Chronic subdural haematoma
Chronic subdural haematoma. While acute haemorrhage is hyperdense, over time there is progressive degradation of the blood products which results in a reduction in the density of the haematoma. In a subacute haematoma (1-3 weeks old), the blood may be of similar density (isodense) to the brain parenchyma, making it difficult to identify. Chronic subdural haematomas, like this one (arrows), are less dense than brain parenchyma, and in fact may be of identical density to CSF.