Which cranial nerve is tested by asking the patient to shrug their shoulders against resistance?

• A. Trigeminal
• B. Vagus
• C. Spinal Accessory
• D. Hypoglossal

Answer: (C)

Testing shoulder shrug strength targets the function of the spinal accessory nerve. This nerve supplies the trapezius and sternocleidomastoid muscles, and the trapezius is the muscle that elevates the shoulders when you shrug. So asking the patient to shrug against resistance directly reveals whether the trapezius and, by extension, the spinal accessory nerve are working properly. If shrug strength is reduced or absent, it points to a problem with this nerve or the trapezius muscle, which can occur after neck surgery or trauma.

Other nerves listed control different functions: the trigeminal nerve mainly handles facial sensation and muscles of mastication; the vagus nerve influences phonation and autonomic functions; the hypoglossal nerve controls tongue movements. Therefore, shrugging against resistance specifically tests the spinal accessory nerve.