The impact of synkinesis on voice restoration in idiopathic vocal fold paralysis patients with different disease courses

To assess the impact of synkinesis on voice restoration in idiopathic vocal fold paralysis (IVFP) patients with different disease courses, a cohort of 130 IVFP patients (comprising 71 males and 59 females; 78 cases with left-sided paralysis and 52 cases with right-sided paralysis) was categorized into two groups according to their disease courses (group 1: < 3 months, group 2: 3-6 months). Each group was subsequently subdivided based on the presence or absence of synkinesis according to the laryngeal electromyography (LEMG) results, as evaluated by two physicians who are board-certified in electrodiagnostic medicine. The specific information of the IVFP patients were blinded to both the two evaluators, and the LEMG results evaluated by them were also blinded to each other. Then the analysis revealed that the individuals in the group 2 (45 cases) demonstrated significantly greater maximum phonation time (MPT) and maximum sound pressure level (SPL_max) compared to those in the group 1 (85 cases) (MPT, 8.34 ± 7.35 s vs 5.55 ± 4.29 s, t = - 2.008, P = 0.049; SPL_max, 94.53 ± 14.72 dB vs 87.88 ± 9.82 dB, t = - 2.101, P = 0.040). Furthermore, the group 2 exhibited a higher prevalence of synkinesis than that in the group 1 (35.56% vs 14.12%, P = 0.005). Notably, within the group 2, the patients with synkinesis had significantly lower MPT values (4.10 ± 1.79 s vs 8.20 ± 5.84 s, t = - 2.569, P = 0.019), as well as higher amplitudes of paralytic recurrent laryngeal nerve (RLN) compared to those without synkinesis (7.71 ± 8.35 mV vs 1.70 ± 1.31 mV, t = - 2.493, P = 0.023). Conversely, in the group 1, no significant differences were observed in the comparison of MPT values or amplitudes of RLN between the individuals with synkinesis and those without synkinesis (MPT, 6.01 ± 5.83 s vs 5.46 ± 4.01 s, t = - 0.334, P = 0.740; the amplitudes of RLN, 2.62 ± 2.35 mV vs 2.74 ± 3.14 mV, t = 0.104, P = 0.917), which were analyzed by Bonferroni (a multiple-comparison correction method, m = 2, ɑ = 0.025), and the P value less than 0.025 represents a significant difference in such condition. These findings suggest that synkinesis adversely affects voice restoration in the IVFP patients with a disease course of 3-6 months, indicating that the IVFP patients should accept diagnosis and treatment within 3 months after onset to improve their voice qualities, avoiding the adverse effects caused by synkinesis.