The Distribution Pattern Of Facial Nerve Fibres And It's Significance In Facial Nerve Regeneration And Restoration After Injury

Objective to study the distribution pattern of facial nerve fibres and it's physiological significance.Methods 36 healthy Wistar rats were divided randomly into 3 group, the partial facial nerve neurotomy group, the complete facial nerve neurotomy and the control group. There were 12 rats in every group. In the partial facial nerve neurotomy group, the 3/4 left side facial nerve canal was opened from the horizontal segment(between the stape to the tendon of tensor tympani muscle) to the stylomastoid foramen, the upper part of the facial nerve near to the proximal end was severed without suturing, and the right side of the rat was left without any managements. In the facial nerve complete neurotomy group, it was as the same as the partial neurotomy group except completely severing the facial nerve. In the control group, it was as the same as the partial neurotomy group apart from no severing to the facial nerve.6 rats were get both sides facial nerve trunks from the horizontal segment to the stylomastoid foramen excised in every group at the first week and the 4th week. The improved trichrome stain were applied to observe the distribution pattern, the degeneration and necrosis, and regeneration of the facial nerve fibers.Results In the partial facial nerve neurotomy group, at the fist week, the facial nerve fibers were in different sizes and shapes and arranged irregularly from the cross section, some myelin sheath of facial nerve fibers were discontinuous or faded away in vesicular shape, some axons were swelling and obscure, or disappeared, the endoneurium was well continuous, the outline of the facial nerve fibers necrosis was left clearly, and there was no obvious regeneration sign; the distribution pattern of the degeneration and necrosis fibers was the cross distribution with the normal facial nerve fibers as a whole, although most of them concentrated on one half part of the facial nerve trunk, there were some normal facial nerve fibers distributed in it, there were some degeneration and necrosis fibers distributed in the other part; there were some facial nerve fibers founded jumping from one facial nerve track to the other track in the term of small nerve bundle in the longitudinal section. At the 4th week the facial nerve fibers regeneration was obvious, the newborn fibers were fleetful and small in diameter, the axons of the newborn fibers were slim with a thin myelin sheath around them, there was no distinct fibrosis in the facial nerve trunk. In the complete facial nerve neurotomy group, the structures of the facial nerve trunks were in a mess, the most facial nerve fibers got necrosis and disintegrated at the fist week; at the 4th week, there was no distinct regeneration, the fibrosis in the facial trunk was obvious. In the control group, the facial nerve fibers distributed equably, the thickness of myelin sheath was consist with the diameter of axons, and there was no obvious degeneration and necrosis in the facial nerve trunk.Conclusions1. The facial nerve fibers aren't parallel all alone in the facial nerve trunk, but jump from one nerve tract to the other tract with the fibers get changed constantly. It makes the sizes, quantities and positions of the facial nerve bundles get changed constantly.2. The distribution pattern of the facial nerve fiber makes it keep the skeleton structure and then guides and promotes facial nerve fibers regeneration, and reduces the fibrosis dramatically.3. The distribution pattern of the facial nerve fibers makes the damaged facial nerve fibers scattered in the whole facial muscle, and then leads to the whole facial muscle functional disorder in the partial facial nerve neurotomy group. Objective To compare the differences of the facial nerve regeneration between the partial injury and the complete injure, and to evaluate the significance of the cross distribution pattern of the facial nerve fibers in the facial nerve fiber regeneration.Methods 48 Wistar rats were divided into 4 groups, the partial facial nerve neurotomy group, the facial nerve squeezing damage group, the complete facial nerve neurotomy group and the control group. There were 12 rats in every group. In the partial facial nerve neurotomy group, the 3/4 left side facial nerve canal was opened from the horizontal segment(between the stape to the tendon of tensor tympani muscle) to the stylomastoid foramen, the upper part of the facial nerve near to the proximal end was severed without suturing, and the right side of the rat was left without any managements. In the facial nerve complete neurotomy group, it was as the same as the partial neurotomy group except completely severing the facial nerve. It was as the same as the complete neurotomy except clamping the facial nerve for 10 seconds instead of severing the facial nerve in the facial nerve squeezing damage group. In the control group, it was as the same as the neurotomy groups apart from no severing to the facial nerve. The facial nerve functions of all rats were evaluated at the first day, the first week and 4th week after injury.6 rats were get both sides facial nerve trunks from the horizontal segment to the stylomastoid foramen excised in every group at the first week and the 4th week. The improved trichrome stain and the immunohistochemistry techniques to neurotrophic factor III (NT-3) were applied to observe the distribution pattern, the degeneration and necrosis, regeneration, and