The brain is located in the cranial cavity, and there is a layer of meninges between the cranial cavity and the brain called the arachnoid membrane. The space between the arachnoid membrane and the brain is called the subarachnoid space, which is filled with cerebrospinal fluid, and the brain is immersed in cerebrospinal fluid. The large blood vessels that supply blood to the brain travel through the subarachnoid space, and all the nerves in the brain also travel out of the subarachnoid space. When a blood vessel in the brain ruptures and bleeds, blood flows first into the subarachnoid space, called a subarachnoid hemorrhage. The typical presentation of a subarachnoid hemorrhage is a sudden onset of severe headache and, in severe cases, coma. The main tool for doctors to diagnose subarachnoid hemorrhage is cranial CT. The typical CT presentation of subarachnoid hemorrhage is shown in the figure below. The traditional medical view is that subarachnoid hemorrhage is an independent disease and has long been treated by neurology. However, modern medicine has confirmed that subarachnoid hemorrhage is not an independent disease, but a common clinical manifestation of many diseases. One of the most common causes is ruptured cerebral aneurysm bleeding (see below), followed by ruptured cerebrovascular malformation, and less common causes are brain tumors and abnormal occlusive cerebrovascular disease. All these causes can be completely cured by surgery, and internal medicine can only treat the symptoms but not the root cause, so it should no longer be a medical disease, but a neurosurgical disease, and should be admitted by neurosurgery. Myth 2: The treatment of subarachnoid hemorrhage is the treatment of headache, and a better headache is a better treatment. The main symptom of subarachnoid hemorrhage is headache, and even if it is not treated, the headache will naturally decrease as the hemorrhage dissipates. However, if the cause of the hemorrhage is not treated, it will definitely bleed again, and then all the pre-treatment will come to naught. Therefore, for patients with subarachnoid hemorrhage, an improvement in headache is never a cure, and the cause needs to be identified and treated. Myth 3: Patients with subarachnoid hemorrhage cannot be transported and can only be treated in situ, and transporting them can cause rebleeding. The key to treating subarachnoid hemorrhage is to prevent rebleeding, and the key to preventing rebleeding is to diagnose the cause of the hemorrhage and treat the cause. For hospitals that are not equipped to diagnose and treat the cause of bleeding (mainly cerebral aneurysms), the treatment is not meaningful and all the previous treatment will be wasted if there is rebleeding. Therefore, it is better to transfer the patient early for the most timely and effective treatment than to wait for death in a hospital that is not equipped to do so. Moreover, there is no evidence that moving a patient leads to rebleeding, and leaving the brain aneurysm untreated is a more fundamental cause of rebleeding. Myth 4: Cerebrovascular examinations cannot be done in the early stages of bleeding. In fact, cerebrovascular examinations (cerebral angiography) are now very safe and do not cause the risk of bleeding, and the risk of waiting is much greater than the risk of examination, so cerebrovascular examinations should be performed as early as possible to find out the cause. Nowadays, CTA examination does not require arterial cannulation and is almost risk-free. It can clearly show the intracranial cerebral vessels and the cerebral aneurysm that causes bleeding (see below) Myth 5: Interventional treatment is safer than craniotomy. The history of cerebral aneurysm clamping, which requires craniotomy, is nearly 100 years old. Especially under the conditions of micro-neurosurgery technology, the procedure has become almost a routine neurosurgical procedure with very reliable results in the hands of experienced neurosurgeons. The principle of the procedure is that the aneurysm neck is clamped shut with a titanium clip and the blood will no longer flow to the aneurysm, so there will be no bleeding. However, for the average person, opening the skull is too scary, so interventional treatment is preferred. Interventional treatment does not require craniotomy and is indeed less invasive, but it is not all-inclusive. For wide carotid aneurysms intervention cannot be performed and it will also may not be performed because of vasospasm. The biggest drawback is the poor long-term outcome, with a recurrence rate of about 30% after 5 years. Moreover, if the patient has hydrocephalus or intracerebral hematoma, the intervention cannot help at all, and surgery is eventually required. In clinical practice, doctors will choose which treatment method to use according to the specific characteristics of the aneurysm and the specific situation of the patient, and there is no phenomenon that intervention is safer than surgery.