Unilateral versus bilateral botulinum toxin injections in adductor spasmodic dysphonia in a large cohort

The primary treatment of adductor spasmodic dysphonia is repeated injections of botulinum toxin type A (Botox) into the thyroarytenoid muscles. Dosing can be performed into either one or both thyroarytenoid muscles. The objective of this study was to evaluate the treatment effect and side effect profile across a large number of injections. This study was performed previously in 2002 on 45 patients.

Individual cohort study.

This is retrospective study of all patients with adductor spasmodic dysphonia with and without tremor treated by the senior laryngologist at George Washington University. In the current study, 272 patients (214 females and 58 males) were included in the current analysis. Duration of effects and side effects (vocal weakness and liquid dysphagia) were recorded into a database for each patient after each injection. These data were analyzed using χ² analysis.

A total of 4,023 injections (2,708 bilateral and 1,315 unilateral) were evaluated in this study. Optimal effect duration (≥3 months) was more commonly seen in the bilaterally injected patients (55%) compared to the unilaterally injected patients (47%) (P = .0001). Optimal side effect duration (≤2 weeks) was better for the unilaterally injected patients (77%) compared to the bilaterally injected patients (73%) (P = .023). Having both optimal effect and side effect in the same injection was more commonly seen in the bilaterally injected patients (36%) compared to the unilaterally injected patients (33%) (P = .0228).

This study shows that bilateral injections of Botox are more effective in producing optimal effect/side effect profiles.

2b Laryngoscope, 130:2659-2662, 2020.