Hypoglossal Nerve

Origin

The hypoglossal nerve originates from the hypoglossal nucleus in the medulla oblongata and emerges from the brainstem in the sulcus between the olive and pyramid.

Course

The hypoglossal nerve leaves the ventral medulla oblongata and wraps dorsally around the vertebral artery as it extends laterally to the hypoglossal canal.

After exiting the skull through the hypoglossal canal, the hypoglossal nerve descends below the angle of the mandible, and between the internal carotid artery and the internal jugular vein. It passes deep to the occipital artery while still running inferiorly, but then turns 90 degrees to run anterior. As it does so, the hypoglossal nerve now passes externally to the occipital artery or, if inferior to the occipital artery, lateral to the external carotid artery.

The hypoglossal nerve continues anteriorly superficial to the external carotid artery but deep to the posterior digastric and stylohyoid muscles. It passes forward medial to the mandible and submandibular gland, running on the lateral surface of the hyoglossus muscle. The hypoglossal nerve passes into the oral cavity as it runs deep to the mylohyoid muscle.

After entering the oral cavity, the hypoglossal nerve sends fibers anteriorly and medially to the muscles of the tongue.

Branches

The hypoglossal nerve gives rise to lingual branches that serve the target muscles.

Supplied Structures

The hypoglossal nerve is a motor nerve. It sends general sensory efferent fibers to the muscles of the tongue, except the palatoglossus muscle, which is supplied by the vagus nerve via the pharyngeal plexus.

List of Clinical Correlates

—Dysarthria

—Obstructive sleep apnea