Research Examines Blast Impact on Human Brain

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.”

U.S. Depart­ment of Defense
Office of the Assis­tant Sec­re­tary of Defense (Pub­lic Affairs)

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