The prognosis of subarachnoid hemorrhage (SAH) caused by aneurysms is very poor, with a 30-day lethality rate as high as 45% even after rigorous and meticulous treatment, and irreversible brain damage in about half of the patients who survive. Based on an annual incidence of SAH of approximately 10/100,000 people, approximately 140,000 people in China are at risk of SAH each year.For these reasons, neurologists in the latter half of the last century blindly assumed that all intracranial aneurysms should be aggressively intervened before hemorrhage. However, with an average population prevalence of aneurysms as high as 2-9%, the vast majority of aneurysms are unhemorrhagic when compared with the low prevalence of SAH, and so, without definitive evidence, we cannot hasten to say that surgical or interventional intervention is warranted as soon as an intracranial aneurysm is detected. The largest international multicenter study is currently being conducted by ISUIA (International Study of Unruptured |ntracranialAneurysms Investigators). The results of the phase I retrospective study showed that in asymptomatic aneurysm patients without a history of subarachnoid hemorrhage, the annual rupture rate of aneurysms with a diameter of less than 10 mm was 0.05%, whereas the rates of those with diameters of 10-25 mm and those with diameters of greater than 25 mm were 1% and 6% or more, respectively.The results of the phase II prospective study, which was conducted with 4,060 subjects from more than 60 treatment centers in the United States, Canada, and Europe, were observed for more than 7 years. The study was conducted in more than 60 treatment centers in the United States, Canada, and Europe with 4060 patients who were observed for more than 7 years. 1692 patients were in the untreated group, 1917 patients were in the microsurgery group, and 451 patients were in the interventional group. Patients in each group were subdivided into two groups, i.e., the group of patients without history of aneurysmal SAH and the group of patients with history of aneurysmal SAH. The results showed that the 5-year cumulative rupture rates in the first group of patients (no history of aneurysmal SAH) were 0% (3-7 mm in diameter), 2.6% (7-12 mm), 14.5% (13-24 mm), and 40% (more than 25 mm) for anterior circulation aneurysms by size, and 2.5%, 14.5%, 18.4% and 50%; for 7 to 12 mm aneurysms, the annual rupture rate was 0.5% for anterior circulation aneurysms and 2.9% for posterior circulation. Shortly after ISUIA was published, a number of neurosurgical teams began to criticize it, arguing that the study’s retrospective group was biased because the patients in that group had aneurysms in sites that were not prone to rupture. In addition, its study subjects were all from a population that had already decided not to intervene, and these aneurysms were thought to be more stable than randomly selected aneurysms from the general population. According to Weir et al, it is irresponsible to base treatment solely on the maximum diameter of the aneurysm. More than 15,000 aneurysms with a maximum diameter of <7 mm rupture each year in the United States, and most of these aneurysms are asymptomatic before rupture.A retrospective study of 4619 patients with unruptured aneurysms by Britz et al. found that survival rates were higher in patients with surgical clamping than in those who were not operated on, supporting early intervention for unruptured aneurysms.Wiebers et al. performed a study of 1692 cases of unsurgically treated, Wiebers et al. studied the 5-year morbidity and mortality rates in 1917 patients with unruptured aneurysms who underwent clamping surgery and 451 patients who underwent endovascular treatment: the natural morbidity and mortality rates of unruptured aneurysms were equal to or higher than those associated with damage caused by clamping surgery or endovascular surgery.Krisht et al. concluded that the 10-year cumulative rate of morbidity, mortality, and severe disability in patients with unruptured aneurysms was not less than 7.5%, and the Krisht et al. concluded that the 10-year cumulative mortality and severe disability rates for patients with unruptured aneurysms were not less than 7.5%, whereas the rates for surgical closure were 0.8% and 3.4%, suggesting that surgical closure may be preferable to leaving the patient untreated if the patient has a life expectancy of not less than 10 years. patients, surgical treatment may benefit patients with unruptured aneurysms by extending life expectancy. Taken together, the current American Heart Association treatment guidelines for the management of unruptured aneurysms are as follows: (1) small incidentally detected intracavernous sinus aneurysms do not require management; large symptomatic intracavernous sinus aneurysms should be managed if age permits and if symptoms are severe or progressive. (ii) All intracranial symptomatic aneurysms should be considered for management; if they are emergencies, they should be treated urgently; for large and giant symptomatic aneurysms, the risk of surgery is high, and management should be centralized and individualized. Aneurysms with a history of SAH should be managed regardless of size, especially if they are located at the top of the basilar artery; the patient's age, health status, and the risk of treatment may influence the management of aneurysms, and they should be closely monitored when treated conservatively. Asymptomatic aneurysms (<10 mm) without a history of SAH should be observed unless the patient is young, has a daughter aneurysm, or has other unique hemodynamic characteristics, etc., that warrant consideration of treatment; those with a family history of SAH should also be considered for management. ⑤ Aneurysms larger than 10 mm should be managed, taking into account age, health status, and risk of aneurysm rupture. For patients without SAH occasional small aneurysms (<6 mm in diameter) with a low risk of bleeding, their treatment is not advocated, but rather close observation. Currently, due to the booming development of interventional materials and interventional techniques, the risk of aneurysm treatment is getting lower and lower, so the Department of Neurointervention at Tiantan Hospital has broadened the indications for interventional treatment of aneurysms.