Question 60

Question:

Following a circus accident, a man is unable to abduct his left arm from a 90 degree position to 180 degrees. Impairment of which of the following nerves could explain this finding?

Correct Answer: B.  Long thoracic nerve

The long thoracic nerve innervates the serratus anterior muscle, which- among its other functions- upwardly rotates the scapula allowing the arms to reach a 180 degree position. The thoracodorsal nerve innervates the latissimus dorsi, which has no function in arm abduction. The axillary nerve innervates the deltoid, which abducts the arm to 90 degrees. The radial nerve innervates the posterior muscles of the arm and forearm, which are not involved in arm abduction. The musculocutaneous nerve innervates muscles of the anterior arm, which are not involved in arm abduction.