Does a brain injury only occur after a physical impact or is it possible that repeated trauma can have the same effect not the brain ?

Good question: If your question is whether or not repeated trauma to other parts of the body can lead to brain injury-the answer is yes.Recent studies with football players has shown that repeated body injuries they sustain are transmitted to the brain.So although there is not a direct brain impact, the brain suffers an injury.These repeated injuries lead to long term issues like chronic traumatic encephalopathy.

Both: Injuries can occur after a single injury which is common but repeated trauma can do the same. This is one of the worries about repeated mild concussions.