The Centers for Disease Control and Prevention estimate that approximately half a million children visit the emergency room each year after a traumatic brain injury (TBI). While neuroscientists are learning more about the many ways TBI can hijack the brain’s natural inflammation pathways and alter white matter in adults, there has been a dearth of similar studies in children. To date, it is difficult to both diagnose TBI in children as well as determine likely outcomes—and the little data that is available suggests that younger brains may be more susceptible to TBI-related damage than older ones. Researchers at the Mind Research Network and the University of New Mexico have now discovered a potential diagnostic biomarker for TBI in children using a special type of neuroimaging technique called diffusion tensor imaging (DTI).
There is a pervasive notion that younger children are more resilient than adults, so kids’ brains should heal faster and better than grownups' after a concussion or TBI. But that particular outlook is changing. Keith Yeates, a neuropsychologist at Nationwide Children's Hospital and professor of pediatrics at the Ohio State University, says there are many reasons why children may be more susceptible to long-term effects after TBI or concussion.
“The pathophysiology of the injury tends to be a little bit different in kids because there are differences in the composition of the brain and there are differences in the size of children’s heads relative to the size of their body,” he says. “Their necks are less strong so they are subjected to different deceleration forces. And from a psychological perspective, young kids still have a lot to learn. They don’t have the stored knowledge and acquired skills like adults to fall back on.”
In a study published in the August 2012 issue of Rehabilitation Psychology, Yeates and colleagues found a link between age of injury and later behavioral deficits reported by parents. That finding supports others showing that younger children appear to fare worse after TBI.
“Children who sustained a severe TBI at a younger age are more likely to have a range of deficits that include deficits in their thinking skills, deficits in their academic skills, and also social problems,” says Yeates. “They tend to have trouble making or keeping friends. And they’re at greater risk for certain types of emotional and behavioral problems.”
Identifying who is at risk
We have few objective markers of what is going on in children’s brains after a concussion or TBI. Often, children visiting the hospital after a head injury are either given a computed tomography (CT) scan or a magnetic resonance imaging (MRI) scan. Andrew Mayer, a researcher at New Mexico’s Mind Research Network, says that these scans are not typically sensitive enough to pick up the underlying pathology.
“What we’ve been trying to do for the last five or six years is look at new techniques that may be more sensitive to the injury,” he says.
David Sharp, a neuroscientist at Imperial College London, using diffusion tensor imaging (DTI), has revealed extensive white matter injury in adults following different types of TBIs.
“This is a kind of MRI scan that allows you to measure the way water molecules move around in the brain. So you can measure these molecules moving in a particular direction along these tracks,” he says. “But after an injury, these tracks get damaged and then you see these water molecules moving in a lot of wacky directions.”
Mayer and colleagues used DTI to examine the brains of 15 children who had recently experienced a concussion. They then repeated the scanning, as well as administering cognitive testing, four months later. They found that structural changes in the children’s white matter remained months after the injury—even after cognitive and other symptoms had disappeared.
“It’s like a burn on your skin. Often, when you have a burn, even after you’ve stopped reporting the pain, you can still look and see the scar and say, ‘This is where I burned myself,’” he says. “Our findings may mean the brain is still healing itself.”
Mayer cautions that this work is still very preliminary. Yet, he argues that it may help doctors better diagnose TBI in the future—and determine who should be benched to avoid risk of further or lasting injury.
But Yeates says that there is still a lot we don’t know about the imaging results. “While these techniques are certainly intriguing and have a lot of potential, we don’t yet know the significance of the brain changes observed,” says Yeates. “So while there is a lot of interest in looking at imaging techniques as potential biomarkers for concussion or mild TBI to help with diagnosis, I believe the prognostic significance of those changes still remains to be seen.”