Recent Observations On The Regeneration Of Facial Nerve And The Changes Of Skin Appendages In Facial Composite Tissue Allotransplantation

Objective:To investigate the anatomy of rabbit's facial nerve, and establish a model of facial composite tissue allotransplantation in rabbits, which includes facial nerve. Then observe the regeneration of facial nerve and the changes of skin appendages in the first 4 weeks after operation.Methods:The facial nerves of domestic rabbits, japanese white rabbitsand livid blue rabbits were anatomized to study the distribution of facial nerve after it exited from skull. And based on the conclusion buccal branches of facial nerve served as nerves allografted.10 japanese white rabbits and 10 livid blue rabbits were chosen as donors and recipients to establish a model of facial composite tissue allotransplantation in rabbits.At the 2nd and the 4th week after transplantation, facial never conduction velocity in the flap was examined , one rabbit was sacrificed to gain the nerve form the anastomotic stoma and observe the transverse and ongitudinal sections with HE staining method and through transmission electron microscope respectively.Skin was gained form the edge of the flap to observe the ongitudinal sections by HE staining at the every week in the first postoperative month.Result: 1.The procedure was succesed in 6 cases of 10 cases.2.The facial never conduction velocity in the 2nd week was not significantly different with that in the 4th week, but significantly lower than the normal. Fibrillation potential of facial nerve denervation was showed by electromyogram.At the 2nd week, large number of nerve fibers denaturalization , sturcture loosen and fracturation in nerve fascicles were observed by Light Microscope, as the same time a small amount of myelinated nerve were regenerated but internal derangement; degeneration and necroses of myelin sheaths, vacuoles degeneration of surrounding tissues, disorder hyperplasia of collagenous fibers and many phagocytes were showed by electron microscope. At the 4th week, there were still large number of nerve fibers denaturalization, but nerve stoma was smooth, myelinated nerves prominently increased in quantity, the nerve fascicles structure was more regular, the diameter of regenerating nerve and the thickness of myelin sheath obviously increased.3. Within the first 4 weeks, there was no lymphocytic infiltration of the skin, the epidermis structure was clear , the basement membrane was continous and complete, the dermal papilla layer was clear; local collagenous fibers whose cell nucleus were normal lined up in disorder.A few cells swelled in the prickle and basal layers at the first week, but many more swelling cells came into being at the next three weeks. With the clear structure , many more cells exhibited swelling, vacuole degeneration or cell nucleus disappeared in hair follicle at the3rd week ,which was the same at the 4th week. At the2nd week , the border lineof the acinar cells and basal layer in sebaceous glands turned to unclear, vacuole degeneration of a few cells appeared; and the number of vacuole degeneration cells increased at the 3rd and 4th week.Conclusions: 1. After allotransplantation, degeneration and necroses of myelin sheaths, vacuoles degeneration of surrounding tissues and sturcture fracturation in facial fascicles nerve of composite tissue occur at the first, but as the same time a small amount of myelinated nerve were regenerated. After 4 weeks nerve stoma was smooth, myelinated nerves prominently increased in quantity, the nerve fascicles structure was more regular, the diameter of regenerating nerve and the thickness of myelin sheath obviously increased.2. Within the first 4 weeks, there was no lymphocytic infiltration of the skin, the epidermis structure was clear , the basement membrane was continous and complete, a lot of cells swelled gradually in the prickle and basal layers ;the dermal papilla layer was clear, local collagenous fibers l line up in disorder but cell nucleus are normal; Retrogressive changes of hair follicle and sebaceous glands gradually occurred. 3. Our operation of facial composite tissue allotransplantation in rabbits showes feasible and easy to master, which provide a new method for study on facial composite tissue allotransplantation including facial nerve.