Study supports use of botulinum toxin for head tremor

Key takeaways:

• Botulinum toxin has often been used to treat head tremor despite limited evidence of its use.
• The current study confirms the safety and effectiveness of botulinum toxin for this condition, a researcher said.

Injections of botulinum toxin were associated with greater improvements in isolated and essential head tremor at 18 weeks compared with placebo, according to data from a randomized trial published in The New England Journal of Medicine.

“Isolated or essential head tremor is a very common movement disorder for which there was no clearly demonstrated treatment as of yet,” Ana Marques, MD, PhD, a neurologist at Centre Hospitalier Universitaire de Clermont-Ferrand in France, told Healio. “Our findings confirm that botulinum toxin injections in splenius capitis muscles is an effective and safe treatment for isolated and essential head tremor, and this will impact the therapeutic attitude of clinicians who can now propose more confidently this treatment to their patients.”

Marques and colleagues conducted a multicenter, double-blind, randomized trial, in which 117 adults with essential or isolated head tremor were assigned in a 1:1 ratio to receive injections of botulinum toxin type A or placebo. The treatments were administered under electromyographic guidance into splenius capitis muscles on the day of randomization and again during week 12. The primary outcome of the study was a 2-point or more improvement in the Clinical Global Impression of Change (CGI) scale at week 18. According to the researchers, CGI scale scores range from 3, indicating “very much improved,” to 3, indicating “very much worse.”

In the botulinum toxin group, 62 patients received the first injection and 50 received the second injection. For the first injection, all patients received 75 IU of botulinum toxin. For the second injection, 27 patients received another 75 IU and 23 patients received a higher dose of 100 IU.

In the placebo group, 55 patients received the first injection and 53 received the second injection.

Overall, 31% of patients in the botulinum toxin group met the primary outcome vs. 9% of those in the placebo group (RR = 3.37; 95% CI, 1.35-8.42). However, the association diminished by week 24, “when the effects of injection might be expected to wane,” Marques and colleagues wrote.

“Interestingly, our findings suggest that increasing the dose above 75 IU in each splenius does not seem to improve efficacy, and this provides a framework to guide clinical practice,” Marques said.

Approximately half of patients in the botulinum toxin group experienced an adverse event, including head and neck pain, posterior cervical weakness and dysphagia. In comparison, 16% of patients in the placebo group experienced an adverse event.

Most adverse events in the botulinum toxin group were mild, according to the researchers. However, two patients experienced severe events that led to hospitalization, including one patient who developed severe dysphagia and another who “described a general feeling of weakness, difficulty in finding words, and dizziness,” the researchers wrote.

“The next steps of our research will be to identify the clinical characteristics of patients that were insufficiently improved with botulinum toxin injections in splenius capitis in order to propose a treatment option for this subgroup as well,” Marques said.