Blasts may cause brain injury even without symptoms

March 3, 2014

Veterans exposed to explosions who do not report symptoms of traumatic brain injury (TBI) may still have damage to the brain's white matter comparable to veterans with TBI, according to researchers at Duke Medicine and the U.S. Department of Veterans Affairs.

The findings, published in the Journal of Head Trauma Rehabilitation on March 3, 2014, suggest that a lack of clear TBI symptoms following an explosion may not accurately reflect the extent of .

Veterans of recent military conflicts in Iraq and Afghanistan often have a history of exposure to explosive forces from bombs, grenades and other devices, although relatively little is known about whether this injures the . However, evidence is building – particularly among professional athletes – that subconcussive events have an effect on the brain.

"Similar to sports injuries, people near an explosion assume that if they don't have clear symptoms – losing consciousness, blurred vision, headaches – they haven't had injury to the brain," said senior author Rajendra A. Morey, M.D., associate professor of psychiatry and behavioral sciences at Duke University School of Medicine and a psychiatrist at the Durham Veterans Affairs Medical Center. "Our findings are important because they're showing that even if you don't have symptoms, there may still be damage."

Researchers in the Mid-Atlantic Mental Illness Research, Education and Clinical Center at the W.G. (Bill) Hefner Veterans Affairs Medical Center in Salisbury, N.C., evaluated 45 U.S. who volunteered to participate in the study. The veterans, who served since September 2001, were split into three groups: veterans with a history of blast exposure with symptoms of TBI; veterans with a history of blast exposure without symptoms of TBI; and veterans without blast exposure. The study focused on veterans with primary blast exposure, or blast exposure without external injuries, and did not include those with brain injury from direct hits to the head.

To measure injury to the brain, the researchers used a type of MRI called Diffusion Tensor Imaging (DTI). DTI can detect injury to the brain's white matter by measuring the flow of fluid in the brain. In healthy white matter, fluid moves in a directional manner, suggesting that the white matter fibers are intact. Injured fibers allow the fluid to diffuse.

White matter is the connective wiring that links different areas of the brain. Since most cognitive processes involve multiple parts of the brain working together, injury to white matter can impair the brain's communication network and may result in cognitive problems.

Both groups of veterans who were near an explosion, regardless of whether they had TBI symptoms, showed a significant amount of injury compared to the veterans not exposed to a blast. The injury was not isolated to one area of the brain, and each individual had a different pattern of injury.

Using neuropsychological testing to assess cognitive performance, the researchers found a relationship between the amount of injury and changes in reaction time and the ability to switch between mental tasks. However, brain injury was not linked to performance on other cognitive tests, including decision-making and organization.

"We expected the group that reported few symptoms at the time of primary to be similar to the group without exposure. It was a surprise to find relatively similar DTI changes in both groups exposed to primary blast," said Katherine H. Taber, Ph.D., a research health scientist at the W.G. (Bill) Hefner Veterans Affairs Medical Center and the study's lead author. "We are not sure whether this indicates differences among individuals in symptoms-reporting or subconcussive effects of primary blast. It is clear there is more we need to know about the functional consequences of blast exposures."

Given the study's findings, the researchers said clinicians treating veterans should take into consideration a person's exposure to explosive forces, even among those who did not initially show of TBI. In the future, they may use brain imaging to support clinical tests.

"Imaging could potentially augment the existing approaches that clinicians use to evaluate brain injury by looking below the surface for TBI pathology," Morey said.

The researchers noted that the results are preliminary, and should be replicated in a larger study.

Explore further: Veterans with traumatic brain injuries and combat-related challenges

Related Stories

Veterans with traumatic brain injuries and combat-related challenges

February 3, 2014
Virginia Commonwealth University researchers have found that among traumatic brain injury-diagnosed veterans treated by the Veterans Health Administration between 2009 and 2011, the majority had a clinician-diagnosed mental ...

Imaging shows long-term impact of blast-induced brain injuries in veterans

December 2, 2013
Using a special type of magnetic resonance imaging (MRI), researchers have found that soldiers who suffered mild traumatic brain injury (MTBI) induced by blast exposure exhibit long-term brain differences, according to a ...

Veterans with mild traumatic brain injury have brain abnormalities

February 7, 2013
Mild traumatic brain injury (TBI), including concussion, is one of the most common types of neurological disorder, affecting approximately 1.3 million Americans annually. It has received more attention recently because of ...

In combat vets and others, high rate of vision problems after traumatic brain injury

February 4, 2013
Visual symptoms and abnormalities occur at high rates in people with traumatic brain injury (TBI)—including Iraq and Afghanistan War veterans with blast-related TBI, reports a study, "Abnormal Fixation in Individuals with ...

Study links PTSD to hidden head injuries suffered in combat

June 6, 2012
Even when brain injury is so subtle that it can only be detected by an ultra-sensitive imaging test, the injury might predispose soldiers in combat to post-traumatic stress disorder, according to a University of Rochester ...

New research on military traumatic brain injury

January 22, 2013
Researchers are making new strides in understanding the health consequences and treatment and rehabilitation needs of combat veterans and other service members affected by traumatic brain injury (TBI). The January-February ...

Recommended for you

Researchers find monkey brain structure that decides if viewed objects are new or unidentified

August 18, 2017
A team of researchers working at the University of Tokyo School of Medicine has found what they believe is the part of the monkey brain that decides if something that is being viewed is recognizable. In their paper published ...

Artificial neural networks decode brain activity during performed and imagined movements

August 18, 2017
Artificial intelligence has far outpaced human intelligence in certain tasks. Several groups from the Freiburg excellence cluster BrainLinks-BrainTools led by neuroscientist private lecturer Dr. Tonio Ball are showing how ...

Study of nervous system cells can help to understand degenerative diseases

August 18, 2017
The results of a new study show that many of the genes expressed by microglia differ between humans and mice, which are frequently used as animal models in research on Alzheimer's disease and other neurodegenerative disorders.

How whip-like cell appendages promote bodily fluid flow

August 18, 2017
Researchers at Nagoya University have identified a molecule that enables cell appendages called cilia to beat in a coordinated way to drive the flow of fluid around the brain; this prevents the accumulation of this fluid, ...

Researchers make surprising discovery about how neurons talk to each other

August 17, 2017
Researchers at the University of Pittsburgh have uncovered the mechanism by which neurons keep up with the demands of repeatedly sending signals to other neurons. The new findings, made in fruit flies and mice, challenge ...

Neurons involved in learning, memory preservation less stable, more flexible than once thought

August 17, 2017
The human brain has a region of cells responsible for linking sensory cues to actions and behaviors and cataloging the link as a memory. Cells that form these links have been deemed highly stable and fixed.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.