Hemodynamic analysis of optimal branch selection for flow-diverting stents in middle cerebral artery bifurcation aneurysms: a pilot study

Background Despite the expanding use of flow-diverting stents (flow diverters—FDs) for middle cerebral artery (MCA) bifurcation aneurysms, their efficacy remains contentious in this complex anatomy. Current studies report conflicting complete occlusion rates (55–92%) and significant branch stenosis/occlusion risks (8–43%), highlighting unmet needs in stent placement strategy. Methods In this retrospective cohort study combining clinical data with computational fluid dynamics (CFD), 20 MCA bifurcation aneurysms (19 patients) treated with FDs were analyzed. Patient-specific models derived from three-dimensional digital subtraction angiography underwent CFD simulations to quantify pre/post-stent hemodynamic changes. Key parameters (inflow rate, wall shear stress, residual flow volume) were compared between aneurysms with complete versus incomplete healing, and the impact of stent placement in branches of varying diameters was analyzed. Results At a median follow-up of 9 months, complete occlusion was achieved in 55% (11/20) and partial occlusion in 25% (5/20). Though not statistically significant, hemodynamic analysis revealed the daughter artery diameter ratio (DR)-stratified efficacy. Stents with a DR between 0.65 and 0.80 placed in smaller-diameter branches more effectively reduced inflow rate, relative inflow rate, and aneurysm wall shear stress. Conversely, stents with a DR between 0.80 and 0.95 were more effective in larger-diameter branches. Conclusion This study indicates that vessel DR could guide intraoperative decisions for FD placement in MCA bifurcations. Prioritizing smaller branches in certain anatomical profiles may enhance flow remodeling without increasing procedural risks. These findings suggest a hemodynamic basis for moving beyond traditional size-based approaches and could inform more precise stent selection in complex bifurcation interventions. Further validation through controlled trials is needed.