Considerations in nerve repair

Multichannel Conduits with Fascicular Complementation: Significance in Long Segmental Peripheral Nerve Injury

Despite the advances in tissue engineering approaches, reconstruction of long segmental peripheral nerve defects remains unsatisfactory. Although autologous grafts with proper fascicular complementation have shown meaningful functional recovery according to the Medical Research Council Classification (MRCC), the lack of donor nerve for such larger defect sizes (>30 mm) has been a serious clinical issue. Further clinical use of hollow nerve conduits is limited to bridging smaller segmental defects of denuded nerve ends (<30 mm). Recently, bioinspired multichannel nerve guidance conduits (NGCs) gained attention as autograft substitutes as they mimic the fascicular connective tissue microarchitecture in promoting aligned axonal outgrowth with desirable innervation for complete sensory and motor function restoration. This review outlines the hierarchical organization of nerve bundles and their significance in the sensory and motor functions of peripheral nerves. This review also emphasizes the major challenges in addressing the longer nerve defects with the role of fascicular arrangement in the multichannel nerve guidance conduits and the need for fascicular matching to accomplish complete functional restoration, especially in treating long segmental nerve defects. Further, currently available fabrication strategies in developing multichannel nerve conduits and their inconsistency in existing preclinical outcomes captured in this review would seed a new process in designing an ideal larger nerve conduit for peripheral nerve repair.

Long-Term Donor-Site Morbidity Following Entire Sural Nerve Harvest for Grafting

PURPOSE

The sural nerve is the autologous nerve used most commonly for grafting. However, recent studies indicate a high rate of complications and complaints after sural nerve removal. In this prospective study, we evaluated donor-site morbidity following full-length sural nerve harvesting on long-term follow-up.

METHODS

Fifty-one legs from 43 patients who underwent complete sural nerve harvesting for brachial plexus reconstruction were included in the study. After an average of 5 years, with a minimum postoperative follow-up of 12 months, sensory deficits in the leg and foot were analyzed using 2.0-g monofilaments. Regions of sensory deficit were marked with a skin marker and photographed. Over these regions of decreased sensation, we tested nociception using an eyebrow tweezer. Patients were also asked about pain, cold intolerance, pruritis, difficulties walking, and foot swelling.

RESULTS

Regions most affected (84% of patients) were over the calcaneus and cuboid. However, in these regions, nociception was preserved. Regions of decreased sensation extended to the calf region in 11 of 51 legs. In 13 patients, we also observed regions of decreased sensation on the proximal leg. In five feet, the sensation was entirely preserved. No patient had any complaints about pain, cold intolerance, itchiness, difficulties walking, or foot swelling.

CONCLUSION

Decreased sensation with nociception preserved was most common along the lateral side of the foot over the calcaneus and cuboid. Removing the entire sural nerve produced no long-term complaints of pain. Sural nerve use appears safe.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic II.

Targeted muscle reinnervation in upper extremity amputations

PURPOSE

Targeted muscle reinnervation (TMR) is a relatively recent surgical innovation that involves the coaptation of major peripheral nerves to a recipient motor branch that innervates an expendable muscle target. The original indication for TMR was augmentation and optimization of myoelectric signals in the amputated limb for use of myoelectric prosthetics. Incidentally, surgeons and patients discovered that the technique also could treat and prevent phantom and residual limb pain. TMR is performed at the time of amputation or delayed any time after the amputation, and TMR can also be performed at any level of amputation. In the upper extremity, studies have detailed the various techniques and coaptations possible at each amputation level to create intuitive myoelectric signals and treat neurogenic pain. Treatment of peripheral nerves in the amputee with TMR should be a consideration for all patients with major upper extremity amputations, especially at large institutions able to support multidisciplinary limb salvage teams. This review article summarizes the current literature and authors' techniques and recommendations surrounding TMR in the upper extremity amputee including techniques relevant to each level of upper extremity amputation.

Development and preclinical evaluation of bioactive nerve conduits for peripheral nerve regeneration: A comparative study

In severe peripheral nerve injuries, nerve conduits (NCs) are good alternatives to autografts/allografts; however, the results the available devices guarantee for are still not fully satisfactory. Herein, differently bioactivated NCs based on the new polymer oxidized polyvinyl alcohol (OxPVA) are compared in a rat model of sciatic nerve neurotmesis (gap: 5 mm; end point: 6 weeks). Thirty Sprague Dawley rats are randomized to 6 groups: Reverse Autograft (RA); Reaxon®; OxPVA; OxPVA + EAK (self-assembling peptide, mechanical incorporation); OxPVA + EAK-YIGSR (mechanical incorporation); OxPVA + Nerve Growth Factor (NGF) (adsorption). Preliminarily, all OxPVA-based devices are comparable with Reaxon® in Sciatic Functional Index score and gait analysis; moreover, all conduits sustain nerve regeneration (S100, β-tubulin) without showing substantial inflammation (CD3, F4/80) evidences. Following morphometric analyses, OxPVA confirms its potential in PNI repair (comparable with Reaxon®) whereas OxPVA + EAK-YIGSR stands out for its myelinated axons total number and density, revealing promising in injury recovery and for future application in clinical practice.

Histologic Comparison of the Fascicular Area of Processed Nerve Allograft Versus Cabled Sural Nerve Autograft

Background

The use of multiple cables of sural nerve autograft is common for peripheral nerve reconstruction when injured nerve caliber exceeds the nerve graft caliber. Although the optimal matching of neural to nonneural elements and its association with functional outcomes are unknown, it is reasonable to consider maximizing the neural tissue structure available for nerve regeneration. No prior studies have compared directly the cross-sectional fascicular area between cabled nerve autografts and size-selected nerve allografts. This study evaluated the cross-sectional fascicular area between native nerve stumps and two reconstructive nerve grafting methods: cabled sural nerve autograft (CSNA) and processed nerve allograft (PNA).

