γγA middle-aged male patient was admitted to the emergency room earlier this month. He came to our hospital for treatment of a fall injury to the hindbrain. A cranial CT showed an intracranial scattered subarachnoid hemorrhage, which was easily misdiagnosed as a traumatic brain injury according to previous thinking. In fact, the patient had a brain aneurysm, an insidious fatal killer, in his skull. The patient was consulted by the Department of Brain Surgery and immediately improved the pre-surgical preparation. During the operation, it was confirmed that the doctor’s judgment was correct, and the patient fell because of a ruptured bleeding anterior cerebral communicating aneurysm, not bleeding from traumatic brain injury. After timely detection of the cause, the patient underwent intracranial aneurysm clamping surgery at the first time, and the patient recovered well after the surgery.γγAn intracranial aneurysm is an abnormal bulge (non-neoplastic) in the wall of an intracranial artery, which is rarely detected until it ruptures because the aneurysm is usually small and does not cause clinical symptoms. A ruptured aneurysm can cause serious pathological changes such as subarachnoid hemorrhage (SAH). The mortality rate of ruptured aneurysms is about 30-40% at first rupture and up to 60% at second rupture, and the disability rate of survivors is very high. The timely diagnosis and treatment of intracranial aneurysms is very critical. This is another case of intracranial vascular lesion that has been treated since the start of neurointervention in our hospital.