Diffusion Tensor Tractrography Visualizes Partial Nerve Laceration Severity as Early as 1 Week after Surgical Repair in a Rat Model Ex Vivo

Abstract

Background: Previous studies in our laboratory have demonstrated that a magnetic resonance imaging method called diffusion tensor imaging (DTI) can differentiate between crush and complete transection peripheral nerve injuries in a rat model ex vivo. DTI measures the directionally dependent effect of tissue barriers on the random diffusion of water molecules. In ordered tissues such as nerves, this information can be used to reconstruct the primary direction of diffusion along fiber tracts, which may provide information on fiber tract continuity after nerve injury and surgical repair. Methods: Sprague-Dawley rats were treated with different degrees of partial transection of the sciatic nerve followed by immediate repair and euthanized after 1 week of recovery. Nerves were then harvested, fixed, and scanned with a 7 Tesla magnetic resonance imaging to obtain DTIand fiber tractography in each sample. Additional behavioral (sciatic function index, foot fault asymmetry) and histological (Toluidine blue staining) assessments were performed for validation. Results: Tractography yielded a visual representation of the degree of injury that correlated with behavioral and histological evaluations. Conclusions: DTI tractography is a noninvasive tool that can yield a visual representation of a partial nerve transection as early as 1 week after surgical repair.