I. Etiology Among intracranial aneurysms, cystic aneurysms are the most common, and the mechanism of their occurrence, enlargement and rupture is one of the hot spots of research in recent years. The theory of congenital or intima-media defect in cystic aneurysms suggests that the intima-media defect at the bifurcation of intracranial arteries is congenital and is the basis of aneurysm formation. However, it was found that the intima-media defect at the bifurcation of intracranial arteries accounted for 80% of both aneurysmal patients and normal people; whether the intima-media defect existed naturally or was caused by probe injury, the internal elastic membrane of the arterial wall could withstand an intraluminal pressure of up to 600 mm Hg; the study of the animal models of aneurysms confirmed that the early changes of aneurysms did not occur in the intima-media defect at the apical end of the bifurcation of the Ring of Willis. The concept of “congenital aneurysm” is therefore rarely mentioned in the foreign literature. The theory of degenerative changes and internal elastic membrane defect is that the internal elastic membrane is the main structure to maintain the strength of the arterial wall, and its degenerative changes are the most important factors for the formation of cystic aneurysms, which are acquired diseases caused by damage to the internal elastic membrane due to pathogenic factors. Second, epidemiologic study At present, intracranial aneurysm is still a very dangerous disease. One-third of patients with aneurysms who bleed die before they have time to get to a medical unit for treatment. Half of the hospitalized patients also die or are left with neurological deficits. In recent years, the medical community has placed great emphasis on the dissemination of knowledge about SAH and intracranial aneurysms so that patients with aneurysms can be diagnosed and treated in a timely manner, and misdiagnosis can be reduced so that more patients can be detected and saved as early as possible. Particular emphasis is being placed on the emergency management of patients with SAH due to ruptured aneurysms, especially in the first few hours after SAH. This includes placing the patient in ICU immediately and performing cerebral angiography in time to clarify the cause of hemorrhage as soon as possible and strive for the timing of surgery. The diagnostic value of 3D-CT angiography on cerebrovascular 3D-CT angiography is a computer processed signal obtained by CT, which can show the color image of cerebrovascular in three dimensions and observe the morphology, size and relationship of blood-supplying arteries of AVMs and aneurysms from different angles on the monitor. 3D-CT angiography is clinically used to make the diagnosis of cerebrovascular disease more detailed and three-dimensional, especially for the determination of the location of the tip and width of aneurysms. The clinical application of 3D-CT imaging makes the diagnosis of cerebrovascular disease more detailed and stereoscopic, especially for determining the tip site and width of aneurysms, which provides detailed information for surgical clamping of aneurysms and resection of giant aneurysms. Recently, it has been reported that the angle analysis of C1-2 segment aneurysm and aneurysm-carrying artery by 3D-CT imaging ensures accurate clipping of the aneurysm during surgery. In recent years, there has been a gradual increase in the number of scholars abroad who advocate emergency surgery after aneurysm rupture. Surgery within a few hours after aneurysm bleeding has been carried out in many units. Decide whether to operate and choose the timing of surgery no longer rely solely on clinical grading. It has been argued that with adequate surgical skill and surgical experience, the risks of early and late surgery are the same. Early surgery reduces the incidence of rebleeding and the sequelae of delayed surgery. For the treatment of cerebral vasospasm, in addition to the continued use of Nimodipin, Japan has developed a new drug, Fasudil hydrochloride, which has been used clinically for more than 5 years with satisfactory results. In addition to continuous preoperative TCD monitoring of cerebral arteries, some people have applied TCD intraoperatively to detect the tumor-carrying arteries in search of measures to prevent and treat complications caused by vasospasm. However, the basic research on cerebral vasospasm has still not made amazing progress in recent years. In recent years, North American multicenter analysis of 772 patients with early and late surgery, early surgery 0-3 days, late surgery 11-32 days, postoperative observation of 6 months results, good postoperative recovery of early surgery is better than late surgery. Unoperated aneurysm rebleeding mortality rate of 70-90%, mostly occurring 24-48 hours after the first bleeding, of which 20-30% due to untimely surgery within 2 weeks rebleeding. Operative mortality and postoperative complications. In half of the patients operated on 0-1 days after SAH, half of the patients had high cerebral tone, and only 20% of the patients had high cerebral tone after 10 days, but no increase in postoperative complications due to cerebral contusion due to high cerebral tone was seen. The incidence of vasospasm is as high as 70-90% within two weeks after hemorrhage, and the mortality rate due to spasm has decreased from 40% in 1960 to 15% in 1980 and 8% in recent years. Early surgical removal of SAH can reduce the incidence of vasospasm. According to incomplete statistics, in the past 10 years, there are more than fifty hospitals in China with neurosurgery surgery treatment of 3246 cases of intracranial aneurysms, and good results have been achieved. Surgical treatment of giant aneurysm: aneurysm with diameter greater than 2.5cm is a giant aneurysm, accounting for 5-7% of intracranial aneurysms, which is still a challenging subject in neurosurgery. The difficulties in treatment are: (1) to protect the patency of blood vessels and their main branches. (2) The aneurysm should be removed to relieve the occupying effect. (3) The aneurysm-carrying artery needs to be reconstructed. There are four main surgical approaches used: A direct clamping and resection of the aneurysm; B reconstruction of the artery after resection of the aneurysm; C application of window aneurysm clamps to reconstruct the aneurysm-carrying artery; and D chronic ligation of the internal carotid artery with isolation of the aneurysm.