Treatment of Middle Cerebral Artery Aneurysms with Flow-Diverter Stents: A Systematic Review and Meta-Analysis of 1036 Aneurysms

BACKGROUND: The role of flow diversion for middle cerebral artery (MCA) aneurysms remains controversial due to frequent involvement of side branches and bifurcations. While outcomes have been reported in cohort studies and case series, the safety and efficacy of this approach remain uncertain. PURPOSE: To evaluate angiographic and clinical outcomes following flow diversion for MCA aneurysms. DATA SOURCES: A systematic literature search was performed across databases in accordance with PRISMA guidelines to identify studies reporting on flow-diverter treatment of MCA aneurysms. STUDY SELECTION: Studies including ≥3 patients treated with flow-diverter devices and reporting angiographic or clinical outcomes were eligible for inclusion. Thirty-three studies encompassing 1,036 MCA aneurysms met criteria, representing the largest cohort to date. DATA ANALYSIS: Data on study design, patient and aneurysm characteristics, treatment details, and angiographic and clinical outcomes were extracted. Pooled estimates with 95% confidence intervals (CIs) were calculated using a random-effects model, with subgroup analyses by aneurysm location and device type. DATA SYNTHESIS: The pooled complete or near-complete occlusion rate was 71% at a mean follow-up of 15 months, with no significant differences across MCA segments (66% proximal, 69% bifurcation, 70% distal) or across device types. The overall complication rate was 13%, predominantly thromboembolic, with a 1% procedural mortality. Functional independence (mRS 0-2) was achieved in 90% of patients. LIMITATIONS: Included studies were predominantly retrospective cohort series and case series with heterogeneity in device type, antiplatelet regimens, follow-up duration, and outcome definitions. Publication bias and underreporting of complications cannot be excluded. CONCLUSIONS: Flow diversion for MCA aneurysms achieves approximately 71% complete or near-complete occlusion with a 13% complication rate. These findings may support its consideration in carefully selected cases, though the retrospective evidence base warrants cautious interpretation.