Subdural effusion following radical surgery for chiasmal region tumors in children. Report of 4 cases.

4 cases of subdural effusion occurring after radical surgery for chiasmal region tumors in children are reported. The pathogenetic mechanisms of this disorder are explained at least partly by a change from internal to external hydrocephalus or brain atrophy in 2 of the 4 cases, whereas the pathogenesis is unclear in the remaining 2 cases. In all 4 cases meningitis did not supervene postoperatively. The subdural effusion may be divided roughly into two types according to symptomatology: "serious type' which presents with severe symptoms and "mild type' which is virtually asymptomatic. The serious type requires immediate surgical procedure, such as continuous subdural drainage and subduroperitoneal shunt, while the mild type should be carefully monitored for the course of subdural effusion by CT scan.