Fig 6. Light micrographs in the cauda equina central (A and B) and peripheral (C and D). to the site of compression after 3 weeks. Proximal to the constriction region, venous dilation and Wallerian degeneration were apparent in the dorsal root, but there was no nerve fiber degeneration in the ventral root (A and B). In contrast, degeneration of nerve fibers was observed in the ventral root distal to the constriction region, a change attributed to arachnoiditis resulting from Wallerian degeneration (C and D). A, artery; DR, dorsal root; SS, subarachnoid space; V, vein; VR, ventral root.