Spinal accessory nerve (cranial XI) palsy produces weakness of which actions?

Spinal accessory nerve (cranial XI) palsy produces weakness of which actions?

• A. Turning the head from side to neutral and raising the shoulders
• B. Chewing
• C. Swallowing
• D. Speech

Answer: (A)

Spinal accessory nerve injury affects two muscles: sternocleidomastoid and trapezius. The sternocleidomastoid turns the head to the opposite side and helps flex the neck, while the trapezius elevates the shoulders (shrug) and helps stabilize the scapula. When this nerve is palsied, you’d see weakness in turning the head away from the affected side and in raising the shoulders. Chewing involves muscles of mastication innervated by the trigeminal nerve, not the spinal accessory nerve, and swallowing or speech rely on other nerves (like glossopharyngeal, vagus, and hypoglossal), so those functions aren’t directly impaired by cranial XI palsy.

Spinal accessory nerve injury affects two muscles: sternocleidomastoid and trapezius. The sternocleidomastoid turns the head to the opposite side and helps flex the neck, while the trapezius elevates the shoulders (shrug) and helps stabilize the scapula. When this nerve is palsied, you’d see weakness in turning the head away from the affected side and in raising the shoulders. Chewing involves muscles of mastication innervated by the trigeminal nerve, not the spinal accessory nerve, and swallowing or speech rely on other nerves (like glossopharyngeal, vagus, and hypoglossal), so those functions aren’t directly impaired by cranial XI palsy.