The Hypoglossal XIIth Cranial Nerve

The XIIth (twelfth) cranial nerve is the hypoglossal nerve.  This is the nerve that controls the muscles of
the tongue.  The hypoglossal nerves pass right through the base of the skull at the occipital condyles to
the neck or atlas C1 vertebra joints on both sides. Jamming of these joints can interfere with the
hypoglossal nerve function, which presents itself as lack of control of the muscles of the tongue.

CranioSacral Therapy provides us with a treatment method that enables a therapist to release the base
of the skull from the neck.  I find it interesting that cranial therapy can alleviate tongue chewing
symptoms for extended periods of time.  In order to determine whether tongue chewing is congenital
(present at birth),  hereditary or just a habit we must consider these factors.


Hypoglossal nerve
From Wikipedia, the free encyclopedia   
http://en.wikipedia.org/wiki/Hypoglossal_nerve

The hypoglossal nerve is the twelfth cranial nerve. The nerve arises from the hypoglossal nucleus and
emerges from the medulla oblongata between the olive and the pyramids. It then passes through the
hypoglossal canal. On emerging from the hypoglossal canal, the nerve picks up a branch from the
anterior ramus of C1. It spirals behind the vagus nerve and passes between the internal carotid artery
and internal jugular vein lying on the carotid sheath. After passing deep to the posterior belly of the
digastric muscle, it passes to the tongue.

It supplies motor fibres to all of the muscles of the tongue, except the palatoglossus muscle which is
innervated by the vagus nerve (X) and the accessory nerve (XI).

Aside from the tongue, the hypoglossal nerve also controls, via the ansa cervicalis, thyrohyoid muscle,
omohyoid muscle, sternothyroid muscle and sternohyoid muscle. The nerve fibres supplying these
muscles all come from the C1 contribution

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

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