Cranial Nerve XI - Spinal Accessory Nerve

Figure 29. Cranial Nerve XI - Spinal Accessory, Accessory

Figure 29. Cranial Nerve XI - Spinal Accessory, Accessory

This is an odd cranial nerve, hence one of its names containing the word spinal. The reason for the name is that the main portion of nerve originates in the spinal cord. The nerve passes from the spinal cord back through the foramen magnum, joins up with cranial nerves IX and X briefly and then cranial root from the brain stem then leaves with IX and X through the jugular foramen. It is purely somatic efferent in function supplying motor innervation branches to the trapezius and sternocleidomastoid muscles.