Improvised? After 4 years we still call it improvised?

For the first time, the U.S. military is treating more head injuries than chest or abdominal wounds, and it is ill-equipped to do so. According to a July 2005 estimate from Walter Reed Army Medical Center, two-thirds of all soldiers wounded in Iraq who don't immediately return to duty have traumatic brain injuries.

Here's why IEDS carry such hidden danger. The detonation of any powerful explosive generates a blast wave of high pressure that spreads out at 1,600 feet per second from the point of explosion and travels hundreds of yards. The lethal blast wave is a two-part assault that rattles the brain against the skull. The initial shock wave of very high pressure is followed closely by the "secondary wind": a huge volume of displaced air flooding back into the area, again under high pressure. No helmet or armor can defend against such a massive wave front.

It is these sudden and extreme differences in pressures -- routinely 1,000 times greater than atmospheric pressure -- that lead to significant neurological injury. Blast waves cause severe concussions, resulting in loss of consciousness and obvious neurological deficits such as blindness, deafness and mental retardation. Blast waves causing TBIs can leave a 19-year-old private who could easily run a six-minute mile unable to stand or even to think.