Musculocutaneous Nerve

Question 1

Nerve roots

Answer 1

C5-C7

Question 2

Motor function

Answer 2

Innervates BBC muscles which flex the upper arm at the shoulder and elbow
Biceps also perform supination

Question 3

Sensory function

Answer 3

Gives rise to lateral cutaneous nerve of forearm, which innervates skin on the lateral surface of the forearm

Question 4

Lesions of musculocutaneous nerve

Answer 4

How? Stab wound to the axilla is most common (relatively uncommon injury as MCN is well protected in axilla)
Motor functions affected - BBC paralysed, flexion of shoulder weakened, flexion of elbow is weakened, supination greatly weakened
Sensory loss - over the lateral side of the forearm

Question 5

Why can shoulder flexion still occur after a musculocutaneous nerve injury?

Answer 5

The pectoralis major muscle still performs this action

Question 6

Why can elbow flexion still occur after a musculocutaneous nerve injury?

Answer 6

The brachioradialis muscle can still perform this action

Question 7

Why can supination still occur after a musculocutaneous nerve injury?

Answer 7

The supinator muscle can still perform this action