[Effect of locally applied corticoids on the morphology of peripheral nerves following neurotmesis and microsurgical suture].

The present work deals with the morphology of cut peripheral nerves anastomosed by primary microsurgical suture. The important question was whether the well-known anti-inflammatory, anti-exudative and fibroblast-inhibiting effects of locally applied glucocorticoids can influence the morphology of degenerating and regenerating peripheral nerves. After cutting the saphenous nerve of the rabbit and prior to its microsurgical suture the synthetic crystalline glucocorticoids methylprednisolone, prednisolone and dexamethasone were applied between the distal and proximal nerve stumps (interfascicular surface application). After a defined time of two days up to a maximum of five weeks the suture site and adjacent parts of the nerve were removed and investigated by light microscopy and electron microscopy. The morphological findings of the degenerating and regenerating nerve structures with and without local application of the different corticoids were compared. The results show that after local application of glucocorticoids the formation of scar tissue and neuromata is decreased, thus supporting the processes of regeneration. This is a result of a reduction of fibroblasts in the new formation of the epineurium and in the endoneurium and a certain protective effect on the perineural cells. Furthermore, the application of the glucocorticoids seems to accelerate the breaking down of myelin and degenerating axons and the new formation of myelin sheaths by "activating" Schwann cells. These facts lead to an enhancement of nerve regeneration after microsurgical suture.