Compared with placebo in adult patients with essential or isolated head tremor, botulinum toxin type A injections into each splenius capitis significantly reduced the severity of symptoms at 18 weeks but not at 24 weeks, a study shows. Botulinum toxin was associated with more adverse events, including head and neck pain, posterior cervical weakness, and dysphagia.
The multicenter, double-blind, randomized trial included 120 patients who received botulinum toxin type A or placebo injections under electromyographic guidance on day 0 and during week 12. The primary outcome was an improvement on the Clinical Global Impression of Change (CGI) scale of at least 2 points at week 6 after the second injection (week 18 after randomization); the CGI scale went from 3 (very much improved) to −3 (very much worse).
“A total of 120 patients were enrolled; 3 patients were excluded during screening, and 117 patients were randomly assigned to receive botulinum toxin (62 patients) or placebo (55 patients) and were included in the intention-to-treat analysis. Twelve patients in the botulinum toxin group and 2 patients in the placebo group did not receive injections during week 12,” the authors write. “The primary outcome — improvement by at least 2 points on the CGI scale at week 18 — was met by 31% of the patients in the botulinum toxin group as compared with 9% of those in the placebo group (relative risk, 3.37; 95% confidence interval, 1.35 to 8.42; P = 0.009). Analyses of secondary outcomes at 6 and 12 weeks but not at 24 weeks were generally supportive of the primary-outcome analysis. Adverse events occurred in approximately half the patients in the botulinum toxin group and included head and neck pain, posterior cervical weakness, and dysphagia.”