Methods

CSNA from matched cadaveric specimens and PNA were used to reconstruct nerve defects in the median and ulnar nerves of six pairs of cadaveric specimens. Nerve reconstructions were done by fellowship-trained hand surgeons. The total nerve area, fascicular area, and nonfascicular area were measured histologically.

Results

The CSNA grafts had significantly less fascicular area than PNA and caliber-matched native nerve. The PNA grafts had a significantly higher percent fascicular area compared with the intercalary CNSA graft.

Conclusions

Fascicular area was significantly greater in PNA versus CSNA. The PNA consistently demonstrated a match in fascicular area closer to the native nerve stumps than CSNA, where CSNA had significantly smaller fascicular area compared with native nerve stumps.

Histomorphometry of the Sural Nerve for Use as a CFNG in Facial Reanimation Procedures

Facial palsy (FP) is a debilitating nerve pathology. Cross Face Nerve Grafting (CFNG) describes a surgical technique that uses nerve grafts to reanimate the paralyzed face. The sural nerve has been shown to be a reliable nerve graft with little donor side morbidity. Therefore, we aimed to investigate the microanatomy of the sural nerve. Biopsies were obtained from 15 FP patients who underwent CFNG using sural nerve grafts. Histological cross-sections were fixated, stained with PPD, and digitized. Histomorphometry and a validated software-based axon quantification were conducted. The median age of the operated patients was 37 years (5-62 years). There was a significant difference in axonal capacity decrease towards the periphery when comparing proximal vs. distal biopsies (p = 0.047), while the side of nerve harvest showed no significant differences in nerve caliber (proximal p = 0.253, distal p = 0.506) and axonal capacity for proximal and distal biopsies (proximal p = 0.414, distal p = 0.922). Age did not correlate with axonal capacity (proximal: R = -0.201, p = 0.603; distal: R = 0.317, p = 0.292). These novel insights into the microanatomy of the sural nerve may help refine CFNG techniques and individualize FP patient treatment plans, ultimately improving overall patient outcomes.

Donors for nerve transplantation in craniofacial soft tissue injuries

Neural tissue is an important soft tissue; for instance, craniofacial nerves govern several aspects of human behavior, including the expression of speech, emotion transmission, sensation, and motor function. Therefore, nerve repair to promote functional recovery after craniofacial soft tissue injuries is indispensable. However, the repair and regeneration of craniofacial nerves are challenging due to their intricate anatomical and physiological characteristics. Currently, nerve transplantation is an irreplaceable treatment for segmental nerve defects. With the development of emerging technologies, transplantation donors have become more diverse. The present article reviews the traditional and emerging alternative materials aimed at advancing cutting-edge research on craniofacial nerve repair and facilitating the transition from the laboratory to the clinic. It also provides a reference for donor selection for nerve repair after clinical craniofacial soft tissue injuries. We found that autografts are still widely accepted as the first options for segmental nerve defects. However, allogeneic composite functional units have a strong advantage for nerve transplantation for nerve defects accompanied by several tissue damages or loss. As an alternative to autografts, decellularized tissue has attracted increasing attention because of its low immunogenicity. Nerve conduits have been developed from traditional autologous tissue to composite conduits based on various synthetic materials, with developments in tissue engineering technology. Nerve conduits have great potential to replace traditional donors because their structures are more consistent with the physiological microenvironment and show self-regulation performance with improvements in 3D technology. New materials, such as hydrogels and nanomaterials, have attracted increasing attention in the biomedical field. Their biocompatibility and stimuli-responsiveness have been gradually explored by researchers in the regeneration and regulation of neural networks.

Injectable Adhesive Hydrogels for Soft tissue Reconstruction: A Materials Chemistry Perspective

Injectable bioadhesives offer several advantages over conventional staples and sutures in surgery to seal and close incisions or wounds. Despite the growing research in recent years few injectable bioadhesives are available for clinical use. This review summarizes the key chemical features that enable the development and improvements in the use of polymeric injectable hydrogels as bioadhesives or sealants, their design requirements, the gelation mechanism, synthesis routes, and the role of adhesion mechanisms and strategies in different biomedical applications. It is envisaged that developing a deep understanding of the underlying materials chemistry principles will enable researchers to effectively translate bioadhesive technologies into clinically-relevant products.

Nerve guidance conduit development for primary treatment of peripheral nerve transection injuries: A commercial perspective

Commercial nerve guidance conduits (NGCs) for repair of peripheral nerve discontinuities are of little use in gaps larger than 30 mm, and for smaller gaps they often fail to compete with the autografts that they are designed to replace. While recent research to develop new technologies for use in NGCs has produced many advanced designs with seemingly positive functional outcomes in animal models, these advances have not been translated into viable clinical products. While there have been many detailed reviews of the technologies available for creating NGCs, none of these have focussed on the requirements of the commercialisation process which are vital to ensure the translation of a technology from bench to clinic. Consideration of the factors essential for commercial viability, including regulatory clearance, reimbursement processes, manufacturability and scale up, and quality management early in the design process is vital in giving new technologies the best chance at achieving real-world impact. Here we have attempted to summarise the major components to consider during the development of emerging NGC technologies as a guide for those looking to develop new technology in this domain. We also examine a selection of the latest academic developments from the viewpoint of clinical translation, and discuss areas where we believe further work would be most likely to bring new NGC technologies to the clinic. STATEMENT OF SIGNIFICANCE: NGCs for peripheral nerve repairs represent an adaptable foundation with potential to incorporate modifications to improve nerve regeneration outcomes. In this review we outline the regulatory processes that functionally distinct NGCs may need to address and explore new modifications and the complications that may need to be addressed during the translation process from bench to clinic.

