The main purpose of the examination of motor function of the tongue is to look for evidence of dysfunction of the hypoglossal (twelfth) cranial nerve. Another purpose for examination of the tongue is to look for fasciculations, particularly in the clinical context in which motor neuron disease (amyotrophic lateral sclerosis) is a consideration.

It is appropriate to assess that the tongue protrudes grossly in the midline and that it can wiggle from side-to-side in all patients during a routine neurologic examination. When a patient is being evaluated for the possibility of motor neuron disease, it is also appropriate to specifically inspect the tongue for fasciculations.

The muscles that move the tongue are supplied by the twelfth cranial nerves, which arise from the medial part of the medulla. The left twelfth nerve, which arises from the left medulla, supplies the muscles on the left side of the tongue and moves the tongue to the right. The right twelfth nerve, which arises from the right medulla, supplies the muscles on the right side of the tongue and moves the tongue to the left.

None (except for a flashlight when needed to look for tongue fasciculations).