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Hypoglossal Nerve Damage
Hypoglossal Nerve (Cranial Nerve 12 / CN XII)


The Hypoglossal Nerve supplies motor fibres to all of the muscles of the tongue (ie
there is
no sensory function) except the Palatoglossus muscle, which is innervated
by the
Vagus Nerve (Cranial Nerve 10 / CN X) or according to some
classifications, by fibres from the
Glossopharyngeal Nerve (Cranial Nerve 9 / CN
IX
) that "hitchhike" within the Vagus.

The
Hypoglossal Nerve is one of the least injured nerves in head injury.  Having
said that though,
Hypoglossal Nerve Palsy (ie ‘paralysis’ of the muscles supplied
by the
Hypoglossal Nerve) is well recognised complication of trauma / infection /
procedures affecting the floor of the mouth, mouth and throat.


Weakness of the tongue manifests itself as a slurring of speech & by ‘wasting’ of
the side of the tongue which has the palsy.

The patient complains that their tongue feels "
thick", "heavy" or "clumsy”.  Lingual
sounds
(i.e., l's, t's, d's, n's, r's etc) are slurred and this is obvious in conversation
even before direct examination.

The function of the
Hypoglossal Nerve is assessed as follows:

  • finer control is demonstrated by the ability to say "la" and "ta"
  • tongue movements to command - from side to side etc the side of the tongue
    that is palsied deviates towards the side of the lesion
Diagram Showing the course of the Hypoglossal Nerve (amongst others).
Photos of Hypoglossal Nerve Palsy affecting the left side of the tongue; the 2nd
photos shows
wasting of the tongue.
Useful Website & Articles:

New England Journal of Medicine

Postgrad Med J 1972.  Hypoglossal Nerve Palsy complicating a case of Infectious
Mononucleosis.

J Accid Emerg Med 1998.  A Rare Case of Hypoglossal Nerve Palsy complicating
a Head Injury.

Acta Anaesthesiol Scand 2004.  Case Report.  Bilateral Hypoglossal Nerve Injury
following the Use of the Laryngeal Mask without the use of Nitrous Oxide.

Eur Neurol 2007.  Isolated Hypoglossal Nerve Palsy.  A Diagnostic Challenge.

J Oral Health Comm Dent 2008.  Idiopathic Unilateral Isolated Hypoglossal Nerve
Palsy.  A Case Report.

Tongue Paralysis after Oro-Tracheal Intubation in a Patient with Primary
Mediastinal Tumour.  2009.

Case Reports in Medicine 2009.  Case Report.  Isolated Hypoglossal Nerve Palsy
due to Infected Impacted Tooth.

Hong Kong Med J 2009.  Pictorial Medicine.  Hypoglossal Nerve Palsy.

Oral Surgery 2010.  Case Report.  Hypoglossal Nerve Palsy Caused by an
Aneurysm of the External Carotid Artery

J Investigative & Clinical Dentistry 2011.  Case Report.  Unilateral Hypoglossal
Nerve Palsy due to Infected Molar - A Rare Entity.

J Medical Case Reports 2011. Case Report.  Inferior Alveolar Nerve Injury with
Laryngeal Mask Airway.

New England J Medicine 2012.  Images in Clinical Medicine.  Denervation  Atrophy 
of the Tongue  after Hypoglossal Nerve Injury
Last Updated 17th October 2013