Craniofacial Muscles

14 Tongue Muscle Response to Neuromuscular Diseases and Speci fi c Pathologies
251
Fig. 14.8 Schema of the
tongue surgery. Dark area
indicate the removed tongue
mass. ( a ) Dorsal view; ( b , c ):
anterior and posterior coronal
views. CP circumvallate
papillae. Empty dots indicate
the implanted ultrasonic
crystals
(Kier et al . 1989 ; Kier and Smith 1985 ; Bailey and Fregosi 2004 ) , this muscular
mass reduction is expected to alter the tongue motor function signi fi cantly.
Furthermore, some types of post-injury adaptations could be less appropriate for the
functional demands and even become a dysfunction rather than a positive adaptation,
which may lead to maladaptive motor function over time. By using digital
ultrasonic techniques in the same pig model receiving ~18–20% tongue volume
reduction through surgery (Fig. 14.8 ), our group examined these immediate and
longitudinal effects on tongue kinematics (Shcherbatyy et al . 2008a, b ) .
As to an immediate effect after surgical tongue volume reduction, the basic feature
of the tongue kinematics still remains but the regularity and amplitude of the
dimensional changes during chewing are diminished. While the major dimensional
losses of the tongue by the surgery are the anterior (66%) and posterior dorsal widths
(16%), the major decreases in tongue kinematics during chewing are found in the
length (~31%) and the anterior width (~44%). Conversely, changes in the posterior
widths and thickness are signi fi cantly enhanced by ~10–20% after the surgery, indicating
an immediate compensatory effect. Anatomically, the orthogonally oriented
intrinsic muscle fi bers are the major components of the anterior 2/3 of the tongue,
and extrinsic fi bers are mainly inserted laterally (hyoglossus and styloglossus) and
compose a large central region of the tongue base (genioglossus) (Napadow et al .
1999b ; Sicher 1960 ; Gray 2000 ; Peter 1995 ; Odeh et al . 1995 ) . Therefore, intrinsic
tongue musculature is the major component of the tongue tissue removed by the
surgery (Fig. 14.8 ), although muscle fi bers from extrinsic tongue musculature,