U.S. Army Rangers fire an AT4 at a range on Camp Roberts, California. When military personnel fire certain powerful weapons, they are exposed to a blast wave that sends blood surging from the body to the brain.
This "tsunami in the body" is one way a blast can injure blood vessels that supply oxygen and nutrients to structures deep in the brain, says Dr. Ibolja Cernak , an expert on blast injuries at Belmont University in Nashville.
"We are talking about the brainstem, we are talking about the cerebellum," Cernak says, "all of the very nicely cushioned brain structures."’
In animals, there is now strong evidence that these structures can be damaged by blast exposures that disrupt blood vessels. In veterans, the effects are harder to measure.
Imaging studies done by the military have found that "blood flow is affected in people who have a career history with blast exposure," says Stephen Ahlers of the Naval Medical Research Command .
Those studies also suggest a decrease in brain volume, an increase in brain inflammation and disrupted connections between neurons.
"There are these long lasting cumulative effects," Ahlers says. From blast to blood to brain
A blast isn’t just like a blow to the head, when it comes to brain injury.
A head impact tends to injure structures near the surface. A blast wave keeps going.The result can be impaired blood flow to an area like the brain stem, which controls breathing, heart rate, and blood pressure."It could be the veteran comes [to the doctor] because of uncontrolled blood pressure," Cernak says. What a doctor may miss, she says, is that "the problem is in the brain stem."In addition to the surge of blood through the brain, a blast wave tends to cause injury as it crosses from one type of tissue to the next."So on the boundaries of the blood vessel and the brain, we will have shearing and potentially structural damage," Cernak says.When the blast wave is from a big explosion, like a bomb, this can cause catastrophic bleeding. But repeated exposure to what the military calls low- level blasts, including those from rocket […]
Blasts from military weapons may injure the brain through its blood vessels
