Feasibility of 7T MRI for imaging fascicular structures of peripheral nerves

Introduction: Evaluation of the nerve fascicular structure can be useful in diagnosing nerve damage, but it is a very challenging task with 3T MRI because of limited resolution. In this pilot study, we present the feasibility of high‐resolution 7T MRI for examining the nerve fascicular structure. Methods: A 3‐dimensional (3D) gradient‐spoiled sequence was used for imaging peripheral nerves in extremities. Images acquired with different in‐plane resolutions (0.42 × 0.42 mm vs. 0.12 × 0.12 mm), and different main field strengths (7T vs. 3T) were compared. Results: The individual nerve fascicles were identified at 0.12 × 0.12 mm resolution in both field strengths but not at 0.42 × 0.42 mm resolution. The fascicular structure was more sharply depicted in 7T images than in 3T images. Discussion: High‐resolution 3D imaging with 7T MRI demonstrated feasibility for imaging nerve fascicular structures. Muscle Nerve 57 : 494–498, 2018     

Autoimmune antibodies to collagen XIII in myasthenia gravis patients

Introduction: Evaluation of the nerve fascicular structure can be useful in diagnosing nerve damage, but it is a very challenging task with 3T MRI because of limited resolution. In this pilot study, we present the feasibility of high‐resolution 7T MRI for examining the nerve fascicular structure. Methods: A 3‐dimensional (3D) gradient‐spoiled sequence was used for imaging peripheral nerves in extremities. Images acquired with different in‐plane resolutions (0.42 × 0.42 mm vs. 0.12 × 0.12 mm), and different main field strengths (7T vs. 3T) were compared. Results: The individual nerve fascicles were identified at 0.12 × 0.12 mm resolution in both field strengths but not at 0.42 × 0.42 mm resolution. The fascicular structure was more sharply depicted in 7T images than in 3T images. Discussion: High‐resolution 3D imaging with 7T MRI demonstrated feasibility for imaging nerve fascicular structures. Muscle Nerve 57 : 506–510, 2018     

Transfer of the extensor indicis proprius branch of posterior interosseous nerve to reconstruct ulnar nerve and median nerve injured proximally:an anatomical study

Proximal or middle lesions of the ulnar or median nerves are responsible for extensive loss of hand motor function. hTis occurs even when the most meticulous microsurgical techniques or nerve gratfs are used. Previous studies had proposed that nerve transfer was more effec-tive than nerve gratfing for nerve repair. Our hypothesis is that transfer of the posterior interosseous nerve, which contains mainly motor ifbers, to the ulnar or median nerve can innervate the intrinsic muscles of hands. hTe present study sought to investigate the feasibility of reconstruction of the deep branch of the ulnar nerve and the thenar branch of median nerve by transferring the extensor indicis proprius branch of the posterior interosseous nerve obtained from adult cadavers. hTe results suggested that the extensor indicis proprius branch of the posterior interosseous nerve had approximately similar diameters and number of fascicles and myelinated nerve ifbers to those of the deep branch of ulnar nerve and the thenar branch of the median nerve. hTese conifrm the feasibility of extensor indicis proprius branch of posterior interosseous nerve transfer for reconstruction of the deep branch of the ulnar nerve and the thenar branch of median nerve. hTis procedure could be a novel and effective method for the functional recovery of the intrinsic muscles of hands atfer ulnar nerve or median nerve injury.     

Long-term results after primary microsurgical repair of ulnar and median nerve injuries. A comparison of common score systems

OBJECTIVE: The aim of this retrospective study was to analyze the long-term results of primary repair of median and ulnar nerve lesions. Clinical influence factors for nerve reconstruction were investigated. Furthermore, current score systems were inquired and evaluated on their effectiveness to illustrate the success of repair. PATIENTS AND METHOD: Sixty-five patients with 71 lesions of the median and ulnar nerve were assessed on average 8.2 years after reconstruction. The results were classified according to the DASH (disability of arm, shoulder, and hand) Score, the Rosen's hand protocol and the Highet Scale. RESULTS: On average the patients regained 70% of their original hand function (evaluated by Rosen Score: median nerve 2.2/for ulnar nerve 1.92 out of 3.0). Although we noticed inferior motor recovery in ulnar nerve lesions, no significant differences between the overall results of both nerves were observed. Neither accompanying artery and flexor tendon injuries nor the suture technique influenced the recovery. The age of the patient was confirmed as an important influence factor. The results of the DASH Score, Rosen Score and Highet Score correlated significantly. CONCLUSION: For a sufficient outcome measurement we underline the importance of evaluation of patient's estimation of their impact on their activities of daily living. For this a combination of the functional Rosen Score and the DASH Score is suggested.     

