By Gregg Zoroya, USA TODAY
WASHINGTON — What has been called the "signature wound" of the wars in Iraq and Afghanistan— the mild brain damage troops suffer from a roadside bomb — might be so unique in its destruction that it could be a newly discovered disease, scientists say.
"Most of us in this room would concur that this (blast-induced brain injury) disease ... perhaps does require a separate category," Army Col. Geoffrey Ling, a neurologist, told a roomful of colleagues at a brain-injury convention this year. "It may actually have some unique features to it, which makes it a very interesting new disease."
CAREGIVERS: The strain can be enormous
Among the new findings: The blast wave causes a more dispersed pattern of brain-cell damage and keeps those cells inflamed for a longer period than occurs with a traditional blow-to-head concussion, according to research posted recently by the Defense and Veterans Brain Injury Center. The center's duties include coordinating traumatic brain injury (TBI) research and clinical care.
Army field studies have shown that more than 10% of troops in Iraq and Afghanistan have suffered at least one concussion or brain injury, the vast majority of those from exposure to a homemade bomb or improvised explosive device. Five percent to 15% of mild TBI patients develop lasting problems with concentration, short-term memory, fatigue and chronic headaches.
7 years ago, a life changed
One of those is former Army Spec. Michael Cain, who lost his right leg below the knee in a roadside explosion in Iraq in 2003. Today, he is still plagued with short-term memory loss, difficulty concentrating and irritability.
"If they tell me some important stuff, like appointments, if I don't write it down or put it in my BlackBerry right away, I'm not going to remember," Cain says.
Unemployed and living on a medical retirement income, Cain says he is uncertain about his future.
Blast-related brain injury is an issue of intense debate within the military medical community.
Detractors argue that any soldier close enough to an explosion to suffer brain damage from the blast wave would be killed by shrapnel. Others assert that long-term symptoms from mild TBI are more likely the result of post-traumatic stress disorder.
Explosions have been a part of war for centuries. But scientists say that because troops serving in Iraq and Afghanistan are wearing body armor, they are surviving bomb blasts that would have killed them in previous wars. As a result, they say, blast wave damage to the brain is more prevalent.
"Blast (in combat) has been around for a while," says Air Force Col. Michael Jaffee, director of the Brain Injury Center. "What is different now is our understanding of blast has never been greater."
The more that scientists learn about how the blast wave damages the brain, the more chance they will have to develop protective measures, such as a new helmet design, Jaffee says.
Different from sports injury
Questions remain about whether mild TBI caused by explosions is more serious than a sports-related blow to the head, scientists say. For now, the two appear to produce similar immediate symptoms such as loss of consciousness, dizziness and memory loss.
In most cases of mild TBI, regardless of the cause, victims appear to recover fully within hours or days, scientists say.
According to a summary of scientific research recently made public by the Pentagon, there are several ways in which exposure to an explosion differs from a blow to the head:
•Damage to wiring in the brain appears more widespread.
•Brain cell inflammation caused by blast waves lasts longer than inflammation caused by a blow to the head.
•In moderate or severe cases of blast-induced brain injury, blood vessels can inexplicably spasm and cut off oxygen flow to the brain for days after the injury. This can happen in a blow to the head but to a far lesser degree.
"Blast-induced neurotrauma is a unique clinical entity," says Ibolja Cernak, a scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., who has studied the effect for a decade.
Many harmful factors
An explosion creates a shock wave traveling at the speed of sound. It also emits toxic fumes, heat and light. Scientists do not yet understand which of these elements, or what combination, causes this unique brain damage.
Scientists at the Massachusetts Institute of Technology, using computer modeling to re-create the blast effect on the human skull, have found that a significant electromagnetic charge also occurs.
"When you compress bone with an incoming shock wave, you are going to generate an electrical field," says Raul Radovitzky, an MIT aeronautical engineer who is working on the project. "The electric fields are ... possibly well beyond accepted standards."
He says more research is necessary to determine whether the field generation is causing brain damage.
For Cain, after seven years of recovery, he wonders why his brain has not yet healed.
"I really wish that they'd go away," he says of symptoms such as short-term memory loss and his tendency to startle easily. "I didn't want them to tell me I had a brain problem, because I was a pretty smart person before. I had straight A's. ... It really frustrates me."
