title: Widening of the basilar bifurcation angle: association with presence of intracranial aneurysm, age, and female sex.
abstract: OBJECTIVE
  Arterial bifurcations represent preferred locations for aneurysm formation, especially when they are associated with variations in divider geometry. The authors hypothesized a link between basilar apex aneurysms and basilar bifurcation (α) and vertebrobasilar junction (VBJ) angles.
  
  
  METHODS
  The α and VBJ angles were measured in 3D MR and rotational angiographic volumes using a coplanar 3-point technique. Angle α was compared between age-matched cohorts in 45 patients with basilar artery (BA) aneurysms, 65 patients with aneurysms in other locations (non-BA), and 103 nonaneurysmal controls. Additional analysis was performed in 273 nonaneurysmal controls. Computational fluid dynamics (CFD) simulations were performed on parametric BA models with increasing angles.
  
  
  RESULTS
  Angle α was significantly wider in patients with BA aneurysms (146.7° ± 20.5°) than in those with non-BA aneurysms (111.7° ± 18°) and in controls (103° ± 20.6°) (p < 0.0001), whereas no difference was observed for the VBJ angle. A wider angle α correlated with BA aneurysm neck width but not dome size, which is consistent with CFD results showing a widening of the impingement zone at the bifurcation apex. BA bifurcations hosting even small aneurysms (< 5 mm) had a significantly larger α angle compared with matched controls (p < 0.0001). In nonaneurysmal controls, α increased with age (p < 0.0001), with a threshold effect above 35 years of age and a steeper dependence in females (p = 0.002) than males (p = 0.04).
  
  
  CONCLUSIONS
  The α angle widens with age during adulthood, especially in females. This angular widening is associated with basilar bifurcation aneurysms and may predispose individuals to aneurysm initiation by diffusing the flow impingement zone away from the protective medial band region of the flow divider.
authors.affiliation: Cerebrovascular and Endovascular Division, Department of Neurosurgery, Tufts Medical Center and Tufts University School of Medicine, Boston, Massachusetts.
authors.forename: Fatih
authors.initials: F
authors.lastname: Tütüncü
authors.forename: Sarah
authors.initials: S
authors.lastname: Schimansky
authors.forename: Merih I
authors.initials: MI
authors.lastname: Baharoglu
authors.forename: Bulang
authors.initials: B
authors.lastname: Gao
authors.forename: Daniel
authors.initials: D
authors.lastname: Calnan
authors.forename: James
authors.initials: J
authors.lastname: Hippelheuser
authors.forename: Mina G
authors.initials: MG
authors.lastname: Safain
authors.forename: Alexandra
authors.initials: A
authors.lastname: Lauric
authors.forename: Adel M
authors.initials: AM
authors.lastname: Malek
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001488:Basilar Artery / Q000473:pathology* / Q000502:physiology*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D057446:Hydrodynamics; D002532:Intracranial Aneurysm / Q000473:pathology* / Q000503:physiopathology* / Q000628:therapy; D016014:Linear Models; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D012720:Severity of Illness Index; D012737:Sex Factors
keywords: AUC = area under the curve; BA = basilar artery; CFD = computational fluid dynamics; IA = intracranial aneurysm; MPR = multiplanar reconstruction; MRA = MR angiography; PCA = posterior cerebral artery; ROC = receiver operating characteristic; VBJ = vertebrobasilar junction; WSS = wall shear stress; basilar bifurcation; bifurcation aneurysms; vascular age dependency; vascular disorders; vessel morphology