IV.B.5 Head: CN XI & CN XII Page 2 of 2

The hypoglosssal nerve CN XII arises from several rootlets of the anterior surface of the medulla.

It passes across the posterior fossa and exits from the hypoglosssal canal.

The nerve innervates the styloglossus, hyoglossus and genioglossus and all of the intrinsic muscles of the tongue.(GSE)

	Predict the clinical findings of injury to the accessory and hypoglossal nerves.
Cranial nerve lesions Cranial Nerve Clinical Findings Example of Lesion Accessory nerve [XI] Paralysis of sternocleidomastoid and trapezius muscles Penetrating injury to the posterior triangle of the neck Hypoglossal nerve Atrophy of ipsilateral muscles of the tongue and deviation toward the affected side; speech disturbance Penetrating injury to the neck and skull base pathology

Predict the most likely locations for injury to cranial nerves XI and XII.