Blast Injury and Traumatic Brain Injury

Adapted from the Defense and Veterans Brain Injury Center

A TBI is caused by a blow or jolt to the head or a penetrating head injury that disrupts the function of the brain. Exposure to blast events can affect the body in a number of ways; in addition, these different injury mechanisms can interact and result in more impairments or prolonged periods of recovery.

• Primary blast injury is the result of exposure to the over-pressurization wave or the complex pressure wave that is generated by the blast itself. This blast over-pressurization wave 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 and organs surrounded by fluid-filled cavities such as the brain and spinal cord are especially susceptible to primary blast injury. The over-pressurization wave dissipates quickly, causing the greatest risk of injury to those closest to the explosion.
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• Secondary blast injury is the result of energized fragments flying through the air; these fragments may cause penetrating brain injury.
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• 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.
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• Finally, 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.

In summary, TBI resulting from blast exposure can be much more complex compared to TBI from other causes. As such, it is challenging to differentiate blast related TBI and/or concussion from other conditions. Finally, it is also difficult to estimate the course of recovery in these cases, as it may vary widely depending on various types of blast injury and other injury variables, such as the size of the blast, distance from the blast, etc. Because of these issues, it may be difficult to assess blast related TBI and concussion in the same manner that other brain injuries are examined. A better approach may be to conduct an evaluation based on the mechanism (cause) of the injury; that is, screen all individual service members exposed to a blast for any symptoms which might be resulting from the effects of blast on the brain.

Difficulties experienced as a result of a closed brain blast injury may include a range of physical, emotional, cognitive, and behavioral symptoms. Many of these symptoms are non-specific, however; that is they occur with other conditions such as depression or combat stress. It requires an experienced clinician who is familiar with the many variables involved in blast injury, and has an understanding of how these variables can affect recovery and ultimately impact return to everyday activities.