Botulinum Toxin Efficacy in Upper Limb Tremor: A Systematic Review and Meta-Analysis

Area of Science:

• Neurology
• Pharmacology
• Medical Treatments

Background:

• Essential tremor (ET) and dystonic tremor syndrome (DTS) are treatable with botulinum toxin (BoNT) injections.
• Previous reviews on BoNT for ET/DTS lacked evidence certainty assessment and clinician-reported outcomes.
• Significant interindividual variability exists in BoNT treatment efficacy.

Purpose of the Study:

• To evaluate the efficacy and safety of botulinum toxin (BoNT) injections for upper limb essential tremor (ET) and dystonic tremor syndrome (DTS).
• To identify factors influencing the effectiveness of BoNT in treating ET and DTS.
• To assess the certainty of evidence for BoNT in ET and DTS treatment.

Main Methods:

• Systematic literature search across major databases (PubMed, Embase, Cochrane Library, Web of Science).
• Application of the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach to rate evidence certainty.
• Meta-analysis of outcomes from randomized controlled trials (RCTs) using standardized mean differences (SMDs).

Main Results:

• Meta-analysis indicated a moderate effect on patient-reported outcomes (SMD: 0.58) but no significant effect on clinically rated tremor severity or grip strength when using post-intervention scores.
• Analysis of change-from-baseline scores revealed an improvement in clinically rated tremor severity (SMD: -1.12).
• Certainty of evidence was rated as low to very low; no clear associations were found between BoNT efficacy and tremor phenotypes or injection strategies.

Conclusions:

• Patient-tailored botulinum toxin (BoNT) injections may offer effective and safe treatment for essential tremor (ET) and dystonic tremor syndrome (DTS).
• Further clinical trials are essential to validate efficacy and safety.
• Future research should focus on identifying optimal patient phenotypes and injection strategies for BoNT therapy in ET and DTS.