Defining differences in patient characteristics between spasmodic dysphonia and laryngeal tremor.

OBJECTIVE: To compare presenting characteristics of patients with adductor spasmodic dysphonia (ADSD), ADSD with laryngeal tremor (ADSD + LT), and laryngeal tremor without ADSD (LT). DESIGN: Cross-sectional analysis. METHODS: Patients treated for laryngeal movement disorders (1990-2016) were included. Analysis of variance and chi square tests measured differences in patient characteristics across the three disease groups. Using ADSD as the referent, multivariable logistic regression models were used to determine whether potential risk factors including patient demographics, family history, presence of potential inciting events prior to disease onset, and coprevalent movement disorders were associated with ADSD + LT or LT. RESULTS: In all, 652 patients with ADSD (n = 377), ADSD + LT (n = 98), and LT (n = 177) were included. ADSD patients were significantly younger than those with ADSD + LT and LT (52.5 ± 13.4, 63.9 ± 11.3, and 69.3 ± 10.5 years, respectively; P < 0.001). Coprevalent movement disorders were more common in ADSD + LT (38.7%) and LT (57.1%) groups than in the ADSD group (11.5%; P < 0.001). Compared to ADSD, patients with ADSD + LT and LT were more likely to develop an additional movement disorder during follow-up. In multivariable analyses, increasing age, female gender, and having a movement disorder at presentation were associated with significantly greater odds of having ADSD + LT or LT when compared to ADSD. CONCLUSION: ADSD + LT patients demonstrate intermediate gender composition and age distributions between those with ADSD and LT. These findings suggest that ADSD + LT may be a distinct phenotype in the spectrum of laryngeal movement disorders. LEVEL OF EVIDENCE: 4 Laryngoscope, 129:170-176, 2019.

Outcomes of Onabotulinum Toxin A Treatment for Adductor Spasmodic Dysphonia and Laryngeal Tremor.

Importance: The relative outcomes of onabotulinum toxin A injections for treatment of adductor spasmodic dysphonia (ADSD), ADSD with lateral laryngeal tremor (ADSD+LT), and lateral LT without ADSD are unclear. Objective: To compare the outcomes of onabotulinum toxin A treatment on ADSD, ADSD+LT, and lateral LT without ADSD. Design, Setting, and Participants: A retrospective cohort study was conducted from January 1, 1990, to September 30, 2016, at a tertiary referral voice center. Participants included 817 patients treated with onabotulinum toxin A injections for diagnosis of ADSD, ADSD+LT, and lateral LT without ADSD. Exposure: Injection of onabotulinum toxin A into the thyroarytenoid/lateral cricoarytenoid muscle complex. Main Outcomes and Measures: Data from patient diaries were used to evaluate patient-perceived effectiveness of onabotulinum toxin A injection. Primary outcomes were (1) patient-reported good voice days (voice breaks or tremor minimized to patient satisfaction) and (2) percentage of injections in which maximal voice quality was reached (significant or complete reduction in vocal tremor or spasms during a treatment cycle). Multivariate analysis of variance tests compared differences in outcomes between groups. Subanalysis was performed to compare outcomes in patients with isolated LT with those who had mixed tremor (lateral with concomitant anterior-posterior and/or vertical components). Results: Of 817 patients treated with onabotulinum toxin A injections for laryngeal movement disorders, 548 patients (12 771 injection sessions) met inclusion criteria (ADSD: n = 328, ADSD+LT: n = 77, lateral LT without ADSD: n = 143). Of these, 408 (80.8%) were women; mean (SD) age was 57.2 (13.7) years. Among patients with tremor, those with isolated LT had better outcomes than those with mixed tremor. In adjusted analysis, good voice days in patients with ADSD, ADSD+LT, and lateral LT without ADSD were 81.1, 75.4, and 71.3 days, respectively (partial η2, 0.05; 95% CI, 0.01-0.09). The percentage of maximally beneficial injections was 88.1% for ADSD, 83.4% for ADSD+LT, and 70.4% for LT without ADSD (partial η2, 0.12; 95% CI, 0.06-0.17). Conclusions and Relevance: Onabotulinum toxin A injections into the thyroarytenoid/lateral cricoarytenoid muscle complex are an effective treatment for ADSD, ADSD+LT, and LT without ADSD; however, the greatest effectiveness was observed among patients with ADSD. Defining tremor directionality may help to prognosticate the effectiveness of onabotulinum toxin A injection among patients presenting with tremor components.