Safety and efficacy of botulinum toxin in Human T-Lymphotropic Virus-1-Associated Myelopathy/Tropical Spastic Paraparesis: A randomized clinical trial

To evaluate the efficacy and safety of botulinum toxin type A (BTA) in the treatment of people with Human T-lymphotropic virus 1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). A randomized, double-blind, placebo-controlled clinical trial, composed of individuals over 18 years old, with HAM/TSP, who had not used BTA to treat spasticity. The primary outcomes were spasticity (Modified Ashworth Scale) and safety (adverse events), and the secondary outcomes were pain (Visual Analogue Scale and Michigan Body Map), functional independence (Functional Independence Measure), functioning level (World Health Organization Disability Assessment Schedule), and quality of life (Short Form Health Survey), assessed right before and 3 months after the intervention. Participants were randomized into two groups: BTA and placebo control (saline). 40 participants (20 in each group) were analyzed. The assessor, neurologists, and participants were blind to group allocation. The average BTA dose per participant was 317U (± 189U) for the hip adductors, hamstrings, triceps surae, and tibialis posterior. There was a small significant difference between groups in favor of the BTA group in general health status (d = 0,33; p = 0,040) related to quality of life. There were no significant differences in spasticity, risk of adverse effects (RR = 1,09; p = 0,749), and in the other outcomes. BTA is safe for people with HAM/TSP. However, the first dose of BTA was unable to improve spasticity, pain, functioning level, and quality of life in people with HAM/TSP 3 months after injection. New application strategies of BTA need to be investigated in people with HAM/TSP.