Botulinum toxin in essential hand tremor - A randomized double-blind placebo-controlled study with customized injection approach

Introduction: To evaluate the safety and efficacy of incobotulinumtoxinA (IncoA) injection for treatment of essential hand tremor. In essential tremor and Parkinson's disease tremor, administration of onabotulinumtoxinA via a fixed injection approach improves the tremor but a high percentage of patients (30-70%) develop moderate to severe hand weakness which has limited its use in clinical practice. Methods: This study was performed from July 2013 to July 2016 on 33 subjects. This is a double-blind, placebo controlled, crossover trial injecting 80-120 units of IncoA into 8-14 hand and forearm muscles using a customized approach. The subjects were followed for 28 weeks. The treatment efficacy was evaluated by the Fahn Tolosa Mann tremor rating score and NIH genetic criteria for tremor severity at 4 and 8 weeks after each of the two sets of treatments. Hand strength was assessed by an ergometer. Results: There was statistically significant improvement in clinical rating score of tremor at 4 and 8 weeks following the IncoA injection. Conclusion: In this study, injection of IncoA treatment via a customized approach improved essential tremor on the clinical scales and patient's perception with a low occurrence of significant hand weakness.