Nerve fiber analysis and the aging process of the vestibulocochlear nerve

Nerve fiber analyses were performed on the human vestibulocochlear nerve stained with Luxol fast blue-periodic acid-Schiff-hematoxylin with use of a combination of an image-analyzer and a computer. The axons were counted and their transverse (cross-sectional) areas were measured in 12 individuals. The average numbers of axons in each vestibular and cochlear nerve were 17,727 and 25,098, and the average transverse areas of their axons were 4.02 and 1.79 microns 2, respectively. Amyloid bodies and intervening Schwann cells in the vestibulocochlear nerve were also counted. The average number of amyloid bodies was 246 per transverse section of the nerve and their average size was 114 microns 2. The average number of intervening Schwann cells was 1,513. Our results indicated that the transverse axonal areas of the cochlear nerve became reduced with age, while the transverse areas of the amyloid bodies in the vestibulocochlear nerve increased with age. The number of vestibular nerve fibers did not seem to change with age.     

回返穿通动脉与面听神经关系的解剖学研究

目的：介绍回返穿通动脉(RPA)与面-听神经的关系，为桥小脑角(CPA)的前庭-耳蜗神经(VN)血管减压术提供有实用价值的解剖学资料。方法：测量20具经甲醛固定的成人尸颅，观察CPA内与面、听神经有关的RPA的解剖结构，重点是与VN间的位置关系。结果：RPA出现率为100％，发出1个分支的有30侧(75．0％)，2个分支的有10侧(25．0％)；位于面神经(FN)、VN之间有32侧(80．0％)，其中87．5％位于FN中外2／3。VN的血管接触率为95％，有2支或2支以上血管与VN接触的有20侧(50．0％)。结论：了解、熟悉RPA与面-听神经的关系，对提高VN显微血管减压术的成功率以及临床影像学的诊断价值具有指导意义。     

Microsurgical anatomy of acoustic neuroma.

Because acoustic neuromas most frequently arise in the posteriorly placed vestibular nerves, they usually displace the facial and cochlear nerves anteriorly (Figs. 11, 12, and 13). The facial nerve is stretched around the anterior half of the tumor capsule. Variability in the direction of growth of the tumor arising from the vestibular nerves may result in the facial nerve being displaced, not only directly anteriorly, but also anterior-superiorly or anterior-inferiorly. The nerve is infrequently found on the posterior surface of the tumor. Because the facial nerve always enters the facial canal at the anterior-superior quadrant of the lateral margin of the meatus, it is usually easiest to locate it here, rather than at a more medial location where the degree of displacement of the nerve is more variable. The cochlear nerve also lies anterior to the vestibular nerve and is most frequently stretched around the anterior half of the tumor. The strokes of the fine dissecting instruments used in removing the tumor should be directed along the vestibulocochlear nerve from medial to lateral rather than from lateral to medial because traction medially may tear the tiny filaments of the cochlear nerve at the site where these filaments penetrate the lateral end of the meatus to enter the cochlea. The landmarks that are helpful in identifying the facial and vestibulocochlear nerves at the brain stem on the medial side of the tumor have been reviewed. These nerves, although distorted by tumor, can usually be identified on the brain stem side of the tumor at the lateral end of the pontomedullary sulcus, just rostral to the glossopharyngeal nerve and just anterior-superior to the foramen of Luschka, flocculus, and choroid plexus protruding from the foramen of Luschka. After the facial and vestibulocochlear nerves are identified on the medial and lateral sides of the tumor, the final remnants of the tumor are separated from the intervening segment of the nerves. In the three approaches to the meatus and cerebellopontine angle--retrosigmoid, translabyrinthine, and middle fossa--a communication may be established between the subarachnoid space and the mastoid air cells that requires careful closure to prevent a cerebrospinal fluid leak.     

