Good to see progress in this area. Not long ago little or no attention was given unless the injury produced a period of unconsciousness and lingering symptoms. Then, concerned was mostly for subdural hematomas, especially with older folks (our brains suffer age atrophy - more rattle room, not to mention the likely use of aspirin etc.).
Maybe it is time to drop the word "mild" when disusing head injuries, as the general interpretation of mild is "trivial" (one of the potential sequelae, death, is far from trivial). That "repeated insults exacerbate the observed abnormalities" seems clear; but, quantifying cause and effect is murky.

Richard Carlson