Which nerve is at risk during neck dissections due to its course in the carotid sheath and its motor to the sternocleidomastoid and trapezius?

Prepare for the Individual Readiness Assurance Test (iRAT) 4 in Head and Neck. Study with multiple-choice questions, comprehensive explanations, and detailed flashcards. Maximize your chances of success with thorough preparation and insightful study resources.

The nerve at risk is the spinal accessory nerve. It supplies motor fibers to the sternocleidomastoid and trapezius muscles, which control turning the head and shrugging the shoulders. In neck dissections, this nerve has a course that brings it into contact with the posterior triangle and the region around the carotid sheath as it travels from the skull, passes deep to the sternocleidomastoid, and then moves toward the trapezius. That places it particularly vulnerable to injury during surgical exposure and dissection in the neck, leading to weakness of SCM and trapezius function, such as difficulty elevating the shoulder and turning the head.

The other nerves don’t fit this scenario: the hypoglossal nerve controls tongue muscles and isn’t responsible for SCM or trapezius; the vagus nerve lies in the carotid sheath but does not innervate these two muscles; the accessory auricular nerve is mainly sensory and does not motorize these muscles.