Diffusion-tensor imaging implicates prefrontal axonal injury in executive function impairment following very mild traumatic brain injury.

Abstract

To determine whether frontal white matter diffusion abnormalities can help predict acute executive function impairment after mild traumatic brain injury (mTBI). 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. 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). Impaired executive function following mTBI is associated with axonal injury involving the DLPFC.