Quantitative Diffusion-Tensor Tractography of Long Association Tracts in Patients with Traumatic Brain Injury without Associated Findings at Routine MR Imaging

Purpose: To evaluate whether quantitative diffusion-tensor tractography can show abnormalities in long association tracts of subjects with symptoms after traumatic brain injury without any visible signs of intracranial or intraparenchymal abnormalities of obvious traumatic origin at routine magnetic resonance (MR) imaging and to determine the number and type of these abnormalities. Materials and Methods: The study was approved by the local ethics committee, and informed consent was obtained from all subjects. Diffusion-tensor tractography was performed at 3.0 T in 106 consecutive clinical patients with traumatic brain injury without abnormalities at conventional MR imaging (age, 16-56 years) and 62 age- and sex-matched control subjects. Volume, mean apparent diffusion coefficient (ADC), and mean fractional anisotropy (FA) were measured in the following tracts: uncinate fasciculus, superior cingulum, temporal cingulum, superior longitudinal fasciculus, arcuate fasciculus, inferior fronto-occipital fasciculus, and inferior longitudinal fasciculus. Statistical analyses were based on repeated-measures analysis of covariance. Results: In control subjects, tract volumes showed large variability whereas FA and ADC showed small variability. In several tracts, mean FA values correlated negatively with the respective volumes. In patients with brain injury, FA values were reduced in both uncinate fasciculi, both inferior fronto-occipital fasciculi, and in the right inferior longitudinal fasciculus compared with control subjects (P < .05). Diffusivity was increased in half of the tracts (P < .05). The tract volumes were not significantly reduced. Conclusion: Quantitative diffusion-tensor tractography is able to show posttraumatic FA and ADC abnormalities in patients with normal findings at conventional MR imaging in several association tracts, most commonly the uncinate fasciculus. (C)RSNA, 2013