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Sex differences after concussion have been studied largely in high school and college athletes, often without reference to comparison groups without concussion. This study sought to evaluate sex differences in outcomes among all children and adolescents presenting to the Emergency Department (ED) for either mild traumatic brain injury (TBI) or orthopedic injury (OI), regardless of mechanism of injury. The study involved a concurrent cohort, prospective study design with longitudinal follow-up. Participants were eight to 16 years old with mild TBI (n = 143) or OI (n = 73). They were recruited and completed an initial assessment at EDs at two children's hospitals. They returned for a post-acute assessment within two weeks of injury and for follow-up assessments at three and six months. Outcomes included child and parent proxy ratings of somatic and cognitive symptoms, and standardized tests of cognitive functioning and balance. Sex did not moderate group differences in balance, fluid or crystallized cognitive ability, or child or parent proxy ratings of somatic or cognitive symptoms. Both parents and children reported more somatic symptoms in girls than boys, but in both groups. Compared with the OI group, the mild TBI group showed significantly lower fluid cognitive ability at the post-acute assessment and significantly higher somatic and cognitive symptoms according to both child and parent proxy ratings across the first two weeks post-injury. The results suggest that sex does not moderate the outcomes of mild TBI in a pediatric ED population. Previous research pointing to sex differences after concussion may reflect the lack of comparison groups, as well as a focus on adolescents and young adults and sport-related concussion. Future research should investigate whether sex moderates the outcomes of pediatric mild TBI in adolescents but not in pre-adolescent children.

This study is the first to examine cognitive outcomes after pediatric mild TBI using the National Institutes of Health Toolbox Cognition Battery (NIHTB-CB), a computerized cognitive test battery. The NIHTB-CB includes two complex measures of attention and executive function that allow differentiation of accuracy and response speed. We compared performance on the NIHTB-CB among children 8–16 years of age with mild TBI (n = 143) versus children with orthopedic injuries (OIs; n = 74) recruited in emergency departments and followed for 6 months post-injury. Mixed-model analyses showed that the mild TBI group showed significantly lower Fluid Cognition composite scores than the OI group at 10 days (group intercept, p = 0.018); the magnitude of group differences declined modestly over time (group × time interaction, p = 0.055). Effect sizes were d = 0.34 at 10 days post-injury, d = 0.27 at 3 months, and d = 0.10 at 6 months. No significant effects of group or time were found for the Crystallized Cognition composite. Analyses of Fluid Cognition subtests indicated that children with mild TBI displayed deficits for as long as 3 months on measures of attention and executive function (e.g., cognitive flexibility, inhibitory control), but not on measures of explicit memory, working memory, or processing speed. The poorer performance of the mild TBI group on measures of attention and executive function was attributable largely to slowed reaction time, not decreased accuracy. The findings suggest that children with mild TBI demonstrate persistent deficits in fluid cognition that are most apparent on tasks that combine demands for both speed and executive function.

Studies of brain morphometry may illuminate the effects of pediatric mild traumatic brain injury (TBI; e.g., concussion). However, no published studies have examined cortical thickness in the early injury phases of pediatric mild TBI using an appropriate comparison group. The current study used an automated approach (i.e., FreeSurfer) to determine whether cortical thickness differed in children following a mild TBI or a mild orthopedic injury (OI), and to examine whether post-acute cortical thickness predicted post-acute and chronic post-concussive symptoms (PCS). Children ages 8.00-16.99 years with mild TBI (n = 136) or OI (n = 70) were recruited at emergency department visits to two children's hospitals, during which parents rated children's pre-injury symptoms retrospectively. Children completed a post-acute (3–24 days post-injury) assessment, which included a 3 Tesla MRI, and 3- and 6-month post-injury assessments. Parents and children rated PCS at each assessment. Cortical thickness was estimated using FreeSurfer. Linear mixed effects and multi-variable negative binomial regression models were used to test study aims, with false discovery rate (FDR) correction for multiple comparisons. Groups differed significantly on left parietal cortical thickness (TBI > OI) after FDR correction. Cortical thickness also varied by brain subregion and age, but not sex. Groups differed significantly on PCS post-acutely (TBI > OI), but not at 3 or 6 months. Right frontal thickness was positively related to post-acute PCS in both groups. Right cingulum thickness predicted chronic PCS in the OI group only. Results highlight the complexity of predicting outcomes of pediatric mild TBI from post-acute neuroimaging biomarkers.