Increased brain activation during working memory processing after pediatric mild traumatic brain injury (mTBI).

PURPOSE: The neural substrate of post-concussive symptoms following the initial injury period after mild traumatic brain injury (mTBI) in pediatric populations remains poorly elucidated. This study examined neuropsychological, behavioral, and brain functioning in adolescents post-mTBI to assess whether persistent differences were detectable up to a year post-injury. METHODS: Nineteen adolescents on average 7.5 months post-mTBI completed neuropsychological testing and an fMRI auditory-verbal N-back working memory task. Parents completed behavioral ratings. The comparison group included 19 healthy controls matched to the mTBI group for demographic variables and N-back task performance. RESULTS: There were no between-group differences for cognition or behavior ratings. The expected decreased accuracy and increased reaction time as N-back task difficulty increased were apparent. The mTBI group showed significantly greater brain activation than controls during the most difficult working memory load condition. CONCLUSION: Greater working memory task-related activation was found in adolescents up to one year post-mTBI relative to controls, potentially indicating compensatory activation to support normal task performance. Differences in brain activation in the mTBI group so long after injury may indicate residual alterations in brain function much later than would be expected based on the typical pattern of symptom recovery, which could have important clinical implications.