title: Hemodynamic differences between unstable and stable unruptured aneurysms independent of size and location: a pilot study.
abstract: BACKGROUND
  While clinical and angiographic risk factors for intracranial aneurysm instability are well established, it is reasonable to postulate that intra-aneurysmal hemodynamics also have a role in aneurysm instability.
  
  
  OBJECTIVE
  To identify hemodynamic characteristics that differ between radiologically unstable and stable unruptured intracranial aneurysms.
  
  
  METHODS
  12 pairs of unruptured intracranial aneurysms with a 3D rotational angiographic set of images and followed up longitudinally without treatment were studied. Each pair consisted of one stable aneurysm (no change on serial imaging) and one unstable aneurysm (demonstrated growth of at least 1 mm diameter or ruptured during follow-up) of matching size (within 10%) and locations. Patient-specific computational fluid dynamics models were created and run under pulsatile flow conditions. Relevant hemodynamic and geometric variables were calculated and compared between groups using the paired Wilcoxon test.
  
  
  RESULTS
  The area of the aneurysm under low wall shear stress (low shear stress area (LSA)) was 2.26 times larger in unstable aneurysms than in stable aneurysms (p=0.0499). The mean aneurysm vorticity was smaller by a factor of 0.57 in unstable aneurysms compared with stable aneurysms (p=0.0499). No statistically significant differences in geometric variables or shape indices were found.
  
  
  CONCLUSIONS
  This pilot study suggests there may be hemodynamic differences between unstable and stable unruptured cerebral aneurysms. In particular, the area under low wall shear stress was larger in unstable aneurysms. These findings should be considered tentative until confirmed by future larger studies.
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Waleed
authors.initials: W
authors.lastname: Brinjikji
authors.affiliation: Department of Bioengineering, Volgenau School of Engineering, George Mason University, Fairfax, Virginia, USA.
authors.forename: Bong Jae
authors.initials: BJ
authors.lastname: Chung
authors.affiliation: Department of Neurosurgery, University of Antioquia, Medellin, Colombia.
authors.forename: Carlos
authors.initials: C
authors.lastname: Jimenez
authors.affiliation: Department of Interventional Neuroradiology, Inova Fairfax Hospital, Falls Church, Virginia, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Putman
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: David F
authors.initials: DF
authors.lastname: Kallmes
authors.affiliation: Department of Bioengineering, Volgenau School of Engineering, George Mason University, Fairfax, Virginia, USA.
authors.forename: Juan R
authors.initials: JR
authors.lastname: Cebral
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017542:Aneurysm, Ruptured / Q000000981:diagnostic imaging / Q000503:physiopathology*; D015901:Angiography, Digital Subtraction / Q000379:methods; D002533:Cerebral Angiography / Q000379:methods; D003198:Computer Simulation; D005260:Female; D005500:Follow-Up Studies; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D057446:Hydrodynamics; D021621:Imaging, Three-Dimensional / Q000379:methods; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D011673:Pulsatile Flow; D012307:Risk Factors; D013314:Stress, Mechanical
keywords: Aneurysm; Subarachnoid