The hypoglossal nerve is the twelfth cranial nerve that arises from the hypoglossal nucleus and emerges from the medulla oblongata. It passes through the hypoglossal canal and gives off branches before innervating all the muscles of the tongue, except for the palatoglossus. The function of the hypoglossal nerve can be tested by having a person poke out their tongue or push against the inside of their cheek with their tongue.

1. TheThe hypoglossal nervehypoglossal nerve is the twelfthis the twelfth cranial nervecranial nerve (XII). The nerve(XII). The nerve
arises from thearises from the hypoglossalhypoglossal nucleusnucleus and emerges from theand emerges from the
medulla oblongatamedulla oblongata in the preolivaryin the preolivary sulcussulcus separating theseparating the oliveolive and theand the
pyramidpyramid. It then passes through the. It then passes through the hypoglossalhypoglossal canalcanal. On emerging from. On emerging from
the hypoglossal canal, it gives off a small meningeal branch and picks upthe hypoglossal canal, it gives off a small meningeal branch and picks up
a branch from thea branch from the anterioranterior ramusramus ofof C1C1. It spirals behind the. It spirals behind the vagusvagus nervenerve
and passes between theand passes between the internal carotid arteryinternal carotid artery andand internal jugular veininternal jugular vein
lying on thelying on the carotid sheathcarotid sheath. After passing deep to the. After passing deep to the posteriorposterior belly of thebelly of the
digastricdigastric musclemuscle, it passes to the submandibular region to enter the, it passes to the submandibular region to enter the
tonguetongue.. It supplies motor fibres to all of the muscles of theIt supplies motor fibres to all of the muscles of the tonguetongue, except, except
thethe palatoglossuspalatoglossus musclemuscle which is innervated by thewhich is innervated by the vagusvagus nervenerve (X).(X).

2. Testing the hypoglossal nerveTesting the hypoglossal nerve
To test the function of the nerve, a person is asked to pokeTo test the function of the nerve, a person is asked to poke
out theirout their tonguetongue. If there is a loss of function on one side. If there is a loss of function on one side
(unilateral paralysis) the tongue will point towards the(unilateral paralysis) the tongue will point towards the
affected side.affected side.
The strength of the tongue can be tested by getting theThe strength of the tongue can be tested by getting the
person to poke the inside of their cheek, and feeling howperson to poke the inside of their cheek, and feeling how
strongly they can push a finger pushed against theirstrongly they can push a finger pushed against their
cheek - a more elegant way of testing than directlycheek - a more elegant way of testing than directly
touching the tongue.touching the tongue.
The tongue can also be looked at for signs of lower motorThe tongue can also be looked at for signs of lower motor
neuron disease, such as fasciculation and atrophy.neuron disease, such as fasciculation and atrophy.