What is a cerebral aneurysm? An aneurysm is an abnormal weakness in the arterial wall that causes the arterial wall to protrude outward into a spherical lesion. This weakness is called a fusiform aneurysm if it involves the entire wall of the artery, a saccular aneurysm if it involves a layer of the artery wall, or a dissecting aneurysm if it separates the artery wall. Among these, hemorrhagic strokes that occur after the rupture of an aneurysm in the brain can lead to severe brain damage and even death. The incidence of cerebral aneurysms is estimated to be 6-7%, meaning that 15 normal people will develop a cerebral aneurysm in their lifetime. Cerebral aneurysms are usually detected when they rupture and cause bleeding into the lumen surrounding the brain tissue (subarachnoid space). Ruptured aneurysms can lead to hemorrhagic stroke, brain damage, and even death. 10-15% of patients with ruptured aneurysms die before they reach the hospital; more than 50% of patients die within three days of bleeding; and half of the remaining patients will have permanent neurological impairment; the age at which aneurysms tend to occur is 40-60 years; the gender ratio of aneurysms is female:male = 3:2. 20% of patients with aneurysms have multiple aneurysms (more than 2 aneurysms). Risk factors associated with the development of cerebral aneurysms are excessive smoking, alcohol abuse, and chronic hypertension. The risk of developing a cerebral aneurysm is also elevated in those with fibromuscular dysplasia and polycystic kidney. The primary goal of treatment for ruptured aneurysms is to stop rebleeding and reduce the risk of recurrence. Treatment of unruptured aneurysms is aimed at preventing their rupture.