Blast Injuries

WHY ARE BLAST INJURIES AN IMPORTANT ISSUE RIGHT NOW?

America's armed forces are sustaining attacks from explosions or blast by rocket-propelled grenades, improvised explosive devices (IEDs), and land mines almost daily in deployed settings. Civilian workers and military personnel working in these combat zones are at increased risk of blast-related trauma, particularly blast-related traumatic brain injury (TBI).

Some of the TBI and concussive injuries associated with significant blast may not be identified acutely for several reasons. Initially, the blast-related TBI or concussion may have occur simultaneously with other more obvious life threatening injuries. Initially, the focus of medical care providers must be on the most life threatening injuries. Sometimes, in the case of a concussion/mild TBI (mTBI) resulting from blast, there may be no outward sign of injury; service members may also be reluctant to endorse acute symptoms because they do not want to be medically evacuated and separated from their unit. Because blast exposure is so common in the combat zones and almost everyone has had some of the acute symptoms of concussion, it may not be identified as problematic until the service member returns home from the deployment.

Finally, concussions and TBI related to significant blast exposure are also likely to have other important co-morbid conditions present. For example, the patient may also have combat stress or depression associated with a return from deployment; it is very challenging for the medical providers in these situations to determine what symptoms are due to the concussion and which symptoms are due to the combat stress or depression.

HOW DOES BLAST EXPOSURE CAUSE A CONCUSSION OR A TRAUMATIC BRAIN INJURY?

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 injuries 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 (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 a 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.
• 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.

WHAT SYMPTOMS MAY INDICATE A BLAST RELATED BRAIN INJURY?

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 experience 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.

WHAT IS DVBIC DOING TO CARE FOR THOSE WITH BLAST INJURIES?

DVBIC works to identify all service members who have sustained a closed brain injury during combat operations and to ensure that they receive the best care available.

Because the effects of blast injury on the brain are still being discovered, DVBIC has led the way in developing a number of important research projects examining specific variables involved in the blast. In addition, DVBIC has been involved in studies on developing combat gear which will better protect the brain should a blast occur.

Finally, DVBIC 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; this technique is known as Magnetoencephalography (MEG).