Blast Injuries and the Brain

A traumatic brain injury caused by an explosion or blast can be more complex compared with a TBI from other causes, like from a car crash or sports injury. In fact, explosive devices can produce multi-trauma injuries in an individual rarely seen outside combat.

According to the Defense and Veterans Brain Injury Center (DVBIC) more than 50 percent of injuries sustained during the conflicts in Iraq and Afghanistan are the result of explosives including bombs, grenades, land mines, mortar/artillery shells, and improvised explosive devices, or IEDs. Since 2006, blasts have been the most common cause of injury among American soldiers treated at Walter Reed Army Medical Center.

What is a blast wave?

A blast injury feels like being hit by a wave and then being pulled back into the ocean — all in intensely rapid succession (Jeffrey Barth, PhD). More scientifically, blast injuries result from the complex pressure wave generated by an explosion, an instantaneous rise in atmospheric pressure that is much higher than normal for humans to withstand. This is called a blast over-pressurization wave (CDC, Mass Casualties).

Mechanisms of blast injuries

There are four basic mechanisms of blast injuries. They are classified as primary, secondary, tertiary, and quarternary.

• Primary blast injury is the explosion itself, which is an atmospheric pressure that hits the individual and pushes on all of the organs of the body. The blast over-pressurization wave, generated by the explosion, travels at a high velocity and is affected by the surrounding environment; for example, the effects of the blast wave may be increased in a closed environment such as a vehicle. Air-filled organs such as the ear, lung, and gastrointestinal tract as well as organs surrounded by fluid-filled cavities such as the brain and spinal cord are especially susceptible to primary blast injury (Elsayed, 1997; Mayorga, 1997). The over-pressurization wave dissipates quickly, causing the greatest risk of injury to those closest to the explosion.
• Secondary blast injury is the result of energized fragments flying through the air; these fragments may cause penetrating brain injury.
• Tertiary blast injury may occur when the individual is thrown from the blast into a solid object such as an adjacent wall or even a steering wheel. These types of injuries are associated with acceleration/deceleration forces and blunt force trauma to the brain similar to that observed following high-speed motor vehicle accidents.
• Quaternary blast injury can occur in the presence of severe blast-related trauma resulting from significant blood loss associated with traumatic amputations or even from inhalation of toxic gases resulting from the explosion (DVBIC).

One or all of these mechanisms of blast injuries can occur simultaneously and can often cause multi-trauma injuries. Injuries can range from a brain injury and lung perforation to a lost limb or a contusion of the eye (CDC).

Symptoms

Difficulties experienced as a result of a brain blast injury can include a range of physical, emotional, cognitive, and behavioral symptoms. Many of these symptoms often occur along with other conditions such as depression or PTSD (DVBIC).

Research

The effects of blast injuries on the brain are still being studied; there is still a great deal to learn about the short- and long-term effects. In an effort to step up preventative measures, the military has implemented new policies such as screening all service members who have been at risk of a concussion — blast-related or not — and making mandatory a detailed evaluation for soldiers who have sustained three concussions before being released back to combat.

DVBIC, for one, has been involved in the validation of several important diagnostic tests for better identifying the blast effects on the brain. These include the use of advanced neuroimaging techniques, such as Diffuse Tensor-weighted Imaging (DTI) and advanced technologies for measuring the function of the brain as the individual works on specific tasks, a technique known as Magnetoencephalography (MEG) (DVBIC).

Proteins are also being studied as biomarkers that would allow combat medics at the point of injury to take a simple prick of the injured person’s finger with an instrument similar to that used by a diabetic to check blood sugar. If positive, the combat medic would know that the proteins associated with concussion or TBI were present in that person’s body. Having a simple blood test like this would be useful not only for the military but for civilians as well (Newsweek).

Sources

• Barth, Jeffrey, PhD. Director, Brain Injury and Sports Concussion Institute, University of Virginia School of Medicine.
• Bast, Andrew (November 7, 2010). ‘We Just Don’t Know,” Newsweek.
• CDC Mass Casualties: Explosions and Blast Injuries: A Primer for Clinicians (2006).
• Coupland, C. R. M., & Meddings, D. R. (1999). Mortality associated with use of weapons in armed conflicts, wartime atrocities, and civilian mass shootings: literature review. British Medical Journal, 319, 410-412.
• Defense and Veterans Brain Injury Center website. http://dvbic.dcoe.mil/
• Elsayed, N. M. (1997). Toxicology of blast overpressure. Toxicology, 121, 1-15.
• Ippolitio, Charles J. (2007). Battlefield tbi: blast and aftermath. Applied Neurology, Vol. 3, No. 8.
• Mayorga, M. A. (1997). The pathology of primary blast overpressure injury. Toxicology, 121, 17-28.