Comparison between normal and reverse orientation of graft in functional and histomorphological outcomes after autologous nerve grafting: An experimental study in the mouse model

BACKGROUND

Autologous nerve grafting has been considered the gold standard for the treatment of irreparable nerve gaps. However, the choice of effective proximodistal orientation of autografts (normal or reversed) is controversial. Therefore, we compared functional and histological outcomes between normal and reversed orientations of autografts in a mouse sciatic nerve model.

MATERIALS AND METHODS

Thirty C57BL/6J mice weighing 20-25 g were assigned to the donor, normally oriented autograft, and reverse-oriented autograft groups (n = 10 per group). A 10-mm section of the sciatic nerve was harvested from a donor mouse. Half the harvested nerve was grafted onto an irreparable gap in a recipient mouse using either a normal or reversed orientation. The sciatic functional index (SFI) was measured biweekly for up to 12 weeks postoperatively. Morphological analysis was performed using immunofluorescence staining for neurofilament (NF) and myelin protein zero (P0) in cross-sectional and whole-mount nerve preparations in 12 weeks postoperatively. Additionally, morphological analysis of the tibialis anterior muscle was performed using hematoxylin and eosin staining. NF or P0-expressing axons were counted and cross-sectional area (CSA) and minimum Feret's diameter of myofibers were measured.

RESULTS

The SFI recovered gradually up to 12 weeks after autografting, but there were no significant differences in the SFI between the normal and reversed orientations. The number of NF-expressing axons in center of graft was significantly higher in the normal orientation than in the reversed orientation (P < .05). However, there were no significant differences in the number and mean intensity of P0-expressing axons between the orientations. The CSA of myofibers was significantly larger in the normal orientation than in the reversed orientation (P < .05).

CONCLUSIONS

Normally oriented autografts promote axonal regrowth and prevent neurogenic muscular atrophy compared with reverse-oriented autografts. However, despite these positive histomorphometric effects, the proximodistal orientation of the autograft does not affect functional outcomes.

DANG (Depth-Adjusted Nerve Guide) - A Technical Note

Traditional surgical approaches to the inferior alveolar nerve (IAN) pose a technical challenge and risk iatrogenic damage to healthy, uninvolved nerve tissue. The use of computer-assisted virtual surgical planning and fabrication of surgical guides has shown efficacy in various craniomaxillofacial surgical procedures, and may provide greater precision in accessing the inferior alveolar canal and allow for a more conservative approach. The addition of a depth control feature to a tooth-borne and bone-borne surgical guide, with the use of a standard contra-angle handpiece, provides safe and efficient access for IAN repair. This report describes this novel technique involving a guided transoral approach to the IAN for excision of a neurofibroma of the inferior alveolar nerve, with immediate peripheral nerve allograft IAN reconstruction.

Effects of Chemical and Radiation Sterilisation on the Biological and Biomechanical Properties of Decellularised Porcine Peripheral Nerves

There is a clinical need for novel graft materials for the repair of peripheral nerve defects. A decellularisation process has been developed for porcine peripheral nerves, yielding a material with potentially significant advantages over other devices currently being used clinically (such as autografts and nerve guidance conduits). Grafts derived from xenogeneic tissues should undergo sterilisation prior to clinical use. It has been reported that sterilisation methods may adversely affect the properties of decellularised tissues, and therefore potentially negatively impact on the ability to promote tissue regeneration. In this study, decellularised nerves were produced and sterilised by treatment with 0.1% (v/v) PAA, gamma radiation (25-28 kGy) or E Beam (33-37 kGy). The effect of sterilisation on the decellularised nerves was determined by cytotoxicity testing, histological staining, hydroxyproline assays, uniaxial tensile testing, antibody labelling for collagen type IV, laminin and fibronectin in the basal lamina, and differential scanning calorimetry. This study concluded that decellularised nerves retained biocompatibility following sterilisation. However, sterilisation affected the mechanical properties (PAA, gamma radiation), endoneurial structure and basement membrane composition (PAA) of decellularised nerves. No such alterations were observed following E Beam treatment, suggesting that this method may be preferable for the sterilisation of decellularised porcine peripheral nerves.

Immediate allograft reconstruction of the infraorbital nerve following resection of polyostotic fibrous dysplasia lesion

Processed nerve allografts (PNA) have increasingly been used as alternative to autogenous nerve grafts to repair nerve injuries in oral-maxillofacial surgeries. This case report describes an immediate PNA reconstruction of infraorbital nerve injury sustained during the ablation of a large expansile polyostotic fibrous dysplasia centered in the left maxilla.

Soft Tissue Sarcoma Follow-up Imaging: Strategies to Distinguish Post-treatment Changes from Recurrence

Soft tissue sarcomas encompass multiple entities with differing recurrence rates and follow-up intervals. The detection of recurrences and their differentiation from post-therapeutic changes is therefore complex, with a central role for the clinical radiologist. This article describes approved recommendations. Prerequisite is a precise knowledge of the current clinical management and surgical techniques. We review recurrence rates and treatment modalities. An adequate imaging technique is paramount, and comparison with previous imaging is highly recommended. We describe time-dependent therapy-related complications on magnetic resonance imaging compared with the spectrum of regular post-therapeutic changes. Early complications such as seromas, hematomas, and infections, late complications such as edema and fibrosis, and inflammatory pseudotumors are elucidated. The appearance of recurrences and radiation-associated sarcomas is contrasted with these changes. This systematic approach in follow-up imaging of soft tissue sarcoma patients will facilitate the differentiation of post-therapeutic changes from recurrences.

