Computational Analysis of Swallowing Mechanics Underlying Impaired Epiglottic Inversion

Objectives/hypothesis: Determine swallowing mechanics associated with the first and second epiglottic movements, that is, movement to horizontal and full inversion, respectively, to provide a clinical interpretation of impaired epiglottic function.

Study Design: Retrospective cohort study.

Methods: A heterogeneous cohort of patients with swallowing difficulties was identified (n = 92). Two speech-language pathologists reviewed 5-mL thin and 5-mL pudding videofluoroscopic swallow studies per subject, and assigned epiglottic component scores of 0 = complete inversion, 1 = partial inversion, and 2 = no inversion, forming three groups of videos for comparison. Coordinates mapping minimum and maximum excursion of the hyoid, pharynx, larynx, and tongue base during pharyngeal swallowing were recorded using ImageJ software. A canonical variate analysis with post hoc discriminant function analysis of coordinates was performed using MorphoJ software to evaluate mechanical differences between groups. Eigenvectors characterizing swallowing mechanics underlying impaired epiglottic movements were visualized.

Results: Nineteen of 184 video swallows were rejected for poor quality (n = 165). A Goodman-Kruskal index of predictive association showed no correlation between epiglottic component scores and etiologies of dysphagia (λ = .04). A two-way analysis of variance by epiglottic component scores showed no significant interaction effects between sex and age (f = 1.4, P = .25). Discriminant function analysis demonstrated statistically significant mechanical differences between epiglottic component scores: 1 and 2, representing the first epiglottic movement (Mahalanobis distance = 1.13, P = .0007); and 0 and 1, representing the second epiglottic movement (Mahalanobis distance = 0.83, P = .003). Eigenvectors indicate that laryngeal elevation and tongue base retraction underlie both epiglottic movements.

Conclusions: Results suggest that reduced tongue base retraction and laryngeal elevation underlie impaired first and second epiglottic movements. The styloglossus, hyoglossus, and long pharyngeal muscles are implicated as targets for rehabilitation in dysphagic patients with impaired epiglottic inversion.

Level Of Evidence: 2b Laryngoscope, 126:1854-1858, 2016.