Intracranial aneurysms are sac-like protrusions formed by localized enlargement of blood vessels. Due to specific histopathological and hemodynamic reasons, aneurysms often grow on blood vessels supplying blood to the brain. The prevalence of aneurysms in adults ranges from 1-5% in autopsy analysis. However, most aneurysms are small and it is estimated that approximately 50-80% of these aneurysms will not rupture during their lifetime. The formation of aneurysms is associated with congenital and acquired factors. The incidence of aneurysms in families with two or more immediate family members with aneurysms or subarachnoid hemorrhage is between 8-9%. Many connective tissue diseases are associated with the formation of aneurysms, presumably primarily because these diseases can cause vascular disease to become abnormal. Studies have shown that the prevalence of aneurysms in patients with polycystic kidney disease (an autosomal dominant disorder) is between 10-15%. Aortic stenosis, myofibrillar dysplasia, and pheochromocytoma are often associated with aneurysms, and it is mainly believed that these conditions can lead to hypertension. Recent data suggest that age older than 50 years, being female, and having a smoking habit are also risk factors for aneurysm development. Most aneurysms have a subarachnoid hemorrhage as the first symptom. Long-term follow-up of patients with unruptured aneurysms reveals an average rupture rate of approximately 2-3% per year (2.3%), with a 10-year involvement rate of 20% and a 15-year involvement rate of 35%. Patients with ruptured aneurysms resulting in subarachnoid hemorrhage are prone to rupture and bleed again. The rate of re-rupture within 24 after the first bleed is 2-4%, and about 15–20% re-rupture within 2 weeks. Studies have shown that the incidence is about twice as high in women as in men, with a peak age of onset between 55 and 60 years, and that subarachnoid is the cause in 5-15% of stroke patients. Another approximately 30% of surviving patients are left with moderate to severe neurological deficits.