Identification of Severities of Spinal Cord Injury during Acute Phase in Rats by Diffusion Tensor Imaging

Background: Diffusion tensor imaging (DTI) was an effective method to identify subtle changes to normal‐appearing white matter (WM). Here we analyzed the DTI data with other examinations, including motor evoked potentials (MEPs), histopathological images, and behavioral results, to reflect the lesion development in different degrees of spinal cord injury (SCI) in acute and subacute stage. Method: Except for 2 Sprague -Dawley rats died from anesthesia accident, the rest 42 female rats were randomized into 3 groups: control (n=6), moderate group (n=18), and severe group (n=18). Moderate (a 50-g aneurysm clip with 0.4-mm thickness spacer) or severe (a 50-g aneurysm clip with no spacer) contusion SCI at T8 vertebrae were induced. Then the electrophysiological assessments via MEPs, behavioral deterioration via the Basso, Beattie, and Bresnaha (BBB) scores, DTI data, and histopathology examination were analyzed. Results: In this study, we found that the damage of WM myelin, MEPs amplitude, BBB scores and the decreases in values of fractional anisotropy (FA) and axial diffusivity (AD) were more obvious in the severe injury group than that of the moderate group. Additionally, the FA and AD values could identify the extent of SCI in subacute and early acute SCI respectively, reflected in the robust correlations with MEPs and BBB scores. While the values of radial diffusivity (RD) showed no significant changes. Conclusions: Our data confirmed that DTI was a valuable in ex vivo imaging tool to identify damaged white matter tracts after graded SCI in rat, which may provide useful information for the early identification of the severity of SCI.