Brain injuries are a result of a combination of physiological genetics, hormone systems, and blood and other chemistries complicated by the myriad of different forces of each impact. Any one can be weak making injury more likely. Plus, as said before, the brain is extremely complex and each injury effects different parts of this complexity.

There are many people who have appeared to endure many head impacts with minimal noticeable injury then one final impact and everything changes.

There is also a big difference between how different individuals relate to their symptoms. Those with higher intellectual skills notice more struggles. Those with higher levels of coordination and balance notice more losses in these areas.

Sydney Crosby had thousands of hits before his life changing hit. They all add up.