Hemodynamic assessment of the development and rupture of intracranial aneurysms using computational simulations.

Intracranial aneurysms manifest themselves as sacculations within a weakened region of the vessel wall and pose substantial neurological risks upon rupture. A primary factor in the development and rupture stages of an aneurysm is hemodynamics and its degrading effects on the aneurysm wall. Wall dynamics and hemodynamics within a fully developed aneurysm were investigated using computational simulation techniques. To study wall dynamics, the aneurysm was modeled as a thing spherical shell with linearly elastic and plastic (viscoelastic) wall behavior. The sensitivity of this model to the biophysical parameters which describe it will assist in the quantitative assessment of factors predisposing to aneurysm rupture and subarachnoid hemorrhage. Flow dynamics simulations were performed for spherical aneurysms with rigid walls. We observed the development and motion of an annular vortex within the lateral sacculation. We also simulated a ruptured aneurysm by placing a tear near the neck of the aneurysm. Flow patterns showed blood flowing out during the initial stages of the flow, but displayed an inflow of blood soon thereafter, as the internal pressure dropped. These results are substantiated by the clinical observations that turbulent flow is observed within the aneurysm as evidenced by reduced bruits.