Prevalence, Geometry, and Hemodynamics of Small and Medium-Sized Intracranial Aneurysms With and Without Blebs in the Chinese Han Population

Abstract

Background: Blebs are small bulges on the surface of intracranial aneurysms (IAs) that increase rupture risk. Among Chinese individuals, the prevalence, distribution, and clinical, geometric, and local hemodynamic characteristics of small- and medium-sized (<15 mm) blebbed IAs remain unclear.

Objectives: To investigate the prevalence, distribution, and associated clinical, geometric, and hemodynamic features of blebs in small- and medium-sized IAs among Chinese patients, and to identify predictors of aneurysm rupture and bleb formation.

Design: A retrospective observational study.

Methods: CTA or DSA data from 214 patients with ruptured (RIAs) and unruptured IAs (UIAs) (<15 mm), with or without blebs, were analyzed. Three-dimensional reconstruction, geometric measurement, and computational fluid dynamics (CFD) analysis were conducted using Mimics and ANSYS Fluent. Hemodynamic parameters were assessed across the neck, body, and dome, and logistic regression was used to identify predictors of rupture and bleb formation.

Results: Aneurysms from 214 patients (93 men, 121 women; mean age 59.90 ± 11.76 years) were analyzed. Blebs were found in 107 aneurysms (56.7% of RIAs, 39.1% of UIAs). They were more frequent in ACoA, PCoA, and bifurcation aneurysms (all P < 0.05) and were associated with rupture. RIAs had larger blebs than UIAs (2.73 ± 1.28 mm vs 2.06 ± 1.07 mm, P = 0.009). Blebbed IAs exhibited larger size, more irregular shape, higher AR, SR, BN, HWR, and lower NWSS, TAWSS, OSI (all P < 0.05). SR was the strongest rupture predictor (AUC = 0.718, SR > 1.3144). Aneurysms at ACoA (OR = 8.812,CI:2.455-31.634), PCoA (OR = 6.376,CI:2.094-19.414), and high SR (OR = 2.738,CI:0.98-7.651) were significant rupture risk factors. PCoA (OR = 2.261,CI:0.759-6.739) and SR (OR = 4.683,CI:1.937-11.324) independently predicted bleb formation.

Conclusion: Blebs are common in small- and medium-sized IAs, especially at the ACoA, PCoA, and bifurcations, and are associated with an increased risk of rupture. Larger blebs are more often seen in ruptured IAs. A high SR is a key predictor of both rupture and bleb formation. Further studies on bleb-related hemodynamics in the neck, body, and dome are warranted.

Keywords: bleb; computational fluid dynamics; geometry; hemodynamics; intracranial aneurysm; prevalence; risk factors; rupture.

Figure 1.

Study Flow Diagram and Graphical Abstract of the Study (A) Study Flow Diagram Explaining the Steps of Our Analysis. AVF: Arteriovenous Fistula; AVM: Arteriovenous Malformation; MMD: Moyamoya Disease; IA: Intracranial Aneurysm; RIA: Ruptured Intracranial Aneurysm; UIA: Unruptured Intracranial Aneurysm; CTA: Computed Tomography Angiography; DSA: Digital Subtraction Angiography; CFD: Computational Fluid Dynamics (B) Graphical Abstract of the Study

Figure 2.

3D Reconstruction, Geometric Measurement, and IA Region Partitioning (A-D) Reconstruction of an IA in 3D With Mimics Research 21.0 (E) IA Geometric Measurement after 3D Reconstruction (F) Aneurysm Geometric Parameter Diagram. H: Height; L: Length; Wneck: Aneurysm Neck; α: Angle of Incidence; β: Aneurysm Angle. The Diameter of the Aneurysmal Vessel (Parent Vessel Average Diameter, Dv) Included the Vessel Diameter for Sidewall-type IAs (Diameter of the Aneurysmal Artery Near the Neck of the Aneurysm (D1) and the Proximal End of the Aneurysmal Artery From the Neck of the Aneurysm (1.5D2) of the Average Diameter of the Vessels) and Bifurcation-Type IAs (Average Diameter of the Aneurysmal Vessels and Their Branches) (G) Diagram Illustrating the Division of the IA Into the Neck, Body, and Dome, Showing the Neck, Body, and Distance Lines

Figure 3.

ROC Curves and Logistic Regression Analysis (A-F) Comparison of the AUC Values of Independent Risk Factors for Rupture and the Presence of Blebs; (A-C) Risk Factors for Rupture; (D-F) Risk Factors for the Presence of Blebs. AR: Aspect Ratio; SR: Size Ratio; BN: Bottleneck Ratio; RIA: Ruptured Intracranial Aneurysm (G-H) Logistic Regression Forest Map (G) Association Between Risk Factors and Aneurysm Rupture (H) Risk Factors for the Presence of Blebs. ACoA: Anterior Communicating Artery; PCoA: Posterior Communicating Artery; ACA: Anterior Cerebral Artery; MCA: Middle Cerebral Artery; PcirA: Posterior Circulation Aneurysm; AR: Aspect Ratio; SR: Size Ratio; BN: Bottleneck Ratio; HWR: Height Width Ratio

Figure 4.

(A-H) A Ruptured MCA Aneurysm With Two Blebs and a Length of 6.88 mm (A) Volume Rendering of a Three-Dimensional Rotational Angiography Image (B-C) Aneurysm Bleb1 and Bleb2 are Visible During Surgery (D) A Rupture Point is Identified Near Aneurysm Bleb2 During Surgery (E) Wall Shear Stress (WSS) Distribution (F) Mean Gradient Oscillatory Number (GON) Distribution (G) Mean WSS Gradient (TAWSSG) Distribution (H) Streamline Distribution (I∼N) Analysis of an Unruptured MCA Aneurysm With No Blebs and a Length of 5.56 mm at an Arterial Bifurcation (I) Volume Rendering of a Three-Dimensional Rotational Angiography Image (J-K) Blebs and the Neck, Body, and Dome of the Aneurysm are Not Visible During Surgery (L) WSS Distribution (M) Time-Averaged Wall Shear Stress (TAWSS) (N) Mean GON Distribution