The electrodiagnosis of ulnar nerve entrapment at the elbow

Entrapment of the ulnar nerve at the elbow is the second most common focal peripheral neuropathy. Recent advances have facilitated the electrodiagnosis of this common nerve entrapment. The goals of electrodiagnosis are to localize ulnar nerve dysfunction, confirm that the disturbance is confined to the ulnar nerve, and assess the severity of ulnar nerve dysfunction. The goal of this review is to highlight the important advances in anatomy, neurophysiology and methodology that impact upon the electrodiagnosis of entrapment of the ulnar nerve at the elbow, illustrate the limits of electrodiagnosis, and discuss methodological issues that may be the subject of further study. Careful attention to elbow position, temperature, and conservative estimates of conduction block should be part of common practice. Awareness of anatomical variations in structural anatomy, anomalous innervation and fascicular arrangement of ulnar nerve fibers are required to interpret electrodiagnostic studies accurately. The most reliable finding is slowing of the ulnar across-elbow motor nerve conduction velocity to less than 50 m/sec while recording from the abductor digiti minimi muscle, and should be carefully interpreted in the presence of a polyneuropathy or other neurogenic process. Alternative techniques such as relative ulnar slowing in different ulnar nerve segments, use of alternative muscles, sensory and mixed nerve techniques provide complementary information, and like all nerve conduction studies are highly operator-dependent and should be used on a case by case basis. Recent studies have focused the electromyographer's attention on the use of shorter across-elbow segments (2-5 cm). This may offer a reasonable trade-off between sensitivity and measurement error and may result in improved electrodiagnosis.     

Repair of long segmental ulnar nerve defects in rats by several different kinds of nerve transposition

Multiple regeneration of axonal buds has been shown to exist during the repair of peripheral nerve injury, which confirms a certain repair potential of the injured peripheral nerve. Therefore, a systematic nerve transposition repair technique has been proposed to treat severe peripheral nerve injury. During nerve transposition repair, the regenerated nerve fibers of motor neurons in the anterior horn of the spinal cord can effectively grow into the repaired distal nerve and target muscle tissues, which is conducive to the recovery of motor function. The aim of this study was to explore regeneration and nerve functional recovery after repairing a long-segment peripheral nerve defect by transposition of different donor nerves. A long-segment(2 mm) ulnar nerve defect in Sprague-Dawley rats was repaired by transposition of the musculocutaneous nerve, medial pectoral nerve, muscular branches of the radial nerve and anterior interosseous nerve(pronator quadratus muscle branch). In situ repair of the ulnar nerve was considered as a control. Three months later, wrist flexion function, nerve regeneration and innervation muscle recovery in rats were assessed using neuroelectrophysiological testing, osmic acid staining and hematoxylin-eosin staining, respectively. Our findings indicate that repair of a long-segment ulnar nerve defect with different donor nerve transpositions can reinnervate axonal function of motor neurons in the anterior horn of spinal cord and restore the function of affected limbs to a certain extent.     

Pearls & Oy-sters: false positives in short-segment nerve conduction studies due to ulnar nerve dislocation

The possibility that a technical error may occur during nerve conduction studies due to ulnar nerve dislocation when the elbow is flexed has recently been suggested. We investigated normal volunteers using ultrasonography to observe the effects of ulnar nerve dislocation during elbow flexion on short-segment nerve conduction studies. We found significant conduction block in all of the subjects with ulnar nerve dislocation, and the finding was defined as a technical error caused by volume conduction. The results of the present study suggest that caution should be exercised when interpreting the results of short-segment nerve conduction studies at the across-elbow segment due to the possibility of technical error induced by ulnar nerve dislocation.     

