Insights into the Mechanisms Underlying the Lower Rupture Risk of Paraclinoid Aneurysms: a Comparative Analysis with Other Aneurysm Locations.

Abstract

Background: Paraclinoid aneurysms exhibit a markedly lower rupture risk compared to intracranial aneurysms (IAs) located in other regions. We aimed to identify the hemodynamic and morphological factors underlying this reduced rupture propensity.

Methods: We analyzed data from 538 unruptured IAs (179 paraclinoid) in the Chinese Intracranial Aneurysm Project (CIAP). Hemodynamic parameters were analyzed using computational fluid dynamics (CFD), and morphological features were quantified using computer-assisted semiautomated measurement (CASAM). Univariate and multivariate logistic regression analyses identified differences between paraclinoid and IAs in other locations.

Results: Paraclinoid aneurysms were independently associated with younger age (OR = 1.031, P = 0.024), female sex (OR = 0.474, P = 0.011), and less frequent use of lipid-lowering medications (OR = 3.156, P < 0.001). Hemodynamically, they exhibited lower combined hemodynamic parameter (CHP; OR = 1.055, P = 0.011), normalized pressure (NP; OR = 1.469, P < 0.001), and low shear area (LSA) ratio (OR = 1.065, P < 0.001). Morphologically, they had smaller maximum diameter (OR = 1.203, P < 0.001), lower non-sphericity index (NSI; OR = 1.099, P = 0.002), larger parent artery diameter (OR = 0.157, P < 0.001), and less frequent bifurcation involvement (OR = 9.361, P < 0.001).

Conclusions: Paraclinoid aneurysms exhibit lower NP, LSA, and CHP, along with smaller maximum diameter, lower NSI, and a sidewall configuration. Collectively, these features are associated with a stable hemodynamic and morphological environment that underlies their lower rupture risk. Future prospective studies with a large cohort are needed to confirm these findings.