It’s a cliche, but it’s true: Traumatic brain injury (TBI) is the signature wound of the wars in Afghanistan and Iraq. And it has been called an invisible injury, since you can’t see it and it typically doesn’t turn up in brain scans.
But a fascinating study has found evidence of chronic traumatic encephalopathy (CTE), a degenerative disease that’s been found in the brains of deceased football players who suffered concussions, in the brain tissue of blast-exposed military service personnel, according to a story on the Boston University School of Medicine (BSUM) website.
Investigators from BU and the Veterans Affairs Boston Healthcare System performed the study, which received wide coverage in the media Thursday.
Laboratory experiments conducted by the researchers discovered that exposure to a single blast equivalent to a typical improvised explosive device (IED) results in CTE and long-term brain impairments that accompany the disease.
And in an interesting twist, they also found that the blast wind, not the shock wave, from the IED blast is actually what leads to TBI and long-term consequences, including CTE.
The research, which represents the first case series of postmortem brains from U.S. military personnel who were exposed to a blast and/or a concussive injury, was published online Wednesday by Science Translational Medicine.
Dr. Lee Goldstein, associate professor at BUSM and Boston University College of Engineering, and Dr. Ann McKee, professor at BUSM and director of the Neuropathology Service for VA New England Healthcare System, led the study and are its senior co-authors.
CTE, which can only be diagnosed by studying a person’s brain after death, is a progressive neurodegenerative brain disease that has been reported in athletes with multiple concussions or subconcussive injuries.
“In early stages, CTE is characterized by the presence of abnormal deposits of a protein called tau in the form of neurofibrillary tangles, glial tangles and neuropil threads throughout the brain,” BUSM stated. “These tau lesions eventually lead to brain cell death. CTE has clinical features in common with TBI, including psychiatric symptoms and long-term cognitive disability involving memory and learning deficits. TBI can impact military personnel exposed to an explosive blast and may affect approximately 20 percent of the 2.3 million servicemen and women deployed since 2001.”
In the study, researchers performed pathological analyses on brain tissue from four military service personnel with known blast exposure and/or concussive injury.
The researchers compared their findings with brain tissue from three young amateur American football players and a professional wrestler, who all had suffered repeated concussions, and four brain samples from comparably-aged normal controls with no history of blast exposure, concussions or neurological disease.
“The investigators found that CTE neuropathology in the brains of blast-exposed military veterans was similar to that found in young athletes with repetitive concussion and consistent with what has previously been observed in brain samples from other athletes with a history of repetitive concussive injury,” according to BUSM.
“Our results showed that the neuropathology from blast exposure, concussive injury, or both were virtually indistinguishable from those with a history of repeat concussive injury,” said McKee, who is the director of the Brain Banks for BU’s Alzheimer’s Disease Center and the Center for the Study of Traumatic Encephalopathy, which are based at the Bedford VA Medical Center.
According to McKe, the findings seem to show that TBI caused by different factors may trigger similar disease pathways in the brain.
“The neuropsychiatric symptoms of CTE that have previously been associated with athletes diagnosed with CTE could also be attributed to military personnel who were exposed to blast,” said Goldstein, who also is affiliated with the BU Photonics Center and served as the study’s lead author.
According to BUSM, to research the impact of a single-blast exposure, investigators worked with experts in blast physics, experimental pathology and neurophysiology at Boston University, VA Boston Healthcare System, White River Junction VA Medical Center, New York Medical College, Fraunhofer Center for Manufacturing Innovation, University of Massachusetts Lowell, Lawrence Livermore National Laboratory, Massachusetts General Hospital and the University of Oxford.
‘The data demonstrated that one blast comparable to that experienced by military service personnel in the field resulted in both neuropathological and behavioral evidence of CTE,” BUSM said, which is a pretty frightening finding.
And these long-term impairments in brain function, affecting learning and memory, were seen just two weeks after exposure to a single blast.
The blast wind from an IED can reach a velocity of up to 330 miles per hour, which is more than the biggest gust of wind ever recorded on earth. That wind violently jerks the head, resulting in brain damage.
The researchers also looked into how they could prevent the brain injury. They found that immobilizing the head during a blast prevented the learning and memory problems associated with CTE that took place when the head wasn’t immobilized.
“Our study provides compelling evidence that blast TBI and CTE are structural brain disorders that can emerge as a result of brain injury on the battlefield or playing field,” Goldstein said in the BUSM piece. “Now that we have identified the mechanism responsible for CTE, we can work on developing ways to prevent it so that we can protect athletes and our military service personnel.”