Computational fluid dynamic analysis of intracranial aneurysmal bleb formation.
BACKGROUND
The management of unruptured aneurysms is controversial, with the decision to treat influenced by aneurysm characteristics including size and morphology. Aneurysmal bleb formation is thought to be associated with an increased risk of rupture.


OBJECTIVE
To correlate computational fluid dynamic (CFD) indices with bleb formation.


METHODS
Anatomic models were constructed from 3-dimensional rotational angiography data in 27 patients with cerebral aneurysms harboring a single bleb. Additional models representing the aneurysm before bleb formation were constructed by digitally removing the bleb. We characterized hemodynamic features of models both with and without the blebs using CFDs. Flow structure, wall shear stress (WSS), pressure, and oscillatory shear index (OSI) were analyzed.


RESULTS
There was a statistically significant association between bleb location at or adjacent to the point of maximal WSS (74%, P = .019), irrespective of rupture status. Aneurysmal blebs were related to the inflow or outflow jet in 89% of cases (P < .001), whereas 11% were unrelated. Maximal wall pressure and OSI were not significantly related to bleb location. The bleb region attained a lower WSS after its formation in 96% of cases (P < .001) and was also lower than the average aneurysm WSS in 86% of cases (P < .001).


CONCLUSIONS
Cerebral aneurysm blebs generally form at or adjacent to the point of maximal WSS and are aligned with major flow structures. Wall pressure and OSI do not contribute to determining bleb location. The measurement of WSS using CFD models may potentially predict bleb formation and thus improve the assessment of rupture risk in unruptured aneurysms.
*Kenneth Jamieson Department of Neurosurgery, Royal Brisbane and Women's Hospital, Brisbane, Australia; ‡Department of Information Technology Services (High Performance Computing), §School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Australia; ¶School of Chemical and Biomolecular Engineering, The University of Sydney, Sydney, Australia.
Jeremy H
JH
Russell
Neil
N
Kelson
Mark
M
Barry
Mark
M
Pearcy
David F
DF
Fletcher
Craig D
CD
Winter
D000792:Angiography; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D057446:Hydrodynamics; D021621:Imaging, Three-Dimensional; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging / Q000473:pathology; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D033081:Shear Strength; D013314:Stress, Mechanical