Determination of the Relationships Between intra- and Extraoral Tongue Hardness, Thickness, and Pressure Using Ultrasonic Elastography

Involved with various bodily functions, including ingestion and swallowing, the tongue is an important organ. We measured resting tongue hardness using real-time tissue elastography (RTE) to establish a simple tongue evaluation for patients who may have limited capacities to follow commands. Relationships between tongue hardness, thickness, and pressure were investigated, using both intra- and extraoral probes. Assessments were performed for a total of 27 healthy adults (11 male, 16 female, average age 26.4 ± 1.8 years). Measurements of tongue hardness and thickness were made using strain ratios (SR), and averaged across nine images. Maximum tongue pressure was determined using a tongue pressure device. A negative correlation was observed between intraorally measured tongue hardness and maximum tongue pressure ( r = −0.76, p < 0.01). A positive correlation between extraorally measured tongue thickness and maximum tongue pressure was observed ( r = 0.59, p < 0.01). Additionally, significant differences were observed between males and females with regards to intraorally measured tongue hardness ( p = 0.02), maximum tongue pressure ( p = 0.02), and extraorally measured tongue thickness ( p < 0.01). The results of this study demonstrated the clinical applicability of RTE-based tongue hardness measurements, and suggest the feasibility of predicting tongue strength based on extraoral tongue thickness measurements.