Internal Kinematics of the Volume-reduced Tongue: A Longitudinal Study

Objective: To examine tongue functional deformation over time after its volume reduction during mastication.

Methods: Ten Yucatan-minipigs (12-week-old, 5 pairs of littermate) were used. Six-ultrasonic-crystals with a “skin-button” for the longitudinal recording were implanted. These crystals were located in tongue body forming a wedge-shaped configuration which allows recording distance changes in various dimensions of the tongue. The volume reduction surgery was performed within the crystal-circumscribed region 10-days after the implantation. Each pair received the surgery at the same day, one with actual tissue removal to reduce tongue volume (reduction) and the other with similar incisions only (sham). Recordings were carried out 1-week before (baseline), and 1(P1) and 4(P4) weeks after the surgery during natural feeding.

Results: Baseline recordings indicated there was no impairment on tongue functional deformation by the implantation. P1 and P4 recordings revealed that feeding behaviors and tongue functional deformations were unchanged over time by sham surgery. However, significant modifications were seen in reduction animals. At P1, more frequent and longer ingestion episodes interposed in masticatory sequence as compared to sham. Changes in body length and anterior-width were significantly decreased (20-35%) while those in posterior-widths and thickness were increased (10-20%) for both chewing and ingestion. Furthermore, the difference of tongue deformational pattern seen in baseline between chewing and ingestion was less distinct, particularly in body length changes. At P4, while the feature of ingestion episode in reduction animals existed, deformational ranges in body length and width partially restored, and were closer to those of other dimensions than the sham.

Conclusions: These results suggest at least in the pig, tongue functional deformation is not subject to the significant changes in rapid growth period, and tongue volume reduction has significant impacts on these functional deformations over time. Therefore, the tongue internal kinematics should be considered as volume-dependent. Funding:NIH grants R01DE15659.