MR properties of rat sciatic nerve following trauma

T-1 and T-2 relaxation times, magnetization transfer (MT), and diffusion an isotropy of rat sciatic nerve were measured at different time intervals fol lowing trauma. The nerve injury was induced by either cutting (irreversible nerve degeneration) or crushing (degeneration followed by regeneration). T he MR properties were measured for proximal and distal portions of the inju red nerve. The portions of the nerve proximal to the induced injury exhibit ed MR characteristics similar to those of normal nerves, whereas the distal portions showed significant differences in all MR parameters. These differ ences diminished in the regenerating nerves within approximately 4 weeks po st injury. In the case of irreversible nerve damage, the differences in the distal nerves were slightly larger and did not resolve even 6 weeks after induced trauma. The MR measurements were correlated with histopathology exa ms. Observed changes in tissue microstructure, such as demyelination, infla mmation, and axonal loss, can result in a significant increase in the avera ge T-1 and T-2 relaxation times, reduction in the MT effect, and decrease i n diffusion anisotropy. MR parameters, therefore, are Very good indicators of nerve damage and may be useful in monitoring therapies that assist nerve regeneration. (C) 2001 Wiley-Liss, Inc.