Flow diversion for distal cerebral aneurysms: a systematic review and meta-analysis

BACKGROUND: Flow diverters (FDs) are increasingly used off-label for distal cerebral aneurysms (DCAs), those located at or beyond the anterior cerebral artery (ACA) A2, middle cerebral artery M2, and posterior cerebral artery P2 segments. However, data on their safety and efficacy remain limited. This systematic review and meta-analysis synthesizes current evidence on FD treatment for DCAs. METHODS: A comprehensive search was performed across PubMed, Scopus, and Web of Science, including studies with ≥5 patients reporting FD treatment of DCAs. Efficacy outcomes included adequate and complete aneurysm occlusion and retreatment rates. Safety outcomes included good functional outcome (modified Rankin Scale (mRS) score 0-2), procedure-related morbidity, mortality, complications, in-stent stenosis, and covered branch occlusion at follow-up. Pooled analyses with 95% confidence intervals (CI) were conducted using a random-effects model. RESULTS: Eighteen studies (441 patients, 70% women; mean age: 57.2±13.6 years) with 445 DCAs were included. Most aneurysms were unruptured (93.7%) and located in the ACA territory (78.4%). Adequate and complete occlusion at last follow-up were 90% (95% CI, 86 to 95) and 79% (95% CI, 74 to 85), respectively. The retreatment rate was 1.6% (95% CI, 0.2 to 3). Good functional outcome was achieved in 97% (95% CI, 95 to 99). Procedure-related complications occurred in 9% (95% CI, 5 to 13), with morbidity and mortality of 1.5% and 0.6%, respectively. In-stent stenosis and covered branch occlusion rates were 3% (95% CI, 0 to 8) and 5.5% (95% CI, 2 to 9), respectively. CONCLUSION: FDs appear to be safe and effective for DCAs, with high occlusion rates and low retreatment and complication rates.