Submaximal stimuli activate different nerve fiber populations at different sites

Theoretically, the largest and fastest nerve fibers are preferentially stimulated with submaximal stimuli. However, it is also well known that intraneural fascicular topography changes substantially along a proximal to distal axis. Because of this change in fascicular topography, we hypothesized that percutaneous submaximal stimuli applied to a nerve at different locations would stimulate different subpopulations of large fibers. We performed a series of collision studies by stimulating the ulnar nerve submaximally at proximal and distal sites at varying levels of stimulation intensity from motor threshold to supramaximal stimulation. The results suggest that variation in intraneural topography at different sites allows different large diameter nerve fiber subpopulations to be activated at submaximal stimuli, and emphasizes the importance of supramaximal stimulation to determine a valid conduction velocity. © 1994 John Wiley & Sons, Inc.     

Three-dimensional reconstruction of human spinal cord based on histological serial sections**☆

BACKGROUND： It is not possible to reconstruct the inner structure of the spinal cord, such as gray matter and spinal tracts, from the Visual Human Project database or CT and MRI databases, due to low image resolution and contrast in macrosection images.
OBJECTIVE： To explore a semi-automatic computerized three-dimensional （3D） reconstruction of human spinal cord based on histological serial sections, in order to solve issues such as low contrast.
DESIGN, TIME AND SETTING： An experimental study combining serial section techniques and 3D reconstruction, performed in the laboratory of Human Anatomy and Histoembryology at the Medical School of Nantong University during January to April 2008.
SETTING： Department of Anatomy, Institute of Neurobiology, Jiangsu Province Key Laboratory of Neural Regeneration, Laboratory of Image Engineering.
MATERIALS： A human lumbar spinal cord segment from fresh autopsy material of an adult male.
METHODS： After 4% paraformaldehyde fixation for three days, serial sections of the lumbar spinal cord were cut on a Leica cryostat and mounted on slides in sequence, with eight sections aligned separately on each slide. All sections were stained with Luxol Fast Blue to reveal myelin sheaths. After gradient dehydration and clearing, the stained slides were coverslipped. Sections were observed and images recorded under a light microscope using a digital camera. Six images were acquired at x25 magnification and automatically stitched into a complete section image. After all serial images were obtained, 96 complete serial images of the human lumbar cord segment were automatically processed with ＂Curves＂, ＂Autocontrast＂, ＂Gray scale 8 bit＂, ＂Invert＂, ＂Image resize to 50%＂ steps using Photoshop 7.0 software. All images were added in order into 3D-DOCTOR 4.0 software as a stack, where serial images were automatically realigned with neighboring images and semi-automatically segmented for white matter and gray matter. Finally, simple surface and volume recon     

Three-dimensional reconstruction of human spinal cord based on histological serial sections

BACKGROUND:It is not possible to reconstruct the inner structure of the spinal cord.such as gray matter and spinal tracts,from the Visual Human Project database or CT and MRI databases,due to low image resolution and contrast in macrosection images.OBJECTIVE:To explore a semi-automatic computerized three-dimensional(3D)reconstruction of human spinal cord based on histological serial sections,in order to solve issues such as low contrast.DESIGN,TIME AND SETTING:An experimental study combining serial section techniques and 3D reconstruction,performed in the laboratory of Hunlan Anatomy and Histoembryology at the Medical School of Nantong University during January to April 2008.SETTING:Department of Anatomy,Institute of Neurobiology,Jiangsu Province Key Laboratory of Neural Regeneration,Laboratory of Image Engineering.MATERIALS:A human lumbar spinal cord segment from fresh autopsy material of an adult male.M[ETHODS:After 4% paraformaldehyde fixation for three days,serial sections of the lumbar spinal cord were cut on a Leica cryostat and mounted on slides in sequence,with eight sections aligned separately on each slide.All sections were stained with Luxol Fast Blue to reveal myelin sheaths.After gradient dehydration and clearing,the stained slides were coverslipped.Sections were observed and images recorded under a light microscope using a digital camera.Six images were acquired at ×25 magnification and automatically stitched into a complete section image.Aftel-all serial images were obtained,96 complete serial images of the human lumbar cord segment were automatically processed with "Curves","Autocontrast","Gray scale 8 bit","Invert","Image resize to 50%"steps using Photoshop 7.0 software.All images were added in order into 3D-DOCTOR 4.0 software as a stack where serial images were automatically realigned with neighbonng images and semi-automatically segmented for white matter and gray matter.Finally,simple surface and volume reconstruction were completed on a personal computer.The reconstructed human lumbar spinal cord segment was interactively observed,cut.and measured.MAIN OUTCOME MEASURES:The reconstructed human lumbar spinal cord segment.RESULTS:Compared with serial images obtained from other image modalities,such as CT,MRI,and macrosections from The Visual Human Project database.the Luxol Fast Blue stained histological serial section images exhibited higher resolution and contrast between gray and white matter.Image processing and 3D reconstruction steps were semi-automatically performed with related software.The 3D reconstructed human lumbar cord segment were observed,cut,and measured on a PC.CONCLUSION:A semi-automatically computerized method,based on histological serial sections,is an effective way to 3D-reconstruct the human spinal cord.     

