title: Magnitude and role of wall shear stress on cerebral aneurysm: computational fluid dynamic study of 20 middle cerebral artery aneurysms.
abstract: OBJECTIVE
  Wall shear stress (WSS) is one of the main pathogenic factors in the development of saccular cerebral aneurysms. The magnitude and distribution of the WSS in and around human middle cerebral artery (MCA) aneurysms were analyzed using the method of computed fluid dynamics (CFD).
  
  
  METHODS
  Twenty mathematical models of MCA vessels with aneurysms were created by 3-dimensional computed tomographic angiography. CFD calculations were performed by using our original finite-element solver with the assumption of Newtonian fluid property for blood and the rigid wall property for the vessel and the aneurysm.
  
  
  RESULTS
  The maximum WSS in the calculated region tended to occur near the neck of the aneurysm, not in its tip or bleb. The magnitude of the maximum WSS was 14.39+/-6.21 N/m2, which was 4-times higher than the average WSS in the vessel region (3.64+/-1.25 N/m2). The average WSS of the aneurysm region (1.64+/-1.16 N/m2) was significantly lower than that of the vessel region (P<0.05). The WSSs at the tip of ruptured aneurysms were markedly low.
  
  
  CONCLUSIONS
  These results suggest that in contrast to the pathogenic effect of a high WSS in the initiating phase, a low WSS may facilitate the growing phase and may trigger the rupture of a cerebral aneurysm by causing degenerative changes in the aneurysm wall. The WSS of the aneurysm region may be of some help for the prediction of rupture.
authors.affiliation: Department of Neurosurgery, Faculty of Medicine, University of Tokyo, Japan. mshoji-tky@umin.ac.jp
authors.forename: Masaaki
authors.initials: M
authors.lastname: Shojima
authors.forename: Marie
authors.initials: M
authors.lastname: Oshima
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Takagi
authors.forename: Ryo
authors.initials: R
authors.lastname: Torii
authors.forename: Motoharu
authors.initials: M
authors.lastname: Hayakawa
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Katada
authors.forename: Akio
authors.initials: A
authors.lastname: Morita
authors.forename: Takaaki
authors.initials: T
authors.lastname: Kirino
mesh_terms: D000368:Aged; D017542:Aneurysm, Ruptured / Q000503:physiopathology*; D002533:Cerebral Angiography; D004730:Endothelium, Vascular / Q000502:physiology*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological