In the injured brain image below:
The subarachnoid space has all but disappeared as the injured brain swells and fills up the small space inside the skull.
The ventricles have become compressed and flattened.
The subdural hematoma creates even more pressure inside the head as the brain swells and has no space to expand within the skull. Because of this increased pressure blood vessels feeding the brain are compressed, depriving the brain of oxygen.
A chronic subdural hematoma is also present indicating repeated trauma.
The surface of the brain now looks smooth, the once rounded gyri are flattened against the inner surface of the skull.