This little number that showed up on Google News reminded me of the conference I went to last year on Traumatic Brain Injury (or TBI if you like three-letter initials).
Traumatic brain injury is rapidly becoming the hallmark injury of soldiers currently serving in the Middle East. This is because our troops are engaging in less traditional shooting-guns-at-each-other warfare and more stumbling-upon-a-roadside-bomb warfare. Thus, soldiers are more likely to get hit by a concussive impact (coming from a shock wave, slamming one's head into the side of an armored vehicle, etc). As Wikipedia says, as many as 15% of U.S. infantry soldiers who return from the Iraq War suffer from this kind of injury.
What a lot of people fail to realize is that the initial injury is often not the worst part of a traumatic brain injury; the most damage typically comes from the brain's response in the hours to days following the actual insult. When you get knocked in the noggin, it sets off a cascade of events that kill even more brain cells, primarily due to excitotoxicity. Yep, when your neurons get excited enough, they can keel over and die. And on top of that, the brain's inflammatory response (when the tissue gets all swelled up) kills even more brain cells.
Oh, and the best part? A concussive head injury can potentiate any additional injuries. Up to months afterwards (depending on the severity of the initial injury), it's possible that even a little tap on the head can cause immediate unconsciousness, coma, and even death. Because of the previous injury, your brain can become super-duper sensitive to even mild impacts.
So, in other words, please don't hit your head too hard. =)