Long-term efficacy, safety, and side effect profile of botulinum toxin in dystonia: A 20-year follow-up

Most long-term studies of the efficacy and safety profile of botulinum toxin (BoNT) in the treatment of dystonia are limited by lack of objective assessments, relatively small sample size, or short follow-up periods. We present one of the longest follow-up studies of BoNT treatment. This is a retrospective, longitudinal study that analyzes data on 89 patients treated with BoNT for dystonia at our Movement Disorders Clinic for up to 26 years (mean follow-up period of 18.5 years). The mean ages at the time of the first and last injections were 49 and 68 years old, respectively. The most common diagnoses were cervical dystonia (N = 51), blepharospasm (N = 34), and oromandibular dystonia (N = 26). The total number of onabotulinumtoxinA units received during the first injection was 140.3 as compared to 224.5 at the last injection (p < 0.0001). The global response effect was 3.18 after the first injection session and 3.57 after the last injection (p < 0.0001). The duration of response after the initial injection session and at the last injection was 16.33 weeks versus 19.42 weeks (p 0.0037), respectively. Adverse events, typically related to injection site, were reported in 19% of the visits. This series of dystonia patients with the longest reported treatment with BoNT provide evidence that in selected patients repeated chemodenervation is associated with sustained symptomatic benefit, decreased latency effect, and prolonged duration of therapeutic response. Despite the higher requirement of mean units per visit over time, only 19% of all treatment cycles are associated with adverse, but tolerable, side effects.