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SAH is bleeding into the subarachnoid space caused by rupture of blood vessel on cerebral basis or brain surface, which is also known as primary subarachnoid hemorrhage, accounting for about 10% in cerebral apoplexy. SAH is a very common and severe cerebral disease. According to the world health organization survey, it is estimated that the incidence of SAH is about 2 per handred thousand people a year in china. |