Objective: To assess the clinical and functional outcomes in patients with upper limb tremor with incobotulinum toxin A injections.

Background: Upper limb tremor can be functionally limiting. Medical therapy for upper limb tremor is ineffective. Botulinum toxin type A has previously been shown to be effective in randomised trials for patients with tremor in multiple sclerosis and essential tremor [1-3]. We postulated these benefits could extend to tremor of different aetiologies.

Method: Patients with relatively proximal upper limb tremor were included. Patients were randomized in a crossover design to receive incobotulinum toxin A or placebo at baseline and the reverse treatment at 16 weeks. Muscle selection and dosing was individualized, based on tremor characteristics. Primary outcome measure was change in Fahn Tolosa Martin tremor rating scale (Part A and B) from baseline to week 12 after treatment with incobotulinum toxin A compared to treatment with placebo. Secondary outcome measures were change in Quality of Life in Essential Tremor Questionnaire (QUEST) and Canadian Occupational Performance Measure (COPM).

Continuous variables were checked for normal distribution. Students T test was used for outcomes fitting a normal distribution. Wilcoxon Rank test was used for non-parametric data. Chi squared test was used for binary outcomes.

Results: 20 patients were randomised. 1 patient dropped out prior to the crossover. There was a statistically significant improvement in tremor rating scale scores at week 12 from treatment with incobotulinum toxin A of -2.3 (95% CI -3.9 to -0.7) vs +0.8 (95% CI -0.9 to +2.6) p=0.01. QUEST scores significantly improved by – 10.8 (95% CI -5.1 to -16.6) vs – 1.6 (95% CI +4.8 to -8.1) p=0.03 at week 12 from treatment with incobotulinum toxin A . COPM performance and satisfaction scores did not significantly differ [Performance score 1.7 (95% CI 0.94 to 2.5) vs 1.1 (95% CI -0.2 to +2.5) p=0.43], [Satisfaction score 1.5 (95% CI 0.3 to 2.8) vs 1.5 (95% CI 0.3 to 2.9) p=0.95]. One patient reported moderate-severe arm weakness 4 weeks after treatment with Incobotulinum toxin A which improved within 4 weeks. Incobotulinum toxin A was otherwise well tolerated.

Conclusion: Incobotulinum toxin A is an effective treatment for upper limb tremor with improved clinician and patient oriented outcomes.

References: [1] Van Der Walt A, Sung S, Spelman T, Marriott M, Kolbe S, Mitchell P, et al. A double-blind, randomized, controlled study of botulinum toxin type A in MS-related tremor. Neurology. 2012;79(1):92.
[2] Brin MF, Lyons KE, Doucette J, Adler CH, Caviness JN, Comella CL, et al. A randomized, double masked, controlled trial of botulinum toxin type A in essential hand tremor. Neurology. 2001;56(11):1523.
[3] 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. Parkinsonism & Related Disorders. 2018;56:65-9.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-randomised-double-blind-placebo-controlled-crossover-trial-of-incobotulinum-toxin-a-treatment-for-upper-limb-tremor/