ARTICLE IN BRIEF
An Institute of Medicine committee surveyed existing research on blast-related injury among Gulf War veterans and recommended more research specifically targeting brain injuries, especially long-term outcomes, as well as other measures to better detect and evaluate the effects of blast waves in military personnel.
The Institute of Medicine (IOM) has released a comprehensive report on blast injuries, including reported neurological sequelae. The study concluded that more research specifically targeting brain injuries is needed, especially long-term outcomes, as well as other measures to better detect and evaluate the effects of blast waves in military personnel.
It is “plausible” that severe or moderate blast traumatic brain injuries (TBI) are associated with permanent neurologic disability, according to the Feb. 13 report, even though studies specifically addressing this are lacking. The study also said there is evidence to suggest that chronic traumatic encephalopathy with progressive cognitive and behavioral decline may result from recurrent blast exposures, although that evidence is also minimal.
Among other health issues, the researchers were tasked with evaluating health effects of the supersonic waves of intense air pressure that follow detonation of an explosive device. According to the report, there is insufficient evidence to determine whether there is any association between the use of current personal protective equipment and prevention of primary blast-induced injuries.
However, when the energy from a blast wave is absorbed by the human body it disrupts multiple body systems, including the venous system and spinal cord, and these in turn can result in potentially harmful changes in brain, according to Committee Chair Stephen L. Hauser, MD, the Robert A. Fishman distinguished professor and chair of the department of neurology at the University of California, San Francisco. The biggest problem is that long-term data are lacking, he told Neurology Today in a telephone interview.
“Acute physical and psychological health outcomes in people who survive blast explosions can be devastating, but the long-term consequences are less clear, particularly for individuals who show no external signs of injury or may not even be aware that they were physical affected by blast exposure,” he said.
“While much of the focus has been on head injuries, blast pressure waves, even to the abdomen, appear to have the potential to affect the autonomous nervous system and travel via the vascular system to the brain,” Dr. Hauser said. “These injuries are multifactorial, and there are deficiencies in segregating them out in the published literature.”
Understanding these cross-system interactions should be a priority for future research, according to Dr. Hauser, adding that it is essential that a standardized definition of blast exposure be established and used in future studies.
Because injuries from blast may go undetected for long periods, the US Department of Veterans Affairs (VA) should also conduct epidemiologic and mechanistic studies to identify biomarkers of blast injury through advanced imaging and molecular methods that could serve as surrogates of exposure, he continued.
Nearly all of the studies the panel reviewed were limited by inadequate objective information about exposure; most relied on self-reported data, and few studies reviewed reported outcome data longer than six months after exposure.
The IOM group found sufficient evidence of post-concussive symptoms and persistent headaches in cases of mild blast-related TBI. Moreover, it determined that in non-blast injuries, severe or moderate TBI, permanent neurologic disability, including cognitive dysfunction, unprovoked seizures, and headache, may result — outcomes reported in TBI studies that have included blast and non-blast mechanisms considered together.
The committee said that there was limited evidence that diffuse brain injury with swelling may be more likely after a blast than in relation to other mechanisms associated with TBI.
The IOM committee said research indicated that blast exposure may result in post-traumatic stress disorder (PTSD), but because there is substantial overlap in the symptoms of PTSD and mild TBI from blast exposure, evidence suggests that most symptoms are accounted for by PTSD rather than as a direct result of blast injury.
The committee said the VA should conduct a rigorous evaluation of existing systems to determine whether current approaches for detecting, treating, and rehabilitating health outcomes from blast injuries are adequate.
While portable blast wave sensors are currently used by some combatants, developing and deploying advanced data collection technologies that can quantitatively measure components of blast waves are needed, as well as better characterization of the exposure environment in real-time, the committee said.
“Blast wave sensors and cameras should be included as a single unit, and should be capable of transmitting data, and this should be linked to self-reported exposure histories and demographic, medical, and operational information,” Dr. Hauser told Neurology Today.
The panel also recommended that the VA create a registry of blast-exposed — not only blast-injured — service members to serve as foundation for long-term studies, as well as using existing military records to identify a cohort of service members who served in the Iraq and Afghanistan wars to use in a prospective study of such long-term effects on health and rehabilitation.
The VA should also determine whether current screening tests administered during the enlistment physical examination might be used to measure possible increased susceptibility to blast injury, and whether additional screening tests of deployed troops might help determine whether a service member has increased susceptibility.
Importantly, the IOM committee said clinicians should ask veterans specifically about exposure to blasts, and the VA should develop standard screening questions specific to blast exposures that can be integrated into its electronic health record system and become part of veterans' military histories. In addition, it recommended that these questions be listed on the military health history pocket card carried by soldiers in the field.
Objective pre-deployment neuropsychological testing data, including advanced imaging for selected cohorts, are also needed, according to Dr. Hauser.
“TBI from blasts may not follow the same clinical rules as other concussion-like head injuries,” he explained. “The clinical rules of the road like ‘seeing stars’ or a short period of being knocked unconscious, may not apply in these injuries. Some individuals may not even be aware that that have suffered a mild TBI while others may have such severe injuries to the body that CNS damage is overlooked and not reported. Also, neurological damage may appear in a more diffuse pattern after blast injury. This diffuse pattern may be a signature that can be seen on [imaging] but more research on this is needed.”
He also said that in addition to VA system research it is important that future research on blast-exposed veterans include outside neurological experts, not just those associated with the military.
“We need to bring the best science available to better understand the neurological consequences of both short- and long-term blast exposures.”
GREATER AWARENESS OF THE ISSUE
Geoffrey Ling, MD, PhD, Col (Retired), FAAN, deputy director of the Defense Sciences Office at the Defense Advanced Research Projects Agency and professor of neurology at the Uniformed Services University of the Health Sciences in Bethesda, MD, who was not involved with the report, told Neurology Today that while more is being learned about the potential long-term latent consequences of blast exposures, and head trauma in general, the biggest gains have been made in general awareness of the issue, followed by prevention and screening — and not just in the military.
“When we started looking into this we learned a lot, and what we were finding caught a lot of people off guard. But in a short period of time, the issue has become accepted — especially the effects of repeated exposure to mild trauma and secondary consequences. In 2000, this was not even on our radar screen, but by 2005 it was very clear that blast exposure was causing mental status changes, and many were subtle and lasting.”
He said that the IOM report provides “a roadmap” for neurologists, researchers, and the military. “It shows us that we still have a lot to learn, but also gives us a process to follow; what we should look at and look for.”
That studies are starting to confirm that blast exposure[s] have milder delayed consequences that have been unrecognized in the past and that are also significant, he told Neurology Today, as is research suggesting that TBI and PTSD may overlap.
“On the field, mild and repeated blast exposure and potential TBI is now recognized and troops are aware of what to look for among their team members — subtle symptoms that may be overlooked by those who are not familiar with an individual. They can tell if something is not right with a friend, even if these are very subtle physical, cognitive, or behavioral changes.”
Above all, he said, it is important to recognize that this is a neurological injury, and neurologists need to be aware of research findings and become more involved.
“Neurologists need to take ownership of screening patients who have had head injuries, including mild concussions, and especially repeated impacts. This is not simply a VA issue.”