Angiographic findings in subdural hematoma correlated with CT attenuation values.

Twenty-eight subdural hematomas in 24 patients were examined by angiography and computed tomography (CT). The angiographic appearance of the hematomas was classified as either crescentic, lentiform, or transitional. The attenuation value of the hematomas was calculated from the CT scans. The mean attenuation of crescentic hematomas (13.8 EMI units--EU: 500 scale) was considerably lower than those of lentiform (21.7 EU) and transitional (19.8 EU) hematomas. The crescentic and transitional hematomas were either subacute or chronic, the chronic crescentic hematomas having an attenuation value at or around serum level. The lentiform hematomas were all more than 24 days old. The relatively high attenuation in chronic lentiform and transitional hematomas was probably caused by rebleeding, and the shape indicates enlargement of the hematomas after membrane formation has occurred. In the chronic, low attenuation crescentic hematomas, no recent bleed and no enlargement had occurred.