Tobacco use and neurogenesis: A theoretical review of pathophysiological mechanism affecting the outcome of peripheral nerve regeneration

Peripheral nerve injury often requires medical intervention. Unfortunately, many patients never have a full recovery, despite a multi-disciplinary approach, including operative intervention and physical and/or occupational therapy. Outcomes are multifactorial, but are largely affected by the original injury severity, and patient comorbidities. A lcoholism, diabetes mellitus and ageing may detrimentally affect the outcomes of nerve injury; however little is known about tobacco's potential impact on nerve regeneration. Tobacco has known immunomodulatory effects, which suggests that it might affect peripheral nerve regeneration and functional recovery following injury. This review characterizes the effects of tobacco use on the complex cellular and chemokine interactions in peripheral nerve regeneration.

Facial nerve transfer for facial reanimation with parotidoplasty approach

BACKGROUND

Facial paralysis has a profound impact on quality of life in affected individuals, primarily through loss of verbal and nonverbal communication. Common facial nerve reanimation techniques include coaptation to the masseteric or hypoglossal nerve. Most techniques require nerve grafts to achieve a tension-free neurorrhaphy. Our report aims to show a surgical adaption to current facial reanimation procedures using a partial parotidoplasty approach in order to avoid challenges caused by interpositional nerve grafts through primary neurorrhaphy.

PATIENTS AND METHODS

The modified surgical approach was performed on four patients, aged 30-67. Length of paralysis ranged from 6 to 13 months. Cause of paralysis included one patient with Bell's palsy in one patient, prior surgery in two patients, and traumatic fracture in the remaining patient. A modified Blair approach is used to expose the parotid capsule. The facial nerve is dissected proximally toward the stylomastoid foramen and distally toward the masseter. The parotid gland substance is sectioned overlying each branch of the facial nerve using ultrasonic dissection or hemostatic scalpel, allowing mobilization of the proximal segment and upper and lower divisions of the facial nerve. The superficial lobe of the parotid is preserved in most cases. The House-Brackmann (H-B) functional scale was used to assess facial nerve function pre- and post-operatively.

RESULTS

All patients showed H-B score V or greater prior to reanimation. Follow-up was conducted at 3-, 6-, and 12-months in all patients with resultant improvement of H-B scores of I in three patients and II in the remaining patient. Only one complication was noted, with one patient developing a right postauricular hematoma that was adequately managed without sequelae. All remaining patients experienced an uncomplicated post-operative course.

CONCLUSION

Our modified approach to facial nerve reanimation works well with a planned parotidoplasty allowing for successful reanimation outcomes without the need for interpositional grafting. This technique may be considered in masseteric and hemi-hypoglossal nerve transfers for the reinnervation of facial muscles.

Donor nerve graft assessment for covering thumb nerve defects: a cadaveric study

BACKGROUND

Even though several studies reported donor autologous nerve grafts for digital nerve defects, there is no report in the literature regarding acceptable graft for thumb nerves. The purpose of this study is to provide guidelines for autologous nerve graft selection by detecting similarities between thumb nerve zones and donor nerve with regard to the number of fascicles and cross-sectional area.

MATERIALS AND METHODS

Five cadavers were used in this study. An anatomical zoning system was defined for thumb nerves (zones 1, 2, 3). Sural nerve (SN), medial antebrachial cutaneous nerve (MABCN), lateral antebrachial cutaneous nerve (LABCN), posterior interosseous nerve (PIN), and anterior interosseous nerve (AIN) were selected as donor nerve grafts. The number of fascicles and surface area (mm2) was defined.

RESULTS

The mean of the fascicle number in zone 1, zone 2, zone 3, AIN, PIN, LABCN, MABCN, and SN were 3.8, 4.7, 6.1, 2.2, 1.8, 4.5, 3.1, and 6.4, respectively. The mean of the surface area in zone 1, zone 2, zone 3, AIN, PIN, LABCN, MABCN, and SN were 2.19, 6.26, 4.04, 1.58, 0.71, 5.00, 3.01, and 8.06, respectively.

CONCLUSIONS

LABCN is the best choice for all zones that has fascicular matching with all three zones of thumb nerves and caliber matching with zones 2 and 3. In zone 1, the best nerve graft is MABCN which has both suitable caliber and fascicle count.

Using the Post-Descendens Hypoglossal Nerve in Hypoglossal-Facial Anastomosis: An Anatomic and Histologic Feasibility Study

BACKGROUND

Hypoglossal-facial anastomosis (HFA) is a popular facial reanimation technique. Mobilizing the intratemporal segment of the facial nerve and using the post-descendens hypoglossal nerve (ie, the segment distal to the take-off of descendens hypoglossi) have been proposed to improve results. However, no anatomic study has verified the feasibility of this technique.

OBJECTIVE

To assess the anatomic feasibility of HFA and the structural compatibility between the 2 nerves when the intratemporal facial and post-descendens hypoglossal nerves are used.

METHODS

The facial and hypoglossal nerves were exposed bilaterally in 10 sides of 5 cadaveric heads. The feasibility of a side-to-end (ie, partial end-to-end) HFA with partial sectioning of the post-descendens hypoglossal nerve and the mobilized intratemporal facial nerve was assessed. The axonal count and cross-sectional area of the facial and hypoglossal nerves at the point of anastomosis were assessed.

RESULTS

The HFA was feasible in all specimens with a mean (standard deviation) 9.3 (5.5) mm of extra length on the facial nerve. The axonal counts and cross-sectional areas of the hypoglossal and facial nerves matched well. Considering the reduction in the facial nerve cross-sectional area after paralysis, the post-descendens hypoglossal nerve can provide adequate axonal count and area to accommodate the facial nerve stump.

