1. In this randomized controlled trial, botulinum toxin was more effective than placebo in treating isolated or essential head tremor at 18 weeks follow-up.
2. Adverse events occurred more frequently in the botulinum toxin group including head and neck pain, posterior cervical weakness, and dysphagia.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Essential tremor is the most common etiology of tremor and one of the most common movement disorders in adults. Botulinum toxin type A, which hinders pre-synaptic release of acetylcholine rendering decreased aberrant muscle movement, has shown varying degrees of efficacy in the treatment of essential hand tremor. However, previous randomized trials investigating its use for the treatment of head tremor are sparse and limited. This study aimed to explore the efficacy and safety of botulinum toxin in patients with isolated or essential head tremor. Overall, it demonstrated that the injection of botulinum toxin was more effective than placebo in reducing the severity of head tremor at 18 weeks but not at 24 weeks using the Clinical Global Impression of Change (CGI) scale. Adverse events occurred more frequently in patients receiving botulinum toxin including head and neck pain, posterior cervical weakness, and dysphagia. The trial did not control for external psychological factors which may have impacted the CGI ratings and was limited by decreased racial diversity in terms of its patient population.
Click to read the study in NEJM
In-Depth [randomized controlled trial]: This randomized, placebo-controlled trial aimed to investigate the efficacy and safety of botulinum toxin in the treatment of isolated or essential head tremor. Patients with isolated or essential head tremor with a rating of two or more on the Fahn-Tolosa-Marin Tremor Rating Scale were selected for the study. Those with dystonic head tremor or head tremor as part of a cerebellar syndrome were excluded. Patients were randomly assigned in a 1:1 ratio to receive botulinum toxin or placebo and injections were administered on day 0 and week 12 into each splenius capitis muscle under electromyographic guidance. The primary outcome was defined as an improvement by at least two points on the CGI scale at 18 weeks (six weeks after the second injection). Following the study, the primary outcome occurred in 19 of 62 patients (31%) in the botulinum toxin group versus 5 of 55 patients (9%) in the placebo group (relative risk, 3.37; 95% Confidence Interval [CI], 1.35 to 8.42; p=0.009). CGI score improvement by at least two points occurred in 44% of patients in the botulinum toxin group and 7% of patients in the placebo group at week 6 (relative risk, 5.99; 95% CI, 2.24 to 16.04); 29% and 9%, respectively, at week 12 (relative risk, 3.19; 95% CI, 1.27 to 8.03); and 23% and 13% at week 24 (relative risk, 1.77; 95% CI, 0.77 to 4.07), suggesting that the effects of the botulinum injections had likely waned by week 24, as expected. Adverse events were generally mild and occurred in 47% of patients in the botulinum toxin group versus 16% of patients in the placebo group including headache or neck pain, posterior cervical weakness, dysphagia, and pain at the injection sites. In summary, this study showed that botulinum toxin was effective in reducing the severity of isolated or essential head tremor at 18 weeks but not at 24 weeks.
Image: PD
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