Clinicopathological classification of chronic subdural hematoma.

Clinicopathological classification of chronic subdural hematoma was made, based on a study of 135 cases; chronic subdural hematoma with a visible inner membrane (type I: 123 cases), acute subdural hematoma in chronic healing stage (type II: 8 cases), and chronic subdural effusion of hemorrhagic type (type III: 4 cases). Type I is an expanding lesion, due to repetitive hemorrhage from outer membrane. It is a traditional hematoma with a distinct inner membrane. Type II is a late healing stage of a previously unrecognized or unoperated acute subdural hematoma, and not an expanding lesion. It has a subdural granulation tissue of irregular thickness with little rebleeding tendency, but it lacks a visible inner membrane. Type III is a variant of chronic subdural effusion, in which a minimum amount of fresh blood is added to a maximum amount of xanthochromic fluids. The latter contains an extremely low level of LDH.