Botulinum Toxin for the Treatment of Tremors

Tremor, an oscillatory movement disorder, is commonly encountered in clinical practice in the setting of a variety of etiologies, such as essential tremor and Parkinson's disease. Despite its high prevalence, treatment options are somewhat limited. Oral medications are often ineffective or limited by side effects, and other treatments, such as deep brain stimulation, are more invasive and costly. Botulinum toxin (BoNT) injections are a well-established therapy in the treatment of dystonia, but its use in the treatment of tremors has not been fully explored. In this review, we discuss the available randomized controlled trials and open-label evidence for the use of BoNT in various tremor etiologies, as well as its injection techniques. While essential tremor is the most studied condition, other tremor etiologies and tremor types such as Parkinson's disease, head tremor, voice tremor, proximal tremor, and tremor due to dystonia and multiple sclerosis have been studied as well. Botulinum toxin injections have provided evidence of significant benefit in outcomes in several trials among these indications, but transient weakness remains a common adverse effect. There is a paucity of well-designed trials as many published studies have relatively small cohorts and results are additionally limited by heterogenous outcome measures, dosages, muscle selection techniques and methods of injection.