Hemodynamics of Focal Versus Global Growth of Small Cerebral Aneurysms
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Background and Purpose
Hemodynamics play a driving role in the life cycle of brain aneurysms from initiation through growth until eventual rupture. The specific factors behind aneurysm growth, especially in small aneurysms, are not well elucidated. The goal of this study was to differentiate focal versus general growth and to analyze the hemodynamic microenvironment at the sites of enlargement in small cerebral aneurysms.
Materials and Methods
Small aneurysms showing growth during follow-up were identified from our prospective aneurysm database. Three dimensional rotational angiography (3DRA) studies before and after morphology changes were available for all aneurysms included in the study, allowing for detailed shape and computational fluid dynamic (CFD) based hemodynamic analysis. Six patients fulfilled the inclusion criteria.
Two different types of change were observed: focal growth, with bleb or blister formation in three, and global aneurysm enlargement accompanied by neck broadening in other three patients. Areas of focal growth showed low shear conditions with increased oscillations at the site of growth (a low wall shear stress [WSS] and high oscillatory shear index [OSI]). Global aneurysm enlargement was associated with increased WSS coupled with a high spatial wall shear stress gradient (WSSG).
For different aneurysm growth types, distinctive hemodynamic microenvironment may be responsible and temporal–spatial changes of the pathologic WSS would have the inciting effect. We suggest the distinction of focal and global growth types in future hemodynamic and histological studies.
KeywordsCerebral aneurysm Aneurysm growth Subarachnoid hemorrhage Computational flow Dynamics
Internal carotid artery
Magnetic resonance angiography
Computed tomographic angiography
Three-dimensional rotational angiography
Wall shear stress
Wall shear stress gradient
Oscillatory shear index
Growth area (of the aneurysm wall)
Low value fraction
High value fraction
Digital subtraction angiography
This study was supported by Swiss National Science Foundation grants (SNF 32003B_160222 and SNF 320030_156813).
Conflict of interest
P. Machi, R. Ouared, O. Brina, P. Bouillot, H. Yilmaz, M.I. Vargas, R. Gondar, P. Bijlenga, K.O. Lovblad and Z. Kulcsár declare that they have no competing interests.
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