The other possibility could have been edema, but edema is characterized by a chronic induration in the white matter. At the subdural surface, note the thickened neo-membrane dura. An old hematoma is not red, thereby indicating chronicity and healing. A new hematoma would generally be more red and yield clotted blood. In a subdural hematoma, the bleeding is ultimately followed by re-organization.
Fibroblasts proliferate, and there is a great deal of regeneration and synthesis of a new membrane.
Blood vessels reorganize thru the new dura membrane. Otherwise, only a brownish neo-membrane remains due to hemosiderin deposition. Occasionally, this is seen in physiological aging, but not to such an extreme. The ventricles are very expanded and there are deep grooves on the brain surface. Infarctions, especially hemorrhagic ones, are often presented on the brain slice as wedge-shaped.