I. What is subarachnoid hemorrhage (SAH) There are three layers of membranes on the surface of the human brain, from the inside to the outside: the soft meninges, the arachnoid, and the dura mater. The cavity between the arachnoid and the soft meninges is called the subarachnoid space, which is normally filled with colorless and transparent cerebrospinal fluid. When the cerebral vessels suddenly rupture for various reasons, blood flows into the subarachnoid space, which is collectively called subarachnoid hemorrhage, or SAH for short. Spontaneous SAH accounts for about 15% of acute cerebrovascular accidents. The most common cause of spontaneous SAH is rupture of intracranial aneurysm, accounting for about 75% of cases; the next cause is cerebrovascular malformation, accounting for about 5-10% of cases; other cerebrovascular diseases include cerebral atherosclerosis, smog disease (Moyamoya disease), etc.; about 10% of patients have unknown causes. Clinical manifestations of spontaneous SAH 1. hemorrhagic symptoms: manifested as sudden onset, often described by patients as “tear-like” headache, mostly full headache and posterior neck pain, accompanied by nausea, vomiting, pale face, cold sweat, convulsions, unconsciousness and even respiratory and cardiac arrest in severe cases, and about 10-15% of patients die before reaching the hospital. About 10-15% of patients die before reaching the hospital. The cranial CT shows a high-density shadow in the subarachnoid space. 2.Loss of neurological function: Different neurological dysfunction can occur depending on the location of the aneurysm. For example, posterior communicating aneurysm often causes arteriovenous nerve palsy; middle cerebral aneurysm rupture causes hemiparesis or/and aphasia; basilar aneurysm rupture causes bilateral abducens nerve palsy or brainstem symptoms, etc. 3.Epilepsy: about 3% of patients can appear in the acute stage, and the incidence is about 10.5% in 5 years. Other symptoms: such as intracranial murmur, arrhythmia, etc. Treatment of spontaneous SAH The treatment of SAH is a comprehensive treatment, including symptomatic treatment and etiological treatment. (1) Symptomatic treatment: (1) Close observation of vital signs, hemostasis, sedation, analgesia, and keeping bowel movement in the acute stage of bleeding; (2) Treatment of dehydration and cranial pressure reduction in case of intracranial hypertension; (3) Prevention of seizures by phenytoin sodium and other drugs within one month after bleeding; (4) Maintenance of water, electrolyte and acid-base balance; (5) Prevention and control of cerebral vasospasm, nutritional support and functional rehabilitation; (6) Whole brain angiography as soon as possible to clarify the cause of bleeding and carry out etiological treatment. (6) Perform whole brain angiography as soon as possible to identify the cause of bleeding and carry out etiological treatment. (2) Etiological treatment: The most important treatment plan for spontaneous subarachnoid hemorrhage is to identify the cause of SAH and then provide targeted treatment. To identify the cause of SAH, non-invasive diagnostic tools such as MRA (magnetic resonance angiography) and CTA (tomography angiography) can be applied, but digital subtraction cerebral angiography (DSA) remains the gold standard for confirming the cause of spontaneous subarachnoid hemorrhage. Through DSA examination, physicians can clarify the nature, location, morphology and severity of the underlying cerebrovascular lesion causing SAH, and further develop the next treatment plan.