Asymmetry of protracted tongue: can it replace the Wada test?
Some asymmetry of body parts (thumbs, cubital crease levels, popliteal crease levels, toes, breasts, gonads and facial structures) is commonly observed. And there is also neurobehavioral asymmetry such as handedness and language lateralization. Since right-handedness is closely associated with left-hemisphere dominance for language, it is known that handedness can be linked with language lateralization. But because cultural and social pressures influence handedness, handedness is able to shift. If so, handedness can't always reflect language lateralization. We can also detect another asymmetry in protracted tongue which is thought to be inherently unchangeable. Some midline deviation of fully protracted tongue is observed in every person. Protractor of the tongue, genioglossus muscle, is solely innervated by contralateral corticobulbar fibers from the inferior part of precentral gyrus. This part is closely related with language expressive area. Therefore, the midline deviation of tongue observed when it is fully protracted could be more related with language lateralization than handedness changeable to external pressures.
Han
Dong-Gyun
DG
Department of Neurology, DaeJeon HanKook Hospital, ChungCheongNam-Do, South Korea. tashihan@empal.com
Lee
Youn-Hee
YH
D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007802:Language; D014059:Tongue / Q000502:physiology*