An advanced imaging technique has revealed that some military personnel with mild blast-related traumatic brain injury have abnormalities in the brain not previously seen with other types of imaging. These abnormalities occur in the brain’s white matter, the wiring system that nerve cells in the brain use to communicate with each other.

Traumatic brain injuries are estimated to have affected as many as 320,000 military personnel in the wars in Iraq and Afghanistan. Most of these are classified as mild traumatic brain injuries, also known as concussions, which can have serious consequences.

A team of researchers from Washington University School of Medicine and the Landstuhl Regional Medical Centre in Germany studied U.S. military personnel evacuated to Landstuhl from Iraq and Afghanistan after exposure to many types of explosive blasts. The Landstuhl Centre has been the central triage point for the wars in Iraq and Afghanistan for many years and is the closest hospital with a reliable MRI scanner.

Using a technique called diffusion tensor imaging, the team found white matter abnormalities in 18 of 63 patients (29%) diagnosed with mild traumatic brain injury. Diffusion tensor imaging assesses the movement of water in tissue. Changes in the patterns of water movement are often linked to injury or disease but the significance of the abnormalities seen in the military personnel is not yet fully understood. The white matter abnormalities were still detectible a year after injury, although their appearance on the scans changed over time.

Mild traumatic brain injury is a controversial topic. Much of the controversy centres on whether symptoms following mild traumatic brain injury are due to structural damage to the brain, disruptions in brain chemistry, psychological factors or a combination of these.

Diffusion tensor imaging has previously been used to study mild brain injury in civilians but did not reveal abnormalities in the areas highlighted by the new study. These regions included the orbito-frontal cortex, an area involved in emotional regulation and reward-based behaviour, and the cerebellum, an area linked to coordination, movement, organization and planning.

These areas of the brain were predicted to be especially vulnerable to blasts based on previously published computer simulations. The results of this new study published in the New England Journal of Medicine (June 2011) suggest that there may be fundamental differences between blast-related traumatic brain injury and the sorts of mild traumatic brain injury sustained by civilians in car accidents, falls, blows to the head and sports injuries.

More work is needed to establish if the brain abnormalities detected in the blast-injured military personnel represent significant damage to the brain’s white matter and whether this damage affects attention, memory, emotional regulation, balance, coordination, sleep and other functions. Likewise, the relationship between mild traumatic brain injury and post-traumatic stress disorder, experienced by many military personnel, is especially important.

Mild traumatic brain injury is a diagnosis based on a history of injury to the head that causes loss of consciousness, memory loss, confusion or other disruption in the function of the brain.  The research team hopes that the advanced MRI-based methods used in this study, while not yet ready for routine clinical practice, will lead to more accurate diagnoses, assist with triage and allow treatment interventions to start early in children and adults with traumatic brain injury in both military and civilian contexts.

 

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