Evolution of chronic subdural hematoma after burr-hole exploration for subdural effusion--case report.

A 57-year-old male developed subdural effusion after head trauma, which remained asymptomatic and unchanged in volume during a follow-up period of 3 months. A typical chronic subdural hematoma (CSDH) developed 6 weeks after burr-hole exploration in spite of the absence of hematoma capsule or blood components in the effusion. The CSDH was successfully treated by irrigation and drainage. This case suggests that the presence of blood in subdural effusion may be the trigger for evolution of CSDH. We recommend that asymptomatic subdural effusion should be followed up without surgical intervention.