If the hyperdense ("bright") areas are blood, what do the surrounding low density areas represent?
This is oedema in the surrounding brain cells. This will continue to cause swelling of the brain parenchyma, raising the ICP and will need monitoring. From the appearance of this scan, the oedema includes both the grey and white matter and is termed "cytotoxic" implying cell destruction (further imaging may be involved).
The right parenchymal haemorrhage and subdural haemorrhage has resulted in increased mass effect within the right hemisphere that has resulted in shift of the midline towards the left.
In addition, there has been effacement of the right lateral ventricle.