Clinical Neuroradiology

, Volume 29, Issue 2, pp 285–293 | Cite as

Hemodynamics of Focal Versus Global Growth of Small Cerebral Aneurysms

  • Paolo Machi
  • Rafik Ouared
  • Olivier Brina
  • Pierre Bouillot
  • Hasan Yilmaz
  • Maria I Vargas
  • Renato Gondar
  • Philippe Bijlenga
  • Karl O Lovblad
  • Zsolt KulcsárEmail author
Original Article


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.


Cerebral 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.

Supplementary material

62_2017_640_MOESM1_ESM.docx (107 kb)
Materials and methods
62_2017_640_MOESM2_ESM.jpg (3.1 mb)
OSI, peak systolic WSSG (Pa/µm) and WSS (Pa) in aneurysms and growth areas for patients p2, p5, p6. Patient representation is row-like. Columns from left to right represent for each patient, the growth area, and the spatial frequency distribution of OSI, peak systolic WSSG and WSS, over the aneurysm (blue) and growth area (yellow), respectively. Medallions, cast the zoom on distributions in growth areas
62_2017_640_MOESM3_ESM.jpg (1.4 mb)
Columns B, D and F, show the histograms (spatial density distribution functions) of OSI, peak systolic WSSG (Pa/µm) and WSS (Pa) in aneurysms (blue) and growth areas (yellow) for patients p1, p3, p4. Medallions, cast the zoom on distributions in growth areas. Columns A, C and E represent the clusterization (in red) of OSI, peak systolic WSSG and WSS patterns in overall growth areas (green), respectively. Patient representation is row-like
62_2017_640_MOESM4_ESM.jpg (832 kb)
Streamlines (colored by velocity) at peak systolic for all cases. The white arrows show the regions of growth


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Copyright information

© Springer-Verlag GmbH Germany 2017

Authors and Affiliations

  • Paolo Machi
    • 1
  • Rafik Ouared
    • 1
  • Olivier Brina
    • 1
  • Pierre Bouillot
    • 1
    • 2
  • Hasan Yilmaz
    • 1
  • Maria I Vargas
    • 1
  • Renato Gondar
    • 3
  • Philippe Bijlenga
    • 3
  • Karl O Lovblad
    • 1
  • Zsolt Kulcsár
    • 1
    • 4
    Email author
  1. 1.Neuroradiology Division, Department of Radiology and Medical InformaticsGeneva University HospitalsGenevaSwitzerland
  2. 2.Laboratory for Hydraulic MachinesÉcole Polytechnique Fédérale de LausanneLausanneSwitzerland
  3. 3.Neurosurgery Division, Department of Clinical NeurosciencesGeneva University HospitalsGenevaSwitzerland
  4. 4.Department of NeuroradiologyUniversity Hospital of ZurichZürichSwitzerland

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