Measurement of forelimb function by digital video motion analysis in rat nerve transection models

Abstract   The object of this study was to demonstrate that digital video motion analysis is a quantitative, valid, and reproducible method for evaluation of function in the rat model of forelimb nerve transection and repair. Median, ulnar, and radial nerves were transected and directly repaired in 220 g Sprague-Dawley rats. Normal rats and sham-operated rats served as controls (six rats in each group). Two-dimensional (2D) digital video motion analysis was used to capture the gait cycle and quantify joint movement and changes in toe spread. Recordings were made preoperatively and at 1, 4, 8, 12, and 16 weeks postoperatively. Wrist and metacarpophalangeal (MP) joint extension decreased after radial nerve injury, and wrist and MP joint flexion decreased after combined median and ulnar nerve injury or injury to the median nerve only. Toe spread decreased after combined median and ulnar nerve injury and after radial nerve injury. Median or ulnar nerve injury alone did not lead to a significant change in toe spread. 2D digital video motion analysis can be used to quantify movement of the wrist and the MP joint in rats. It is a valid method to evaluate functional deficit and recovery after nerve injury and repair in the forelimb.     

尺神经前置动物模型的建立及其神经生化研究

目的 建立尺神经前置的动物模型并从分子水平上评价尺神经前置的安全性.方法 取健康成年SD大鼠20只,建立右前肢尺神经前置模型,左侧(非手术侧)作为自身对照,术后1个月处死大鼠,取双侧尺侧腕屈肌称重及下颈段脊髓(C_6～T_1)切片,通过Nissl染色、还原型辅酶Ⅱ-黄递酶(NADPH-d)组织化学染色、植物凝集素(IB4)染色、胆碱乙酰基转移酶(CHAT)免疫组织化学染色观察颈髓前角、后角神经元的形态,电镜观察颈髓前角ChAT免疫阳性运动神经元的超微结构.结果 与对照侧[(93.2±7.29)mg]比较,大鼠尺神经前置侧尺侧腕屈肌质量[(92.3±9.13)mg]无明显变化,差异无统计学意义(t=0.910,P=0.378);Niss1染色、NADPH-d、IB4、ChAT免疫组织化学染色结果均显示大鼠尺神经前置侧和对照侧相比较细胞形态无明显改变,阳性细胞数量差异均无统计学意义(P>0.05);电镜结果显示颈髓前角ChAT免疫阳性运动神经元的超微结构无明显改变.结论 动物实验基础上尺神经前置术是安全的.     

Morphometric studies of sural nerve in childhood

Sural nerve myelinated fiber density and myelinated fiber diameter distribution have been examined in 27 control subjects, ranging in age from 1 day to 59 years. Total transverse fascicular area was measured in 10 of the subjects. There is an exponential decline in myelinated fiber density from birth to adult life. The predicted normal density (D) at any age may be derived from the formula D = (1 X 10(3]/(0.0699 + 0.00725 square root t). The distribution of myelinated fiber diameters is unimodal in the first 4 months of life, and there is a definite bimodal distribution by 2 years of age. Total transverse fascicular area of sural nerve increases progressively from values of about 0.25 mm2 in the first week to about 0.82 mm2 at 9 years. Control values for sural nerve morphometry in childhood are essential for accurate interpretation of biopsies in patients with peripheral neuropathy.     

Electrophysiological findings in localized hypertrophic mononeuropathy.

