title: Association of Hemodynamic Factors With Intracranial Aneurysm Formation and Rupture: Systematic Review and Meta-analysis.
abstract: BACKGROUND
  Recent evidence suggests a link between the magnitude and distribution of hemodynamic factors and the formation and rupture of intracranial aneurysms. However, there are many conflicting results.
  
  
  OBJECTIVE
  To quantify the effect of hemodynamic factors on aneurysm formation and their association with ruptured aneurysms.
  
  
  METHODS
  We performed a systematic review and meta-analysis through October 2014. Analysis of the effects of hemodynamic factors on aneurysm formation was performed by pooling the results of studies that compared geometrical models of intracranial aneurysms and "preaneurysm" models where the aneurysm was artificially removed. Furthermore, we calculated pooled standardized mean differences between ruptured and unruptured aneurysms to quantify the association of hemodynamic factors with ruptured aneurysms. Standard PRISMA guidelines were followed.
  
  
  RESULTS
  The hemodynamic factors that showed high positive correlations with location of aneurysm formation were high wall shear stress (WSS) and high gradient oscillatory number, with pooled proportions of 78.8% and 85.7%, respectively. Positive correlations were largely seen in bifurcation aneurysms, whereas negative correlations were seen in sidewall aneurysms. Mean and normalized WSS were significantly lower and low shear area significantly higher in ruptured aneurysms.
  
  
  CONCLUSIONS
  Pooled analyses of computational fluid dynamics models suggest that an increase in WSS and gradient oscillatory number may contribute to aneurysm formation, whereas low WSS is associated with ruptured aneurysms. The location of the aneurysm at the bifurcation or sidewall may influence the correlation of these hemodynamic factors.
authors.affiliation: Department of Neurosurgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Anil
authors.initials: A
authors.lastname: Can
authors.forename: Rose
authors.initials: R
authors.lastname: Du
mesh_terms: D017542:Aneurysm, Ruptured / Q000134:cerebrospinal fluid / Q000473:pathology* / Q000503:physiopathology; D006439:Hemodynamics; D006801:Humans; D002532:Intracranial Aneurysm / Q000134:cerebrospinal fluid / Q000473:pathology* / Q000503:physiopathology; D013345:Subarachnoid Hemorrhage / Q000134:cerebrospinal fluid / Q000473:pathology / Q000503:physiopathology