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Original Investigation
December 21, 2020

Assessment of Botulinum Neurotoxin Injection for Dystonic Hand Tremor: A Randomized Clinical Trial

Author Affiliations
  • 1Department of Neurology, All India Institute of Medical Sciences, New Delhi, India
  • 2Department of Biostatistics, All India Institute of Medical Sciences, New Delhi, India
JAMA Neurol. Published online December 21, 2020. doi:10.1001/jamaneurol.2020.4766
Key Points

Question  Are botulinum neurotoxin (BoNT) injections effective in treating upper-extremity dystonic tremor?

Findings  In this randomized clinical trial of 30 adults, a mean difference of 10.9 units on the Fahn-Tolosa-Marin Tremor Rating Scale was found between the BoNT and placebo groups 6 weeks after injection, a significant difference in favor of BoNT.

Meaning  In patients with upper-extremity dystonic tremor, electromyographically guided individualized BoNT injections were beneficial for achieving tremor control without unacceptable hand weakness.

Abstract

Importance  There is an unmet need for safe and efficacious treatments for upper-extremity dystonic tremor (DT). To date, only uncontrolled retrospective case series have reported the effect of botulinum neurotoxin (BoNT) injections on upper-extremity DT.

Objective  To assess the effect of BoNT injections on tremor in patients with upper-extremity DT.

Design, Setting, and Participants  In this placebo-controlled, parallel-group randomized clinical trial, 30 adult patients with upper-extremity DT treated at a movement disorder clinic in a tertiary care university hospital were randomized in a 1:1 ratio to BoNT or saline injection, 0.9%, using a computer-generated randomization sequence. Randomization was masked using opaque envelopes. The participant, injector, outcome assessor, and statistician were blinded to the randomization. Participants were recruited between November 20, 2018, and December 12, 2019, and the last follow-up was completed in March 2020.

Interventions  Participants received electromyographically guided intramuscular injections of BoNT or placebo into the tremulous muscles of the upper extremity. Injection patterns and doses were individualized according to tremor phenomenologic findings.

Main Outcomes and Measures  The primary outcome was the total score on the Fahn-Tolosa-Marin Tremor Rating Scale 6 weeks after the intervention. Outcomes were assessed at baseline, 6 weeks, and 12 weeks. All patients were offered open-label BoNT injections after 12 weeks and reassessed 6 weeks later.

Results  A total of 48 adult patients with a diagnosis of brachial dystonia with DT were screened. Fifteen were ineligible and 3 refused consent; therefore, 30 patients (mean [SD] age, 46.0 [18.6] years; 26 [86.7%] male) were recruited, with 15 randomized to receive BoNT and 15 to receive placebo. In the intention-to-treat group, the Fahn-Tolosa-Marin Tremor Rating Scale total score was significantly lower in the BoNT group at 6 weeks (adjusted mean difference, –10.9; 95% CI, –15.4 to –6.5; P < .001) and 12 weeks (adjusted mean difference, –5.7; 95% CI, –11.0 to –0.5; P = .03). More participants in the BoNT group reported global improvement on the Global Impression of Change (PGIC) assessment (PGIC 1, 2, and 3: BoNT: 4 [26.7%], 6 [40.0%], and 5 [33.3%]; placebo: 5 [33.3%], 10 [66.7%], and 0, respectively; P = .047). Subjective hand weakness (BoNT: 6 [40.0%]; placebo: 4 [28.6%], P = .52) and dynamometer-assessed grip strength (mean difference, –0.2 log10[kgf/m2]2/Hz-Hz; 95% CI, –0.9 to 0.4 log10[kgf/m2]2/Hz-Hz; P = .45) were similar in both groups.

Conclusions and Relevance  In this randomized clinical trial, botulinum neurotoxin injections were superior to placebo in reducing tremor severity in upper-extremity DT. An individualized approach to muscle selection and dosing was beneficial without unacceptable adverse effects.

Trial Registration  Clinical Trials Registry of India (http://ctri.nic.in) Identifier: CTRI/2018/02/011721

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