The impact of circle of Willis integrity and variations on clinical and radiological outcomes after posterior communicating arteries covered by flow diverter devices.

Flow diverter (FD) treatment of intracranial aneurysms frequently requires coverage of posterior communicating arteries (PComAs), yet the impact of Circle of Willis (CoW) variations on vessel patency and clinical outcomes remains incompletely understood. This study investigated the relationship between CoW anatomical variations and outcomes after FD coverage of PComAs. We retrospectively analyzed 164 consecutive patients with 170 covered PComAs, including 25 fPCAs, treated with FDs. Digital subtraction angiography was used to evaluate CoW configuration and vessel changes. Primary endpoints included PComA patency and clinical outcomes. Secondary endpoints included aneurysm occlusion rates and vessel diameter changes. Multivariate logistic regression analyses were performed to identify predictors of PComA patency, with particular attention to CoW anatomical variations. Of the 170 PComAs, 58 (34.12%) demonstrated narrowing or occlusion without neurological deficits. Incomplete CoW (OR 2.45, 95% CI 1.23–4.86; p = 0.011) and younger age (OR 0.97, 95% CI 0.94-1.00; p = 0.028) independently predicted PComA narrowing/occlusion. In fPCA cases (n = 25), 13 vessels (52%) showed narrowing/occlusion. Bilateral fPCAs were associated with an increased risk of PComA narrowing/occlusion (OR 6.61, 95% CI 1.50-29.18; p = 0.013). Quantitative analysis revealed a significant reduction in covered fPCA diameter (p < 0.01) with compensatory enlargement of ipsilateral posterior cerebral arteries (p = 0.013). Incomplete CoW configurations, particularly bilateral fPCAs, heighten PComA compromise risk post-FD. Compensatory vascular remodeling likely prevents ischemia despite anatomical changes. Preprocedural CoW evaluation is critical, especially in fPCA cases requiring posterior circulation preservation. These findings may advocate anatomy-driven FD treatment strategies.