IncobotulinumtoxinA injections administered using a customized injection approach and specific muscle selection may improve essential hand tremor and patient’s perception as well as reduced the incidence of hand weakness in individuals with Parkinson disease, according to a study published in Parkinsonism & Related Disorders.

In this double-blind placebo-controlled cross-over study, investigators sought to assess the efficacy and safety of incobotulinumtoxinA using a customized injection approach for treating essential hand tremor. The study included 33 patients with essential tremor who were randomly assigned to receive incobotulinumtoxinA or placebo injections. Treatment was administered using an injection pattern customized to each patient, targeting 8 to 14 muscles of the hand and forearm. All participants were clinically evaluated in order to identify the primary muscles involved in their tremor.

Participants were followed over 28 weeks, and outcomes were assessed at 4 and 8 weeks after the initial injection, and at 4, 8, and 12 weeks following the second injection. Tremor severity was assessed using the Fahn Tolosa Marin tremor rating score and the National Institutes of Health Collaborative Genetic Criteria. An ergometer was used to assess hand strength. The Patient Global Impression of Change was used to evaluate the participants’ perception of their outcomes.

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On the tremor severity scale, participants in the incobotulinumtoxinA vs placebo group showed significant improvement at both 4 and 8 weeks, but no further improvement considered statistically significant was detected at weeks 12 and 16, indicating that the average response to incobotulinumtoxinA lasts between 8 to 12 weeks. More than half (53%) of participants in the incobotulinumtoxinA group and 15% in the placebo group reported an improvement in their condition using the Patient Global Impression of Change scores. Mild hand weakness was only reported by 6 patients in the incobotulinumtoxinA group and 4 patients in the placebo group.

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Limitations of the study included a small sample size and the lack of quality-of-life outcome measures.

The study investigators conclude that incobotulinumtoxinA is a clinically significant intervention used to improve hand tremor, and that a customized injection approach using muscle selection can help lower the incidence of hand weakness in patients with essential tremor, positively influencing their perception.

This study was funded by Merz Pharmaceuticals.


Mittal SO, Machado D, Richardson D, Dubey D, Jabbari B. Botulinum toxin in essential hand tremor – A randomized double-blind placebo-controlled study with customized injection approach [published online June 12, 2018]. Parkinsonism Relat Disord. doi: 10.1016/j.parkreldis.2018.06.019