The The hypoglossal nervehypoglossal nerve is the twelfth is the twelfth cranial nervecranial nerve (XII). The (XII). The nerve arises from the nerve arises from the hypoglossalhypoglossal nucleus nucleus and emerges from the and emerges from the medulla oblongatamedulla oblongata in the preolivary in the preolivary sulcussulcus separating the separating the oliveolive and the and the pyramidpyramid. It then passes through the . It then passes through the hypoglossalhypoglossal canal canal. .

On emerging from the hypoglossal canal, it gives off a small On emerging from the hypoglossal canal, it gives off a small meningeal branch and picks up a branch from the meningeal branch and picks up a branch from the anterioranterior ramusramus of of C1C1. It spirals behind the . It spirals behind the vagusvagus nerve nerve and passes between the and passes between the

internal carotid arteryinternal carotid artery and and internal jugular veininternal jugular vein lying on the lying on the carotid sheathcarotid sheath. After passing deep to the . After passing deep to the posteriorposterior belly of the belly of the digastricdigastric muscle muscle, it passes to the submandibular region to enter , it passes to the submandibular region to enter the the tonguetongue. . It supplies motor fibres to all of the muscles of the It supplies motor fibres to all of the muscles of the tonguetongue, except the , except the palatoglossuspalatoglossus muscle muscle which is innervated by which is innervated by

the the vagusvagus nerve nerve (X). (X).

Testing the hypoglossal nerveTesting the hypoglossal nerve

To test the function of the nerve, a person is asked to To test the function of the nerve, a person is asked to poke out their poke out their tonguetongue. If there is a loss of function . If there is a loss of function on one side (unilateral paralysis) the tongue will on one side (unilateral paralysis) the tongue will point towards the affected side.point towards the affected side.

The strength of the tongue can be tested by getting The strength of the tongue can be tested by getting the person to poke the inside of their cheek, and the person to poke the inside of their cheek, and feeling how strongly they can push a finger pushed feeling how strongly they can push a finger pushed against their cheek - a more elegant way of testing against their cheek - a more elegant way of testing than directly touching the tongue.than directly touching the tongue.

The tongue can also be looked at for signs of lower The tongue can also be looked at for signs of lower motor neuron disease, such as fasciculation and motor neuron disease, such as fasciculation and atrophy.atrophy.