Considerations for initial dosing of botulinum toxin in treatment of adductor spasmodic dysphonia

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 χ(2) 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.