Defining Optimal Coiling Packing Density for Complete Occlusion of Large and Giant Intracranial Aneurysms Treated with Flow Diverters and Adjunctive Coiling

Introduction: Flow diversion (FD) is a conventional treatment for large and giant intracranial aneurysms. However, combining it with coiling might improve occlusion rates. This study aims to explore the impact of combining FD with coiling and analyze the required packing density for optimal aneurysm occlusion.

Methods: This retrospective cohort study compared large (10-15 mm), very large (15-25 mm), and giant (≥25 mm) intracranial aneurysm treatments with FDs alone versus FD + coiling at two large healthcare institutions from 2015 to 2023. Outcomes included aneurysm occlusion (Raymond-Roy classification), retreatment, complications, and modified Rankin Scale (mRS) at last follow up. Propensity score matching (PSM) and multivariable logistic regression adjusted for confounders. Coiling packing densities were analyzed, and AUC-ROC was used to assess their association with occlusion rates.

Results: After PSM, 130 patients were matched to the FD-only group while 65 were matched to the FD + coiling group. FD + coiling had higher complete aneurysm occlusion rates (72.3% vs. 57.7%; P=0.06) and higher thrombotic complications (6.2% vs. 0%; P=0.01). Multivariate analysis showed significant improvement in occlusion with FD + coiling (Odds Ratio (OR)=2.03; 95% Confidence Interval (CI): 1.04-4.05; P=0.02) but complications rates were not significantly different. ROC analysis revealed an AUC of 0.65 for coiling packing density; PD ≥12-14% was not significantly associated with higher occlusion rates (OR=2.00; 95% CI: 0.47-8.58; P=0.35). Subgroup analysis showed PD ≥12-14% significantly improved occlusion in only very large or giant aneurysms (OR=8.6; 95% CI: 1.33-18.58; P=0.02).

Conclusion : In this study, the combination of FD with coiling at a threshold packing density of 12-14% significantly enhanced the rates of complete occlusion for large and giant aneurysms compared to using FD alone. Although coiling packing density did not significantly predict higher occlusion rates beyond the 12-14% threshold, its effect was particularly pronounced in very large or giant aneurysms.