Warren has trouble remembering a lot of things. Which isn't surprising, considering that several pieces of shrapnel tore through his skull after insurgents outside Kandahar blew up his truck with a rocket-propelled grenade in May.
Since 2000, traumatic brain injury, or TBI, has been diagnosed in about 180,000 service members, the Pentagon says. But some advocates for patients say hundreds, if not thousands, more have suffered undiagnosed brain injuries. A Rand study in 2008 estimated the total number of service members with TBI to be about 320,000.