HEMODYNAMIC-CHANGES IN RECURRENT INTRACRANIAL TERMINAL ANEURYSM AFTERENDOVASCULAR TREATMENT

Rationale and Objectives. Multiple cases of recurrence of aneurysms af ter endovascular treatment have been reported. The purpose of the curr ent hemodynamic study was to identify changes in shear stress and pres sure associated with the recurrence of terminal intracranial aneurysms after endovascular occlusion. Methods. Using a finite element method, a pulsed flow with a non-Newtonian viscosity of blood was simulated w ithin the aneurysm cavity. A recurrent terminal intracranial aneurysm of a patient originally treated with balloon occlusion was then studie d. This was based on a physiologic pulsatile flow, which was observed in the middle cerebral artery. Before and after the balloon occlusion, local maximum wall shear stress and pressure drop at the neck of the aneurysm were calculated and compared with the normal shear stress. Re sults. Although the maximum shear stress at the right neck of the aneu rysm was significantly reduced after balloon insertion, it was still 2 .5 times greater than the normal maximum shear stress. This was attrib utable to the presence of a portion of the aneurysmal neck (residual n eck), which was not obliterated by the balloon. The balloon also helpe d to reduce the maximum pressure inside the aneurysm by approximately 15%. Hemodynamic changes in the residual aneurysm neck, where the shea r stress and the pressure are high, and other factors may be responsib le for the recurrence of aneurysms after balloon or coil occlusion. Co nclusion. Residual necks after balloon occlusion, coil occlusion, or b oth are attributable to the geometric orientation of the aneurysm with respect to parent and daughter vessels and the variety of configurati ons of the balloon and coils used to occlude the aneurysms. Inadequate reduction in local shear stress found in these residual necks is an i mportant factor in the recurrence and rupture of the aneurysm after en dovascular occlusion.