People can experience many headaches in their lifetime, including headaches from colds and fevers, headaches from poor sleep, and headaches from prolonged stress and strain, but there is one type of headache that must be a cause for concern. Sudden and severe headache under activity needs to be alerted, this kind of headache is swelling or bursting pain, which is unbearable. It can be limited or full headache, and sometimes the pain can occur in the upper neck. It is persistent and unrelieved or progressively aggravated, and is often accompanied by nausea and vomiting; there may be disturbance of consciousness or mental symptoms such as irritability, delirium, and hallucinations. It has been described as the most painful headache of a lifetime. This headache is most likely caused by spontaneous subarachnoid hemorrhage. Causes of spontaneous subarachnoid hemorrhage include ruptured intracranial aneurysm, primary pericentral hemorrhage, cerebrovascular malformation, hypertensive atherosclerosis, smog, cerebral artery entrapment, central nervous system arteritis, hematologic disease, and intracranial tumors. However, more than 80% of patients are bleeding from ruptured intracranial aneurysm, and the condition of ruptured intracranial aneurysm bleeding is critical, and the mortality rate of re-rupture bleeding is high, so it needs urgent treatment, so it needs to go to hospital immediately and check cranial CT and CTA to make a clear diagnosis.