Repeated Blast Exposures Result in Increased Neurobehavioral Symptoms

Alice Lium

October 15, 2009

October 15, 2009 (Baltimore, Maryland) — In cases of blast injury, it appears to be important for physicians to ask how many times the patient has been exposed to blasts; subtle symptoms after multiple exposures to mild traumatic brain injury (mTBI) may indicate a build-up of neurobehavioral problems or a dosing effect with multiple blasts, a new study suggests.

"The take-home is that people with significant numbers of exposures are the people who have the most clinical symptoms and will need the most clinical care," said Louis French, PsyD, of Walter Reed Army Medical Center, Washington, DC. It's important that physicians pay attention to this in service members who go outside of the system for care, he added.

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Dr. Louis French describes typical symptoms after blast injuries.

The findings were reported here at the American Neurological Association 134th Annual Meeting.

This cross-sectional study of service members at Walter Reed included 182 patients divided into 3 groups: those exposed to 1 blast, 2 blasts, or to 3 or more blasts. Blasts had to be severe enough to knock them down or cause injury. Patients indicated their symptoms on the Neurobehavioral Symptom Inventory, and researchers then compared the 1-blast group vs the 2-blast group, 1 blast vs 3 blasts, and 2 blasts vs 3 blasts.

"We see that there is an increment in the symptom burden as you increase the number of blasts, with the exception that between 1 and 2 blasts, there is a dramatic drop in the symptoms," said lead author Olavos Vanconcelos, MD, from Walter Reed. "This was a finding that was not expected, and we still don't know what it means."

Dr. Olavo Vasconcelo of Walter Reed Army Medical Center explains his poster on mTBIs.

Dr. French agreed, "One possibility is that after they've been through the second blast, they become somewhat used to the effects, and emotionally or neurologically they acclimate to the deficits, or the exposure. But," he added, "the system is fragile, such that the third blast is the straw that broke the camel's back."

Asked for comment on these new findings, Jeffrey Lewis, MD, from the San Antonio Military Medical Center in Texas, noted, "It could be that the changes we normally don't see after a single blast predispose someone to an even greater degree of impairment with multiple exposures." Dr. Lewis's unrelated study with sophisticated resonance image techniques, also presented here, showed that the effects of military blast mTBIs increase over time.

Blast a Signature Injury

Some 70% of injuries in the current conflicts in Iraq and Afghanistan, including brain injuries, are from exposure to a blast, so it is important to understand the implications of such a common injury, explained Dr. French. The patients in the current study were young men who were evacuated from the Iraq and Afghan theaters of war for serious injuries. Those with moderate or severe TBI or penetrating head wounds were excluded from the study. Mild head injuries, though, often accompany other, more serious injury.

In cases of repeated blast exposure, Dr. French noted that a team effort is important. "One of the things that we find is that if we deal with this purely from a neurological standpoint, we are going to be missing some aspects of the clinical presentation of these people. If we deal with it purely from a behavioral health standpoint, and psychiatry treats the patients, we're going to be missing an important aspect of this. If physical medicine rehab docs deal with them solely, they're going to missing part of it."

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Dr. Olavo Vasconcelos’ call to action for clinicians.

However, Dr. Vasconcelo noted: "It's critical we look at these results, which are very preliminary, with caution." Because the study relied on memory that may be affected by the stress of combat, "people with some lesser degree of symptoms may not recall every incident of what might be a common occurrence over there," Dr. French added.

Further, he noted that this is not a completely generalizable population. With no women in the study, gender bias could not be ruled out, and these people are among the most seriously injured of any group. "We don't know what [these results] mean for the civilian population," said Dr. Vasconcelo. "This is a very homogenous population of service members, and they are in very hostile situation as they go about their work every day. We don't know if this symptom increment has anything to do with changes in their brains."

In future work, the researchers hope to look at more details. "What we didn't do but will do in the future is to see whether the neurobehavioral symptoms correlate with stress symptoms," Dr. French added. "It may very well be there are greater rates of mood disorders and [posttraumatic stress disorder] in the people with more exposure [to blasts]. We do know that people with more combat exposure have higher rates of [posttraumatic stress disorder], so these may be related."

The authors have disclosed no relevant financial relationships.

American Neurological Association 134th Annual Meeting: Abstracts T120 and T119. Presented October 13, 2009.


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