| Facial nerve anastomosis often bring synkinesis movement, it is an abnormal synchronization of movement involving the voluntary and reflex activity of muscles that normally do not contract together. It's thought to be an result of nerve fiber misdirection in the facial nerve regeneration. There have been a lot of researchs on it for a better result. Neurotrophic factors CNTF and GDNF combine a nerve conduit, to bridge the end of main trunk of facial nerve, local site for a better circumstance, or guiding nerve regeneration, as two methods to be concern.Neurotrophic factors is a kind of biomacromolecular, such as polypeptide or protein, and secrete by target tissue or glial cell, is essence to nerve's survive, differentiation, axon elongation and keep working. Some will pros the axon extension, the others will suppress it. And axon will extension with the regulation of those factors. Our previously study have show that exogenic neurotrophic factors not only promote axon generation, motor end plate regeneration, but also reduce the aberrant regeneration of recurrent laryngeal nerve. So, with the help of nerve conduits, follow researches have been done.First of all, nerve trace methods were evaluation on the base of the anatomy of facial nerve and facial nerve nucleus. The rat weight around 350g. Its show that extro-cranium facial branch lying on the surface of muscles, and the main trunk of facial leave cranium from stylomastoid foramen, major branchs derive from main trunk right after the posterior edge of parotid gland. The longth of main trunk is 4.21±0.29mm, and diameter is 0.73±0.07mm, those data is helpful for the selection of nerve conduits and surgery approaches. Facial nerve nucleus locate middle of brainstem, extension caudally from 1.60±0.17 mm post of interaural line, longitudinal length is 1.65±0.05mm, and transversal diameter is 1.62±0.10mm. afterward, three neuron-tracer DiI,FG. TB were apply on the buccal branches of facial nerve, there is no significant difference between those tracers, the transport velocity of TB is high than the rest. Furthermore, they fade away slowly than report, it still gleam even after 3 months. In order to find a better method for tracing, DiI,were applied on the buccal branches in three way:intra-muscles injection of solution, crystal smear on the stump of nerve, and crystal was stuck into it after half cut of rubbed nerve fasciculus. The result tell us that intra-muscle injection have the lowest efficiency compare with the orthers, but the rest two have likely efficiency, P=0.672. Compare with the standard way-stump crystal smear, the third way posses three advantages:never function could be preserve partially, less tracer use, furthermore, the less tracer getting into blood, the better of background.Secondly, the compound biodegradable PLGA/chitosan nerve conduit with CNTF and GDNF was used to bridge the adult SD rat facial nerve main trunk. DiI and TB were apply on the zygomatic and buccal branchs respectively 45 days later. The double labeled neurons and the aberrant neurons with DiI, the portion misdirection is were compare between those three group, the neurotrophic factor's effect on the aberrant nerve regeneration were quantity evaluation. The nerve state also evaluate by the evocation of facial nerve electromyogram(EMG). The result show, the misdirection rate of facial nerve motor neuron is different between those group. The misdirection rate of control group is higher than others group, CNTF group and GDNF group is alike. The proportions of misdirected facial nerve neuron in Control group is 17.98%, CNTF group is 13.48%, and GDNF is 14.24%. The latter two is superior to control group. With the lOmA1OV electrical stimulus, the proportions of operated side to normal side of evocated facial nerve EMG amplitude is 36%,51.4% and 57.5%, respectively, with the difference is significant,(P=0.01), CNTF group and GDNF group is better than the control group.In one words, the CNTF and GDNF combine with biodegradable PLGA/chitosan nerve conduit can reduce the aberrant regeneration of the adult SD rat facial nerve after it's section. And this found may benefit the facial nerve repair in the clinic. |
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