Effects of hydrocortisone on the sciatic nerve crush injury in adult rat -A light microscopic study

A wide range of agents including corticosteroids & vitamin-C have been shown to possess some neuro-regenerative effect in peripheral nerve injury, but histopathological support for such claims remains scanty. Therefore, the present study was planned to assess the role of local administration of hydorcortisone in the healing of experimentally induced sciatic nerve crush injury. 30 rats obtained from the central animal facility were divided into one control and four experimental groups of 6 rats each. Walking track prints of each animal was taken before induction of injury and at weekly intervals postoperatively. Under general anaesthesia and aseptic condition the sciatic nerve crush-injury was induced in the mid-thigh region with Kocher's forceps. 0.5 ml of cortisol was instilled at the site of injury and wound was closed. The 2nd dose of cortisol was given after two weeks. Sciatic nerve function was assessed from the walking track analyses. At the end of the study period (3 to 6 weeks), animals were sacrificed and nerves were immersion fixed in Karnovsky's fixative. Tissue samples were either stained en-block with Osmic acid or 07–10 μm thick paraffin sections were stained with H& E, Cresyl violet & Luxol fast blue and Van Gieson's stain. It was observed that the animal on the operated side developed weakness, had altered gait and revealed lengthening of foot prints. The sciatic nerve function index ranged from -70 to -55 at 1 and 6 weeks post-operatively. Light microscopy-as compared to control, after one week of injury the nerve fibres were swollen, showed fragmentation by 3 weeks and complete degeneration along with marked removal of debris of degeneration by six weeks. Macrophages were associated with degenerating myelin sheath and Schwann cells along with the endoneurial fibroblasts showed remarkable proliferation and were visible as prominent fascicles alternating with the degenerating nerve fibres. However, during the period of study no intact nerve fibre was seen to cross the actual site of nerve injury. It was concluded, that though the local administration of hydrocorticsone appears to perceptibly improve the functional recovery, absence of concomitant supportive histopathological findings remains to be explained and therefore, the topical use of steroids to either reduce the post-injury nerve dysfunction or improve nerve regeneration warrants further study.