Noninvasive analysis of overactive muscle structure and elasticity after botulinum toxin type A injection: a systematic review and meta-analysis.
Marine Devis, Frédéric Lecouvet, Thierry Lejeune and 1 others
PMID 38958691WHAT IT FOUND
Botulinum toxin injections temporarily improve muscle elasticity at four weeks, but show no structural change at short-term.
At long-term, muscle volume decreases in children with cerebral palsy. This suggests caution regarding reinjection timing in this population.
Key findings
01Muscle elasticity showed a statistically significant improvement with a medium effect size at short-term (4 weeks) after injection.
02No statistically significant within-group difference was found for muscle thickness, pennation angle, or echo-intensity at short-term.
03Normalized muscle volume showed a statistically significant decrease with a small effect size at long-term (24 weeks).
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
The methodological quality of included studies was mostly low to fair. Only three randomized controlled trials were included; most were pre-post observational studies. There was high heterogeneity in measurement protocols and outcome definitions, which prevented meta-analysis for several structural outcomes. Many studies did not specify the number of previous injections, making it difficult to assess cumulative effects. The number of subjects in some meta-analyses was small, reducing statistical power. Concomitant treatments like rehabilitation or casting were often present, making it hard to attribute effects solely to the toxin.
Declared interests
The authors declared no conflicts of interest. The study was not reported to be funded by a commercial entity selling the treatment.
The easy way to misread this
Do not assume that the temporary improvement in muscle elasticity reflects a permanent change in muscle structure. The study found no significant structural changes at short-term, and the long-term decrease in muscle volume was small and based on limited data, primarily in children with cerebral palsy.