Answer to Too Much of a Good Thing

Correct answer is C, the spinal accessory nerve. Cranial nerve XI innervates the trapezius and sternocleidomastoid (SCM) muscles. The patient suffers loss of turning his head to the contralateral side of the incision following the surgery. Hence, his ipsilateral SCM was denervated during the surgery. Indeed, the accessory nerve injury most likely occurs due to iatrogenic causes, such as posterior and lateral cervical triangle surgeries. During carotid artery endarterectomy, it is usually the hypoglossal nerve that is at most risk of injury, albeit these complications are relatively low. Nevertheless, CN XI is at risk when the posterior triangle is entered during neck surgery.

Answer to this question is based on material presented in lecture 2 of the Head and Neck Lecture Series.

1 = Great auricular n.

2 = Transverse cervical n.

3 = Spinal accessory n.

4 = Upper root of ansa cervicalis

5 = Lower root of ansa cervicalis