Blast Injuries Are an Important Issue
(U.S. Army Photo by SGT. Gustavo Olgiati/Released)America's deployed service members sustain attacks from explosions or blasts by rocket-propelled grenades, improvised explosive devices (IEDs), and land mines. Civilians and military personnel working in combat zones are at an increased risk of blast-related trauma, particularly traumatic brain injury (TBI).
Some of the TBI and concussive injuries associated with significant blast may not be identified at the time of injury for several reasons. Blast-related TBI or concussion may occur simultaneously with other more obvious severe injuries. Initially, the focus of medical care providers must be on the most life-threatening injuries. Sometimes, in the case of a mild TBI (mTBI)/concussion resulting from a blast, there may be no outward sign of injury. Service members also may be reluctant to report acute symptoms because they do not want to be medically evacuated and/or separated from their units. Because blast exposure is so common in combat zones and many of the acute symptoms of concussion are quite common, the TBI may not be identified as problematic until the service member returns home.
Finally, patients with blast-related TBIs are likely to have co-existing conditions. For example, the patient also may have combat stress or depression associated with deployment. It can be very challenging for medical providers in these situations to determine which symptoms are due to the concussion and which are due to combat stress or depression.
How Blast Can Cause a TBI
A TBI is caused by a blow or jolt to the head or a penetrating head injury that disrupts the function of the brain. Every blast event and TBI is different and can affect the body in a number of ways. Below are four known mechanisms of injuries that can result in 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 environment; for example, the effects of the blast wave may be increased in a closed environment such as a vehicle, or lessened by being behind a wall. The greatest risk of injury is to those closest to the explosion.
Secondary blast injury is the result of fragments (shrapnel) 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 a wall, a window or even a steering wheel. These types of injuries are similar to those 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 from amputations or the inhalation of toxic gases from the explosion.
In summary, TBI resulting from blast exposure can be much more complex compared to TBI from other causes. It is also difficult to estimate the course of recovery in these cases, as it varies from service member to service member and depends on a number of variables such as the size of the blast, distance from the blast, etc.
Warden DL, French LM, Shupenko L, Fargus J, Riedy G, Erickson ME, Jaffee MS & Moore DF. (2009). Case Report of a Soldier with Primary Blast Brain Injury. Neuroimaging; 47(2): T152-T153. [abstract]