A forgotten facial nerve tumour: granular cell tumour of the parotid and its implications for treatment

We present a rare case of a facial nerve granular cell tumour in the right parotid gland, in a 10-year-old boy. A parotid or neurogenic tumour was suspected, based on magnetic resonance imaging. Intra-operatively, strong adhesions to surrounding structures were found, and a midfacial nerve branch had to be sacrificed for complete tumour removal. Recent reports verify that granular cell tumours arise from Schwann cells of peripheral nerve branches. The rarity of this tumour within the parotid gland, its origin from peripheral nerves, its sometimes misleading imaging characteristics, and its rare presentation with facial weakness and pain all have considerable implications on the surgical strategy and pre-operative counselling. Fine needle aspiration cytology may confirm the neurogenic origin of this lesion. When resecting the tumour, the surgeon must anticipate strong adherence to the facial nerve and be prepared to graft, or sacrifice, certain branches of this nerve.     

Congenital bilateral facial nerve hypoplasia with sensorineural hearing loss: a case report

A 3-year-old child presented with congenital bilateral facial nerve palsy with bilateral profound sensorineural hearing loss. High Resolution Computed Tomogram (HRCT) of the temporal bones found bilateral atresia of cochlear nerve canals, incomplete partition of the cochleae and narrow facial nerve canals. Magnetic resonance imaging (MRI) revealed bilateral hypoplasia of facial nerves and aplasia of both vestibulocochlear nerves. There have been no other reported cases with this presentation. The possible aetiology and treatment options for the patient are discussed. We highlighted the review of aplasia/hypoplasia of the facial nerve and hypoplasia of cochlear nerve canal.     

Connections of the facial and vestibular nerves: an anatomic study

The facial and vestibulocochlear nerves emanate from the brain stem and then run parallel to each other within the internal auditory canal prior to their more peripheral distribution. Although anatomic connections between the facial and cochlear nerves have been described, reports outlining facial-vestibular anastomoses are few and may be found primarily in the non-English literature. The present study documents the existence of vestibulofacial neural connections as part of an anatomic dissection of 17 fresh human temporal bones.     

Interaction between Schwann Cells and Osteoblasts In Vitro

Aim Given the well-known properties of Schwann cells in promoting nerve regeneration, transplanting Schwann cells into implant sockets might be an effective method to promote sensory responses of osseointegrated implants. The aim of this study was to evaluate the interaction between Schwann cells and osteoblasts. Methodology Schwann cells derived from the sciatic nerves of neonatal rat were co-culured with osteoblasts using Transwell inserts. The proliferation of Schwann cells in the co-culture system was evaluated using methylthiazol tetrazolium (MTT) colorimetric method. Moreover, the secretions and mRN A levels of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) were measured by enzyme-linked immunosorbent assay (ELISA) and quantitative real-time PCR, respectively. In order to test the effect of Schwann cells on osteoblasts, alkaline phosphatase (ALP) staining and Alizerin red staining wereperformed as well.Results Schwann cells, which were co-cultured with the osteoblasts, showed an intact proliferation during the observation period. Moreover, the gene expression and synthesis of BDNF and NGF were not impaired by the osteoblasts. Meanwhile, co-cultured osteoblasts exhibited a significant increase in the proliferation on day 3 and 6 (P< 0.05). Co-culture of these two types of cells also led to a more intense staining of ALP and an elevated number of calcified nodules.Conclusion These findings demonstrate that, in the in vitro indirect co-culture environment, Schwann cells can maintain their normal ability to synthesize neurotrophins, which then enhance the proliferation and differentiation of osteoblasts.     

The border between the central and the peripheral nervous system in the cat cochlear nerve: a light and scanning electron microscopical study

