Evidence-based consensus in children and adolescents following uncomplicated mTBI indicates acute cognitive symptoms resolve over time with minimal long-term impact. However, traditional paper-and-pencil neuropsychological measures used in many studies have been criticized for lacking sensitivity to subtle changes in attention and executive functions. The National Institutes of Health Toolbox Cognition Battery (NIHTB-CB) is a computerized tool assessing overall cognition, fluid cognition, and crystallized cognition with few studies in pediatric mTBI. The aim of this study is to continue to explore the utility of the NIHTB-CB in adolescents recovering from mTBI compared to orthopedic injuries (OI) and healthy controls (HC).

The current pilot study utilized a prospective cohort design with longitudinal follow-up in three cohorts of high school student-athletes aged 14-18 (N= 52). Participants with mTBI (n= 17) or OI (n= 15) sustained during sport were recruited within 10 days of injury from a quaternary care setting. An age- and gender-matched cohort of healthy controls (HC) in an active sport season was included for community comparison (n= 20). The NIHTB-CB was administered as part of a neuropsychological screening battery at enrollment and one month after medical clearance (mTBI and OI) or eight weeks after enrollment (HC).

Results of a 3(group) x 2(time) ANOVA revealed a main effect of time (p < .001), but not group (p = .06), on the overall Fluid Cognition Composite. The mTBI group showed significantly lower performance on a measure of attention/inhibitory control (Flanker) compared to healthy controls acutely post-injury (p = .04; d = 0.72) and following clinical recovery (p < .01; d = 0.98), with no decline observed in the magnitude of group differences over time. The mTBI and OI groups exhibited deficits in performance on a measure of cognitive flexibility (Dimensional Change Card Sort) compared to the HC group acutely post-injury (both p < .01; d = 1.09-0.93). The magnitude of group differences between the OI and HC groups declined over time (p > .05; d = 0.68), whereas the mTBI group continued to show significantly lower performance following clinical recovery compared to the HC group (p = .02; d = 0.81). The mTBI, OI, and HC groups did not exhibit significant differences in working memory, explicit memory, or processing speed acutely post-injury and following clinical recovery (all p > .05; all d = 0.52 - 0.05). No significant effects of group (p = .16), time (p = .67), or the interaction (p = .45) were found on the Crystalized Cognition Composite.

Adolescents with mTBI demonstrated deficits on the NIHTB-CB measures of attention and executive functions acutely post-injury and extending beyond clinical recovery compared with healthy controls in this study. These subtle yet persistent deficits in cognitive performance lend support to the growing body of literature suggesting that alterations in neurotransmission may persist beyond resolution of clinical symptoms of mTBI. Further work is needed in larger samples to better understand trends in cognitive deficits and to identify clinical correlates persisting beyond clinical recovery from mTBI.