New research performed at the University of Illinois at Chicago College of Medicine has shown through diffusion tensor imaging, or Diffusion MRI, that patients with traumatic brain injury, even mild traumatic brain injury have structural changes in the white matter of their brains that account for cognitive impairments.
Diffusion tensor imaging is a new technology of magnetic resonance imaging (MRI) that measures the diffusion of water molecules in the brain. It also allows diffusion to be measured in multiple directions so that researchers can map the directions of the fibers and examine the connectivity of different regions in the brain. In particular the researchers used it to examine the connectivity of white matter in the brain and examine the structural changes found in white matter after traumatic brain injury. The researchers especially examined patients who had chronic traumatic brain injury.
The study was lead by Dr. Marilyn Kraus, associate professor of psychiatry and neurology at the University of Illinois at Chicago. She and her colleagues examined a range of patients with traumatic brain injury including mild and severe. What they found was that even patients who had no loss of consciousness or minimal loss of consciousness had structural changes in their white matter.
The researchers studied 37 traumatic brain injury patients. Twenty patients had mild TBI and 17 had moderate to severe TBI. All of the patients were studied six months after their injury date, and most of the people studied were people who were functioning very well and either working or in school. The researchers also studied 18 healthy people and gave them diffusion tensor imaging screenings. They also tested the healthy volunteers to evaluate their memory, their attention spans, and their executive functions. Executive functions are a set of cognitive functions that control and regulate other abilities and behaviors, particularly goal-oriented actions such as starting, stopping, and changing behavior.
The researchers learned that the mild to severe TBI patients who showed structural changes in their white matter (all TBI patients) also showed deficiencies in their cognitive abilities associated with thinking, memory, and attention. The patients they studied who had more severe traumatic brain injuries had even more structural changes in their white matter and showed permanent changes in their cognitive abilities.
Researchers already know that specific areas of the brain are involved in specific functions like thinking, memory, cognition, and motor skills. But they are now learning that what is more important is that white matter connects the major areas of the brain. While the major areas of the brain seem healthy, if white matter is changed, then the major areas of the brain cannot function normally.
Most of the mild traumatic brain injury patients did not report any cognitive difficulties, but the researchers were able to detect permanent damage, nonetheless.
The researchers were able to decipher two different types of damage to white matter. The axons in white matter, which allow one neuron to communicate with another, can be damaged, but also the myelin that surrounds the axon as a protective covering can be damaged. If the myelin is damaged it will interfere with signals between the brain and other parts of the body. If an axon is damaged, the brain damage is permanent.
The researchers observed that mild traumatic brain injury patients had less myelin damage, while more severely injured patients had both myelin and axonal damage.
Traumatic brain injury is becoming an important study because it is becoming the number one injury in veterans returning from war, especially the Iraq war. It is also becoming common for athletes to have chronic concussions. Their studies particularly show that chronic traumatic brain injury has a significant impact on a patient’s ability to recover.
Sherri McGinnis González, “Imaging shows structural changes in mild traumatic brain injury,” University of Illinois at Chicago.