White Matter Microstructure and Connectivity in mTBI Patients with Distinct Neuropsychiatric Phenotypes

Traumatic brain injury (TBI) is highly prevalent and difficult to characterize. Based on the Glasgow Coma Scale, the majority of TBI patients are diagnosed as mild TBI (mTBI), which can be associated with a wide array of outcomes ranging from full recovery to debilitating and long-lasting neurologic symptoms. These neurobehavioral symptoms have large deleterious impacts on not only the patients, but their families, colleagues, and the community. Recent work used a battery of cognitive and behavioral tests early postinjury to classify mTBI patients into phenotypes that predicted clinical outcomes later: patients of the neuropsychiatrically distressed (ND) phenotype exhibited degraded neuropsychological functioning while patients of the emotionally resilient (ER) phenotype recovered well over the first 6 months post-injury. This study aimed to seek a physical explanation of these phenotypes by analyzing diffusion MRI (dMRI) derived parameters including diffusion tensor imaging (DTI) and edge density imaging (EDI). Analyses of longitudinal data from a cohort of 68 patients (30 NDs and 38 ERs) and 40 uninjured controls showed that axial diffusivity (AD) was lower in certain white matter tracts at 6 month post-injury in the ER but not the ND patients. Edge density trended a longitudinal increase in the ND but not the ER patients. The variability of these parameters exhibited a complex pattern that would require future investigations. The current neuroimaging evidence revealed differences in the dynamic healing processes for the ND and ER patients