CONCLUSION

Using the post-descendens hypoglossal nerve for side-to-end anastomosis with the mobilized intratemporal facial nerve is anatomically feasible and provides adequate axonal count for facial reanimation. When compared with use of the pre-descendens hypoglossal nerve, this technique preserves C1 fibers and has a potential to reduce glottic complications.

Reinnervation of the Diaphragm After Bilateral Phrenic Nerve Resection and Immediate Reconstruction Using a Contralateral Phrenic Nerve Autograft

A patient affected by a voluminous synovial sarcoma of mediastinum received radical surgery, resulting in injury of both phrenic nerves. Because of the cancer location, reconstruction of the left phrenic nerve was not possible, so to prevent the patient's ventilator dependence, the right phrenic nerve was reconstructed via an autograft from the residual proximal stump of the contralateral one. In 3 months, the right hemidiaphragm function showed a full recovery, documented by ultrasonographic and radiographic assessment of diaphragmatic excursion, and the patient was weaned from mechanical ventilation. When a nerve autograft is indicated, the sural nerve still remains the criterion standard, because of the low morbidity of the donor site and ease of harvesting; however, in particular situations, such as in this unique case, the choice of an orthotopic graft may offer promising results.

3D biofabrication for soft tissue and cartilage engineering

Soft tissue injuries (STIs) affect patients of all age groups and represent a common worldwide clinical problem, resulting from conditions including trauma, infection, cancer and burns. Within the spectrum of STIs a mixture of tissues can be injured, ranging from skin to underlying nerves, blood vessels, tendons and cartilaginous tissues. However, significant limitations affect current treatment options and clinical demand for soft tissue and cartilage regenerative therapies continues to rise. Improving the regeneration of soft tissues has therefore become a key area of focus within tissue engineering. As an emerging technology, 3D bioprinting can be used to build complex soft tissue constructs "from the bottom up," by depositing cells, growth factors, extracellular matrices and other biomaterials in a layer-by-layer fashion. In this way, regeneration of cartilage, skin, vasculature, nerves, tendons and other bodily tissues can be performed in a patient specific manner. This review will focus on recent use of 3D bioprinting and other biofabrication strategies in soft tissue repair and regeneration. Biofabrication of a variety of soft tissue types will be reviewed following an overview of available cell sources, bioinks and bioprinting techniques.

Obturator to tibial nerve transfer via saphenous nerve graft for treatment of sacral plexus root avulsions: A cadaveric study

INTRODUCTION

In cases of sacral nerve avulsion injuries, proximal nerve stumps are not available because of its protected position in pelvis, and results of nerve repair or graft are unsatisfactory. Nerve transfer can reduce the regeneration time and improve the results of recovery.

HYPOTHESIS

The obturator nerve transfer to the tibial nerve via saphenous nerve graft is possible and feasible.

MATERIALS AND METHODS

Ten male adult cadaveric lower limbs dissected to identify the location of the anterior branch of obturator nerve, the saphenous nerve and the medial gastrocnemius branch. The saphenous nerve was cut from its origin and transferred to the anterior branch of obturator nerve. As well, it was cut distally and transferred to the medial gastrocnemius branch. After nerve coaptation, surface area and fascicle count were determined by histological methods.

RESULTS

In all limbs, the proximal and distal stumps of saphenous nerve were reached the anterior branch of obturator and the medial gastrocnemius branch, respectively without tension. The mean of fascicle number in the anterior branch of obturator nerve, proximal and distal stump of the saphenous nerve and stump of medial gastrocnemius nerve branch were 2.90±0.99, 4.50±2.70, 4.00±2.26 and 4.30±1.25, respectively.

DISCUSSION

This study showed that it is possible to transfer the obturator nerve to the medial gastrocnemius branch via saphenous nerve bridge; and their histological parameters are match in a good manner. Therefore, this technique is suggested for patients with sacral nerve avulsion injuries.

LEVEL OF EVIDENCE

IV, case series of cadaveric study.

Nerve Repair and Orthodromic and Antidromic Nerve Grafts: An Experimental Comparative Study in Rabbit

Purpose

Although many surgeons have anecdotally described reversing the polarity of the autograft with the intent of improving regeneration, the optimal orientation of the autogenous nerve graft remains controversial. The aim of this study was to compare (1) the outcomes of orthodromic and antidromic nerve grafts to clarify the effect of nerve graft polarity and (2) the outcome of either form of nerve grafts with that of nerve repair.

Methods

In 14 of the 26 rabbits used in this study, a 1 cm defect was made in the tibial nerve. An orthodromic nerve graft on one side and an antidromic nerve graft on the other were performed using a 1.2 cm long segment of the peroneal nerve. In the remaining 12 rabbits, the tibial nerve was transected completely and then repaired microscopically on one side but left untreated on the other. Electrophysiologic studies were performed in all animals at 8 weeks after surgery, and the sciatic nerves were harvested.

Results

Compound motor action potential was visible in all rabbits treated by nerve repair but in only half of the rabbits treated by nerve graft. There was no significant difference in the compound motor action potential, nerve conduction velocity, or total number of axons between the orthodromic and antidromic nerve graft groups. However, in both groups, the outcome was significantly poorer than that of the nerve repair group.

Conclusion

There was no significant difference by electromyographic or histologic evaluation between orthodromic and antidromic nerve grafts. Direct nerve repair with moderate tension may be a more effective treatment than nerve grafting.

