Blasts from explosives have long been known to cause mild traumatic brain injury in combat veterans, but a new study by Seattle experts sheds light on how — and where — lasting harm may occur.
Using brain scans from dozens of former soldiers, plus similar research in mice, scientists at the University of Washington and the Veterans Affairs Puget Sound Health Care System have identified the cerebellum — the area of the brain critical for coordinating movement, balance and certain cognitive skills — as particularly vulnerable to repeated blasts.
The findings could prompt studies into ways to prevent and treat mild traumatic brain injury, or mTBI, which has been called the “signature injury” of recent wars in Iraq and Afghanistan. An estimated 250,000 to 500,000 members of the military have been diagnosed with mTBIs.
“What’s interesting is that these types of TBI wouldn’t be on most people’s radar,” said James S. Meabon, an expert in psychiatry and geriatrics at UW and the VA Puget Sound. He is the lead author of the paper published this month in the journal Translational Science Medicine. “If you’re not getting a moderate to severe type of injury, most people would shrug that off.”
More than 40 veterans who participated in the study experienced an average of 21 mild traumatic brain injuries as a result of explosions, with some enduring more than 100 such injuries. The more blasts they were exposed to, the more they showed lower levels of glucose metabolism, a marker of brain activity, in the cerebellum, the study found.
Damage from repeated blasts was detected in the cerebellums of mice, which are broadly similar to those in humans, researchers said. Researchers created “shock tubes” to test simulated blast effects in the rodents.
In mice, the explosions ruptured parts of the blood-brain barrier and led to the loss of certain neurons in the cerebellum. They revealed a buildup of proteins associated with dementia and Alzheimer’s disease.
Further neuroimaging in mice and humans showed additional structural changes in the cerebellum, including damage to the fibers that connect regions across the brain.
“We need to pay more attention to the cerebellum,” said David Cook, a VA scientist and UW research associate professor of medicine in pharmacology.
The findings could help veterans such as William “Tye” Kerby, 34, a Marine who served three combat tours to Iraq, said Dr. Elaine Peskind, who co-directs the Mental Illness, Research, Education and Clinical Center at VA Puget Sound.
Kerby, who left the Marines in 2006 after suffering at least three mTBIs, has had problems with headaches, irritability and memory loss. He lives in Renton with his wife and two children. He said he agreed to participate in the study to seek treatment and to contribute to research.
“Anything I can do to help the other guys out there that have got this going on and will have this going on, I want to do,” he said.
The study’s findings suggest scientists should pay more attention to how mTBI affects the cerebellum to understand the emotional difficulties veterans face, Peskind said.
Dr. Brent Masel, national medical director for the Brain Injury Association of America, said he wasn’t “terribly surprised” at findings that the cerebellum appeared to be vulnerable to repeated blasts.
But Masel, who was not involved with the study, said the research offers potentially important insight into the chronic harm from blast-induced mild trauma.
“It’s a piece of the puzzle, and eventually we’ll be able to put it together,” he said.