The brains of injured patients (top) with slowed brain wiring show a loss of myelin in green and red. Injured patients with normal-speed wiring (bottom) show mostly intact myelin, in blue.
Why do some youngsters bounce back quickly from traumatic brain injuries and others suffer devastating side effects for years? New research by scientists from UCLA and the University of Southern California suggests that damage to the fatty sheaths around the brain’s nerve fibers — and not the severity of the injury itself — explains the difference. The study identifies biomarkers that physicians could use to predict which children require closer monitoring after a brain injury because they are at a higher risk for poorer prognosis.
The study is the first to combine imaging scans with recordings of the brain’s electrical activity to reveal how damage to myelin, the protective coating around the brain’s circuitry, affects how quickly children and teens can process and recall information after a concussion or other head trauma. “Just as electrical wires are insulated 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,” says Christopher Giza, MD (RES ’94, FEL ’96, ’00), director of the UCLA Steve Tisch BrainSPORT Program and professor of pediatrics and neurosurgery. “We suspected that trauma was damaging the myelin and slowing the brain’s ability to transmit information, interfering with patients’ capacity to learn.”
To test their hypothesis, the scientists assigned a series of mental tasks to 32 youngsters ages 8 to 19, each of whom had suffered a moderate-to-severe brain injury in the previous five months. The tests evaluated processing speed, short-term memory, verbal-learning ability and reasoning and judgment. The UCLA team recorded the electrical activity in the participants’ brains to test how quickly nerve fibers transmitted information and then imaged the wiring to assess its structural soundness.
When the scientists compared the results to tests from 31 healthy participants, they discovered dramatic differences. Half of those in the brain-injury group showed widespread damage to their myelin. Those patients’ combined scores on the cognition tests were, on average, 12.2 percent lower than those with healthy brains, and their brain wiring worked at one-third the speed of healthy participants’. In the brains of the other 16 patients in the brain-injury group, the myelin was mostly intact. Those participants processed information as quickly as the healthy children. They also performed cognitive tasks 9 percent better than those who had more myelin damage, although not as well as the people without brain injuries.
The next phase of the research will be to explore how brain biomarkers change during a patient’s first year of recovery. “This is when most people recapture some cognitive function,” says Robert Asarnow, PhD, professor of psychiatry and biobehavioral sciences and psychology at the Jane and Terry Semel Institute for Neuroscience and Human Behavior at UCLA.
“Callosal Function in Pediatric Traumatic Brain Injury Linked to Disrupted White Matter Integrity,” Journal of Neuroscience, July 2015