Craniofacial Muscles

Chapter 14
Tongue Muscle Response
to Neuromuscular Diseases and Speci fi c
Pathologies
Zi-Jun Liu
14.1 Overview
The tongue is the only muscular organ in the craniofacial region and plays fundamental
roles in almost all oral motor functions, including drinking, ingestion, chewing,
swallowing, respiration, and speech. A number of neuromuscular diseases, such as
epilepsy, multiple sclerosis, cerebral palsy, muscular dystrophy, Parkinson’s and
Huntington’s diseases, and myasthenia gravis, signi fi cantly affect tongue motor
functions. These negative impacts include reduced or complete loss of control in
moving the tongue (tongue displacement) and/or changing the shape of the tongue
(tongue deformation), tongue spasm or convulsion, muscle dystonia, and ankyloglossia.
Several sensational disorders may also occur due to these neuromuscular
diseases, including burning tongue, loss of taste function (ageusia), decreased ability
to taste (hypogeusia), and changes in taste (dysgeusia). In recent decades, extensive
studies have demonstrated that tongue size, volume, position, and neuromuscular
activity, especially in the tongue base, are signi fi cantly implicated in obstructive
sleep apnea (OSA), a potential life-threatening disorder of breathing, which affects
2–4% of the adult population (Schwab 2003 ; Schwab et al . 2003 ) .
In addition to the complex network of interwoven fi bers and fi ber bundles from
four intrinsic and four extrinsic tongue muscles which facilitate complicated and
delicate tongue kinematics, the tongue also has a large network of subdividing nerve
branches and blood supply. Studies have shown that the hypoglossal nerve alone has
more than 50 primary branches innervating tongue musculature (Mu and Sanders
1999 ) . Unlike other body motor organs, the tongue is composed almost entirely of
Z.-J. Liu (*)
Department of Orthodontics , University of Washington , Seattle , WA 98195 , USA
e-mail: zjliu@uw.edu
L.K. McLoon and F.H. Andrade (eds.), Craniofacial Muscles: A New Framework
for Understanding the Effector Side of Craniofacial Muscle Control,
DOI 10.1007/978-1-4614-4466-4_14, © Springer Science+Business Media New York 2013
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