New research suggests damage to the fatty sheaths around the brain’s nerve fibers — not injury severity — might explain why some youngsters bounce back quickly from a traumatic brain injury while others suffer side effects for years.
A study conducted by researchers at UCLA and the University of Southern California identified possible biomarkers physicians could use to predict higher-risk patients who require closer monitoring. The findings were published in the July 15 edition of the Journal of Neuroscience.
Traumatic brain injury is the single most common cause of death and disability in children and teens, according to the CDC. One of the most commonly damaged brain areas is the corpus callosum, a large band of nerve fibers that connects the two hemispheres of the brain, according to a Journal news release. Damage to this area can cause long-lasting cognitive deficits in some children.
According to the abstract, the study combined imaging scans with recording of the brain’s electrical activity to show how damage to the protective coating around the brain’s nerve fibers affects how quickly children and teens can process and recall information after a concussion or other head trauma.
“Just as electricians insulate electrical wires to shield their connections, the brain’s nerve fibers are encased in a fatty tissue called myelin that protects signals as they travel across the brain,” Christopher Giza, MD, director of the UCLA Steve Tisch BrainSPORT Program, said in a news release. Giza also is a professor of pediatrics and neurosurgery at UCLA’s David Geffen School of Medicine and Mattel Children’s Hospital. “We suspected that trauma was damaging the myelin and slowing the brain’s ability to transmit information, interfering with patients’ capacity to learn,” he said in the release.
To test their hypothesis, the scientists assigned a series of mental tasks to 32 patients ages 8-19. Each had suffered a moderate to severe brain injury in the past five months. The tests evaluated the patient’s processing speed, short-term memory, verbal learning and cognitive flexibility. The researchers used electroencephalography to record how quickly the brain’s nerve fibers could transmit information and diffusion-weighted imaging to assess the corpus callosum’s structural soundness.
When the scientists compared the patients’ results to those of a matched control group of 31 children who had not suffered a brain injury, they discovered dramatic differences.
Half of the brain-injury group showed widespread damage to the myelin insulating their brain’s circuitry, the researchers found. These patients performed 14% more poorly on the cognitive tests and their wiring worked three times slower than the control group children’s.
Scans of the other 16 patients in the brain-injury group showed their myelin was nearly intact, and their brains were able to process information as quickly as healthy children’s. They performed 9% better on the cognitive tasks than the youngsters with more myelin damage, though not as well as the uninjured controls.
“Our research suggests that imaging the brain’s wiring to evaluate both its structure and function could help predict a patient’s prognosis after a traumatic brain injury,” first author Emily Dennis, PhD, a postdoctoral researcher at USC’s Keck School of Medicine, said in the release.
“Our next step will be to explore how brain biomarkers change during a patient’s first year of recovery when most people recapture some cognitive function,” principal investigator Robert Asarnow, PhD, said in the release. Asarnow is a professor of psychiatry and psychology at UCLA’s Semel Institute for Neuroscience and Human Behavior and College of Life Sciences.
The research was supported by funding from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the National Institute of Biomedical Imaging and Bioengineering and the National Cancer Institute.
Study abstract: http://www.jneurosci.org/content/35/28/10202.short