The transition between the central (CNS) and peripheral nervous system (PNS) in cranial and spinal nerve roots, referred to here as the CNS-PNS border, is of relevance to nerve root disorders and factors that affect peripheral-central regeneration. Here, this border is described in the cat cochlear nerve using light microscopical sections, and scanning electron microscopy of the CNS-PNS interfaces exposed by fracture of the nerve either prior to or following critical point drying. The CNS-PNS border represents an abrupt change in type of myelin, supporting elements, and vascularization. Because central myelin is formed by oligodendrocytes and peripheral myelin by Schwann cells, the myelinated fibers are as a rule equipped with a node of Ranvier at the border passage. The border is shallower and smoother in cat cochlear nerve than expected from other nerves, and the borderline nodes are largely in register. The loose endoneurial connective tissue of the PNS compartment is closed at the border by a compact glial membrane, the mantle zone, of the CNS compartment. The mantle zone is penetrated by the nerve fibers, but is otherwise composed of astrocytes and their interwoven processes like the external limiting membrane of the brain surface with which it is continuous. The distal surface of the mantle zone is covered by a fenestrated basal lamina. Only occasional vessels traverse the border. From an anatomical point of view, the border might be expected to be a weak point along the cochlear nerve and thus vulnerable to trauma. In mature animals, the CNS-PNS border presents a barrier to regrowth of regenerating nerve fibers and to invasion of the CNS by Schwann cells. An understanding of this region in the cochlear nerve is therefore relevant to head injuries that lead to hearing loss, to surgery on acoustic Schwannomas, and to the possibility of cochlear nerve regeneration.     

Research of the chorda tympani nerve in cholesteatoma]

OBJECTIVE: To investigate the ultrastructure of the chorda tympani nerve and analyze the taste and facial nerve functions in patients with cholesteatoma. METHODS: 1. The tympanic segments of chorda tympani nerves were collected for ultrastructural investigations in 19 cholesteatoma cases who underwent canal-wall-down tympanoplasty. 2. All these patients received a spatial (regional) taste test preoperatively and postoperatively, respectively. Multiple loci were tested in a given order (front of the tongue, foliate papillae, circumvallate papillae, and soft palate). The solutions used in this study were 1.0 mol/L sodium chloride (salty), 1.0 mol/L sucrose (sweet), 0.032 mol/L citric acid (sour) and 0.001 mol/L quinine hydrochloride (bitter). The analyses of variance was used. 3. House-Brackmann facial nerve grading system was conducted to evaluate the facial nerve function preoperatively and postoperatively. RESULTS: 1. There were obvious ultrastructural damages in all the chorda tympani nerves, such as swelling (100%), disarrangement (100%), vacuoles formation of myelin (89%), edema of Schwann cells (95%), intracytoplasmic vacuoles in Schwann cell (89%) and proliferation of the collagen tissue (89%). 2. Two patients complained of change of taste after operation. The analyses of variance showed that the taste function of the ipsilateral side of tympanoplasty were not statistically altered for each stimulus at each locus (P > 0.05). 3. No facial palsy occurred postoperatively. CONCLUSION: This research suggested that the chorda tympani nerves underwent ultrastructural changes in patients with cholesteatoma. The dissection of chorda tympani nerve would not affect the taste and facial nerve functions.     

Repair of motor nerve gaps with sensory nerve inhibits regeneration in rats

OBJECTIVE: Sensory nerve grafts are often used to reconstruct injured motor nerves, but the consequences of such motor/sensory mismatches are not well studied. Sensory nerves have more diverse fiber distributions than motor nerves and may possess phenotypically distinct Schwann cells. Putative differences in Schwann cell characteristics and pathway architecture may negatively affect the regeneration of motor neurons down sensory pathways. We hypothesized that sensory grafts impair motor target reinnervation, thereby contributing to suboptimal outcomes. This study investigated the effect of motor versus sensory grafts on nerve regeneration and functional recovery. STUDY DESIGN: The authors conducted a prospective, randomized, controlled animal study. METHODS: Fifty-six Lewis rats were randomized to seven groups of eight animals each. Five-millimeter tibial nerve defects were reconstructed with motor or sensory nerve grafts comprised of single, double, triple, or quadruple cables. Tibial nerve autografts served as positive controls. Three weeks after reconstruction, nerves were harvested for histologic examination and quantitative histomorphometric analysis. Wet muscle masses provided an index of functional recovery. RESULTS: Nerve regeneration was significantly greater across motor versus sensory nerve grafts independent of graft cross-sectional area or cable number. Motor grafts demonstrated increased nerve density, percent nerve, and total fiber number (P < .05). Normalized wet muscle masses trended toward improved recovery in motor versus sensory groups. CONCLUSIONS: Reconstruction of tibial nerve defects with nerve grafts of motor versus sensory origin enhanced nerve regeneration independent of cable number in a rodent model. Preferential nerve regeneration through motor nerve grafts may also promote functional recovery with potential implications for clinical nerve reconstruction.     

