Optimal Timing For Hypoglossal-facial Nerve Anastomosis With Predegenerated Nerve Graft

Objective:The aim of this study is to combined with predegenerated nerve graft for the treatment of facial palsy by the hypoglossal—facial nerve anastomosis with microsurgical suturing in adult rats after facial nerve injury, and a result of immediate and delayed repair, and to evaluate the effectiveness of graft nerve suturing in reanimation of facial paralysis of the rabbit models.Methods:All the 56 rats were randomly assigned to eight groups,normal group,group of immediate HFA,group of delayed HFA for 1 week,group of delayed HFA for 2 weeks,group of delayed HFA for 3 weeks,group of delayed HFA for 1 month, group of delayed HFA for 3months, and group of facial never injuries by turns. Meanwhile prepare the autologous nerve grafts of predegeneration for the control groups before repair one week, then end-to-end anastomose the predegenerated hypoglossal nerve and facial nerve. Three months later, the treatment was assessed by the angle analysis,electrophysiological examination,electron microscopy analysis.Results:1. Three months after nerve suture,the group of immediate HFA and the group of delayed HFA for 1 week were found a higher recovery of facial symmetry compared to other groups(P<0.05), There was no significant difference between the two groups(P=0.705). The group of delayed HFA for 1 month and 3 months a lower recovery of facial symmetry. 2. Evaluation for muscle reinnervation was conduced with the study of evoked electromyogram of orbicularis oris. As our study shows,the group of immediate HFA and the group of delayed HFA for one week had shorter latency than other groups of delayed HFA(P<0.05), There was no significant difference between the two groups(P=0.385);Meanwhile, the amplitude of the group of delayed HFA for one week was larger than that of immediately sutured and other delayed sutured ones; the group of delayed HFA for one month and three months had longer latency and smaller amplitude than the group of immediate HFA and other group of delayed HFA did. So we draw the conclusion that the group of delayed HFA for one week showed equal or even better curative effect than the group of immediate HFA did when the electrophysiological parameters were concerned;The group of delayed HFA for one month and three months showed apparently poorer curative effect than the immediately sutured and other delayed sutured ones did, which confirmed that the target muscles were fully recovered after any type of nerve suture. 3. Figured out the passing rate of myelinated fibers growing from the proximal stump to the distal stump. Observed the form of regenerated fibers under an electron microscope. Calculated the cavity area and the thickness of the regenerated myelin sheath with a computer image processing system. From the study,we could see that the number of myelinated fibers of the group of immediate HFA and the group of delayed HFA for one week was significantly higher than that of other groups of delayed suture(P<0.05),There was no significant difference between the two groups(P=0.108). whereas the number of the groups of delayed suture for one month and three months was apparently lower than that of the group of immediate HFA and other groups of delayed HFA, There was no significant difference between the two groups(P=0.181). Under the electron microscope,the figure of regenerated fibers of the group of immediate HFA and the group of delayed HFA for one week was very similar with that of the normal myelinated fibers; the fibers are relatively thick,the cross sections of the fibers were ellipse shaped,and the myelin sheaths were thick. With the computer image processing system.We saw that in the group of the immediate HFA, the cavity area of the regenerated myelin sheaths were larger than that of the group of delayed HFA for one week and other groups of delayed HFA, There was no significant difference between the two groups(P=0.068). In the case of thickness of regenerated myelin sheaths, the group of immediate HFA and the group of delayed HFA for one week took the superiority to other groups of delayed HFA,and these two groups showed no difference with the normal group(P=0.057), but the thickness of regenerated myelin sheaths of the group of delayed HFA for one week were larger than the group of the immediate HFA. All these told us that from all kinds of criteria taken from the regenerated myelinated fibers. The curative effect of the group of delayed HFA for one week was as good as that of the immediately sutured group. The curative effect was poor if repaired the facial nerve one to three months after the trauma.Conclusions:From all the above,the hypoglossal-facial nerve anastomosis method combined with predegenerated nerve graft was effective for the treatment of complete facial palsy in adult rats after facial nerve injury. we verified that repairing facial nerve one week after trauma could get as good curative effect as immediate suturing of the nerve.Facial nerve regenerated poorly if it was repaired one to three months after trauma.The result is of some value to clinical works,that is,if immediate repair of facial nerve is impossible, repairing it one week alter trauma is also ideal.Meanwhile,try to repair the facial nerve within three months.