Brain aneurysm is like an “untimely bomb” in the head, a considerable number of patients do not have any symptoms, only found by physical examination, but once it ruptures and bleeds, that is, the “bomb” explodes, it often causes a catastrophic blow to the human body, which may produce hemiplegia, aphasia, coma and even death. The consequences can be hemiplegia, aphasia, coma and even death. So, how do brain aneurysms actually form? As we all know, there are many arteries on the surface and deep in the brain parenchyma, and these arteries come from the branches of the internal carotid artery and the vertebrobasilar artery, which are distributed in the brain like the roots of a tree in the soil. The roots of the tree can develop aneurysms, and so can bulges in the weaknesses of the walls of the cerebral arteries, which are called cerebral aneurysms. Some aneurysms are formed congenitally during embryonic development of cerebral blood vessels, or there are congenital developmental defects in the walls of cerebral arteries (especially at the bifurcation of cerebral arteries), coupled with the involvement of acquired factors such as hypertension and atherosclerosis in adulthood, resulting in the local formation of aneurysms; some aneurysms are purely acquired, such as arteritis, atherosclerosis, trauma, etc. causing damage to the intima of arteries, coupled with the continuous impact of blood flow Once the aneurysm ruptures, the blood inside the artery overflows into the subarachnoid space, which is a very serious cerebrovascular event, termed subarachnoid hemorrhage. Clinically, patients often complain of severe blast-like or knife-like headaches, accompanied by jet vomiting, and in severe cases, convulsions, hemiparesis, aphasia, coma, or even sudden death. According to statistics, 10-15% of patients die before they can reach the hospital. Because of the dangerous course of ruptured cerebral aneurysm, it is not too much to describe cerebral aneurysm as an “untimely bomb” buried in the brain.