Radial Nerve

Question 1

Nerve roots

Answer 1

C5-T1

Question 2

Sensory function

Answer 2

Lower lateral cutaneous nerve of the arm - lateral aspect of upper arm, below deltoid
Posterior cutaneous nerve of arm - posterior surface of upper arm
Posterior cutaneous nerve of forearm - strip of skin down middle of posterior forearm
Superficial branch of radial nerve - dorsal surface of lateral 3 and a half digits and associated palm area

Question 3

Motor function

Answer 3

Innervates triceps brachii (extension of elbow)

Innervates majority of extensor muscles in forearm (extension of wrist and fingers, supination of forearm)

Question 4

Radial nerve injury in axilla

Answer 4

Dislocation of humerus at glenohumeral joint or fracture of proximal humerus (can also happen via excessive pressure on axilla)
Patient unable to extend forearm, wrist and fingers, unopposed flexion of wrist (wrist drop)
Loss of sensation over lateral and posterior upper arm, posterior forearm and dorsal surface of lateral 3 and a half digits

Question 5

Radial nerve injury in the radial groove

Answer 5

Fracture of the shaft of the humerus
The triceps brachii may be weakened, but is not paralysed. The deep branch of the radial nerve is affected, so the muscles in the posterior compartment of the forearm are paralysed. The patient is unable to extend the wrist and fingers. Unopposed flexion of wrist occurs, known as wrist drop.
The superficial branch of the radial nerve will be damaged, resulting in sensory loss on the dorsal surface of the lateral three and half digits, and their associated palm area.