MR shows lingering effects of concussion in kids

Diffusion tensor imaging (DTI) showed ongoing white matter structural changes in children who suffered a mild traumatic brain injury (TBI) up to five months after the injury despite the resolution of clinical symptoms, according to a study published in the Dec. 12 issue of The Journal of Neuroscience. The findings suggest DTI could be used to diagnose pediatric concussions and highlight the potential benefit of using advanced imaging techniques to monitor recovery in children following concussions.

Recent studies have suggested that children’s brains are more vulnerable to the effects of TBI than adult’s brains.

Andrew R. Mayer, PhD, from The Mind Research Network in Albuquerque, and colleagues devised a prospective study to compare white matter injuries at the acute phase and three to five months after injury in children with mild TBI with healthy controls.

“Based on past studies, we predicted there would be increased anisotrophic diffusion [FA/fractional anisotrophy] during the semi-acute phase of injury and that these injuries would resolve during the normal course of recovery (3-5 months after injury),” wrote Mayer et al.

The study population included 15 10- to 17-year-olds with mild TBI and 15 age- and education-matched controls.

During the initial visit, within 21 days of injury, 3T MR showed mean FA was elevated for all patients in the TBI group. Researchers were able to use increased FA to distinguish 14 of 15 healthy controls and 13 of 15 mild TBI patients. They also observed subtle cognitive deficits in the domains of attention and processing speed among the TBI patients during this visit.

The cohort for the second visit, three to five months after injury, was comprised of 10 healthy controls and 10 children with mild TBI. Although between-group differences in cognitive deficits resolved by this visit, increased FA remained evident for the TBI patients. Thus, diffusion metrics had not recovered after TBI. “If replicable, these findings provide a potential physiological basis for worse outcomes after a temporally proximal second injury,” wrote Mayer et al.

The relationship between cognitive deficits and diffusion abnormalities was weak, which suggests that the two may measure independent processes that have different time courses of recovery, according to Mayer and colleagues.

The researchers noted previous studies have suggested an increased incidence of diffuse axonal injury, cytotoxic edema and vasogenic edema among pediatric TBI patients compared with adult TBI patients. However, research has not yet determined whether these differences are related to biomechanical factors, incomplete myelination of white matter tracts or physiological factors.

“Additional prospective studies examining recovery of function/biomarker in pediatric mild TBI are therefore critical for the development of more objective criteria about when it is truly safe for children to return to physical activity,” wrote Mayer and colleagues.

Despite the small number of patients, the findings mark "an important step forward in our understanding of the effects of mild traumatic brain injury on the developing brain," Christopher Giza, MD, from the Brain Injury Research Center at the University of California, Los Angeles, who was not involved in the study, said in a press release.

"Further work is needed to determine whether the changes in white matter present at four months represent a prolonged recovery process or permanent change in the brain," Giza added. "Determining the duration of the structural changes, and whether these changes have clinical implications, remain critical areas for future studies," he said.