Localized hypertrophic mononeuropathy (LHM) is a rare foccal neuropathy associated with perineurial cell proliferation due to an undefined stimulus. We report a case of LHM involving the proximal ulnar nerve in a 13-year-old boy. Serial clinical and electrophysiological observations were done, including intraoperative recordings directly from the nerve on two occasions. The evolution of abnormalities, as documented by electrophysiological and immunohistochemical studies, is compatible with a process of progressive thinning of myelin sheaths, culminating in axonal degeneration in later stages. Intraoperative recording of nerve action potentials was used to guide surgical management of the lesion. Ultimately, there was a good clinical and electrophysiological response to resection of the lesion and sural nerve fascicular grafting.     

Blind source separation of peripheral nerve recordings

Prosthetic devices can be controlled using signals recorded in parts of the body where sensation and/or voluntary movement have been retained. Although neural prosthetic applications have used single-channel recordings, multiple-channel recordings could provide a significant increase in useable control signals. Multiple control signals can be acquired from recordings of a single implant by using a multi-contact electrode placed over a multi-fasciculated peripheral nerve. These recordings can be separated to recover the individual fascicular signals. Blind source separation (BSS) algorithms have been developed to extract independent source signals from recordings of their mixtures. The hypothesis that BSS algorithms can recover individual fascicular signals from nerve cuff recordings at physiological signal-to-noise ratio (SNR approximately 3-10 dB) was investigated in this study using a finite-element model (FEM) of a beagle hypoglossal nerve with a flattening interface nerve electrode (FINE). Known statistical properties of fascicular signals were used to generate a set of four sources from which the neural signals recorded at the surface of the nerve with a multi-contact FINE were simulated. Independent component analysis (ICA) was then implemented for BSS of the simulated recordings. A novel post-ICA processing algorithm was developed to solve ICA's inherent permutation ambiguities. The similarity between the estimated and original fascicular signals was quantified by calculating their correlation coefficients. The mean values of the correlation coefficients calculated were higher than 0.95 (n = 50). The effects of the geometric layout of the FINE electrode and noise on the separation algorithm were also investigated. The results show that four distinct overlapping fascicular source signals can be simultaneously recovered from neural recordings obtained using a FINE with five or more contacts at SNR levels higher than 8 dB making them available for use as control signals.     

慢性特发性轴索性多神经病的病理及免疫组化研究

目的 研究慢性特发性轴索性多神经病(chronic idiopathic axonal polyneuropathy,CIAP)病理改变特点,并探索腓肠神经炎细胞CD3、CD20、CD68抗体及其微小血管内皮细胞膜结合性血栓调节蛋白(thrombomodulin,TM)、内皮源性一氧化氮合酶(endothelial-nitricoxide synthase,e NOS)的表达规律。方法 10例经过临床、电生理、腓肠神经活检病理检查证实的CIAP患者,均进行腓肠神经活检标本的常规病理组织学染色以及以抗CD3、CD20、CD68、TM、e NOS、v WF(von Willebrand factor,v WF)抗体作为第一抗体的免疫组织化学染色。结果 10例患者腓肠神经病理检查显示有髓神经纤维轻-中度减少,伴随轴索变性和再生,部分可见轻微脱髓鞘改变,4例患者出现毛细血管基底膜肥厚。4例患者腓肠神经神经束衣间小血管周围有散在分布的CD68阳性单核细胞浸润。所有患者血管内皮细胞v WF、e NOS、TM均正常表达。结论 CIAP病理特点为轴索损害为主,发病可能和体液免疫异常有关,部分患者毛细血管基底膜肥厚提示血管内皮细胞可能受损,但内皮细胞功能相关蛋白表达初步提示正常。     

Responsiveness of the somatosensory system after nerve injury and amputation in the human hand

We studied the responsiveness of the somatosensory system in humans after prolonged deprivation of peripheral input. Eight patients with traumatic transection of the median or ulnar nerve and 6 patients with amputation of a finger or hand underwent microneurography and intraneural stimulation. Bundles of nerve fibers were electrically stimulated through a microelectrode placed in the affected nerve proximally to the site of damage or in the case of amputees, in a nerve fascicle supplying the stump. During intraneural stimulation the subjects with nerve injuries reported distinct percepts in the hypoesthetic skin. Their projections were usually confined to the territory of a single or two adjacent palmar digital nerves, similar to the fascicular territories of healthy nerves in control subjects, but there was much less microneurographically recordable afferent activity than in normal subjects. In amputees intraneural stimulation evoked sensations in a phantom digit or digits in over three fourths of the fascicles studied. We conclude that (1) the somatosensory system remains able to process information from a nerve fascicle that has lost its cutaneous territory, and (2) somatosensory localization remains accurate despite the presumed central reorganization that takes place after nerve division or amputation. This lack of functional adaptation has important implications with regard to our understanding of human central nervous system plasticity.     

