Oropharyngeal structural dynamics during mastication and swallowing associated with tongue base volumetric changes

To analyze oropharyngeal dynamics during mastication and swallowing in a minipig model with volumetric enlargement and reduction of the tongue base.

Six same-sex sibling pairs of 8-9-months-old Yucatan minipigs were analyzed. Of each pair one minipig was fed with high-calorie pellets to reach obesity (BMI > 51) for volumetric enlargement of the tongue base while the other was normal-weighted (BMI < 37) receiving surgical coblation for volumetric reduction. At baseline and week-5 post-surgery x-ray video fluoroscopy was recorded during unrestrained feeding with barium-mixed diet at 30-frames-per-second for 5-10 min. Chewing cycles and swallowing episodes were traced using video-analysis software calibrated by implanted 2 mm ultrasonic-crystals. Tracing points were located at the soft palate (posterior-1/3), epiglottis (anterior-1/3), tongue base (midpoint), and pharyngeal wall (posterior-1/3). The coordinate was set at the alveolar ridge of the upper molar for X-axis and perpendicularly over the distal surface of the last molar for Y-axis. Directional movements over the coordinate, distance changes of each structure (structural), and between structures (inter-structural) were measured.

The structural dynamics during early chewing were significantly higher at baseline compared to week-5 in the volume-enlarged group (p < 0.05). At baseline, movements of the pharyngeal wall in the normal-weighted minipigs were larger than those of obese ones during jaw opening (p < 0.05). At week-5, both groups showed different inter-structural dynamics (epiglottis-pharyngeal wall) during swallowing, significantly wider in the volume-reduced compared to the volume-enlarged groups (p < 0.05).

Volumetric alterations of the tongue base substantially modify the pharyngeal dynamics during chewing and swallowing evidenced by decreasing structural and inter-structural moving distances overtime for both groups.