Disorders of the 12th cranial nerve (hypoglossal nerve) cause weakness or wasting (atrophy) of the tongue on the affected side. This nerve moves the tongue.

Causes include a tumor or bone abnormality at the base of the skull, a stroke, infection of the brain stem, or an injury to the neck, such as that due to surgical removal of a blockage from an artery in the neck (endarterectomy). Amyotrophic lateral sclerosis (Lou Gehrig's disease) can also damage the hypoglossal nerve.

The tongue becomes weak on the affected side and eventually wastes away (atrophies). As a result, people have difficulty speaking, chewing, and swallowing. Damage due to amyotrophic lateral sclerosis causes tiny, subtle twitching movements (fasciculations) on the surface of the tongue.

Magnetic resonance imaging (MRI) is usually done to look for a tumor or evidence of a stroke. A spinal tap (lumbar puncture may be necessary if cancer or infection is possible. Treatment depends on the cause.

Last full review/revision July 2007 by Michael Rubin, MD