Long-Lasting Effect after Single Hyaluronate Injection for Unilateral Vocal Fold Paralysis: Does Concentration Matter?

Background: Early injection laryngoplasty (EIL) using hyaluronic acid (HA) is an effective treatment for glottic insufficiency in patients with acute unilateral vocal fold paralysis (UVFP). Most patients benefit by showing improvement in voice and quality of life and implied reduced need for permanent laryngoplasty. However, injected HA might resolve within a short period, so its long-term outcomes and the need for secondary procedures need to be clarified. Methods: Patients who underwent EIL with HA for acute UVFP from January 2015 to December 2018 were included. The factors that may associate with the prognosis including voice performance and laryngeal configuration at presentation, the cause of UVFP, and the type of HA for EIL were analyzed. Results: Ninety-four patients were included for analysis, with a mean follow-up period of 25.1 months (95% CI: 22.8–27.4 months). After primary HA injection, 22 patients (23.4%) underwent secondary procedures (rate: 13.1% per person-year), and most (63.6%) of the events occurred after one year from the first injection. The rate of secondary procedures within the first 12 months was 9.0% (14.1% and 4.3% for low-concentrated HA (LHA) and high-concentrated HA (HHA), respectively). The incidence of the secondary procedures was higher in the LHA group (18.2%) (p = 0.026) than in the HHA group (7.5%). Conclusions: The rate of secondary procedures was lower than the prediction based on the resorption time of HA, a finding that could be partly accounted for by both natural nerve recovery and a long-lasting effect of EIL. EIL with HHA had a lower rate of re-treatment than that with LHA, suggesting a better clinical utility for acute UVFP.