A Shock Wave of Brain Injuries

About 1,800 U.S. troops, according to the Department of Veterans Affairs, are now suffering from traumatic brain injuries (TBIs) caused by penetrating wounds. But neurologists worry that hundreds of thousands more -- at least 30 percent of the troops who've engaged in active combat for four months or longer in Iraq and Afghanistan -- are at risk of potentially disabling neurological disorders from the blast waves of IEDs and mortars, all without suffering a scratch.