Hypoglossale

Hypoglossale, in medical usage, refers to the hypoglossal nerve, the twelfth cranial nerve (CN XII), a predominantly motor nerve that supplies the muscles of the tongue. The term derives from Greek roots meaning under the tongue.

Anatomy and course: The hypoglossal nerve arises from the hypoglossal nucleus in the ventral medulla. Its fibers exit the brainstem between the olive and the pyramid and travel to the skull, emerging through the hypoglossal canal in the occipital bone. After exiting, the nerve descends anteriorly, passing deep to the posterior belly of the digastric and the hyoglossus muscle before reaching the tongue. A small branch carries C1 fibers that join the nerve to innervate the thyrohyoid and geniohyoid muscles.

Function: The hypoglossal nerve provides motor innervation to all intrinsic tongue muscles and to most extrinsic tongue muscles, including genioglossus, hyoglossus, and styloglossus, enabling movements essential for speech, swallowing, and bolus manipulation. The palatoglossus muscle is innervated by the vagus nerve (CN X) via the pharyngeal plexus.

Clinical significance: Lesions of CN XII cause ipsilateral tongue weakness, atrophy, and fasciculations, with the tongue deviating toward the side of the lesion on protrusion. Cortical or supranuclear (UMN) lesions produce milder symptoms and typically result in tongue deviation away from the lesion due to bilateral cortical control, whereas intrinsic LMN lesions yield pronounced ipsilateral deficits. Hypoglossal nerve pathology may result from trauma, tumors, stroke, or iatrogenic injury during procedures in the neck or skull base.