Cerebral effusion formed after craniocerebral surgery mainly refers to subdural effusion, which is formed due to the damage to the arachnoid membrane during the surgery, and the broken arachnoid membrane makes it easy for the cerebrospinal fluid to seep into the subdural and form subdural effusion. Subdural effusion is seen in elderly patients because the brain atrophy of the elderly is more obvious and the subdural space is larger, so it is easy to accumulate fluid. Once subdural effusion occurs, patients with a small amount of effusion may not need special treatment, and regular checkups are sufficient. If the amount of effusion is large, treatment can be given to activate blood circulation and remove blood stasis, improve microcirculation, and promote the absorption of effusion. If the effusion is not absorbed after conservative treatment with medication, but becomes larger and larger, and the patient develops compression symptoms, such as limb paralysis, headache, nausea, vomiting, and seizures, he/she needs to undergo drilling and drainage of the effusion.