I have also been looking for some of the same information and this is what i have found so far:

case study of a girl who sustained 11 concusions:

http://www.nj.com/news/index.ssf/200...ncussions.html

Quote: "Her head inadvertently hit the elbow of the vice principal walking by. Soon after, she passed out. Concussion No. 11."


Another article:

"Is it true I am more likely to get a concussion after already having one?"

http://scienceline.org/2008/04/ask-heger-concussion/


And another:

"Routine Head Hits in School Sports May Cause Brain Injury"

http://www.sciencedaily.com/releases...1114133738.htm


And the last:

"Soccer's concussion problem"

http://espn.go.com/sports/soccer/new...rotect-players

Quote:" In 2004, he again had multiple concussions, from increasingly weaker blows to the head. By the 2005 preseason the slightest contact to his head would trigger his concussive symptoms."


Hope some of this can help.

-GlassHead