Measuring Hyoid Excursion Across the Life Span: Anatomical Scaling to Control for Variation.

Purpose A method for controlling for sex-based differences in measures of hyoid movement using an internal anatomical scalar has been validated in young healthy individuals. Known anatomical changes with aging necessitate validation of this methodology in a mixed-age sample. The primary aim of this study was to validate a method for controlling for sex-based differences in measures of hyoid movement across the life span. Measurement error as a potential source of variability was addressed to inform best practice recommendations. Method Two distinct data sets previously collected using identical protocols were combined for this study to achieve a data set of young (< 40 years) and older (> 65 years) healthy adults. Data included videofluoroscopic swallow studies with three swallow trials each of 5 and 20 ml thin liquid barium. Previously reported methodology was replicated to validate the use of an anatomical scalar for measuring hyoid excursion in this sample. Hyoid movement was measured using 2 methods (rest-to-peak displacement and peak only) in 3 planes of movement (anterior, superior, and hypotenuse), was expressed in millimeters and individually scaled units relative to C4, and normalized using the C2-C4 vertebral distance. Mixed-model repeated-measures analyses of variance were run with each of the 6 hyoid measures as the dependent variable (in both millimeters and C2-C4 units), within-subject factors of sex and bolus volume, and a between-subjects factor of age group. We predicted that the C2-C4 scalar would adequately control for sex-based differences across age groups. Results Significant differences in absolute hyoid movements (millimeters) were observed by sex, bolus volume, and age group. When measured in %C2-C4 units, all differences between males and females were neutralized. Significant differences between 5- and 20-ml boluses were found for all peak position measures. Significant differences between young and older individuals were found for all peak position measures. Conclusion Expressing hyoid excursion as a percentage of the C2-C4 distance appears valid for use across the life span. Peak position is preferable over displacement measures for quantifying hyoid excursion for research and clinical purposes.