CN XI SCM Trapezius — FRCA Primary MCQ

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EasyAnatomyCN XI SCM TrapeziusFRCA Primary

The accessory nerve (CN XI) has a spinal root that innervates:

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Correct answer: C — Sternocleidomastoid and trapezius

The spinal root of CN XI arises from the anterior horn cells of C1-C5 and ascends through the foramen magnum to exit via the jugular foramen. It innervates sternocleidomastoid (ipsilateral head rotation) and trapezius (shoulder elevation/shrug). Accessory nerve injury causes: inability to shrug the shoulder and weakness of head turning.

Reference: RCoA 2021 Primary FRCA Curriculum