Angiographic characteristics of certain subdural collections of fluid.

The presence of abnormal amounts of fluid in the subdural space has been referred to as subdural hematoma, subdural effusion and subdural hygroma. These are supposed to be differentiated by the appearance of the fluid and the presence of membranes in the dubdural space. Although both hygroma and chronic subdural hematoma are liquid, space-occupying lesions which cause pressure in the underlying brain, we have found that there are definite angiographic, clinical and prognostic differences between them. These differences are described.