12th Cranial Nerve – Lesions of the Hypoglossal nerve

Definition:

Hypoglossal nerve lesions are pathological processes which negatively affect the nerve’s function. Lesions affecting cranial nerve XII are uncommon.

Causes:

Causes of isolated Hypoglossal nerve palsies are rare but include:

  • malignancies
  • cerebrovascular accidents
  • space occupying lesions
  • head and neck trauma
  • infection
  • certain autoimmune pathologies

Examination:

 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 are the most easily appreciated.

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.