Excerpted from "The Invisible War on the Brain"
Caroline Alexander, National Geographic February 2015
BOOM: In the field a single blast event represents a virtually simultaneous amalgam of distinct components, each equally damaging. Ignition sparks a chemical reaction, an instantaneous expansion of gases that pushes out a spherical wall of gas and air faster than the speed of sound. This shock wave envelops any object it encounters in a balloon of static pressure. During this fleeting stage – the primary blast effect – the individual does not move. An abrupt fall in pressure follows, creating a vacuum. Then comes the secondary blast effect, a rush of supersonic wind that floods the vacuum, hurling and fragmenting objects it encounters, weaponizing debris as high-speed, penetrating projectiles. The wind itself causes the tertiary blast effects, lifting human beings or even 15-ton armored vehicles in the air, slamming them against walls, rocks, dust roadsides. The quarternary blast effects are everything else – fire that burns, chemicals that sear, dust that asphyxiates.
The mystery lies in the effects of the primary blast. Theories range wildly: Is it the shock wave’s entry to the brain through cranial orifices – eyes, nose, ears, mouth – that causes injury and, if so, how? Or is external shock pressure to the chest channeled inside vasculature up through the neck and into the brain? Does the transmission of complex wave activity by the skull into the semiliquid brain cause an embolism? Does pressure deform the skull, causing it to squeeze the brain? Is the explosive noise damaging? The flash of light? The majority of soldiers diagnosed with blast-induced neurotrauma have also been hurled or rattled by blast wind. Is military neurotrauma, then, simply an exotic form of concussion?
The tests in Colorado arose from a landmark 2008 study by the military of breachers , those soldiers whose job it is to set explosives and who for years had been reported to suffer a high incidence of neurological symptoms. The study, conducted by the US Marine Corps Weapons Training Battalion Dynamic Entry School, followed students and instructors over a two-week explosives training course. It turned out that for days after the larger explosions, breachers reported dull aches in the chest and back “like someone had punched them,” as well as headaches that started with shooting pains in the forehead, progressed down the temples, behind the ears and up through the jawline.”
More significantly, neurobehavioral tests administered before and after the course showed a “slight indication of declining performance among the instructors” who typically are exposed to more blast events than students are. This suggested that repetitive exposure even to low-level blasts – even over just a two week period – could be damaging. The breacher study went some way toward bringing blast-induced neurotrauma into focus. As Lee Ann Young, one of the study’s leaders, noted, it motivated six follow-on research initiatives that continue today. Previously, many in the military and medical communities had found it difficult to believe that a low-level blast could inflict significant injury. “Our most recent experience was with Gulf War syndrome where, despite many efforts to find consistent threads, we came up mostly dry on specific causes,” Col. Christian Macedonia (Ret.), the former medical sciences advisor to the chairman of the Joint Chiefs of Staff, told me. So there were insane shouting matches in the Pentagon, strange as it may sound now, as to whether blast-related TBI actually existed.” In a paper published as recently as 2008, researchers at the Center for Military Psychiatry and Neuroscience Research, Walter Reed Army Institute of Research, concluded that the troubling symptoms were strongly associated with PTSD and that “theoretical concern” about the neurological effects of blast exposure was essentially unfounded.
This excerpt leads us to believe the author’s purpose in the article as a whole is probably:
