The primary goal of endovascular treatment can be prevention of recurrent subarachnoid hemorrhage (SAH), prevention of primary SAH, or alleviation of symptoms such as mass effect or thromboembolic events.Different endovascular treatment strategies may be applied for large and giamt aneurysms and include parent vessel occlusion with balloons or coils ; selective coil occlusion sparing the parent artery and selective coil occlusion with aid of a supporting device (balloon, stent) ; selective occlusion with Onyx and parent vessel occlusion after bypass surgery.