The damage that might be caused to the brain by riding a violently fast roller coaster is consistent with

this damage is called a subdural hematoma. This isn't always an emergency situation, but can be a medical emergency. It is caused by head injury that bursts blood vessels and causes pooled blood to begin pushing on the brain. It can cause vomiting, slurred speech, confusion, vomiting, headaches an may even lead to a coma. In mild cases it may cause no symptoms at all.