Cerebellar hemorrhage of 10 ml or more requires surgery. The cerebellum is located in the posterior cranial fossa, which is much smaller in volume compared to the cerebral hemispheres, so cerebellar hemorrhage can cause severe intracranial pressure elevation even if the bleeding volume is small. Since the fourth ventricle is located in the cerebellar hemisphere, cerebellar hemorrhage may compress the fourth ventricle and cause occlusion of the fourth ventricle, resulting in obstruction of the cerebrospinal fluid circulation pathway causing obstructive hydrocephalus, thus causing a rapid rise in intracranial pressure and leading to severe symptoms of increased intracranial pressure, manifesting as vomiting and even life-threatening coma. Therefore, if the bleeding volume of cerebellar hemispheres is 10 ml or more, surgery is required, which is usually done by craniotomy.