The cause of hydrocephalus after cerebral aneurysm surgery is due to blood deposition, blocking the normal circulation pathway of cerebrospinal fluid. Because after the rupture of cerebral aneurysm or after surgery, the bleeding caused by subarachnoid hemorrhage, subarachnoid hemorrhage is diffuse in the brain of the various interstitial spaces, once the amount of bleeding is relatively large, in the process of later cerebrospinal fluid circulation and the absorption of the hematoma, it is easy to produce similar to the sediment accumulation effect, gradually build up, and ultimately, make the original is not particularly smooth cerebrospinal circulation pathway, such as the interventricular foramen, the fourth ventricle, and other holes will form a blockage of the normal circulation pathway of cerebrospinal fluid, and the corresponding other holes. In the end, the cerebrospinal fluid circulation pathway, such as the interventricular foramen, the fourth ventricle, and other corresponding foramina, will be restenotic, and eventually occlusion will be formed. This is the cause of hydrocephalus after cerebral aneurysm surgery, so sometimes hydrocephalus is formed more rapidly and requires emergency extraventricular puncture and drainage to save the patient’s life.