Computed tomography of cranial subdural and epidural hematomas: variation of attenuation related to time and clinical events such as rebleeding.

Forty-one cases of subdural and nine of epidural hematomas were studied with regard to attenuation and the time between trauma and computed tomography scanning. The attenuation of the hematomas showed a consistent decrease with time during the first 4 weeks. High attenuation of chronic subdural hematomas is explained by a sudden or continuous rebleeding. No correlation was found between the attenuation of the hematoma and the attenuation of venous blood from the same patient.