Definition of Cranial nerve XII

Cranial nerve XII: The twelfth cranial nerve is the hypoglossal nerve. The twelve cranial nerves, the hypoglossal nerve included, emerge from or enter the skull (the cranium), as opposed to the spinal nerves which emerge from the vertebral column.

The hypoglossal nerve supplies the muscles of the tongue. (The Greek "hypo-", under and "-glossal" from "glossa", the tongue = under the tongue).

Paralysis of the hypoglossal nerve affects the tongue. It impairs speech (it sounds thick) and causes the tongue to deviate toward the paralyzed side. In time, the tongue diminishes in size (atrophies).