Sgt. Zachary Mayne, former team leader of 3rd Ranger Battalion, has suffered two separate combat traumatic brain injuries (TBIs) during his deployments to Afghanistan. In an interview with SOFREP, he said that,

…my second blast TBI definitely shifted my views on the whole issue. I only had headaches for a few days from the first, and I felt guilty receiving a Purple Heart for something so insignificant. The second one changed almost every important aspect of my life. My mood, sleep, attention, memory, confidence, and energy were thrown off-balance. My shrapnel wounds healed within a few weeks, but I’m still dealing with the fallout from the TBI over a year and a half later. Ironically, if you aren’t covered in blood, people don’t take your injuries as seriously — especially other Rangers. I was guilty of that too. It’s the wounds that didn’t make me bleed that have caused the most damage in my life and there aren’t even scars I can point to for them.”

The study of TBIs has been an emerging medical science of late. More attention has shifted to the injuries sustained in car accidents, sports injuries and of course, service members exposed to explosions. Improvised Explosive Devices (IEDs) have been a hallmark of the Global War on Terror, an effective way for otherwise poorly trained and poorly armed insurgents to do significant damage to American troops. IEDs can be victim operated, timed or controlled remotely and will cause a wide variety of injuries, ranging from amputations to severe shrapnel wounds — and traumatic brain injuries.

Upon further medical investigation, researchers have found some distinct differences between blast TBIs and the kind of TBI that you would get from a football game or a car accident. The Centers for Disease Control and Prevention (CDC) says that, “Bombs and explosions can cause unique patterns of injury seldom seen outside combat.” According to the Department of Neuroscience from the Uniformed Services University,

Although explosive blast TBI (bTBI) shares many clinical features with closed head TBI (cTBI) and penetrating TBI (pTBI), it has unique features, such as early cerebral edema and prolonged cerebral vasospasm. Evolving work suggests that diffuse axonal injury (DAI) seen following explosive blast exposure is different than DAI from focal impact injury. These unique features support the notion that bTBI is a separate and distinct form of TBI.”

A distinguishing feature from combat/explosion-related TBIs is the overpressure. If you imagine a car accident or a football player getting struck in the head, their brain might travel inside their skull and hit the opposite side causing a concussion, which can be very serious. This can happen during an explosion, but the overpressure brings about a whole slew of other problems. Overpressure acts like a wave, and it passes through the skull and thereby potentially damaging every part of it. For example, according to the CDC, “The eye, with its protective orbit, tarsal plates, and tough sclera, is resistant to traumatic rupture resulting from a blast overpressure wave. Given enough force, however, rupture can occur.”

There are four primary mechanisms of injury when it comes to explosions:

  • Primary blast injury: This is the overpressure (colloquially known as the “shockwave”), blasting out in all directions from the source of the explosion. It can bounce off walls and in many instances even gain momentum as it travels. The pressurized air slams into the victim, passing through him/her. This can do serious damage to the brain, but it can also seriously affect the lungs, abdominal areas, ears and other significant parts of the body. The misconception from movies is that the fire from an explosion is what kills you — in reality, it’s most likely the overpressure.
  • Secondary blast injury: The shrapnel and debris that hits you is known as the secondary blast injury. This could be the built-in fragmentation in an IED or hand grenade, or it could be rocks on the ground nearby.
  • Tertiary blast injury: This happens when the victim is thrown to the ground or up against a wall. The injuries sustained by that impact can be just as, if not more deadly than any of the others — depending on what they are getting rammed into.
  • Quaternary blast injury: Finally, the quaternary blast injury refers to the rest of the injuries sustained by the blast. This could include burns from a resulting fire, toxic gasses from the explosive, or asphyxiation, to name a few.

The fact that these blasts affect the brain can do more than what one might typically expect from an injury elsewhere on the body, and this is where the science gets quite complicated. There can be issues with memory loss (both short-term and long-term), behavioral and emotional changes, and it can even affect basic cognitive functions.