Botulinum toxin for the treatment of tremor

Tremor is a key clinical feature of several common neurological disorders. Adequate management of tremor has been an unmet need in clinical practice. Most of the anti-tremor medications have limited efficacy and are associated with undesirable adverse effects, especially in elderly patients. Several studies have reported good outcomes with the use of botulinum neurotoxin (BoNT) for the treatment of tremor. This article aims to systematically review these studies and to highlight the role of BoNT in the management of tremor. A PubMed search was performed in August 2018 to identify articles pertinent to this review. Majority of the studies that have assessed the efficacy of BoNT in tremor, enrolled patients with essential tremor (ET), Parkinson's disease (PD), and dystonic tremor. Results of these studies suggest clinically meaningful improvement in hand tremor in both ET and PD and vocal tremor in ET after BoNT therapy. Additionally, BoNT has been reported to be efficacious in alleviating head and palatal tremor, tremor in multiple sclerosis, and proximal positional tremor. It is apparent that BoNT injections tailored to the needs of individual patients yield better efficacy and lower adverse effects compared to fixed-muscle-fixed-dose approach. BoNT individualized approach adds to the armamentarium for patients who have medically refractory tremors or those who are unable to tolerate the anti-tremor medications. The studies are limited and mostly open-label; thus, randomized placebo-controlled studies are needed to prove the efficacy of BoNT in various tremor conditions.