Mechanism underlying the prevention of aneurismal rupture by coil embolization

(Object) Endovascular treatment with Guglielmi detachable coil has been developed as a less invasive treatment for cerebral aneurysm. The aim of this study is to clarify the mechanism of the preventive effect of coil embolization. (Method) Two aneurysm models were employed. One was a T-shaped bifurcation tube with a spherical dome made of glass, which was used for the measurement of pressure and visualization of flow pattern. The other model was a T-shaped glass tube with a spherical elastic silicone dome, which was used for the measurement of aneurismal wall displacement due to pulsation of flow. (Result) 1, Guglielmi detachable coil caused no change in intra-aneurismal fluid pressure. 2, Coil insertion obstructed and slowed intra-aneurismal flow. This flow stagnation in the aneurysm might promote thrombus formation. 3, With increase in numbers of coils anchored at the intra-aneurismal wall, the displacement of the wall was considerably depressed. This suggests that coil insertion decreases the stress on the aneurismal wall. (Conclusion) 1, Coil insertion depresses the pulsatile aneurysm wall movement, and diminishes the stress of the aneurysm wall. 2, Coil insertion obstructs intra-aneurismal flow and facilitates thrombus formation in the aneurysm. These two factors may operate synergistically to prevent aneurysm rupture.