What happens in stage four of intracranial pressure?

A. In stage four, the brain tissue no longer remains stable; it shifts due to high pressure. B. CSF levels may decrease initially in compensation but are not the hallmark of stage four. C. Cerebral blood flow decreases due to increased pressure, leading to ischemia. D. Stage four is marked by brain herniation, where increased intracranial pressure causes brain tissue to shift from high-pressure areas to lower-pressure areas, which can be life-threatening.