The people rarely heard of subarachnoid hemorrhage, very also unfamiliar, but familiar with brain hemorrhage, cerebral hemorrhage and other diseases, so relatives a subarachnoid hemorrhage, are the first contact, the first time I heard, in essence, subarachnoid hemorrhage is cerebral hemorrhage, is a special type of brain hemorrhage, we must first know what is the brain arachnoid? The arachnoid membrane is thin and transparent, devoid of blood vessels and nerves, it envelops the entire brain tissue, but does not penetrate deep into the cerebral sulcus. The potential gap between this membrane and the soft meninges on the surface of the brain is easy to separate, and the gap contains cerebrospinal fluid, which is connected to the subarachnoid space of the spinal cord through the greater occipital foramen. Subarachnoid hemorrhage refers to the rupture of a blood vessel in the cerebral base or superficial part of the brain, and blood enters the subarachnoid space directly. Blood mixes with cerebrospinal fluid in the subarachnoid space to form a subarachnoid hemorrhage, and in severe cases, a hematoma can form. Why can subarachnoid hemorrhage occur? There are many causes of subarachnoid hemorrhage, but by far the most common are congenital intracranial aneurysms and cerebrovascular malformations, followed by hypertension, atherosclerosis, intracranial tumors, blood disorders, arteritis caused by intracranial infections, and a very small percentage of subarachnoid hemorrhages for which no cause has been identified. Intracranial aneurysms are the most common cause of subarachnoid hemorrhage, reaching more than 90%. So, what is an intracranial aneurysm? And how do they occur? For example, we ride bicycles in our daily lives, bicycle inner tube, with time, tire aging, inner tube somewhere is getting thinner and thinner, over time, the formation of a small bulge, and then frequent use of the rupture, we call the air leak, if we do not repair the tire, it may burst the tire, why there will be a small bulge, it must be the bicycle factory, the tire processing process somewhere on the thin, leaving hidden problems for the future . The same goes for the intracranial, an artery in the skull, with age, a part of the artery is getting thinner and thinner, with high blood pressure, external triggers, gradually forming a small bulge, gradually forming an aneurysm, with the passage of time the aneurysm can rupture and bleed, this blood out in the subarachnoid space, causing a series of clinical symptoms, if no longer treated, can bleed again crisis life. So how is it diagnosed? In clinical cases of sudden onset of severe head pain, CT can usually clarify the subarachnoid hemorrhage, but to know the cause of the hemorrhage, we need to further investigate the intracranial vascular images of CTA or DSA cerebral angiography. The diagnosis is easier. How to treat intracranial aneurysm? There are two ways to treat aneurysm, one is neurointerventional, which is to enter the artery inside the skull without opening the skull and use catheter to fill the aneurysm cavity directly, so that the aneurysm will not rupture and bleed again, but it is not suitable for patients who already have intracranial hematoma. This procedure is more suitable for patients with intracranial hematoma, younger patients with better health, and older patients who cannot tolerate craniotomy are generally not selected. The choice between craniotomy and intervention is patient-specific and depends on the choice of the neurosurgeon. In conclusion, subarachnoid hemorrhage is not a scary condition, but must be seen at the first opportunity at a local hospital with a better neurosurgery department.