Shock Waves to the System
Story by Jackie Powder • Infographic by Karbel Multimedia
During the Balkan conflicts in the 1990s, Ibolja Cernak, MD, PhD, ME, MHS, saw patients with no visible injuries who, months after a blast, experienced symptoms such as extreme headaches, memory loss and confusion.
She wanted to learn more so she joined a first-responder team with the Military Medical Academy (MMA) in Belgrade in 1997 and was dispatched to Kosovo. There, she began to develop a theory that the brain—even without a direct hit to the head—could be seriously injured by primary blast waves that last just milliseconds.
“When you have an explosion, the detonation releases a huge amount of kinetic energy that packs the air molecules so tightly that it forms a front of compressed air that feels like something solid hit you,” explains Cernak, now chair of Military and Veterans’ Clinical Rehabilitation at the University of Alberta in Edmonton, Canada.
In her state-of-the art lab, she studies brain trauma in animal models, employing shock tubes to simulate blast conditions similar to those soldiers are exposed to in an operational environment.
“During an explosion, the entire body of the soldier is exposed to the blast field—and not only the head,” she says. “What that means is we have multiple responses in multiple organs … and potential damage to the immune and endocrine systems from the pressure of primary shock waves. All these changes play a pivotal role in the development of blast TBI.”
Another leading TBI researcher, Daniel Perl, MD, leads a team of scientists studying brain specimens from deceased service members.
“Our feeling is that if you don’t understand the underlying problem of what’s happening in the brain tissue, then it’s going to make diagnosis, prevention and treatment very difficult,” explains Perl, who directs the federal Center for the Study of Neuroscience and Regenerative Medicine.
“Ideally, we’ll find some changes that are unique to blast exposure,” he says.
New Johns Hopkins-led research, published in November 2014 in Acta Neuropathologica Communications, may yield some answers. Scientists discovered a distinctive honeycomb pattern of broken and swollen nerve fibers in the brains of five Iraq and Afghanistan combat veterans who survived multiple IEDs and died later of other causes. The tiny wounds—different from brain damage caused by car crashes or collision sports—were identified in brain regions that affect decision-making, memory and reasoning, and may be “the signature of blast injury,” said senior author Vassilis Koliatsos, MD, MBA, professor in Pathology, Neurology, and Psychiatry and Behavioral Sciences at the Johns Hopkins School of Medicine. The injuries, he says, “may help explain why some veterans who survive IED attacks have problems putting their lives back together.”
The Physics of Brain Injury
A blast wave generated by an explosion starts with a single surge of high pressure that compresses air molecules.
This is followed by a rapid drop in pressure that creates a vacuum effect.
Blast overpressure compresses the abdomen and chest, initiating oscillating waves in the blood that deliver the kinetic energy to every organ.
Air-filled organs, including lungs, the GI tract and middle ear, are especially affected.
The blast wave energy moves through the torso to the brain.
This can potentially cause damage to tiny cerebral blood vessels, stretching and damaging neural cells in the brain.
Numerous potential short- and long-term effects may follow.
Multiple blast-related TBIs may cause neurodegenerative impairments similar to chronic traumatic encephalopathy or Alzheimer’s.
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