1.What is subarachnoid hemorrhage (SAH)? There are three layers of meninges, from the outside to the inside: dura mater, arachnoid and soft meninges. What is arachnoid membrane? The arachnoid is a transparent membrane that forms a potential subdural space between the dura mater and the soft meninges, and a subarachnoid space between the soft meninges, which contains cerebrospinal fluid. Subarachnoid hemorrhage can be divided into two categories: primary and secondary. Primary subarachnoid hemorrhage occurs when blood flows directly into the subarachnoid space after a rupture of a blood vessel on the surface of the brain. Secondary subarachnoid hemorrhage is caused by cerebral parenchymal hemorrhage breaking into the subarachnoid hemorrhage. Only primary subarachnoid hemorrhage, referred to as subarachnoid hemorrhage, is described here. It accounts for approximately 6% to 8% of acute cerebrovascular disease, and is more common in young and middle-aged adults. It has been suggested that subarachnoid hemorrhage is not an independent disease, but a group of clinical syndromes caused by multiple causes or diseases occurring out of the blood flow into the subarachnoid space. The most common causes are intracranial aneurysms and cerebrovascular malformations, which account for more than 80% of the disease, with the former being more common than the latter. The former is more common than the latter. It occurs in middle and old age. Other causes include cerebral arteritis, intracranial tumors, hematologic diseases, cerebral thrombosis, intracranial reticulovascular abnormalities, after thrombolytic or anticoagulant therapy, and those with unknown causes. At the time of onset, about half of the patients had been emotionally excited or overexerted, which induced the rupture of the diseased vessels. 2.What are the main manifestations of subarachnoid hemorrhage? The main manifestations are as follows: (1) Patients have sudden onset, and a few have a history of headache, dizziness, blurred vision or long intermittent migraine before onset. In addition, there may be dizziness, dizziness, high blood pressure or high and low blood pressure fluctuations. In some people who have migraine with blurred vision, they should be alert to the presence of intracranial aneurysm or the possibility of aneurysm enlargement with imminent rupture. (2) Common triggering factors include heavy physical labor, strenuous exercise, emotional excitement, coughing, straining to defecate, drinking alcohol, running, sexual intercourse and other triggering factors, and then sudden onset of severe head swelling pain or splitting pain, which is unbearable and later becomes dull pain or throbbing pain. It is accompanied by nausea, vomiting, neck tonicity and positive meningeal irritation sign. (3) About 50% of patients have transient disturbance of consciousness or irritability at the onset, followed by coma. A few have hemiparesis, oculomotor disorders and seizures. 3.What tests are needed for subarachnoid hemorrhage? (1) Cranial CT or MRI: CT is a fast and safe means of diagnosing subarachnoid hemorrhage and should be the first choice for this disease. In addition, it is a guideline for choosing treatment methods and dynamic observation of the disease. (2) Lumbar puncture cerebrospinal fluid examination: seeing uniform bloody cerebrospinal fluid is the main basis for the diagnosis of subarachnoid hemorrhage. However, if subarachnoid hemorrhage has been detected by CT, lumbar puncture is not necessary. If CT is not available or if no accumulation of blood is seen on CT (negative), lumbar puncture of cerebrospinal fluid must be performed cautiously in those with high suspicion of subarachnoid hemorrhage. (3) Cerebral angiography: The most common causes of subarachnoid hemorrhage are intracranial aneurysm and cerebrovascular malformation, because digital subtraction angiography (DSA) and magnetic resonance angiography (MRA) can clarify the site of aneurysm or arteriovenous malformation and blood supply arteries, understand the collateral circulation and arterial spasm, strive for early cerebral angiography, and after clarification, try to strive for early surgery, which is the only way to reduce the morbidity and mortality rate. It is beneficial. The diagnostic value of digital subtraction angiography (DSA) is the greatest. 4.What are the complications of subarachnoid hemorrhage? (1) Rehemorrhage: Most often occurs within 4 weeks of the onset of the disease, and is particularly common in the second week. The bleeding artery rupture has not yet been repaired, and is triggered by premature waking up, emotional excitement and exertion. (2) Hydrocephalus: Acute hydrocephalus occurs mostly in the acute phase, where the patient’s condition suddenly deteriorates, with headache, vomiting, and worsening of impaired consciousness, a significant increase in cerebrospinal fluid pressure on lumbar puncture examination, and CT confirmation of hydrocephalus. Another kind of hydrocephalus is called traffic hydrocephalus, which occurs 2-4 weeks after the disease, manifesting as dementia, weakness of both lower extremities and urinary and fecal disorders. hydrocephalus is found in CT, and the increase of cerebrospinal fluid pressure in lumbar puncture examination is not obvious, also called normal cranial pressure hydrocephalus. (3) Cerebral artery spasm: It can appear early in the onset or 1 to 2 weeks, and occurs in about 25% of patients. The manifestation is hemiparesis or increased impairment of consciousness. No rebleeding of cerebrospinal fluid on lumbar puncture, foci of cerebral infarction visible on CT, and evidence of cerebral artery spasm can be found on digital subtraction angiography (DSA) or Doppler ultrasound.