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Veterans with Mild Traumatic Brain Injury Have Brain Abnormalities

Axial view of control probable TBI

Mild traumatic brain injury, including concussion, is one of the most common types of neurological disorder, affecting approximately 1.3 million Americans annually. It has received more attention recently because of its frequency and impact among two groups of patients: professional athletes, especially football players; and soldiers returning from mid-east conflicts with blast-related traumatic brain injury. An estimated 10 to 20 percent of the more than 2 million U.S. soldiers deployed in Iraq or Afghanistan have experienced traumatic brain injury.

A recent study by psychiatrists from the Iowa City Veterans Medical Center and University of Iowa Health Care finds that soldiers returning from Iraq and Afghanistan with mild traumatic brain injury have measurable abnormalities in the white matter of their brains when compared to returning veterans who have not experienced traumatic brain injury. These abnormalities appear to be related to the severity of the injury and are related to cognitive deficits. The findings were published online in December in the American Journal of Psychiatry.

"In the military population we studied, patients with traumatic brain injury have more alterations, sometimes called 'potholes,' in the white matter of their brains than patients without a history of traumatic brain injury," says senior study author Ricardo Jorge, MD, professor of psychiatry at the University of Iowa. "The more severe the injury, the more white matter abnormalities occur. There is also a correlation between increased numbers of potholes and increased severity of cognitive alterations in executive functions -- the ability to make a plan or a decision, for example."

Despite its prevalence, diagnosing mild traumatic brain injury is difficult, often relying on a patient’s recollection of a possible past head injury. In addition, symptoms of mild traumatic brain injury tend to be wide-ranging and non-specific, including problems with vision, hearing, balance, emotions, and thinking. There are currently few good tools available to identify the condition or monitor the brain’s recovery or deterioration.

Jorge and his colleagues used an magnetic resonance imaging-based brain-scanning technique called diffusion tensor imaging to study the brains of 72 veterans with mild traumatic brain injury and 21 veterans without mild traumatic brain injury. Diffusion tensor imaging measures the diffusion of water along thin fibers known as axons that form connections between brain cells. When axons are intact, water flow (diffusion) follows the axon boundaries and has a well-defined directionality. When the axon is damaged, water diffuses in many directions, a situation referred to as low fractional anisotropy.

"Decreased directionality of the water diffusion is a measure of lower integrity in the white matter," Jorge says.

Analysis of the diffusion tensor imaging data allowed the researchers to detect areas of lower integrity in the patients' white matter even though these so-called potholes are scattered randomly throughout the brain and occur in different places in different patients.

Veterans with mild traumatic brain injury had a significantly more potholes than veterans without traumatic brain injury. The difference in the number of potholes was not influenced by age, time since trauma, a history of mild traumatic brain injury unrelated to deployment, or coexisting psychological problems like depression, anxiety, or post-traumatic stress disorder. The number of potholes did, however, correlate with poorer performance on cognitive tests measuring decision-making and planning skills.

The team also examined the brains of civilians with non-combat-related mild traumatic brain injury who were assessed early after the injury. These patients have even more white matter potholes than the military group.

Although the results suggest that diffusion tensor imaging measurements might hold promise as a tool for detecting and tracking mild traumatic brain injury in the brain, Jorge cautions that the current study is not large or specific enough to confirm that diffusion tensor imaging-detected potholes are a biomarker for traumatic brain injury brain damage.

"To establish if this diffusion tensor imaging approach is a useful technique for diagnosing mild traumatic brain injury, we need to replicate these findings in a larger study and with patients who have mild traumatic brain injury from other causes," he says.

The study was conducted at the Iowa City Veterans Affairs Medical Center and was funded by the Veterans Administration and by a grant from the National Institute of Neurological Disorders and Stroke (5R01NS55827).

The team included researchers from the University of Iowa Departments of Psychiatry and Radiology, the Iowa Consortium for Substance Abuse Research and Evaluation; the Iowa City Veterans Affairs Medical Center; Erasmus University Medical Centre, Rotterdam, the Netherlands; and University of Cantabria, Santander, Spain.