Dosage Changes in Long-Term Botox Use for Laryngeal Dystonia

Abstract

Objective Botulinum toxin (BTX) injections continue to be the mainstay of treatment for laryngeal dystonia (LD). Many patients are entering their 2nd and 3rd decade of treatment. In this study, the dosage consistency of BTX injections over time was examined in patients with long-term BTX use for LD. Methods Retrospective chart review, 1990–2007. Patients with adductor-type LD who had received at least 20 injections to the thyroarytenoid (TA) muscles were included in the study. The change of total dose and patient-reported effective weeks were investigated; data of the first 5 injections were excluded to eliminate initial dose searching. Results 55 patients (11 male, 44 female, mean age 60.6) with a mean follow-up period of 149.9 ± 43.7 months (range 44 to 211 months) were identified. Total number of treatment episodes was 1825 with a mean of 33.18 ± 10.37 (range 20 to 58) and a mean interval of 19.1 ± 1.3 (range 2 to 118) weeks. The average total dose of BTX for each treatment episode was 2.15 ± 0.37 U (range 0.125 to 10.00 U). The total dose trended downward over time; this trend became statistically significant at 13th injection. The overall mean duration of effect was 15.5 ± 1.1 (range 1 to 58) weeks and did not show a significant change over time. Conclusions The BTX dose needed for a constant response in the treatment of LD decreases over time, raising the concern that neural recovery from repeated BTX is not infinite.