated, the fingers are flexed and the thumb adducted.