Morphological and Hemodynamic Differences Between Aneurysmal Middle Cerebral Artery Bifurcation and Contralateral Nonaneurysmal Anatomy

Abstract

Background: The morphological and hemodynamic features differ between middle cerebral artery (MCA) bifurcations with and without aneurysms.

Objective: To investigate the morphological and hemodynamic differences between aneurysmal MCA bifurcation and contralateral nonaneurysmal anatomy.

Methods: Computed tomography angiography of 36 patients with unilateral small saccular MCA bifurcation aneurysms was evaluated. The parent-daughter angles (φ1 for larger branch and φ2 for smaller branch), bifurcation angle (φ = φ1 + φ2), inclination angle (γ angle), and their relationships with the MCA bifurcation locations were analyzed. Computational fluid dynamics simulation was performed in 6 cases to explore the hemodynamics influenced by the bifurcation morphology.

Results: The φ angle was significantly higher in aneurysmal than contralateral nonaneurysmal bifurcations (160.8° ± 31.0° vs 99.0° ± 19.2°, respectively; P = .000); the φ1, φ2, and γ angles were also higher. However, by regression analysis combined with MCA bifurcation locations, only the φ angle might be associated with the aneurysm presence (odds ratio = 1.120, 95% confidence interval = 1.059-1.185) and a φ angle cut-off of 124.8° was established. Computational fluid dynamics simulation demonstrated that flow resistance of the wider aneurysmal MCA bifurcation was significantly higher than that on the contralateral side.

Conclusion: A larger φ angle was more prevalent in aneurysmal than nonaneurysmal MCA bifurcations, and the higher flow resistance caused by the larger φ angle might be a potential hemodynamic factor associated with MCA aneurysm presence.

Keywords: Computational fluid dynamics; Computed tomography angiography; Intracranial aneurysm; Middle cerebral artery; Morphology.