A personal, private decision by the families of eight Iraq and Afghanistan combat veterans may have contributed to a significant discovery in the understanding of brain trauma caused by exposure to bomb blasts.

The brains of eight veterans, all exposed to blasts from high explosives in combat, have been found to have microscopic scarring in the star-shaped cells that line the junctions between their gray and white matter, change patterns previously undetected by medical imaging such as CT or MRI scans.

Most significant, researchers for the study, published June 9 in the premier scientific journal the Lancet Neurology, found that the brains of three veterans who died just days after blast exposure showed signs of trying to repair themselves from this microscopic damage.

The findings are the first physical evidence of brain injury resulting from exposure to high explosives, damage that has been called an "invisible wound," since it does not show up on any tests or scans.

Researchers with the Defense Department's Center for Neuroscience and Regenerative Medicine say the results could account for the physical and behavioral changes seen in some troops after they return from war.

"This is clearly a first step towards developing better means for diagnosis, prevention and treatment, now that we know somewhat of the nature of the problem, of the damage," said Dr. Daniel Perl, director of the Brain Tissue Repository at the center.

The research focused on eight veterans: five with chronic blast exposure and three with acute exposure. Some of the veterans also had brain injuries as a result of impact, such as a concussion. Several had died of drug overdoses, and one committed suicide.

The veteran who died by suicide, for example, was a military retiree who served with distinction for more than 25 years. According to his wife, he had been exposed to multiple blasts, both during training and in combat, and, after retirement, sought medical treatment for headaches as well as memory problems and cognitive changes.

He had been treated for PTSD, depression and anxiety, and a month before he died of a self-inflicted gun shot wound, had an MRI that showed no evidence of brain damage.

But the post-mortem analysis done at brain repository showed a brownish dust — scarring, according to Perl — along his brain's gray matter and elsewhere.

The authors say the blast wave causes damage at the interface of the brain's structural boundaries, to which the brain reacts with scar tissue.

While examining the brains of former troops to understand the relationship between combat exposure and traumatic brain injury is not new, this study differs from previous ones that explore the effects of concussion or impact-related injury, Perl said.

Researchers, including Perl, have long looked to troops to understand the development of and susceptibility to chronic traumatic encephalopathy, or CTE, the wasting disease that has caused behavioral changes and dementia in NFL and NHL players, but few scientists have examined how blast exposure can affect brain cells.

The scarring found in the Lancet Neurology study differs from CTE, which results from the buildup of a protein, tau, in the brain and is thought to be related to multiple concussions.

"CTE is an accumulation, and that takes years to develop," Perl said. "The service members we are describing develop these symptoms rather quickly, and they come back from deployment with these persistent symptoms. We believe it's related to the damage of the blast wave."

The brains of the exposed veterans were compared with a civilian control group, including several subjects who had died of opioid overdoses.

No members of the control group had the telltale scarring of blast exposure.

The research could have widespread implications for military personnel with physical and mental health changes following deployment to a war zone.

It also could have an impact on the future diagnosis and treatment of civilians, who increasingly are at risk for blast exposure from terrorist attacks, wrote the authors.

For now, however, more research must be done to confirm Perl's findings and translate it into operational medicine.

"We've made what we believe is a significant breakthrough. Through the research, we can come up with better means of prevention, diagnosis and treatment," Perl said.

He added that in order to follow up on the scientific discovery, however, researchers need more veteran subjects, and he asked military personnel — or their families — to consider making the same decision as those who already have left their brains to the military brain repository.

He added that troops could learn more about the repository and request information about making a donation through the center's website.

"This study could not have been done without the families of service members donating brains for research on military traumatic brain injury," Perl said.

Patricia Kime covers military health care and medicine for Military Times. She can be reached at pkime@militarytimes.com.