Diffusion-Tensor Imaging Implicates Prefrontal Axonal Injury in Executive Function Impairment Following Very Mild Traumatic Brain Injury

PURPOSE: To determine whether frontal white matter diffusion abnormalities can help predict acute executive function impairment after mild traumatic brain injury (mTBI). MATERIALS AND METHODS: This study had institutional review board approval, included written informed consent, and complied with HIPAA. Diffusion-tensor imaging and standardized neuropsychologic assessments were performed in 20 patients with mTBI within 2 weeks of injury and 20 matched control subjects. Fractional anisotropy (FA) and mean diffusivity (MD) images (imaging parameters: 3.0 T, 25 directions, b = 1000 sec/mm(2)) were compared by using whole-brain voxelwise analysis. Spearman correlation analyses were performed to evaluate associations between diffusion measures and executive function. RESULTS: Multiple clusters of lower frontal white matter FA, including the dorsolateral prefrontal cortex (DLPFC), were present in patients (P < .005), with several clusters also demonstrating higher MD (P < .005). Patients performed worse on tests of executive function. Lower DLPFC FA was significantly correlated with worse executive function performance in patients (P < .05). CONCLUSION: Impaired executive function following mTBI is associated with axonal injury involving the DLPFC.