Current Status of Therapeutic Approaches against Peripheral Nerve Injuries: A Detailed Story from Injury to Recovery

Peripheral nerve injury is a complex condition with a variety of signs and symptoms such as numbness, tingling, jabbing, throbbing, burning or sharp pain. Peripheral nerves are fragile in nature and can easily get damaged due to acute compression or trauma which may lead to the sensory and motor functions deficits and even lifelong disability. After lesion, the neuronal cell body becomes disconnected from the axon's distal portion to the injury site leading to the axonal degeneration and dismantlement of neuromuscular junctions of targeted muscles. In spite of extensive research on this aspect, complete functional recovery still remains a challenge to be resolved. This review highlights detailed pathophysiological events after an injury to a peripheral nerve and the associated factors that can either hinder or promote the regenerative machinery. In addition, it throws light on the available therapeutic strategies including supporting therapies, surgical and non-surgical interventions to ameliorate the axonal regeneration, neuronal survival, and reinnervation of peripheral targets. Despite the availability of various treatment options, we are still lacking the optimal treatments for a perfect and complete functional regain. The need for the present age is to discover or design such potent compounds that would be able to execute the complete functional retrieval. In this regard, plant-derived compounds are getting more attention and several recent reports validate their remedial effects. A plethora of plants and plant-derived phytochemicals have been suggested with curative effects against a number of diseases in general and neuronal injury in particular. They can be a ray of hope for the suffering individuals.

The Nerve to Thyrohyoid Muscle as a Novel Donor Nerve for Laryngeal Reinnervation

Objectives:

Recurrent laryngeal nerve (RLN) injury may be a consequence of surgical procedures of the skull base, neck, and chest, with adverse consequences to function and quality of life. Laryngeal reinnervation offers a potentially stable improvement in vocal fold position and tone. The classic donor nerve is the ansa cervicalis, but is not always available due to damage or sacrifice during previous neck surgeries. Our objective was to introduce the nerve to the thyrohyoid (TH) muscle as an alternate donor nerve for reinnervation, which has not previously been described.

Methods:

Case series of two patients using the TH nerve for laryngeal reinnervation after RLN injury, with description of surgical harvest.

Results:

Follow-up results are available for 10 months (one patient) and 3 years (one patient) demonstrating both subjective and objective improvement in function. GRBAS scores were reduced. Maximal phonation time was improved. Patient rating of voice was stable or improved postoperatively. One patient described significant preoperative dyspnea which was significantly improved postoperatively, from a score of 24 to 10 out of 40 on the dyspnea handicap index. VHI was improved in one patient, but scores elevated in the other, despite a change from “moderately severe impairment” to “normal voice” subjectively. Neither patient experienced significant complications from the procedure.

Conclusion:

Laryngeal reinnervation procedures provide good outcomes in pediatric patients. When ansa cervicalis is not available as a donor nerve, the nerve to TH provides a reasonable alternative.

Assessment of the Effect of Autograft Orientation on Peripheral Nerve Regeneration Using Diffusion Tensor Imaging

PURPOSE

Given no definite consensus on the accepted autograft orientation during peripheral nerve injury repair, we compare outcomes between reverse and normally oriented autografts using an advanced magnetic resonance imaging technique, diffusion tensor imaging.

METHODS

Thirty-six female Sprague-Dawley rats were divided into 3 groups: sham-left sciatic nerve isolation without injury, reverse autograft-10-mm cut left sciatic nerve segment reoriented 180° and used to coapt the proximal and distal stumps, or normally oriented autograft-10-mm cut nerve segment kept in its normal orientation for coaptation. Animals underwent sciatic functional index and foot fault behavior studies at 72 hours, and then weekly. At 6 weeks, axons proximal, within, and distal to the autograft were evaluated using diffusion tensor imaging and choline acetyltransferase motor staining for immunohistochemistry. Toluidine blue staining of 1-μm sections was used to assess axon count, density, and diameter. Bilateral gastrocnemius/soleus muscle weights were compared to obtain a net wet weight. Comparison of the groups was performed using Mann-Whiney U or Kruskal-Wallis H tests to determine significance.

RESULTS

Diffusion tensor imaging findings including fractional anisotropy, radial diffusivity, and axial diffusivity were similar between reverse and normally oriented autografts. Diffusion tensor imaging tractography demonstrated proximodistal nerve regeneration in both autograft groups. Motor axon counts proximal, within, and distal to the autografts were similar. Likewise, axon count, density, and diameter were similar between the autograft groups. Muscle net weight at 6 weeks and behavioral outcomes (sciatic functional index and foot fault) at any tested time point were also similar between reverse and normally oriented autografts.

CONCLUSIONS

Diffusion tensor imaging may be a useful assessment tool for peripheral nerve regeneration. Reversing nerve autograft polarity did not demonstrate to have an influence on functional or regenerative outcomes.

Vascularization Strategies for Peripheral Nerve Tissue Engineering

Vascularization plays a significant role in treating nerve injury, especially to avoid the central necrosis observed in nerve grafts for large and long nerve defects. It is known that sufficient vascularization can sustain cell survival and maintain cell integration within tissue‐engineered constructs. Several studies have also shown that vascularization affects nerve regeneration. Motivated by these studies, vascularized nerve grafts have been developed using various different techniques, although donor site morbidity and limited nerve supply remain significant drawbacks. Tissue engineering provides an exciting alternative approach to prefabricate vascularized nerve constructs which could overcome the limitations of grafts. In this review article, we focus on the role of vascularization in nerve regeneration, discussing various approaches to generate vascularized nerve constructs and the contribution of tissue engineering and mathematical modeling to aid in developing vascularized engineered nerve constructs, illustrating these aspects with examples from our research experience. Anat Rec, 301:1657–1667, 2018. © 2018 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.

Peroneal Nerve Repair of a 9 Year Old: Return of Motor Function after 2 Years

Major factors that influence functional nerve recovery, postrepair, are length of the nerve defect, type of injury, operative technique, time until treatment, and age of the patient. We present a severe motor nerve defect in a complicated peroneal nerve injury in a 9-year-old that showed functional return after a delayed period of 23 months with sural nerve cable grafting. This case revealed the increased resiliency and regenerative capacity of motor end plates in young patients. In conclusion, autograft for a deep peroneal nerve repair, by means of sural nerve graft, proved to be an acceptable option in children.

