This isn't a big risk, because most concussions result from auto accidents. But athletes, particularly in certain sports, run a higher risk long-term brain damage from repeat concussions. This is a sudden, rapid swelling of the brain that can be fatal. Second Impact Syndrome is extremely rare, occurring in only the tiniest fraction of repeat concussions. It's preventable, too, which is why parents and coaches should learn the risks and signs of concussion.
Many people mistakenly think concussion always involves a loss of consciousness.
In general, concussion is defined as a change in mental status. The person may or may not black out. Signs of a concussion include confusion and memory loss. Symptoms of concussion can be subtle, with the person forgetting one little thing, or they can be more obvious, like garbled speech or lack of motor coordination. Concussion may also involve dizziness, nausea and vomiting.