Histopathological changes following removal of the perineurium.

Using microsurgical techniques, the perineurial sheath was stripped off the sciatic nerves of rats over a 0.5 cm length at a point where the nerve consists of a single fascicle. The nerves were excised 0 to 84 days after the injury, and were examined in semi-thin transverse section. A new sheath, closely resembling normal perineurium, became organized during the first 10 days; it appeared uniformly over the length of the injured segment. The new perineurial sheath was probably formed by endoneurial fibroblasts migrating from within the fascicle. In undamaged specimens, the asons immediately beneath the excised perineurium underwent no degenerative changes.