2020 Volume 24 Issue 1 Pages 47-55
Purpose: This study aimed to clarify the features of pre-swallow bolus transport in persons with severe motor and intellectual disabilities (SMID) by comparing movement of the jaw, tongue and hyoid bone in persons with SMID and healthy adults.
Subjects and Methods: Seven healthy adults and 14 persons with SMID underwent videofluoroscopic examination of swallowing while swallowing 3 to 5 mL of paste food. The range of movement of the jaw, tongue and hyoid bone during pre-swallow bolus transport were measured in the coordinate plane with the second and fourth cervical vertebra as the reference line. The onset and termination of jaw and hyoid movement in the vertical direction, and tongue movement in the centripetal and centrifugal directions along seven equiangular directions emanating from the center of the tongue were timed using frame-byframe analysis. Persons with SMID were classified in two groups: the normal-transport (NT) group that needed the same number of transport cycles as healthy adults, and the disordered-transport (DT) group that needed more transport cycles than healthy adults. The results were compared using the Kruskal-Wallis test with Dunn’s multiple comparison test.
Results and Discussion: Each group included 7 subjects. Multiple comparison showed the duration of the intercuspal phase was significantly shorter in the DT group than in healthy adults (p ＝ 0.015) and the NT group (p＝0.002), and the duration of contact of the anterior area of the tongue and hard palate was significantly shorter in the DT group than in healthy adults (p＝0.023) and the NT group (p＝0.001). Furthermore, the bolus transit time was significantly longer in the DT group than in healthy adults (p＝0.001) and the NT group (p＝0.001). The timing of termination of the intercuspal phase of the DT group was immediately after the onset of hyoid upward movement which also represents the appearance of tongue pressure. The results suggest that instability of the jaw shortens the duration of the intercuspal phase and results in shortening the duration of contact of the anterior area of the tongue and hard palate, which has an important role as an anchor when the tongue propels the bolus posteriorly.
Conclusion: In persons with SMID that needed more transport cycles than healthy adults, the duration of the intercuspal phase and the contact of the anterior area of the tongue and hard palate were significantly shorter, and the bolus transit time was significantly longer than in healthy adults and persons with SMID that needed the same number of transport cycles as healthy adults.
