Botulinum toxin type A for treating voice tremor

Background: Voice tremor, like spasmodic dysphonia and other tremor disorders, may respond to botulinum toxin type A injections. Objective: To evaluate the safety and efficacy of botulinum toxin type A injections as treatment for voice tremor. Design: A randomized study of 3 doses of botulinum toxin type A with 6 weeks of follow-up. Setting: A single-site tertiary care center. Participants and Methods: Thirteen subjects (11 women, 2 men; mean age, 73 years) with voice tremor and no spasmodic dysphonia or head, mouth, jaw, or facial tremor were entered into this study. Patients received 1.25 U (n = 5), 2.5 U (n = 5), or 3.75 U (n = 3) of botulinum toxin type A in each vocal cord. All patients were evaluated at baseline and postinjection at weeks 2, 4, and 6. Main Outcome Measures: The primary outcome measure was the patient tremor rating scale, with secondary measures including patient-rated functional disability, response rating scale, independent randomized tremor ratings, and acoustical measures. Results: All patients at all dose levels noted an effect from the injection. The mean time to onset of effect was 2.3 days (range, 1-7 days). For all patients combined, mean tremor severity scale scores (rated by patients on a 5-point scale) improved 1.4 points at week 2,1.6 points at week 4, and 1.7 points at week 6. Measures of functional disability, measures of the effect of injection, independent ratings of videotaped speech, and acoustic measures of tremor also showed improvement. The main adverse effects at all doses were breathiness and dysphagia. Conclusion: Voice tremor improves following injections of botulinum toxin type A.