Dosage Changes In Patients With Long-term Botulinum Toxin Use For Laryngeal Dystonia

OBJECTIVE: To investigate the dosage consistency of botulinum toxin injections in patients with long-term treatment for laryngeal dystonia. STUDY DESIGN: Chart review. SUBJECTS AND METHODS: Patients with laryngeal dystonia who had received at least 20 injections to the thyroarytenoid muscle were selected. Change of botulinum toxin dose, patient-reported effective weeks, and intervals between injections were investigated; data from the first five injections were excluded to eliminate initial dose titration. RESULTS: Fifty-five patients with an average follow-up of 12.5 years were identified. Mean dose of botulinum toxin was 2.37 ± 1.6 U at the sixth injection; there was a decrease in mean dose over time, which became statistically significant at the 13th injection with a mean dose of 2.02 ± 1.16 U. Mean duration of good effect and treatment intervals showed no significant change over time. CONCLUSION: Botulinum toxin dose needed for a constant response in treatment of laryngeal dystonia decreases over time, without any accompanying change in effective weeks and intervals.