Flow diversion for middle cerebral artery bifurcation aneurysms: multicenter retrospective cohort study

BACKGROUND AND OBJECTIVES: Flow diversion for middle cerebral artery (MCA) bifurcation aneurysms remains challenging due to jailed branch considerations and limited evidence. We aimed to evaluate the efficacy and safety of flow diverters (FDs) in this setting, with outcomes grouped by bifurcation subtype. METHODS: We retrospectively collected cases from three centers in which flow diversion was used to treat MCA bifurcation aneurysms. We collated and analyzed demographic, clinical, and aneurysm characteristics; procedural details; and peri-procedural and follow-up safety and efficacy outcomes. Outcomes were assessed overall and by bifurcation subtype (true (TBA) and variant (VBA) bifurcation aneurysms). RESULTS: We included 195 unruptured and previously untreated MCA bifurcation aneurysms. Periprocedural complications comprised ischemic events in 7.2% and hemorrhage events in 0.5% of all patients. During clinical follow-up (median 17.1 months), new ischemic events occurred in 7.4% and hemorrhagic events in 0.6% of all patients. At imaging follow-up (median 12.7 months), complete occlusion (Raymond-Roy I) was 59.5%, with 11.0% residual neck. Adequate occlusion (Raymond-Roy I-II) was lower in TBA than in VBA (63.0% vs 80.3%). Multivariable Cox regression revealed that a sac-like origin of the jailed branch and a higher jailed-to-FD branch diameter ratio were independent predictors of incomplete occlusion at 12 months. Sensitivity analyses confirmed robustness across different subtypes. The optimal predictive threshold for this ratio differed by subtype (TBA=0.81; VBA=0.70). CONCLUSION: Flow diversion is a reasonable endovascular option for MCA bifurcation aneurysms, particularly for variant bifurcations. Pre-procedural assessment of the intended jailed branch may help to improve mid-term occlusion rates.