面神经液压与面神经电图的相关性研究

目的　探讨面神经电图作为面神经减压手术指征的病理生理学基础。方法　利用电生理仪和伺服微变量微压系统 ,对正常和压榨伤后面瘫不同时期的豚鼠 ,作面神经电图检查 ,再采用微创测压法进行面神经液压的测量 ,得出面神经损伤后不同时期的面神经动作电位降幅及相应的面神经液压 ,并观察不同时期面神经光镜和电镜下的组织学改变。结果　面神经损伤 3d至 3周 ,随着面神经液压的升高 ,面神经动作电位降幅百分数亦增加 ,二者间有明显相关性 ,损伤后 2周和 3周 ,面神经液压和面神经动作电位降幅的相关系数分别为 0 88和 0 51。神经液压的变化与面神经Wallerian变性各期组织学改变相一致。结论　在面瘫 3周内 ,面神经电图的改变可间接反映面神经液压的变化 ,并可为面神经减压术的时机提供客观、可靠的实验依据。     

Research of relationship between endoneurial fluid pressure and electroneurography of the facial nerve]

OBJECTIVE: The relationship between endoneurial fluid pressure (EFP) and electroneurography (ENoG) of the facial nerve was studied in order to evaluate the ENoG as the basis of pathophysiology of the decompression of the facial nerve. METHODS: The values of ENoG were recorded by an instrument of physiology on the normal and crushed facial nerves of guinea pigs. Endoneurial fluid pressures were measured by a servo-nulling micropipette system at the same time. After the EFP were measured, the facial nerves were removed and fixed properly for examination under the light and electron microscope in order to determine the differences from various periods after injury. RESULTS: EFP in the facial nerve was changed significantly during the period of three days to three weeks later after crushed injury, and the percentage of degenerated facial nerve fibre was the same. There was positive correlation between ENoG and EFP. After crushed injury 2 and 3 weeks, the coefficient was 0.88 and 0.51, respectively. It could be found that extensive edema in endoneurial and perivascular spaces of the facial nerve occurred in early stage of injury, but numerous Schwann cells proliferation appeared in the later period. CONCLUSION: The change of ENoG could reflect the value of EFP relatively within three weeks after crushed injury. It was suggested that ENoG could be useful in evaluating the pathogenesis underlying facial palsy. And it could be provided a basis indication for decompression of the facial nerve.     

Schwann cell tumors of the facial nerve

An unusual group of tumors originating from Schwann cells of the facial nerve has been studied. Twenty-three neurilemmomas were found in 17 patients. Nine originated in the temporal bone, and the remaining 14 tumors arose from the peripheral portion of the facial nerve. All tumors were treated by excision, with partial or total resection of the facial nerve. The resultant facial nerve deficit was then reconstructed with a hypoglossal nerve crossover or a free autogenous nerve graft.     

Vascular permeability to fluorescent substance in human cranial nerves

It has recently been reported that in the facial canal, the facial nerve shows enhancement on gadolinium-enhanced magnetic resonance imaging in patients with clinically normal facial nerves. However, the mechanism of this enhancement has not yet been sufficiently clarified. The present study investigated the permeability of blood vessels in human cranial nerves that were obtained from surgically treated patients. The patients received an intravenous injection of sodium fluorescein 45 minutes before nerve resection. For histologic observation, the nerves were removed and frozen at -70 degrees C, and the sections were then cut at 4-microm thickness with a freezing microtome. The localization of the tracers was examined with a fluorescence microscope. Fluorescence was observed in the external nerve sheath and slightly in the endoneurium of these nerves, but was not observed within nerve fibers. These findings indicate that the vascular barrier in human peripheral nerves is incomplete.     

