Mandibular Movement During Swallowing in Patients with Tinnitus: An Instrumented Case-Control Study

Objectives: This study aimed to determine whether adults with tinnitus exhibit altered phase-specific mandibular kinematics during saliva swallowing and increased prevalence of tongue thrust and Eustachian-tube insufficiency versus tinnitus-free controls. Methods: This was a cross-sectional case-control study including adults with tinnitus and controls. Standardized computerized kinesiography recorded three spontaneous saliva swallows per participant. Primary outcomes were opening/closing time (OCT) and post-closure stabilization time (STT); total swallowing time (SWT) was secondary. Tongue thrust (TT) and tubal insufficiency (TI) were assessed clinically. Distributional assumptions were checked with Shapiro-Wilk; between-group comparisons used two-sided Mann-Whitney U tests and Fisher's exact tests (TT, TI). Effect sizes included rank-biserial correlation (r), Hodges-Lehmann median difference (Δ), and odds ratios (ORs) with 95% confidence intervals. Co-occurrence of TT and TI and their relationships with OCT, STT, and SWT were evaluated within strata (cases vs. controls) using Fisher's exact test, φ, Mann-Whitney U tests, and Spearman's ρ. Given the marked imbalance in age and sex between groups, unadjusted non-parametric comparisons were complemented by multivariable models with adjustment for age and sex. An omnibus non-parametric combination test summarized case-control differences across OCT, STT, and SWT. Results: Statistical analysis was performed on 77 cases with tinnitus and 78 controls. Tinnitus cases showed longer OCT (1.75 ± 0.92 vs. 1.12 ± 0.62 s; p < 0.001; r ≈ 0.40; Δ ≈ +0.60 s) and STT (1.44 ± 0.88 vs. 0.84 ± 0.62 s; p < 0.001; r ≈ 0.42; Δ ≈ +0.60 s), while SWT differed modestly and was not significant (2.75 ± 0.69 vs. 2.57 ± 0.65 s; p = 0.115; r ≈ 0.15; Δ ≈ +0.18 s). TT was more frequent in cases (18.2%) than controls (6.4%; OR = 3.05, 95% CI 1.08-8.61; p = 0.029), whereas TI occurred in 16.9% of cases and 0% of controls (corrected OR = 32.85, 95% CI 1.92-563.49; p < 0.001). Within tinnitus cases, TT and TI did not show meaningful co-occurrence (φ ≈ -0.03; p = 1.00). TT+ tinnitus patients exhibited markedly prolonged OCT compared with TT- (median 2.22 vs. 1.45 s; Δ ≈ +0.88 s; r ≈ 0.60; p < 0.001), whereas STT and SWT were minimally affected; TI was not materially associated with any swallowing-time parameter. Spearman analyses confirmed a moderate monotonic association between TT and OCT in tinnitus cases (ρ ≈ 0.40; p < 0.001), with all other correlations small and clinically negligible. Age- and sex-adjusted analyses confirmed longer OCT and STT in tinnitus cases, whereas SWT remained non-significant; TT and TI also remained more frequent in cases after adjustment. The omnibus test indicated a clear global separation between groups across OCT, STT, and SWT (permutation p < 0.001). Conclusions: Adults with tinnitus exhibit a distinct swallowing signature characterized by prolonged OCT and STT, together with higher prevalence of TT and TI. TT in tinnitus patients is specifically linked to a pronounced prolongation of OCT, while STT and SWT remain largely unchanged, and TI shows no relevant impact on kinematic indices.