Botulinum Toxin for Essential Tremor and Hands Tremor in the Neurological Diseases: A Meta-Analysis of Randomized Controlled Trials

Tremor is a common movement disorder. Essential tremor (ET) is the most common etiology of tremor, while hands tremor is the most disabling type of tremor. This study aimed to explore the effects of Botulinum toxin (BoNT) on tremor within 6 weeks of treatment, and the muscular weakness adverse effect within 6 weeks specifically in randomized controlled trials. PubMed, Embase, and Cochrane Library databases were searched. Tremor severity and grip strength after BoNT treatment were investigated. BoNT significantly attenuated hand tremor severity in patients with either essential tremor (ET), Parkinson's disease or multiple sclerosis (Standardized mean difference [SMD] = -0.59, 95% confidence interval [CI], -0.95 to -0.24, p = 0.001, I² = 46%). Regarding people with ET, BoNT significantly reduced their tremor severity, including hands tremor and head tremor within 6 weeks of treatment (SMD = -0.58, 95% CI, -0.28 to -0.88, p = 0.002, I² = 0%). Electromyography (EMG) but not anatomical guidance BoNT injection provided significant benefit on the relief of tremor in both conditions. The principal adverse event was weakness, but it did not worse within 6 weeks of BoNT treatment (SMD = -0.35, 95% CI, -0.83 to 0.12, p = 0.07, I² = 57%), as assessed by the subjective grip strength. In conclusion, BoNT was an effective treatment for the hand tremor and ET, and EMG guidance injection was preferred. In addition, the muscular weakness adverse effect was not significant.