Considerations for Initial Dosing of Botulinum Toxin in Treatment of Adductor Spasmodic Dysphonia

Abstract

Objectives To assess the effect on voice improvement and duration of breathiness based on initial dose of onabotulinum toxin A (BTX-A) in the management of adductor spasmodic dysphonia (SD) and to compare voice outcomes for initial bilaterally injected doses of 1.25 units (group A) vs 2.5 units (group B) of BTX-A. Study Design Case series with chart review of patients with adductor SD treated at a tertiary care facility from 1990 to 2011. Setting Academic subspecialty laryngology practice. Methods Demographic data (age and sex), voice rating, duration of voice improvement, and breathiness were evaluated and compared between groups A and B using the Student t test and χ2 analysis. Results Of 478 patients identified, 305 (223 in group A, 82 in group B) patients met inclusion criteria. The average age was 56.2 years in group A and 57.4 years in group B ( P = .5). The female to male ratio was 2.91 for group A vs 3.56 for group B ( P = .61). Good voice outcomes (grade 3 or 4) were reported by 91% of group A patients vs 94% of group B ( P = .75). The average duration of voice improvement was 99.7 days for group A and 108.3 days for group B ( P = .54). The average duration of breathiness was 10.88 days for group A vs 15.42 days for group B ( P = .02). Conclusion Patients injected with 1.25 units bilaterally had a statistically significant shorter duration of breathiness without a statistically significant difference in clinical effectiveness or voice outcome. It is therefore recommended that a relatively low initial BTX-A dose be used with subsequent titration to achieve improved voice outcomes.