Implications of Synkinesis in Unilateral Vocal Fold Paralysis

Abstract

Objectives In patients with unilateral vocal fold paralysis (UVFP), laryngeal electromyography (LEMG) occasionally observes synkinesis in laryngeal muscles, a condition that could impair vocal fold mobility and voice control. This study aims to evaluate the impact of synkinesis on UVFP patients. Study Design A retrospective case-control study. Setting Medical center. Subjects and Methods Patients with UVFP onset >6 months were recruited (N = 104). The outcome measurements included LEMG, quantitative LEMG analysis of thyroarytenoid-lateral cricoarytenoid (TA-LCA) muscle complex, glottal gap measured by videolaryngostroboscopy, voice-related quality of life, and voice acoustic analysis. Results According to the LEMG analysis, 8 patients (8%) had synkinesis, and 96 (92%) did not. In the synkinesis group, TA-LCA turn frequency in the lesioned side was comparable to that in the healthy side ( P = .52). Patients in the synkinesis group had higher TA-LCA turn frequency ( P = .001), higher probability of cricothyroid muscle dysfunction ( P = .04), and better voice-related quality of life ( P = .01) but objective voice outcomes comparable to those in the nonsynkinesis group. Conclusions Patients with synkinesis will have near-complete restoration in TA-LCA turn frequency but still experience voice impairment, a finding that is compatible with the mechanism of aberrant reinnervation. However, patients with synkinesis have better disease-related quality of life than do those without synkinesis.

Main branch of ACN‐to‐RLN for management of laryngospasm due to unilateral vocal cord paralysis

“…5 LEMG performed during phonation and inspiration is the gold standard for diagnosing laryngeal synkinesis. 25 In the present study, preoperative LEMG findings indicated that TA muscle recruitment in all patients was mixed or full interference during a sniff and phonation with exertion, whereas TA recruitment during a sniff was greater than or equivalent to that during phonation with exertion, consistent with the definition of synkinesis provided by Maronian. 18 Preoperative video recordings also showed that the involved vocal cords were in the midline in 53.8% (7 of 13) of cases, found to be concave during quiet breathing, and showed bulging or paradoxical adduction during a sniff in 61.5% (8 of 13) of patients.…”

Laryngeal adductor function following potassium titanyl phosphate laser welding of the recurrent laryngeal nerve

“…With respect to the RLN, adductor and abductor axons are distributed within the nerve . With axonal regrowth, synkinetic reinnervation—misguided adductor and abductor regeneration—can occur . Although the LNW technique in the study promoted higher adductor recovery compared to microsuture repair, LNW may have also increased the rate of synkinetic adductor axon reinnervation to abductor muscles.…”

Compound Motor Action Potential Measures Acute Changes in Laryngeal Innervation

“…33 In this case, reinnervation could increase the CMAP amplitude; however, this may not render improved laryngeal function since a component of the reinnervation is synkinetic. 34 With some forms of iatrogenic injury, the RLN may be stretched during retraction resulting in neurapraxia 5 -typically causing a transient conduction block. 17 Following acute neurapraxia, stimulation of the RLN proximal to the injury site does not generate any CMAP amplitude, making determination between neurapraxia and complete transection difficult.…”

“…33 In this case, reinnervation could increase the CMAP amplitude; however, this may not render improved laryngeal function since a component of the reinnervation is synkinetic. 34…”