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Research Examines Blast Impact on Human Brain

By Donna Miles
American Forces Press Service

FORT DETRICK, Md., April 12, 2011 – There’s little debate about the risk of a brain injury when a service member gets a blow to the head -- whether from an enemy round or from crashing against a wall or being inside a vehicle during an explosion.

But some of the foremost academic researchers from around the world, working in cooperation with the Defense Department’s Blast Injury Research Program, are trying to determine exactly what happens to a service member’s brain when it’s exposed to a blast, but with no direct head impact.

Their answers could change the way the military protects tens of thousands of deployed troops from improvised explosive devices, mortar rounds and other explosions, Michael J. Leggieri Jr., director of the Defense Department’s Blast Injury Research Program Coordinating Office, told American Forces Press Service.

DOD has long recognized the risks of overpressure and shock waves associated with blasts on the human body, Leggieri said.

For the past 18 years the Army Medical Research and Material Command based here has conducted a robust research program focused on occupational exposures to blasts -- such as when an artillery crewman fires a howitzer.

As a result, the command helps the Army evaluate the blast impact of every weapons system before it’s fielded.

But the current conflicts, and the frequency of percussive blasts and explosions, leave researchers questioning: What effect are they having on the brain, and how can we better protect service members against traumatic brain injuries?

The answer isn’t as easy as it may appear, Leggieri explained. That’s because, despite decades of study in the United States and around the world about brain injury, no one completely understands what happens to the human brain during a blast.

In fact, DOD has a lot of clinical data about the impact of blasts on the brain, but that’s from animal studies, Leggieri said. Comparing animal data to humans, particularly when dealing with something as complex as the brain, raises as many questions as it answers, he said.

In terms of humans, DOD has just one confirmed clinical case of a deployed service member who suffered a brain injury in a blast without hitting his head, Leggieri said.

“We know a lot about what happens when you get hit in the head or hit your head against something and it causes a brain injury,” Leggieri said. “That has been studied for decades, primarily by the automotive industry. Impact is something we know quite a bit about. But this whole question about blast is still a question.”

And although the Army is at work on its second-generation helmet sensor with plans to field it soon to about 30,000 soldiers, there’s still no clear indication of what those blast readings will mean in terms of the brain.

Theories abound in how blasts can cause brain injuries, Leggieri said. One prevalent theory advocates that the blast shock wave causes the skull to flex and as a result, damages the brain. Another theory actually has nothing to do with the head. It supports the idea that the blast pressure squeezes the thorax -- much the way fingers squeeze a tube of toothpaste. The result, theorists say, is a sudden vascular surge that goes up into the brain, causing an injury.

Getting to the bottom of what exactly happens is more than a scientific exercise, Leggieri said, it’s critical to finding the best way to protect service members.

The first theory might support a new kind of combat helmet protection, or modification to the current helmet. The latter might call for modified body armor. But providing the wrong solution, no matter how well-intentioned, could actually backfire in adding more weight and less mobility to the warfighter.

“If you are restricting their ability to perform the mission, you are actually putting them at risk because now they can’t do what they need to do to survive,” Leggieri said. “So you have got to be very careful about what protection systems you put on a soldier. You have to make sure they are really effective at what they are supposed to be doing.

“My point is, if you don’t understand the mechanism, you can’t possibly protect against it,” he added. “You may end up doing something that has no effect whatsoever.”

Leggieri assembled a forum of about 100 of the world’s leading brain-injury researchers to determine, first, whether their work shows that blast-induced mild traumatic brain injuries actually exist, and, if so, what happens within the brain to cause them.

“With this expert panel, we are reaching out to this community of modelers, clinicians, and experimentalists who do animal research in blasts, and getting these communities to finally work together and to communicate with each other,” he said. “We are going to have them help us pin down what we don’t know and to get to a solution.”

The meeting proved to be a huge success. Attendees “started to communicate, to share information, to come up with ideas about how we might approach this,” Leggieri said.

What’s needed, they agreed, is a validated mathematical model to show how a blast interacts with the human head, and how that might cause a brain injury. Current models -- and there are several -- are based on simulations that can’t be scientifically validated, Leggieri said.

So Leggieri established a DOD Brain Injury Modeling Expert Panel, made up of 19 leading modelers from academia, industry and government. So far they have met four times, with their fifth and final session slated for this summer.

“Their work is going to help us develop a research roadmap that will take us from where we are today … to a validated model of blast-induced brain injury that we can say with confidence is an accurate model of what happens to humans,” Leggieri said.

That milestone, he said, will help the Defense Department better tailor protective systems for its service members.

“The goal and the focus are on how to prevent this,” he said. “Let’s understand it and find a way to prevent it. If we can make a difference just in these areas, I think would be a huge advancement.”


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U.S. Army Medical Research and Materiel Command


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