Photocrosslinkable Gelatin/Tropoelastin Hydrogel Adhesives for Peripheral Nerve Repair

Suturing peripheral nerve transections is the predominant therapeutic strategy for nerve repair. However, the use of sutures leads to scar tissue formation, hinders nerve regeneration, and prevents functional recovery. Fibrin-based adhesives have been widely used for nerve reconstruction, but their limited adhesive and mechanical strength and inability to promote nerve regeneration hamper their utility as a stand-alone intervention. To overcome these challenges, we engineered composite hydrogels that are neurosupportive and possess strong tissue adhesion. These composites were synthesized by photocrosslinking two naturally derived polymers, gelatin-methacryloyl (GelMA) and methacryloyl-substituted tropoelastin (MeTro). The engineered materials exhibited tunable mechanical properties by varying the GelMA/MeTro ratio. In addition, GelMA/MeTro hydrogels exhibited 15-fold higher adhesive strength to nerve tissue ex vivo compared to fibrin control. Furthermore, the composites were shown to support Schwann cell (SC) viability and proliferation, as well as neurite extension and glial cell participation in vitro, which are essential cellular components for nerve regeneration. Finally, subcutaneously implanted GelMA/MeTro hydrogels exhibited slower degradation in vivo compared with pure GelMA, indicating its potential to support the growth of slowly regenerating nerves. Thus, GelMA/MeTro composites may be used as clinically relevant biomaterials to regenerate nerves and reduce the need for microsurgical suturing during nerve reconstruction.

Emerging Strategies on Adjuvant Therapies for Nerve Recovery

Current strategies for promoting faster and more effective peripheral nerve healing have utilized a wide variety of techniques and approaches. Nerve grafts, conduits, and stem cell therapy all have their respective advantages. However, there are still some difficulties in attaining complete functional recovery with a single treatment modality. The utilization of adjuvant treatments, in combination with current standard-of-care methods, offers the potential to improve patient outcomes. This paper highlights the current landscape of adjuvant treatments for enhancing peripheral nerve repair and regeneration.

Neurotrophically Induced Mesenchymal Progenitor Cells Derived from Induced Pluripotent Stem Cells Enhance Neuritogenesis via Neurotrophin and Cytokine Production

Adult tissue‐derived mesenchymal stem cells (MSCs) are known to produce a number of bioactive factors, including neurotrophic growth factors, capable of supporting and improving nerve regeneration. However, with a finite culture expansion capacity, MSCs are inherently limited in their lifespan and use. We examined here the potential utility of an alternative, mesenchymal‐like cell source, derived from induced pluripotent stem cells, termed induced mesenchymal progenitor cells (MiMPCs). We found that several genes were upregulated and proteins were produced in MiMPCs that matched those previously reported for MSCs. Like MSCs, the MiMPCs secreted various neurotrophic and neuroprotective factors, including brain‐derived neurotrophic factor (BDNF), interleukin‐6 (IL‐6), leukemia inhibitory factor (LIF), osteopontin, and osteonectin, and promoted neurite outgrowth in chick embryonic dorsal root ganglia (DRG) cultures compared with control cultures. Cotreatment with a pharmacological Trk‐receptor inhibitor did not result in significant decrease in MiMPC‐induced neurite outgrowth, which was however inhibited upon Jak/STAT3 blockade. These findings suggest that the MiMPC induction of DRG neurite outgrowth is unlikely to be solely dependent on BDNF, but instead Jak/STAT3 activation by IL‐6 and/or LIF is likely to be critical neurotrophic signaling pathways of the MiMPC secretome. Taken together, these findings suggest MiMPCs as a renewable, candidate source of therapeutic cells and a potential alternative to MSCs for peripheral nerve repair, in view of their ability to promote nerve growth by producing many of the same growth factors and cytokines as Schwann cells and signaling through critical neurotrophic pathways. stemcellstranslational Medicine2018;7:45–58

Nanotechnology for Neuroscience: Promising Approaches for Diagnostics, Therapeutics and Brain Activity Mapping

Unlocking the secrets of the brain is a task fraught with complexity and challenge - not least due to the intricacy of the circuits involved. With advancements in the scale and precision of scientific technologies, we are increasingly equipped to explore how these components interact to produce a vast range of outputs that constitute function and disease. Here, an insight is offered into key areas in which the marriage of neuroscience and nanotechnology has revolutionized the industry. The evolution of ever more sophisticated nanomaterials culminates in network-operant functionalized agents. In turn, these materials contribute to novel diagnostic and therapeutic strategies, including drug delivery, neuroprotection, neural regeneration, neuroimaging and neurosurgery. Further, the entrance of nanotechnology into future research arenas including optogenetics, molecular/ion sensing and monitoring, and piezoelectric effects is discussed. Finally, considerations in nanoneurotoxicity, the main barrier to clinical translation, are reviewed, and direction for future perspectives is provided.

Host non-inflammatory neutrophils mediate the engraftment of bioengineered vascular networks

Notwithstanding remarkable progress in vascular network engineering, implanted bioengineered microvessels largely fail to form anastomoses with the host vasculature. Here, we demonstrate that implants containing assembled human vascular networks (A-Grafts) fail to engraft due to their inability to engage non-inflammatory host neutrophils upon implantation into mice. In contrast, unassembled vascular cells (U-Grafts) readily engage alternatively polarized neutrophils, which in turn serve as indispensable mediators of vascular assembly and anastomosis. The depletion of host neutrophils abrogated vascularization in U-Grafts, whereas an adoptive transfer of neutrophils fully restored vascularization in myeloid-depleted mice. Neutrophil engagement was regulated by secreted factors and was progressively silenced as the vasculature matured. Exogenous addition of factors from U-Grafts reengaged neutrophils and enhanced revascularization in A-Grafts, a process that was recapitulated by blocking Notch signaling. Our data suggest that the pro-vascularization potential of neutrophils can be harnessed to improve the engraftment of bioengineered tissues.

