12th Cranial Nerve – Tests for the Hypoglossal nerve


The use and interpretation of medical examinations to determine the integrity and adequate function of the hypoglossal nerve (twelfth cranial nerve).


Test procedure:

Commonly tested with the glossopharyngeal and vagus nerves, lesions to the hypoglossal nerve are appreciated by having the patient open their mouth and examining the tongue.


Test findings (inc Positive & Negative results):

Lesions affecting cranial nerve XII produces characteristic clinical manifestations, of which unilateral atrophy of the tongue musculature with deviation to the side of the lesion and fasciculations.

The hypoglossal nerve can be sub-divided into five segments; a different type of lesion may exist in any of these segments, therefore the diagnosis of such a lesion is greatly facilitated by the use of both computed tomography and/or magnetic resonance imaging.


Causes of isolated hypoglossal nerve palsies are rare but include: malignancies, cerebrovascular accidents, space occupying lesions, head and neck trauma, infection, certain autoimmune pathologies.