Post-Traumatic Stress Disorder Is Associated with Neuropsychological Outcome but Not White Matter Integrity after Mild Traumatic Brain Injury

The aim of this study was to examine neuropsychological functioning and white matter integrity, in service members and veterans (SMVs) after mild traumatic brain injury (MTBI), with versus without post-traumatic stress disorder (PTSD). Participants were 116 U.S. military SMVs, prospectively enrolled from the Walter Reed National Military Medical Center (Bethesda, MD), who had sustained an MTBI (n = 86) or an injury without TBI (i.e., Injured Control [IC]; n = 30). Participants completed a battery of neuropsychological measures (neurobehavioral and -cognitive), as well as diffusion tensor imaging (DTI) of the brain, on average 6 years post-injury. Based on diagnostic criteria for PTSD, participants in the MTBI group were classified into two subgroups: MTBI/PTSD-Present (n = 21) and MTBI/PTSD-Absent (n = 65). Participants in the IC group were included only if they were classified as PTSD-Absent. The MTBI/PTSD-Present group had a significantly higher number of self-reported symptoms on all neurobehavioral measures (e.g., depression), and lower scores on more than half of the neurocognitive domains (e.g., processing speed), compared to the MTBI/PTSD-Absent and IC/PTSD-Absent groups. There were no significant group differences for the vast majority of DTI measures, with the exception of a handful of regions (i.e., superior longitudinal fascicle and superior thalamic radiation). These results suggest that there is 1) a strong relationship between PTSD and poor neuropsychological outcome after MTBI and 2) a lack of a relationship between PTSD and white matter integrity, as measured by DTI, after MTBI. Concurrent PTSD and MTBI should be considered a risk factor for poor neuropsychological outcome that requires early intervention.