Additional injection laryngoplasty as a salvage treatment for unilateral vocal fold paralysis.

Objectives: Injection laryngoplasty (IL) has been widely used as an initial treatment option for unilateral vocal fold paralysis (UVFP). An additional (second) IL is considered a salvage treatment for unsatisfactory outcomes of initial IL resulting from inadequate injection or early resorption of the injection material. This study aims to evaluate the efficacy of additional IL, distinguishing between "salvage" (within 4 months) and "repeated" injections (beyond 4 months), and to analyze prognostic factors for successful outcomes.

Methods: This retrospective study involved patients who received IL at Asan Medical Center from January 2014 to December 2020. Voice parameters were collected after each procedure, and those who conducted the statistical analysis were blinded to the study subjects. Among the 65 patients who underwent additional IL, 51 patients were enrolled in this study. Postinjection grade, roughness, breathiness, asthenia, strain (GRBAS) scales were used to determine satisfactory treatment outcomes. Success of the additional IL was defined as a postinjection grade of dysphonia score of 0 or 1, with a reduction in grade compared with the preinjection grade.

Results: The mean age of the patients was 61.6 years. Out of a total of 51 patients, 37 were men participating in the study. The odds ratio represents the likelihood of success in the second IL. Improved voice outcome after the additional IL was maintained in 23 (45%) patients. Compared with the failure group, the success group had a longer injection time interval between the initial and additional injection (9.1 vs. 7.4 months, respectively, p = 0.010). The success group had a higher proportion of patients with injection intervals >6 months (73.9% vs. 42.9%, p = 0.026). Logistic regression analysis revealed an injection interval >6 months had an odds ratio of 0.265 (confidence interval: 0.080-0.874, p = 0.029).

Conclusions: Additional injections would benefit the patients whose voice outcomes are maintained for a longer period (>6 months) after the first injection.