They tire easily, forget often and lose their balance and concentration without warning. They struggle to make peace with personality changes that have made them barely recognizable.
A soldier's story
Carr, 39, dispatched to Iraq as a sergeant in the Army National Guard, was a medic with the 1st Infantry Division when a roadside bomb exploded alongside his Humvee. The concentrated power of six 155 mm artillery shells buried in a mound of debris blew into the vehicle's open side window. It knocked him out for less than half a minute. Trained as a medic, Carr calmly talked the Humvee's gunner through the steps of bandaging his head, which was bleeding from shrapnel wounds.
Carr underwent surgery to remove a rock and shrapnel from his head, but his skull hadn't been fractured. On standard CT scans done at Balad Air Base in Iraq, his brain appeared unhurt.
But upon returning home, the signs began to change. Carr was plagued by debilitating daily headaches and regularly "yelled like a drill sergeant" at his wife and kids with no provocation. He slept much of the day and forgot to eat for days at a time. His efforts to recall his childhood drew a blank. He was forgetful, distracted.
A civilian's story
Ewing, 60, a supervising equipment officer for the city of Victorville, near the Mojave Desert, was helping to unload a tractor-trailer when the truck's contents shifted. The rolling canisters knocked him backward. Ewing fell, slamming his head into the inside wall of the truck.
CT scans, magnetic resonance imaging and brain-wave monitoring showed no abnormalities.
But Ewing has lost brainpower and independence.
Because his central vision has shifted sideways and his peripheral vision has dimmed, he misjudges distances and walks into things. He is easily disoriented and becomes dizzy from sudden movement and changes of orientation. He forgets to turn off the stove, or to check for cars before stepping into the street. His reading and writing skills have fallen to roughly sixth-grade levels, his wife says.
Larry Ewing was once the kind of guy, she says, who would stand in line at the bank for 20 minutes and come out knowing the life story of the person who stood behind him. Now, she says, he will not initiate conversations, and he answers questions with few words in a barely audible tone. He ends chats abruptly or rambles too long.
Similar cases, difficult diagnosis
Both men had believed recovery was around the corner. Their doctors greeted their persistent complaints with soothing reassurances that nothing was fundamentally wrong. Friends told them they looked great and asked when they were going to get a job or go back to work.
Even their wives wondered what kept their outwardly healed husbands from getting on with life.
One day, Carr's psychiatrist, a former Army reservist who spent time in Afghanistan, told him of a new study emerging from the military's increasing research into the detection, prevention and treatment of brain injury. Many of the symptoms of PTSD, for which Carr was being treated, mimic the symptoms of traumatic brain injury, said Carr's physician, Dr. Bruce Capehart.
When the results of a lengthy battery of cognitive tests made it clear that Carr's brain had sustained serious injury, Carr felt a powerful sense of relief.
Although not a soldier, Ewing similarly benefited from military research on new diagnostic imaging technologies. An alphabet soup's worth of tests - CT scans, MRIs, EEGs - all had failed to show brain abnormalities, but an imaging technique improved and promoted by the military finally exposed the cause of Ewing's cognitive troubles: inert and sluggish activity of cells throughout multiple areas of his brain.
The long-term prognosis is uncertain for both men. But with proper diagnosis, they have begun long-term rehabilitative treatment. Military research has begun to explore which of many treatments can best help brain-injury victims regain at least some lost skills.
