Have you researched around about concussions & such?
Concussions are strange & powerful things... can change a lot and including personality changes.
I was in an auto accident, concusssion, knocked out, skull fracture...etc.
I do things now (3 years later) that I found unusual and blame the accident/concussion for it...or, perhaps its old age?
Sometimes while talking to poeple - I get all tonque tied (never used to do that before). I still find my concentration can shift from one thing to the other and not even realize it.
And yes....You can experience personality changes - mood swings, etc. I've had people tell me that *I'm not as nice as I used to be*....
My new personality wants to grab their neck and strangle them!! (laugh) does that confirm what they said? (laugh)
Try researching more about concussions and sports injuries.... YOu might learn alot.