Angiographic outcomes after indirect revascularization in pediatric Moyamoya disease: a systematic review and Meta-analysis.

Moyamoya disease is a rare progressive cerebral vasculopathy characterized by narrowing or occlusion of the internal carotid arteries, leading to the formation of fragile collateral vessels and a high risk of ischemic events, especially in pediatric patients. Although direct revascularization techniques are commonly used, they are technically challenging in children due to vascular fragility and anatomy. Indirect revascularization techniques favor the formation of new blood vessels through alternative flow routes. Their efficacy is usually assessed using the Matsushima scale, which measures the degree of revascularization achieved. This study aims to describe postoperative angiographic outcomes of indirect revascularization techniques in pediatric patients with Moyamoya disease. A systematic review and meta-analysis was performed following PRISMA guidelines, searching six databases (PubMed, Embase, Scopus, Web of Science, CENTRAL and Google Scholar) for observational studies that evaluated indirect revascularization techniques in pediatric patients with Moyamoya disease. Seventeen studies comprising 1360 hemispheres were included. Primary outcomes were the proportions of angiographic revascularization according to grades A, B, and C of the Matsushima scale. Secondary outcomes included postoperative clinical complications such as stroke, transient ischemic attacks (TIAs), seizures, bleeding, mortality, and functional status assessed using the modified Rankin scale (mRS ≤2). Meta-analyses were performed with random-effects models in R (version 4.2.3) and risk of bias was assessed with the MINORS tool. Meta-regression was applied to explore possible predictors of outcomes. The certainty of evidence was assessed with the GRADE approach. The combined proportions of hemispheres achieving Matsushima grades A, B and C were 47.1% (95% CI: 38.4-55.9; I2 = 84.4%), 38.2% (95% CI: 32.0-44.9; I2 = 84.4%) and 12.3% (95% CI: 9.3-16.0; I2 = 47.0%), respectively. Postoperative complications were low: stroke 8.3%, TIA 7.2%, seizures 2.5%, bleeding 2.7% and mortality 0.8%. Good functional status (mRS ≤2) was achieved in 82.1% of patients. Meta-regression revealed that unilateral vs. bilateral procedures significantly predicted Matsushima grade B outcomes (p = 0.002). The risk of bias was low to moderate. The certainty of evidence was generally low to moderate, except for mortality which showed high certainty. Indirect revascularization techniques in pediatric Moyamoya show favorable angiographic and clinical results, with low complications and high functional independence. According to the Matsushima scale, about 47% of the hemispheres achieved grade A, 38% grade B and 12% grade C. Pial synangiosis and EDAMS were more effective in grade A, whereas EDAS showed a lower proportion in grade A and slightly more in grade C. Postoperative complications were low and most patients achieved good functional status (mRS ≤2). These findings suggest the safe and effective use of indirect techniques, although the high heterogeneity and methodological limitations evidence the need for randomized studies to validate and optimize these results in the long term.