Hemodynamic characteristics at the rupture site of cerebral aneurysms: a case study

Hemodynamics play an important role in the mechanisms of aneurysm formation, growth, and rupture. However, little is known about the hemodynamics of rupture sites.

We incidentally acquired 3-dimensional images before and at the moment of rebleeding of a cerebral aneurysm in a patient. Comparison of these 2 images enabled precise identification of the rupture site. On the basis of computational fluid dynamics simulation, we propose that there are characteristic hemodynamic parameters of the rupture site in cerebral aneurysms. We evaluated flow velocity, wall shear stress (WSS), pressure, and the oscillatory shear index to determine characteristic parameters at the rupture site. Among the hemodynamic parameters in the cardiac cycle, the rupture site was most markedly distinguished by a combination of low WSS at end diastole and high pressure at peak systole. The flow patterns around the rupture site uniquely changed in the cardiac cycle. The rupture site was an impingement zone at peak systole. Flow separation at the rupture site was observed at end diastole.

In this case, a region with low WSS at end diastole and high pressure at peak systole was at the rupture site. A possible mechanism of rupture in this particular aneurysm is that low WSS at end diastole caused degeneration and thinning of the aneurysm wall and that high pressure at peak systole (impingement zone) resulted in rupture of the thinning wall.