Traumatic brain injury: Diffusion-weighted MR imaging findings

BACKGROUND AND PURPOSE: Diffuse axonal injury (DAI) accounts for a signific ant portion of primary intra-axial lesions in cases of traumatic brain inju ry, The goal of this study was to nse diffusion-weighted MR imaging to char acterize DAI in the setting of acute and subacute traumatic brain injury. METHODS: Nine patients ranging in age from 26 to 78 years were examined wit h conventional MR imaging (including fast spin-echo T2-weighted, fluid-atte nuated inversion-recovery, and gradient-echo sequences) as well as echo-pla nar diffusion-weighted MR imaging 1 to 18 days after traumatic injury, Lesi ons were characterized as DAI on the basis of their location and their appe arance on conventional MR images. Trace apparent diffusion coefficient (ADC ) maps were computed off-line with the diffusion-weighted and base-line ima ges. Areas of increased signal were identified on the diffusion-weighted im ages, and regions of interests were used to obtain trace ADC values. RESULTS: In the nine patients studied, isotropic diffusion-weighted images showed areas of increased signal with correspondingly decreased ADC, In one case, decreased ADC was seen 18 days after the initial event, CONCLUSION: Decreased ADC can be demonstrated in patients with DAI in the a cute setting and may persist into the subacute period, beyond that describe d for cytotoxic edema in ischemia.