Theoretical Exploration into Blast-Related Brain Injuries
What have we learned about blast, in terms of a head injury? There is a lot that we've learned in terms of science. And what I mean by science is the physics of the blast. Today I know more about P10 explosives and shockwaves than I ever knew when I was in graduate school. I didn't think that was even going to be a topic of interest for the neuroscientific community. So we've learned a lot. Is it applicable to what's happening in Iraq and Afghanistan? There seems to be two big camps out there. One is that the--and I'm overstating this, probably, a bit-- or simplifying it a bit--but there is a camp that says that these blast head injuries are very unique. It's a whole new set of an injury. And from a scientific point of view, in an odd way, that's really fun because that means we have a whole new injury to study. In a humanitarian way, this is really problematic because we're making the same recommendations to the military about blast concussions that were made to the National Football League, and maybe things are different. Maybe we're giving them the wrong information if it's completely a different injury and it doesn't have any of the other characteristics. There's another camp of our science that believes that it's not that unique. It is different in terms of the biomechanical events that occur, that move the head or shake the head, but the actual injury itself is pretty common. It's similar to what we've actually seen in other types of concussions. That being said, the mechanism by which blast produces a concussion also has very different types of theoretical basis, and people are trying to study. Some people think that because of the armament that people have now and the exposure of the types of blasts that they get, that this is from a thoracic concussion that causes a wave that goes up and hurts the brain. Then there's a theory that the pressure wave--the best way to think about it is if you're underwater in your home swimming pool and somebody shouts at one end, you can hear this wave go across-- and they think that this wave actually penetrates the helmet and penetrates the skull, and that's what causes the injury. And then there's another group that says that all it is just like being hit with a tsunami of an air blast, and it has an over-pressure and an under-pressure, much like being pushed into shore and then drug out afterwards. And what this does is just violently moves the head back and forth or rotates it the same way that you would in a boxing match or football match, and that's what causes the concussion. A curious problem in terms of trying to apply these types of theories or models to the blast head injury is that pure blast head injury is very rare in Iraq and Afghanistan. It's always a blast plus you get thrown and hit your head. Or, it's an MRAP--a vehicle--that gets blown up and you have horrible burns. At UCLA where we have our operation, men-- a lot of the individuals will come through BAMC--Brooke Army Medical Center--for burns, and when they come up to UCLA for their reconstructive surgery we'll do the scans for their brain injury. And the injuries look pretty much like what I've seen in car accidents or other types of injuries. They've just been misdiagnosed. They didn't even think to look, but they're there. So they've been treating them for multiple sclerosis, or they've been treating them for psychiatric disorders, and they don't have psychiatric disorders. They have brain injury, and they need to go to rehab. So we've learned to focus on this, and there are lots of models, both tissue and animal models that people are addressing in terms of utilizing this. We don't at UCLA. And it has potential that this may be able to be transferable, but we won't know for a long time, I don't think. What I think is going to happen is that there's a lot of engineers that are trying to come up with the right kind of biomarkers to determine if you've had a blast concussion. And there are also some very neat engineers in nanotechnology using dosimeters that individuals could wear either on their protective gear or inside their helmet or next to the skin to determine how much of a wave they've actually been exposed to-- a pressure wave or an under-pressure wave. The treatment for these individuals that have had these types of injuries in Iraq and Afghanistan acutely after brain injury, by a medic or a corpsman, is a big challenge because they are already carrying over 150 pounds of equipment. And tourniquets are actually more important in terms of acute care than monitoring a concussion in the battlefield. So it's not that it doesn't have the right priority, but the way that we learn about a disorder or about a blast injury is to find a brain that has a blast injury and either take it out after the individual dies and see what it looks like and try to model that, or we image it very closely as soon as it occurs or after it occurs and try to see what it looks like and see what sort of signature characteristics it has. And this year Admiral Mullen ordered the first implementation of deployment of MRIs in Iraq and Afghanistan, and I guess they're going to put them all in Afghanistan now. And there was a lot of resistance to that. They didn't want them there. Why? I don't know, but there was a lot of resistance to having that type of imaging in Afghanistan.
The research into the hows and whys of blast injuries continues — from the impact of pressure waves to the push and pull of air blasts.
Posted on BrainLine October 24, 2011.
David Hovda, PhD is the director of the UCLA Brain Injury Research Center. He is past president of the National Neurotrauma Society and past president of the International Neurotrauma Society. He has served as chair of study sections for the National Institute for Neurological Disease and Stroke.
Produced by Noel Gunther, Ashley Gilleland, and Brain King, BrainLine.