ARTICLE IN BRIEF
✓ Preliminary data reported by military physicians suggest that both eardrum perforation and loss of consciousness could be used by medics to identify soldiers who should be referred for observation for mild traumatic brain injury rather than return to duty.
In the first prospective study of its kind, military doctors in Iraq reported that blast-related eardrum damage and immediate loss of consciousness after an explosion may serve as biomarkers for mild concussive brain injury.
Because symptoms of mild traumatic brain injury may not be readily apparent, or may not appear for days or weeks after a blast, military physicians are eager to find new neuropsychological screening methods.
The findings, by doctors at the Air Force Theater Hospital at Balad Air Base in Iraq, a front-line, level 1 trauma hospital, were reported in a letter to the editor in the Aug. 23 issue of The New England Journal of Medicine (357:830–831).
Although the findings are preliminary, they suggest both eardrum perforation and loss of consciousness could be used by medics to identify soldiers who should be referred for observation rather than return to duty, Lt. Col. Michael Xydakis, MD, who wrote the letter, told Neurology Today in a telephone interview.
“This is just the beginning. We're hoping to take this to a whole new level of in-theater neuropsychological screening for possible sequelae of blast exposure,” said Dr. Xydakis, assistant professor of surgery with the Uniformed Services University of the Health Sciences in Bethesda, MD.
“We're basically looking for ways to make better triage decisions. If we can identify enough biomarkers [of mild brain injury], it might be possible to predict who is at risk.”
There is very little medical data on the effects of blast injuries on the CNS, especially repeated exposures, he noted. “The effect is essentially unknown at this time. There are no changes in the CNS that can be detected to indicate mild brain injury. This study is the first in the medical literature to identify these as possible biomarkers,” he said.
The Balad hospital treated 682 blast-injury victims between October 1 and December 1, 2006, but for purposes of the study, 210 male US soldiers were included as subjects. Neuro-otologic examinations performed in the immediate post-trauma period found a 35.2 percent incidence of tympanic-membrane perforation, including 37.8 percent of patients with rupture of both eardrums. Nearly 36 percent of the soldiers lost consciousness.
According to Dr. Xydakis, there was a significant association between eardrum perforation and loss of consciousness (relative risk, 2.76), and while 37 percent of the subjects had been wearing ear protection, which significantly reduced their risk of eardrum damage, the protection did not alter the association between perforation and loss of consciousness.
“Our observation that there was a significant association between barotraumatic tympanic-membrane perforation and concussive brain injury suggests that physicians who are treating blast survivors with tympanic-membrane perforation need to have a high index of suspicion for concomitant neurologic injury,” he wrote.
Traumatic brain injury has become the signature wound of the Iraq conflict, largely due to the frequent use of improvised explosive devices (IEDs), typically detonated as soldiers travel along the country's roads in vehicles. A total of 10,953 IED attacks, at an average of 30 per day, were reported in 2005, the last full year for which the military has released records.
Unfortunately, the Iraq conflict presents a unique opportunity to study the effects of blast exposure, noted Dr. Xydakis. “Historically, the only places where this has been studied before have been after bombings in Northern Ireland and Israel, the Madrid train bombing, and in Oklahoma City.”
The ability to do a prospective study has never been possible before, added study co-author Gerald Grant, MD, assistant professor of pediatric neurosurgery at Duke University Medical Center in Durham, NC.
“This is really initial work in our search for brain injury biomarkers,” he told Neurology Today in a telephone interview. “This was a step-off to do what we're doing now, which is a larger prospective study looking for neuropsychological biomarkers.”
The team is also studying retinal and even olfactory changes, he noted. “The larger question is whether loss of consciousness correlates with neurological injury, to what degree, and what criteria should be in place for evaluating these patients.”
In the field, he noted, physicians have to make very quick triage decisions. “Unless there is clearly a physical need for ongoing hospital care, these soldiers are usually sent back in six to twelve hours and we have no way of following them after that.”
Blast injuries have become so common in Iraq, however, that it would be impossible to keep all soldiers under observation after exposure to a blast, he said.
“If we hold all soldiers back, we are going to lose a lot of manpower in the field,” he continued. “Almost all of these soldiers want to get back to their unit as soon as possible. Of course this increases their risk of being exposed to subsequent blasts… Clearly they're vulnerable seven to ten days after a blast, and any repeat blast injury within that time can be very serious — this is really what drove our study.”
“We know that almost everyone in a blast suffers some loss of consciousness or amnesia, and that among blast patients who arrive comatose there is a very high incidence of bilateral membrane perforation. What we need is a way to detect injuries in those who are still walking around and appear fine,” said Dr. Grant.
A MANPOWER ISSUE?
“It's a small step, but it is a step,” commented Jordan Grafman, MD, chief of the Cognitive Neuroscience Section at NINDS.
“This was sort of an accidental finding,” he told Neurology Today in a telephone interview. “Many blasts can cause mild brain damage without injuring the eardrum, so we're always looking for some biomarker.”
The physics of blast exposure on the body remain almost unknown, he noted, but the effects can be of various intensities, depending on distance from the explosion and the degree of protection a person is wearing.
“The study is somewhat helpful, but the bottom line remains that it is possible to suffer a mild brain injury without any eardrum damage or even loss of consciousness. We need some way to identify those individuals that a field medic sees that appear okay but later we find there's been some kind of brain injury.”
The current study does not provide this, he told Neurology Today.
“I think the authors were able to observe this under disciplined conditions, and therefore felt they needed to write something they hope will prove to be the case at some later date.”
He noted that the current procedure of returning functioning blast-exposed soldiers to duty with instructions to be cognizant of any changes in their mental status, and to report these to a medic or commanding officer, is unreasonable.
“If you're talking about white, or even gray matter damage, it's often accompanied by loss of cognitive insight. If we're releasing these soldiers to the field with instructions to report any changes in their mental state, it probably won't happen because the person who suffers a mild brain injury is the least able to observe it in themselves. If a platoon leader sees them as filling a necessary niche and they appear to be doing well, they are not going to encourage them to report symptoms, either.”
What is needed is observation by trained neurologists and psychologists, Dr. Grafman said. “Maybe some neurologists will read this and step up to the plate.”
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