三叉神经-血管复合体虚拟磁共振成像方法探讨

目的 探讨适合三叉神经-血管复合体虚拟解剖观察的MRI成像及重建方法.方法 对6例三叉神经痛患者术前应用3D - FIESTA序列及3D-TOF序列进行扫描,所获得资料分别导入Dextroscope系统,对三叉神经血管复合体的各结构进行虚拟重建,比较两种序列的单独及融合重建效果.结果 6例资料均逼真重建出三叉神经及相关解剖结构.3D - FIESTA序列对神经及细小血管的重建优于3D-TOF序列,而3D-TOF序列对血流速度快的基底动脉及椎动脉的重建优于3D - FIESTA序列,两种序列融合重建效果更佳.结论 应用MRI、3D-FIESTA及3D-TOF数据进行虚拟重建均可清晰显示三叉神经-血管复合体,二者融合重建可取长补短,效果更佳.     

The role of a barrier between two nerve fascicles in adjacency after transection and repair of a peripheral nerve trunk

Aberrant reinnervation of target organs caused by misdirected axonal growth at the repair site is a major reason for the poor functional outcome usually seen after peripheral nerve transection and repair. The following two studies investigate whether criss-crossing of regenerating rat sciatic nerve axons between tibial and peroneal nerve fascicles can be reduced by using a barrier at the coaption site. The left sciatic nerve was transected and repaired at mid-thigh as follows: epineural sutures (group A, A-II), fascicular repair of tibial and peroneal nerve fascicles (group B, B-II), fascicular repair of tibial and peroneal nerve fascicles separating the two fascicles with a pedicled fat flap (group C), Integra (group D) or non-vascularized autologous fascia (group C-II). In the control groups E and D-II, only the left tibial fascicle was transected and repaired. Four and 5 months postoperatively, the outcome of regeneration was evaluated by histology, by retrograde tracing, and by assessment of the muscle force of the gastrocnemius and tibial anterior muscles. The tracing experiments showed that specificity of muscle reinnervation significantly improved when a barrier was employed, which significantly or clearly improved muscle twitch tension in groups C and D. However, muscle contraction force was not better when fascia was used as barrier. The histological picture indicated that this inferior result in group C-II was due to nerve compression caused by fibrotic scar tissue at the site of the fascia graft. Results of this study show that a pedicle fat flap and Integra used as barrier significantly prevent aberrant reinnervation between two sutured nerve fascicles in adjacency resulting in improved motor recovery in rats. Non-vascularized autologous fascia however, reduces also criss-crossing of regenerating axons between the fascicles, but causes significant nerve compression.     

数字化人体大脑结构分割及三维重建

目的 建立人体大脑三维数字化可视模型，为脑外科手术计划的制定及在计算机上实现大脑精确模拟提供解剖学框架。方法 从中国数字化可视人体数据集中选取一男一女2套头部薄层连续横断面图像，对大脑主要结构进行半自动分割，并采用面绘制与体绘制相结合的方法进行三维重建。结果 获得一男一女2套大脑主要结构被精细分割的头部薄层断面数据集，对大脑灰质和白质、基底核团、脑室及海马等结构进行了三维重建。重建结构可多结构、多色彩模式显示，可在三维空间绕任意轴旋转，可对三维结构进行任意缩放及透明显示。结论 面绘制与体绘制相结合的重建方法克服了面绘制缺乏内部解剖信息，过于模式化的缺点，为三维重建提供了一种新的研究方法。重建的大脑及内部主要结构真实、逼真，再现了各结构的自然形态及在空间中的确切位置，提供了一个初步的大脑数字解剖学模型，也为自动分割算法的研究提供了精细的模板。