A correlation study of endoneurial fluid pressure and electroneurography of the facial nerve

OBJECTIVE: The relationship between endoneurial fluid pressure (EFP) and electroneurography (ENoG) of the facial nerve was studied in order to evaluate the pathophysilogical basis of ENoG to serve as the criteria for decompression of the facial nerve. METHODS: While the values of ENoG were recorded by an instrument for physiology on the normal and crushed facial nerves of guinea pigs, EFPs were measured at the same time by a servo-nulling micropipette system. After the elevated EFP was measured, the facial nerves were removed and then fixed properly for examination under the light and electron microscope in order to determine the differences from various periods after injury. RESULTS: With the change of EFP in the facial nerve during the period from day 3 to the third week after crushed injury, the percentage of degenerated facial nerve fiber increased. There was a positive correlation between ENoG and EFP. The coefficient was 0.88 and 0.51 in the second and third week after crushed injury, respectively. Extensive edema in endoneurial and perivascular spaces of the facial nerve could be found at the early stage of injury, while proliferation of numerous Schwann cells appeared at the later stage. CONCLUSION: The change of ENoG could reflect the value of EFP relatively within 3 weeks after crushed injury. Our data indicate that ENoG could be useful to evaluate the pathogenesis underlying facial palsy.     

睫状神经营养因子在喉返神经再生过程中的表达及分布

OBJECTIVE: To explore the expression and distribution of ciliary neurotrophic factor(CNTF) mRNA and its protein in laryngeal nerve regeneration. METHODS: The recurrent laryngeal nerves were sectioned and then sutured in twelve dogs. Both proximal and distal stumps of sutured region were sectioned on different postoperative days and the sections were separately used for CNTF immunohistochemistry and CNTF mRNA in situ hybridization. The area and intensity of reactive product were measured by computer image processing system. RESULTS: Strongly reactive product of CNTF mRNA and its protein deposited in myelin-related Schwann cells in normal laryngeal nerves. At week 2 following neurorrhaphy, there was very little hybridization signal and detectable CNTF immunoreactivity in distal stump and no regenerated nerve fibbers were found. At week 3, reactive product of CNTF mRNA and its protein was detected in thin Schwann cell processes ensheathing regenerated axons, while reactive product was not found in the proliferating Schwann cells which didn't ensheathe axons. CNTF immunoreactivity was also detected in the regenerated nerve axons. After long survival times, hybridization signal and the CNTF immunoreactivity in Schwamm cells became more widespread, and the area and intensity of reactive product significantly increased, but even at the longest survival time, they were still significantly less than those in intact nerve. The same change of CNTF mRNA and its protein was observed in a short segment proximal to the sutured region. CONCLUSION: CNTF expression could depend on Schwann cell-axon regeneration. The level of CNTF expression stands in striking contrast to the up-regulation of nerve growth factor in peripheral nerve degeneration and regeneration. These suggest that the exogenous CNTF might provide a supportive environment for axonal regeneration.     

An ultrastructural study of the neuromuscular junctions of the cat intrinsic laryngeal muscles. II. Synapse formation by autonomic nerves

The purpose of this study is to identify the origin of the nerve terminals of unknown origin observed at the previously denervated neuromuscular junctions in the cat intrinsic laryngeal muscles. The results were as follows: 1. Until 3 weeks after the transection of the recurrent laryngeal nerve, no nerve terminals were found at the neuromuscular junctions of the intrinsic laryngeal muscles except for the cricothyroid muscle, and no nerve fibres were detected in the Schwann tubes formed by Schwann cells and perineural cells. In addition, autonomic nerves around the vessels in the muscles were markedly decreased. 2. At 6 weeks, accompanied by an increase of autonomic nerves around the vessels, nerve fibres and nerve varicosities containing a number of large granular vesicles were observed in the Schwann tubes. 3. From 9 to 30 weeks, nerve terminals containing large granular vesicles were found at the neuromuscular junctions in all cases, even though the superior laryngeal nerve or the vagal nerve was transected on the ipsilateral side. 4. A spontaneous discharge was recognized in 6/8 cases after 6 weeks, but an evoked electromyogram could not be recognized. 5. The synaptic vesicles of the nerve terminals were labelled by 5-hydroxydopamine (5-OHDA), which was used as a marker for the sympathetic nerve. From these results, it was indicated that if the transected recurrent laryngeal nerve was prevented from regenerating, the autonomic nerves around the vessels entered into the Schwann tubes and reached the denervated neuromuscular junctions, instead of the motor nerve. The effect of autonomic nerves on muscle fibres was discussed.     

