Assessing Occlusion and Recovery in Large and Giant Intracranial Aneurysms: A Comparative Retrospective Study of Flow Diversion Alone Versus Combined With Coiling and the Role of Packing Density

BACKGROUND AND OBJECTIVES: Flow diversion (FD) is a conventional treatment of large and giant intracranial aneurysms. The aim of this study was to explore the impact of combining FD with coiling and analyze the required packing density (PD) for optimal aneurysm occlusion. METHODS: This retrospective study compared large (10-15 mm), very large (15-25 mm), and giant (≥25 mm) intracranial aneurysm treatment with FDs alone vs FD + coiling at 2 large institutions from 2015 to 2023. Outcomes included aneurysm occlusion (Raymond-Roy classification), retreatment, complications, and modified Rankin Scale at last follow-up. Coiling PDs were analyzed, and receiver operator curve area under the curve was used to assess their association with occlusion rates. Propensity score matching and multivariable logistic regression adjusted for confounders. RESULTS: After propensity score matching, 130 patients were matched to the FD-only group, whereas 65 were matched to the FD + coiling group. The FD + coiling group showed higher complete aneurysm occlusion rates (72.3% vs 57.7%; P = .06), with OR = 2.03; 95% CI: 1.04-4.05; P = .02 in multivariate analysis. Hemorrhagic complications occurred only in FD-only patients (3.1%) whereas infarct complications were only observed in FD + coiling patients (6.2%). Nevertheless, FD + coiling demonstrated superior functional outcomes with all patients achieving modified Rankin Scale 0-1 at the last follow-up vs 86.2% in FD-only ( P = .03). Receiver operator curve analysis determined that the optimal PD for coiling to achieve aneurysm occlusion is 12% to 14%, with an area under the curve of 0.65. Increasing the PD beyond this does not significantly improve occlusion rates, except in very large or giant aneurysms (OR = 8.6; 95% CI: 1.33-18.58; P = .02). CONCLUSION: In this study, FD with minimal coiling at a PD of 12% to 14% significantly enhanced complete aneurysm occlusion and functional recovery in patients with large aneurysms compared with using FD alone. PD above 12% to 14% threshold up to 26% impact on occlusion rates is particularly pronounced in very large or giant aneurysms.