the NT-3 distribution of the facial nerve fibers.Results In the partial facial nerve neurotomy group, the left side facial nerve function of all rats got paralyzed at the first day after the injury, the blink reflex in 5 rats got recovered partially and the vibrissae movement in 9 rats returned at the first week after the injury, the blink reflex in 12 rats got fully recovered and the vibrissae movement in 12 rats well returned at the 4th week after the injury. In the facial nerve squeezing damage group, the left side facial nerve function of all rats got paralyzed at the first day after the injury, the blink reflex in 1 rats got recovered partially and the vibrissae movement in 2 rats returned at the first week after the injury, the blink reflex in 4 rats got fully recovered and the vibrissae movement in 5 rats well returned at the 4th week after the injury. In the complete facial nerve neurotomy group, the left side facial nerve function of all rats got paralyzed at the first day after the injury, there was no sign of recovery at the first and 4th week. In the control group, there were 2 rats whose left side facial nerve functions got slight impediment and got full recovery at the first week, the facial nerve functions in all the other rats have no sign of impediment. In the partial neurotomy group, at the fist week, the facial nerve fibers were in different sizes and shapes and arranged irregularly from the cross section, some myelin sheath of facial nerve fibers were discontinuous or faded away in vesicular shape, some axons were swelling and obscure, or disappeared, the endoneurium was well continuous, the outline of the facial nerve fibers necrosis was left clearly, and there was no obvious regeneration sign; the distribution pattern of the degeneration and necrosis fibers was the cross distribution with the normal facial nerve fibers as a whole, although most of them concentrated on one half part of the facial nerve trunk, there were some normal facial nerve fibers distributed in it, there were some degeneration and necrosis fibers distributed in the other part; there were some facial nerve fibers founded jumping from one facial nerve track to the other track in the term of small nerve bundle in the longitudinal section. At the 4th week the facial nerve fibers regeneration was obvious, the newborn fibers were fleetful and small in diameter, the axons of the newborn fibers were slim with a thin myelin sheath around them, there was no distinct fibrosis in the facial nerve trunk. In the squeezing damage group, the structures of the facial nerve trunks were in a mess, the most facial nerve fibers got necrosis and disintegrated at the fist week, there were many newborn facial nerve fibers. In the complete neurotomy group, the structures of the facial nerve trunks were in a mess, the most facial nerve fibers got necrosis and disintegrated at the fist week; at the 4th week, there was no distinct regeneration, the fibrosis in the facial trunk was obvious. In the control group, the facial nerve fibers distributed equably, the thickness of myelin sheath was consist with the diameter of axons, and there was no obvious degeneration and necrosis in the facial nerve trunk. The NT-3 was founded strong positive in the axons of the uninjured facial fibers and week positive or negative in the myelin sheaths and the remnants of degeneration and necrosis at the first week in the partial injury group. There was weak positive or negative expression in the control group.Conclusions1. The regeneration and function recovery of facial nerve either in the partial neurotomy injury or in the squeezing injury is far better and earlier than that in the complete injury.2. The regeneration and function recovery of facial nerve in the squeezing injury is far better and earlier than that in the complete injury, even thought most of the facial nerve fibers get degeneration and necrosis with only little left.3. The NT-3 was founded strong positive in the axons of the uninjured facial nerve fibers in the partial injury group. It indicates that the left uninjured facial nerve fibers are important for facial nerve regeneration and restoration when facial nerve is partially injured.4. There is a great possibility that the undamaged fibers develop some branches at ends to control the adjacent muscle fibers which makes the facial nerve function recovered quickly in partial injury group. Objective To report the complications of cranial nerver surgery through retrosigmoid approach.Methods To review 516 cases of cranial nerve surgeries through retrosigmoid approach for hemifacial spasm(HFS), trigeminal neuralgia(TN) and glossopharyngeal neuralgia(GPN). There were 208 cases of HFS, of which 117 cases took the procedure of facial nerve splitting(FNS) alone and 91 cases took the compound procedure of microvascular decompression(MVD) and FNS. There were 273 cases of TN treated by the procedure of MVD and selective neurectomy. There were 35 cases of GPN treated by the procedure of neurectomy.Results Of the complications,2(0.4%) cases died, the hearing impairment ranged from mild to severe occurred to 31(6.0%)cases in which 4(0.8%) cases presented total heating loss, and the postoperative cerebellospinal leakage occurred to 29(5.6%) cases.Conclusion The mortal and severe complications might occur even though the MVD, FNS and neurectomy procedures were a safe treatment for HFS, TN, and GPN in the retrosigmoid cranial nerver surgery. It was essential to pay great attention to the entire procedure to avoiding them.