A novel staged parent artery occlusion following extracranial-intracranial bypass for giant intracranial aneurysms: case series and hemodynamic insights via 4D flow MRI.

For complex intracranial aneurysms (CIAs), extracranial-intracranial (EC-IC) bypass with immediate parent artery (PA) occlusion is an accepted strategy but is associated with a high postoperative infarction rate. This study explores the efficacy of a novel staged therapy, characterized by a first-stage EC-IC bypass followed by second-stage PA occlusion, with a focus on aneurysm change and hemodynamic outcomes. Thirty-six patients with CIAs undergoing staged therapy from January 2018 to November 2022 were prospectively recruited. Hemodynamic analysis was performed using 4D flow MRI and computational fluid dynamics (CFD) based on CT angiography. Operation-related complications, postoperative hemodynamics, and aneurysm change were documented. Following first-stage bypass, aneurysms disappeared in 6 patients (16.7%), increased in size in 8 patients (22.2%), and remained unchanged in 22 patients (61.1%). Of the 16 cases (44.4%) available for 4D flow analysis, postoperative flow in the donor vessel increased gradually, peaking at 4.26 times the preoperative value by the 6th day after bypass, before subsequently decreasing. Hemodynamic patterns in the PA varied. In cases in which wall shear stress (WSS) and streamline velocity decreased (n = 4), 4D flow analysis revealed a decreasing trend in PA flow after the turning point, which corresponded with aneurysm resolution. Conversely, in cases with increased WSS and streamline velocity (n = 12), 4D flow analysis showed an increasing trend in PA flow after the turning point, corresponding with aneurysm enlargement or stability. Of 29 cases receiving second-stage PA occlusion, aneurysms disappeared in 27 patients (93.1%) and decreased in size in 2 patients (6.9%). Two patients developed ischemic events at 7 and 10 days postprocedure, respectively. At the latest follow-up, 91.7% (33/36) of the cases showed aneurysm resolution, without the development of hemorrhagic events. Staged therapy appears to be a promising treatment for CIAs, yielding favorable outcomes. Hemodynamic evaluation is instrumental in assessing aneurysm changes after bypass and may help determine the optimal timing for second-stage treatment.