Radial nerve

Question 1

What spinal routes is the radial nerve derived from?

Answer 1

C5-T1

Question 2

What is the origin of the radial nerve?

Answer 2

Posterior cord

Posterior divisions of all three trunks

Question 3

What is the course of the nerve?

Answer 3

Passes behind the axillary artery to enter posterior compartment
Winds around the spiral groove of the humerus between heads of triceps
Enters antecubital fossa in front of the lateral epicondyle of the humerus between brachialis and brachioradialis muscles
Branches in proximal forearm- Superficial branch descends under brachioradialis to end in dorsum of hand
Deep branch pierces supinator muscle and descends along the posterior interosseous membrane

Question 4

What is the sensory supply of this nerve?

Answer 4

Posterior arm and forearm
Lateral 2/3 of the dorsum of hand
Dorsal aspect of lateral 3 and 1/2 fingers

Question 5

What is the motor supply of this nerve?

Answer 5

Posterior compartment of arm: Triceps- extends forearm, adducts shoulder
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

How could this nerve be injured?

Answer 6

Crutch, Honeymoon or Saturday night palsy

Fractures of proximal humerus, shaft of humerus, radius

Question 7

What are the features of injuring this nerve?

Answer 7

Wrist drop (can’t extend)
Absent triceps and supinator reflex
Weak elbow, wrist, finger MCPJ, thumb extension
Wasting of triceps
Numbness over posterior arm, posterior forearm and radial distribution of dorsum of hand