脑前循环系统主要由大脑前动脉、前交通动脉、大脑中动脉及后交通动脉组成 ,它约占颅内动脉瘤的 87%～ 97%左右 [1 ] 。由于该系统动脉瘤部位深、变异多 ,周围有重要结构 ,加上该系统动脉瘤生长方向变化多 ,术前病人情况均较重 ,使手术治疗难度大、危险性高 ,我科自 1998年以来 Anterior circulation system mainly consists of the anterior cerebral artery, anterior communicating artery, middle cerebral artery and posterior communicating artery, which accounts for about 87% to 97% of intracranial aneurysms [1]. Because of the aneurysm site of the system, the depth and variability, around the important structure, combined with the system aneurysm growth direction changes, preoperative patients are serious, so that the surgical treatment of large, high risk, our department since 1998 since