Biomechanical basis for lingual muscular deformation during swallowing

Our goal was to quantify intramural mechanics in the tongue through an asse ssment of local strain during the physiological phases of swallowing. Subje cts were imaged with an ultrafast gradient echo magnetic resonance imaging (MRI) pulse sequence after the application of supersaturated magnetized ban ds in the x and y directions. Local strain was defined through deformation of discrete triangular elements defined by these bands and was depicted gra phically either as color-coded two-dimensional strain maps or as three-dime nsional octahedra whose axes correspond to the principal strains for each e lement. During early accommodation, the anterior tongue showed positive str ain (expansive) in the anterior-posterior direction (x), whereas the middle tongue showed negative strain (contractile) in the superior-inferior direc tion (y). During late accommodation, the anterior tongue displayed increase d positive x-direction and y-direction strain, whereas the posterior tongue displayed increased negative y-direction strain. These findings were consi stent with contraction of the anterior-located intrinsic muscles and the po sterior-located genioglossus and hyoglossus muscles. During propulsion, pos terior displacement of the tongue was principally associated with positive strain directed in the x and y directions. These findings were consistent w ith posterior passive stretch in the midline due to contraction of the late rally inserted styloglossus muscle, as well as contraction of the posterior located transversus muscle. We conclude that MRI of Lingual deformation du ring swallowing resolves the synergistic contractions of the intrinsic and extrinsic muscle groups.