The safety and efficacy of onabotulinumtoxinA injections for children and adolescents with chronic migraine: A systematic review and meta-analysis.

[OBJECTIVE] To qualitatively and quantitatively summarize the evidence for the use of onabotulinumtoxinA injections in children and adolescents with migraine.

[BACKGROUND] There are limited evidence-based treatment options for youth with migraine, especially youth with chronic migraine (CM). OnabotulinumtoxinA injections are an established evidence-based treatment for adults with CM. While several studies have assessed their safety and efficacy among adolescents with CM, there are no published systematic reviews summarizing the pediatric evidence.

[METHODS] We carried out a systematic review, reported according to the Preferred Reporting Items for Systematic Review and Meta-Analysis, aiming to identify studies that included five or more children and adolescents aged ≤18 years with a diagnosis of migraine, who were treated with ≥50 units (U) of onabotulinumtoxinA and had outcomes assessed ≥4 weeks after one or more injection cycle. Both observational studies and randomized controlled trials (RCTs) were eligible for inclusion. Two investigators independently carried out the first (titles and abstracts) and second (full text) screening stages, as well as data extraction and quality appraisal. The American Academy of Neurology risk of bias grading scheme was used to assess study risk of bias. Studies with adequate data were pooled using random effects meta-analyses, and Hedge's g standardized mean differences with 95% confidence intervals (CIs) were generated to estimate the effect sizes of the continuous outcomes included. Studies lacking data required for meta-analysis were summarized qualitatively.

[RESULTS] We screened 634 studies and included 14 studies comprising 491 participants, of whom 489 had CM. Two studies were RCTs, 12 were observational uncontrolled studies, and all but one study included only youth with CM. Five Class IV observational uncontrolled studies were amenable to pooling in meta-analyses. After a mean of 2-2.6 injection cycles, headache frequency was shown to decrease significantly after treatment with onabotulinumtoxinA (Hedge's g = 0.97, 95% CI 0.58-1.35; p < 0.0001), as did severity (Hedge's g = 1.24, 95% CI 0.55-1.94; p = 0.0005), with both estimates having a large effect size magnitude. A Class I parallel-group RCT of one injection series (155 U, 74 U, or placebo), powered to detect a change in 4 headache days per month, did not find outcome differences between the active and placebo treatment arms. A Class IV crossover RCT showed superiority of active (155 U) versus placebo injections. The remaining Class IV observational studies that were excluded from the meta-analyses all showed improved outcomes with onabotulinumtoxinA injections over time. No serious adverse events related to treatment occurred.

[CONCLUSION] OnabotulinumtoxinA injections have established safety for use in children and adolescents with CM and are likely effective in reducing headache frequency and severity over time. However, in the absence of an adequately powered parallel-group RCT assessing the efficacy of multiple injection cycles, it remains unclear if this intervention is superior to placebo.