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What About White Matter?

The Role of Connective Fibers in Brain Injury Recovery

When scientists talk about brain injury, they're usually talking about damage to gray matter, which makes up the parts of the brain that contain nerve cells. Many studies have shown damage to gray matter can cause long-lasting cognitive disability. Yet white matter, the tissue containing nerve cell fibers that connect gray matter, may reveal a roadmap to recovery, according to new research from Northwestern Medicine.

Traumatic brain injury affects approximately 13 million people in the United States and Europe. These injuries can affect the mental skills people need to plan and achieve goals, control behavior, work independently and maintain social relationships. Neuroplastic changes in the brain – including recovery – can take place immediately after damage, allowing for some potential restoration of the affected functions.

To this end, the Northwestern Medicine study revealed critical insight into the role of cortical disconnection as a factor in recovery. The loss of white matter proved to be a reliable predictor of recovery. Verbal functions in particular were shown to be most affected by white matter damage.

Performance and prevention

The scientists, led by Irene Cristofori, PhD, a postdoctoral fellow in the lab of senior author Jordan Grafman, PhD, professor in Physical Medicine and Rehabilitation, Neurology and Psychiatry and Behavioral Sciences at Northwestern University Feinberg School of Medicine, studied about 200 American male combat veterans. Of the participants, 164 had sustained penetrating brain injuries during combat, and a control group of 43 had not. The scientists measured the men’s mental flexibility, planning ability and reasoning skills by testing verbal fluency, switching tasks and question-based problem solving.

The brain scans connected lower performance with both gray matter and white matter damage. Loss of gray matter was more relevant in tests associated with the left frontal lobe, but verbal ability was best predicted by damage to white matter. The scientists’ findings mirrored results from patients with brain tumors or history of stroke, who also suffered damage to white matter.

By revealing the role of white matter in brain injury recovery, the Northwestern Medicine scientists also drew new attention to preserving white matter to prevent long-term impairment. Neurosurgeons should be extra cautious when removing white matter, recommends Cristofori. Helmet companies could also produce helmets better designed to prevent the damage that occurs when lesions penetrate more deeply into the brain.