睫状神经营养因子在喉返神经再生过程中的表达及分布

目的　阐述喉返神经修复后神经干睫状神经营养因子 (ciliaryneurotrophicfactor,CNTF)的表达及分布。方法　切断并立即缝合犬喉返神经为神经修复再生模型 ,采用原位杂交及免疫组织化学方法检测CNTFmRNA及其蛋白的表达 ,结合图像分析技术 ,测定反应产物的灰度值及面积百分率。结果　正常神经CNTFmRNA及其蛋白反应产物位于包绕轴突及髓鞘的雪旺细胞中。神经修复术后 2周神经纤维降解 ,CNTFmRNA及其蛋白表达迅速下降 ,3周后随着神经的再生CNTFmRNA及其蛋白表达逐渐增加 ,表达产物仍位于包绕再生轴突及髓鞘的雪旺细胞中 ,CNTF蛋白还出现于再生的轴突中。 18周后虽然神经再生完成 ,但反应产物灰度值及面积百分率仍明显低于正常状态。结论再生神经CNTF的表达与轴突再生有关 ;表达呈下调型 ,提示补充外源性CNTF可能改善神经再生微环境。     

MRI of the vestibular nerve after selective vestibular neurectomy

CONCLUSION: In patients with Ménière's disease and persisting vertigo attacks after vestibular neurectomy (VNx) MRI of the vestibulocochlear nerve can identify residual vestibular nerve fibres that could be responsible for the vertigo attacks. OBJECTIVE: To test if MRI of the vestibulocochlear nerve can corroborate the presence of residual vestibular nerve fibres in patients with persisting vertigo attacks and residual vestibular function after VNx. MATERIALS AND METHODS: Vestibulocochlear nerve bundles of seven post-VNx unilateral Ménière's patients were imaged using 1.5 Tesla MRI with steady state free precession (SSFP) sequences. Reformatted MR images orthogonal to the vestibulocochlear nerve axis in internal auditory canal were compared on the VNx and intact sides. Vestibular function was assessed with caloric tests, three-dimensional head impulse tests and vestibular evoked myogenic potentials. Of the seven patients only one was asymptomatic (totally free of vertigo); six had continued to experience vertigo attacks, albeit not as long or as severe as before VNx. RESULTS: On the VNx side, MRI showed intact facial and cochlear nerves in all seven patients. In the six symptomatic patients, although superior and inferior vestibular nerve bulk and signal were reduced, residual bulk suggestive of inferior vestibular nerve was evident, correlating with evidence of residual posterior canal function on impulsive testing in all six symptomatic patients. In the asymptomatic patient, superior and inferior vestibular nerves were absent on MRI and impulsive testing revealed no residual posterior canal function.     

体外培养诱导外周血淋巴细胞促进大鼠面神经再生的实验研究

目的:通过在神经缺损处局部回输体外分离培养纯化的淋巴细胞,了解此种方法促进面神经损伤修复的效果。方法:将20只Wistar大鼠的面神经颊支剪断并立即缝合(其余3支反折缝合)制成面神经损伤模型大鼠,将其分成淋巴细胞组和对照组,每组10只,每组再分成2周组和8周组。淋巴细胞组局部回输体外分离培养的外周血淋巴细胞,对照组作对照。于2周和8周测定面神经颊支-触须肌复合动作电位传导速度,辣根过氧化物酶(HRP)神经逆行示踪测定面神经核团的神经元阳性数目。结果:淋巴细胞组面神经颊支-触须肌复合动作电位传导速度8周时为0.64±0.07,与对照组(0.56±0.07)相比,差异有统计学意义(P<0.05)。HRP神经逆行示踪测定面神经核团神经元阳性数目,淋巴细胞组2周及8周与对照组同时间段相比差异均无统计学意义(均P>0.05)。结论:体外分离培养纯化的淋巴细胞在局部应用于神经损伤处对面神经再生修复可起一定的促进作用。