"The brain," Fishman said, "is basically a computer whose parts are microscopic gelatin globs. You rearrange the pattern of those globs and you've destroyed their function."
The effects can be subtle or severe. And, although the military tries to make sure bomb victims receive prompt treatment, experts are learning that some troops sustained multiple blasts whose symptoms can be cumulative.
"It's sort of like a football player," said Alison Cernich, a neuropsychologist at the Baltimore VA. "You shake it off. They think, 'Today I was in a firefight, and it was very stressful.' That's why they are tired, but they don't attribute it necessarily to brain injury."
The cases of Jason Ehrhart and Larry Perry are more complex - and perhaps more typical - than those of patients who survived blast injuries looking perfectly intact.
Ehrhart, who is 22 and lives with his parents in the Howard County community of Dayton, suffered burns over 60 percent of his body, lost a leg and spent three months in a coma before waking up in a stateside military hospital.
But his head appeared unscathed, except for a pressure sore that his parents say developed over months of hospitalization.
Perry, who lives in North East, sustained so many elbow fractures and bone infections that doctors ultimately removed the entire joint. Now, he's learning to function with a "flail elbow," one bound only by soft tissue.
Along with their physical struggles, both are working hard to recover memory through occupational therapy and psychotherapy - with the help of electronic devices such as computers and Palm Pilots. All are provided directly or indirectly by the VA.
The servicemen have improved, but they have far to go. Perry, 26, still has trouble remembering tasks without checking his hand-held organizer. Ehrhart, more severely injured, often forgets what he was told minutes earlier and is relearning basic skills such as brushing his teeth and writing his name.
"I'd like to go to college," the former Howard Community College student said recently, sitting in the furnished basement of his family's home, where an aide helps him relearn the tasks of daily living. "I want to go to the University of Maryland, where my mom went."
Upbeat as she is about her son's recovery, his mother is setting modest goals.
"I can't see you going to school and trying to think during a lecture and retaining any of that," said Pam Estes, who along with her husband, Michael Estes, has been a tireless advocate for his care.
