Longitudinal Changes of DTI Parameters During Acute and Sub-Acute Phase Following Mild Traumatic Brain Injury Using Tract-Based Spatial Statistics Analysis: The Preliminary Results

Tong Zhu¹, Jeffrey Bazarian², Jianhui Zhong¹

DTI studies of both human mTBI subjects and animal TBI models have shown different alteration patterns of tensor derived parameters, such as fractional anisotropy (FA), axial and radial diffusivity, with the accompanying neurological impairments following initial concussions. In this study, we performed a prospective longitudinal study of mTBI patients with three DTI scans for each subject to characterize the acute (within 24 hrs), late acute (1 week) and sub-acute (1 month) phase following mTBI. The tract-based spatial statistics (TBSS) was performed to achieve voxelwise statistical comparisons of longitudinal changes of DTI parameters for quantification of white matter micro-structural alterations. In 13 mTBI patients and 21 healthy controls analyzed so far we observed decreased FA and increased radial diffusivity in several major white matter tracts such as the genu corpus callosum, the anterior corona radiata and the internal capsule, although our findings are only approaching significance (p<0.1) due to the small number of subjects and subtle DTI changes in acute mTBI. Different from increased radial diffusivity due to demyelination in the recovery phase (9-15 months) of TBI, increased radial diffusivity as well as consequently decreased FA in the acute phase of mTBI may reflect possible neurofilament misalignments which create projections of the principal diffusivity onto the transverse plane.