Therapeutic effects of botulinum toxin A at different dilutions in hemifacial spasm patients: a multicenter, randomized, double⁃blind and self-crossover controlled trial

Abstract

Background At present, the concentration of botulinum toxin A (BTX-A) injection in the treatment of hemifacial spasm (HFS) is different in various reports, and the efficacy and adverse drug reactions incidence are varied. Few randomized controlled trials are related to this subject. The aim of this study is to evaluate the efficacy and safety of two concentrations of BTX-A in the treatment for HFS. Methods Eighty patients with HFS from 4 research centers were included in this multicenter randomized double-blind self-crossover controlled trial. Patients were randomly assigned to high-density group (given injection of 50 U/ml BTX-A) and low-density group (given injection of 25 U/ml BTX-A). They were subjected to a cross-over repetitive injection of BTX-A of different concentrations after recurrence. Therapeutic efficacy and adverse effect were compared between two groups. Results Both high-density and low-density BTX-A were effective. Cohen spasms strength grade scores before and after the treatment in high-density group were 2.89 ± 0.53 vs 0.24 ± 0.46, while in low-density group was 2.89 ± 0.55 vs 0.24 ± 0.46 (P = 0.000, for all). The therapeutic efficacy was not different between the two groups in different concentration order (P > 0.05). But the lasting time of therapeutic efficacy was much longer in high-density group than that of low-density group (4.18 ± 0.49 months vs 3.26 ± 0.44 months, P = 0.000). Within three months, there was no significant difference between the two groups in the decrease of Cohen spasms strength grade scores (2.65 ± 0.62 vs 2.66 ± 0.66, P = 0.863). Four months after treatment, it was different between the two groups in the decrease of Cohen spasms strength grade scores (2.60 ± 0.65 vs 1.70 ± 0.72, P = 0.000). Five months after treatment, it was also different between the two groups in the decrease of Cohen spasms strength grade scores (1.56 ± 0.94 vs 0.25 ± 0.49, P = 0.000). After six months of treatment, there was no significant difference between the two groups in the decrease of Cohen spasms strength grade scores (0.08 ± 0.27 vs 0.05 ± 0.22, P = 0.515). There were no allergic reactions and systemic adverse effects. The adverse effect of the high-density group was more than that of the low-density group (26.56% vs 7.81%, P = 0.000). All of the adverse effects were mild and temporary, and no special intervention was involved. The duration of adverse effect was longer in high-density group [(5.71 ± 1.61) weeks vs (3.16 ± 0.62) weeks, P = 0.000]. Conclusion This study showed that injection of BTX⁃A with different concentrations in HFS patients was safe and effective. With high-density, the repeated injection interval time was longer; the pain of patients was reduced; the cost of treatment was low; but adverse drug reactions were relatively evident and lasted for a longer period of time.