SAN ANTONIO—Recent Department of Defense (DoD) studies indicate that exposure to varying intensities of explosive blast is associated with varying levels of traumatic brain injury (TBI), according to research presented at the 64th Annual Meeting of the American Epilepsy Society.
Colonel Geoffrey Ling, MD, PhD, a Program Manager at the DoD’s Defense Advanced Research Projects Agency (DARPA) and Chairman of the Neurology Department and Director of the Division of Critical Care Medicine at the Uniformed Services University of the Health Sciences in Bethesda, Maryland, made one of several presentations on how the DoD and the Department of Veterans Affairs (VA) have responded to TBI from blast injury. This injury has been called the signature wound of Operation Enduring Freedom and Operation Iraqi Freedom. Other speakers discussed the DoD’s new policies regarding the evaluation and management of mild TBI and the VA’s efforts to cope with an expected increase in TBI-related epilepsy among veterans.
Different Blasts, Different Injuries
DARPA has been working on a large research program to explore the mechanisms of blast injury for the last year and a half, said Dr. Ling. The program’s animal model arm exposed pigs, rats, and primates to very low-level bomb explosions and used such measures as gait analyses and angiograms to determine the blasts’ effects. Its clinical arm studied Marines who were exposed to bomb explosions as part of their training regimen and who were given neurobehavioral testing, fMRIs, and sleep studies.
“We have learned that there are three levels of TBI associated with blast in these preclinical models,” Dr. Ling said. “The subjects can actually withstand exposure if the blast is about 20 pounds per square inch (PPI). At about 20 to 40 PPI, however, you start seeing neuroinflammatory changes that can persist for days or weeks, particularly at the higher levels of inflammation. They resolve over time, but they can lead to some neurocognitive degeneration at the higher levels and are associated with increasing transient neurologic deficits—primarily, gait and early cognitive changes. Moderate TBI occurs at roughly 50 to 75 PSI and is associated with functional deficits that are much more persistent. And with severe TBI, you see widespread process breakdown of large amounts of tissue and vasospasm.”
A More Proactive Approach
In addition to its ongoing research efforts, the DoD recently has adopted a much more proactive approach to the evaluation and management of concussion, said Commander Jack W. Tsao, MD, DPhil, FAAN, Director of the Traumatic Brain Injury Programs for the US Navy Bureau of Medicine and Surgery and Associate Professor of Neurology and Neuroscience at Uniformed Services University of the Health Sciences.
“Prior to June 21, 2010, the DoD expected personnel to come forward to their commander and say, ‘Hey, I think I may have a concussion. I don’t think I can fight,’” he said. “Well, service members didn’t come forward. Or their attitude was, ‘Hey, it probably wasn’t a concussion. I’m going to tough it out.’’”
In contrast, the new policy is a “culture shift” and requires service members who experience certain events that might have caused a concussion to undergo a medical evaluation, a minimum rest period, and medical clearance before returning to duty. The DoD’s new concussion examination is based on the one used by the National Football League (Standard Assessment of Concussion), takes less than 10 minutes to perform, and can be administered by non-neurologists.
When a service member is diagnosed with concussion, providers implement a treatment plan that usually consists of rest, Dr. Tsao said. Before the service member can return to duty, he or she must undergo exertional testing to determine whether exercise leads to cognitive impairment, headaches, or visual disturbances. In addition, service members who experience a loss of consciousness after a head injury have to go to a combat hospital, where they generally receive a CAT scan.
“The DoD’s algorithms further define what happens if you have more than one concussion,” Dr. Tsao added. “If you have a second concussion within 12 months, resolution of clinical symptoms followed by additional rest days is required. If you have a third concussion, you are not only restricted from sports and other activities where you may be reconcussed, but you also receive a comprehensive evaluation before you’re allowed to return to duty. The comprehensive evaluation is an examination by a neurologist and includes neuropsychologic testing and functional testing. There are three possible outcomes—you are returned to full duty, you return to duty with operational restrictions, or they send you home.”
Veterans and Posttraumatic Epilepsy