title: Impact of bifurcation angle and inflow coefficient on the rupture risk of bifurcation type basilar artery tip aneurysms.
abstract: OBJECTIVE Risk factors for aneurysm rupture have been extensively studied, with several factors showing significant correlations with rupture status. Several studies have shown that aneurysm shape and hemodynamics change after rupture. In the present study the authors investigated a static factor, the bifurcation angle, which does not change after rupture, to understand its effect on aneurysm rupture risk and hemodynamics. METHODS A hospital database was retrospectively reviewed to identify patients with cerebral aneurysms treated surgically or endovascularly in the period between 2008 and 2015. After acquiring 3D rotational angiographic data, 3D stereolithography models were created and computational fluid dynamic analysis was performed using commercially available software. Patient data (age and sex), morphometric factors (aneurysm volume and maximum height, aspect ratio, bifurcation angle, bottleneck ratio, and neck/parent artery ratio), and hemodynamic factors (inflow coefficient and wall shear stress) were statistically compared between ruptured and unruptured groups. RESULTS Seventy-one basilar tip aneurysms were included in this study, 22 ruptured and 49 unruptured. Univariate analysis showed aspect ratio, bifurcation angle, bottleneck ratio, and inflow coefficient were significantly correlated with a ruptured status. Logistic regression analysis showed that aspect ratio and bifurcation angle were significant predictors of a ruptured status. Bifurcation angle was inversely correlated with inflow coefficient (p < 0.0005), which in turn correlated directly with mean (p = 0.028) and maximum (p = 0.014) wall shear stress (WSS) using Pearson's correlation coefficient, whereas aspect ratio was inversely correlated with mean (0.012) and minimum (p = 0.018) WSS. CONCLUSIONS Bifurcation angle and aspect ratio are independent predictors for aneurysm rupture. Bifurcation angle, which does not change after rupture, is correlated with hemodynamic factors including inflow coefficient and WSS, as well as rupture status. Aneurysms with the hands-up bifurcation configuration are more prone to rupture than aneurysms with other bifurcation configurations.
authors.affiliation: 1Department of Neurosurgery, Tohoku University Graduate School of Medicine; and.
authors.forename: Sherif
authors.initials: S
authors.lastname: Rashad
authors.affiliation: Departments of2Neuroanaethesia.
authors.forename: Shin-Ichiro
authors.initials: SI
authors.lastname: Sugiyama
authors.affiliation: 1Department of Neurosurgery, Tohoku University Graduate School of Medicine; and.
authors.forename: Kuniyasu
authors.initials: K
authors.lastname: Niizuma
authors.affiliation: 3Neuroendovascular Therapy, and.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Sato
authors.affiliation: 4Neurosurgery, Kohnan Hospital, Sendai,Japan.
authors.forename: Hidenori
authors.initials: H
authors.lastname: Endo
authors.affiliation: 3Neuroendovascular Therapy, and.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Omodaka
authors.affiliation: 3Neuroendovascular Therapy, and.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Matsumoto
authors.affiliation: 1Department of Neurosurgery, Tohoku University Graduate School of Medicine; and.
authors.forename: Miki
authors.initials: M
authors.lastname: Fujimura
authors.affiliation: 1Department of Neurosurgery, Tohoku University Graduate School of Medicine; and.
authors.forename: Teiji
authors.initials: T
authors.lastname: Tominaga
mesh_terms: D000328:Adult; D000368:Aged; D017542:Aneurysm, Ruptured / Q000000981:diagnostic imaging*; D015901:Angiography, Digital Subtraction; D001488:Basilar Artery / Q000000981:diagnostic imaging*; D002533:Cerebral Angiography; D016208:Databases, Factual; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D013314:Stress, Mechanical
keywords: AUC = area under the curve; HD = hands-down; HN = hands-neutral; HU = hands-up; ROC = receiver operating characteristic; WSS = wall shear stress; aneurysm; aspect ratio; basilar artery; bifurcation; rupture; vascular disorders