Symptoms of traumatic brain injury, or TBI, include memory deficit, headaches, vertigo, anxiety and apathy or lethargy.

By Greq Zoro, USA TODAY

Scientists trying to understand traumatic brain injury from bomb blasts are finding the wound more insidious than they once thought.

They find that even when there are no outward signs of injury from the blast, cells deep within the brain can be altered, their metabolism changed, causing them to die, says Geoff Ling, an advance-research scientist with the Pentagon.

The new findings are the result of blast experiments in recent years on animals, followed by microscopic examination of brain tissue. The findings could mean that the number of brain­-injured soldiers and Marines — many of whom appear unhurt after exposure to a blast — may be far greater than reported, says Ibolja Cernak, a scientist with the Johns Hopkins University Applied Physics Laboratory.

This cellular death leads to symptoms that may not surface for months or years, Cernak says. The symptoms can include memory deficit, headaches, vertigo, anxiety and apathy or lethargy. ”These soldiers could have hidden injuries with long-term consequences,” he says. Physicians and scientists are calling TBI the “signature wound” of the Iraq war because of its increasing prevalence among troops.

In the animal studies, scientists say they have found a fundamentally different wound than the “brain concussion” historically associated with undetected brain injuries. Military and civilian scientists worry whether a generation of service members could emerge from the Iraq and Afghanistan wars with some form of brain damage steadily more severe.

Hidden injuries

Army Sgt. Gary Boggs may be such a case. When he was wounded by a roadside bomb in Iraq in 2003, doctors believed his worst injury was a blinded left eye, along with shrapnel wounds to his left arm and ruptured eardrums.

No one spoke of brain damage during his hospital treatment and convalescence. Boggs said he never considered the possibility until he took a medical retirement from the Army and started a job this year as a financial adviser. Boggs couldn’t keep up with a job-study program, forgetting paragraphs he had just read.

“It was really getting hard for me,” says Boggs, 32, of Melbourne Beach, Fla. “I finally swallowed my pride and asked for help from the VA (Department of Veterans Affairs). I said, ‘I think something is wrong with me.’ “

He was diagnosed with mild traumatic brain injury and receives medication to focus his thoughts.

Brain injury experts such as Cernak fear Boggs may be at the front of a new wave of TBI victims.

Cernak’s research on blast-related brain injury dates back to the study of wounded soldiers in her native homeland of the former Yugoslavia during the Balkans conflict of the 1990s.

It was in the Balkans where Cernak first; discovered that soldiers exposed to blasts who suffered no apparent head wounds displayed brain damage symptoms over a period of months or more than a year.

“You can give her credit for being a pioneer,” Ling says.

Can’t be detected with imaging tests

When the war in Iraq began, clinicians treating the wounded began noticing similar symptoms. Some screenings at military bases showed that 10% to 20% of returning troops may have suffered such head wounds.

“We’ve had patients who have been in a blast, who we tested. They looked OK. And they came back later, and they were not OK,” says Maria Mouratidis, head of brain injury treatment at the National Naval Medical Center in Bethesda, Md.

To make matters worse, whatever damage occurred was so microscopic that it could not be found with imaging tests.

“This is a new beast,” says Alisa Gean, a San Francisco-based traumatic brain injury specialist who treated soldiers this year at an Army [post] in Germany.

The microscopic damage changes brain cell metabolism, Cernak says, creating a cascading effect that leads to the premature aging and death of neurons that cannot be replaced.

In a presentation before a committee of the National Academy of Sciences last month, Cernak said the damage was caused by the blast pressure wave, an invisible surge of compressed air traveling near the speed of sound. Kinetic energy from this pressure wave ripples through the body, injuring brain cells, Cernak said.

All of this occurs in less than a second after the blast, she said. Moreover, she said, body armor is no protection against this blast wave.

Ling says other factors can contribute to TBI, not just pressure. “Pressure is our leading candidate for no other reason than it is the one we’ve studied the most,” he says. ‘We are playing catch-up.”

Concerned about the potential number of wounded, Congress this year authorized $150 million for brain injury research in an emergency spending bill passed in May for the Iraq and Afghanistan wars.

Repeated exposure to blame?

Roadside bombs, also called improvised explosive devices (IEDs), are the cause of most cases of brain injury and account for almost 80% of all wounds to U.S. troops. Many troops caught near these explosions can suffer symptoms such as perforated eardrums, ringing in the ears, blurred vision, memory lapses and headaches.

Soldiers often shake off the effects and return to combat, says Barbara Sigford, VA director of physical medicine. Ling and other scientists say repeated blast exposure can aggravate any brain damage.

Pentagon medical policy analysts have grappled with the idea of pulling troops out of combat after being exposed to multiple blasts. However, the science is too preliminary for such a dramatic change in policy, says Army Col. Tony Carter, one of those analysts. “If (soldiers) could have damage and they were otherwise functionally OK, but the damage could show up much later, then essentially what we would be saying is, ‘Anybody exposed to blast leaves theater,’ ” Carter says.

“That would be very, very difficult to do. You don’t know (how many blast exposures are too many). Half a dozen? One? I mean, what’s the tipping point?”