Introduction Leptomeningeal collaterals (LMCs) sustain cerebral perfusion during large vessel occlusion, but their prognostic value after endovascular thrombectomy (EVT) remains uncertain. We evaluated the association between collateral status and outcomes in acute ischemic stroke (AIS) treated with EVT. Methods PubMed, Embase, Web of Science, and the Cochrane Library were searched from inception to July 2025 for studies comparing good versus poor LMC status in patients with AIS treated with EVT. The primary endpoint was functional independence at 90 days, defined as a modified Rankin Scale (mRS) score of 0–2. Secondary endpoints included successful reperfusion (modified Treatment in Cerebral Infarction (mTICI) 2b–3), near complete/complete reperfusion (mTICI 2c–3), symptomatic intracranial hemorrhage (sICH), and 90 day mortality. Random effects models pooled relative risks (RRs) with 95% confidence intervals (CIs). Results Eight studies including 2661 patients (1446 good and 1215 poor collaterals) were analyzed. Good collaterals were associated with higher near complete to complete reperfusion (mTICI 2c–3; RR 1.18, 95% CI 1.03 to 1.35; P=0.019) and functional independence (RR 1.44, 95% CI 1.09 to 1.88; P=0.009), and with a lower risk of sICH (RR 0.53, 95% CI 0.39 to 0.72; P<0.001) and 90 day stroke related mortality (RR 0.60, 95% CI 0.39 to 0.92; P=0.019). No association was found for successful reperfusion (mTICI 2b–3; RR 1.01, 95% CI 0.93 to 1.10). Conclusion Good LMC status was associated with improved angiographic and functional outcomes and lower hemorrhagic and mortality risks after EVT. Collateral assessment provides prognostic information and supports risk stratification, but should be interpreted alongside ischemic core burden and clinical context rather than used to exclude patients from treatment. Trial registration PROSPERO CRD420251159841.
Almeida et al. (Mon,) studied this question.