CHANGES IN WATER DIFFUSION DUE TO WALLERIAN DEGENERATION IN PERIPHERAL-NERVE

The authors report NMR measurements of the changes in water diffusion brought about by in vivo Wallerian degeneration due to either crush- o r tie-injuries in the sciatic nerve of the frog, Using a pulsed-gradie nt spin-echo sequence with a diffusion measurement time of 28 ms, the degree of diffusion coefficient anisotropy {D(longitudinal)/D(transver se)} 4 weeks after injury in both crush- and tie-injured nerves (2.3 /- 0.4 and 1.7 +/- 0.1, respectively) is significantly less than in no rmal frog sciatic nerve (3.9 +/- 0.4), The decrease of anisotropy in t he degenerated nerves is due to both a decrease in longitudinal diffus ion and an increase in transverse diffusion, The changes in diffusion coefficients are compared with the degree of axonal and myelin breakdo wn observed in light and electron micrographs of the nerves.