Hypoglossal Nucleus

nucleus nervi hypoglossi

The hypoglossal nucleus is the motor nucleus of cranial nerve XII. It lies near the midline in the dorsal medulla under the hypoglossal triangle of the fourth ventricle floor and supplies all the muscles of the tongue except palatoglossus.

Anatomical Data

Structure & Connections

Location	Dorsal medulla, close to the midline beneath the hypoglossal trigone, extending down to the level of the obex and below
Parts	Motor neurons for intrinsic and extrinsic tongue muscles
Connections	Hypoglossal nerve Corticobulbar fibres (mainly from the opposite hemisphere for genioglossus) Nucleus of the solitary tract and reticular formation (swallowing and breathing)
Blood Supply	Anterior spinal artery; Vertebral artery paramedian branches

Biomechanics

Function & Actions

Controls tongue movements for speech, chewing and swallowing, and helps keep the airway open during sleep.

Clinical Relevance

Clinical Notes

A lower motor neuron lesion of the nucleus or nerve causes tongue wasting and fasciculation on the same side, and the tongue points toward the weak side when protruded. Tongue fasciculations are a key clinical sign of bulbar involvement in motor neuron disease. Hypoglossal nerve stimulation is used to treat obstructive sleep apnoea.

Pathology

Common Injuries & Conditions

Medial Medullary Syndrome

Infarction involving the hypoglossal nucleus or fascicles causing ipsilateral tongue weakness with contralateral hemiplegia.

Tongue Fasciculations in Motor Neuron Disease

Twitching and wasting of the tongue from degeneration of hypoglossal motor neurons.

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