Nanotechnology in neurosurgery: thinking small, dreaming big

Nanotechnology has the power to transform neurosurgery by facilitating intervention at the cellular and subcellular level. The unique properties of nanomaterials will not only improve the management of conditions traditionally treated through neurosurgery, but also make neurosurgical intervention possible for diseases where there are currently limited treatment options. Specifically, nanotechnology appears to be a promising tool for improving molecular imaging, seamlessly integrating diagnosis and therapy in neuro-oncology, identifying targets for selective neuromodulation, as well as promoting neuroregeneration. Despite the vast potential benefits of nanotechnology in neurosurgery, problems related to neurotoxicity and the long-term medical and social consequences must be adequately addressed before nanotechnology becomes a component of surgical care.

Surgical technique and results of cable graft interpositioning of the facial nerve in lateral skull base surgeries: experience with 213 consecutive cases

OBJECTIVE The aim in this study was to review the technique and outcomes of cable graft interpositioning of the facial nerve (FN) in lateral skull base surgeries. METHODS The authors retrospectively evaluated data from patients who had undergone cable graft interpositioning after nerve sacrifice during skull base tumor removal between June 1987 and May 2015. All patients had undergone lateral skull base approaches to remove tumors at a quaternary referral center in Italy. Facial nerve function was evaluated before and after surgery using the House-Brackmann (HB) grading system. RESULTS Two hundred thirteen patients were eligible for study. The mean follow-up was 44.3 months. The most common pathology was vestibular schwannoma (83 cases [39%]), followed by FN tumor (67 cases [31%]). Facial nerve tumors had the highest incidence of nerve interruption (67 [66%] of 102 cases). Preoperative FN function was normal (HB Grade I) in 105 patients (49.3%) and mild (HB Grade II) in 19 (8.9%). At the last postoperative follow-up, 108 (50.7%) of the 213 patients had recovered to Grade III nerve function. Preoperative HB grading of the FN was found to have a significant effect on outcome (p = 0.002). CONCLUSIONS Cable graft interpositioning is a convenient and well-accepted procedure for immediate restoration of the FN. The study results, over a large number of patients, showed that the stitch-less fibrin glue-aided coaptation technique yields good results. The best possible postoperative result achieved was an HB Grade III. The chances of a good postoperative result increase when FN function is normal preoperatively. Slow-growing tumors of the cerebellopontine angle had a favorable outcome after grafting.

Harnessing supramolecular peptide nanotechnology in biomedical applications

The harnessing of peptides in biomedical applications is a recent hot topic. This arises mainly from the general biocompatibility of peptides, as well as from the ease of tunability of peptide structure to engineer desired properties. The ease of progression from laboratory testing to clinical trials is evident from the plethora of examples available. In this review, we compare and contrast how three distinct self-assembled peptide nanostructures possess different functions. We have 1) nanofibrils in biomaterials that can interact with cells, 2) nanoparticles that can traverse the bloodstream to deliver its payload and also be bioimaged, and 3) nanotubes that can serve as cross-membrane conduits and as a template for nanowire formation. Through this review, we aim to illustrate how various peptides, in their various self-assembled nanostructures, possess great promise in a wide range of biomedical applications and what more can be expected.

The Glia Response after Peripheral Nerve Injury: A Comparison between Schwann Cells and Olfactory Ensheathing Cells and Their Uses for Neural Regenerative Therapies

The peripheral nervous system (PNS) exhibits a much larger capacity for regeneration than the central nervous system (CNS). One reason for this difference is the difference in glial cell types between the two systems. PNS glia respond rapidly to nerve injury by clearing debris from the injury site, supplying essential growth factors and providing structural support; all of which enhances neuronal regeneration. Thus, transplantation of glial cells from the PNS is a very promising therapy for injuries to both the PNS and the CNS. There are two key types of PNS glia: olfactory ensheathing cells (OECs), which populate the olfactory nerve, and Schwann cells (SCs), which are present in the rest of the PNS. These two glial types share many similar morphological and functional characteristics but also exhibit key differences. The olfactory nerve is constantly turning over throughout life, which means OECs are continuously stimulating neural regeneration, whilst SCs only promote regeneration after direct injury to the PNS. This review presents a comparison between these two PNS systems in respect to normal physiology, developmental anatomy, glial functions and their responses to injury. A thorough understanding of the mechanisms and differences between the two systems is crucial for the development of future therapies using transplantation of peripheral glia to treat neural injuries and/or disease.

Ultrasonographic and Surgical Findings of Acute Radial Neuropathy Following Blunt Trauma

Ultrasonographic study is useful for decision making of treatment for focal neuropathy with unusual electrodiagnostic findings. We present a patient with severe acute radial neuropathy with sensory sparing around the distal arm secondary to twisting of the radial nerve following blunt trauma. A 24-year-old man with a 2-week history of left wrist drop and severe pain around the left elbow presented after hitting the left distal arm on the doorknob. The left wrist and finger extensions were grade 0, but elbow extension could not be tested because of severe pain during this action. The left superficial radial sensory territory was intact. Electrodiagnostic findings suggested severe left radial neuropathy around the distal arm with sensory sparing. Ultrasonographic study demonstrated 2 stenotic lesions around the distal arm and absence of the left superficial radial sensory nerve. Surgical exploration revealed 2 stenotic lesions with twisting of the nerve, concordant with ultrasonographic study. End-to-end anastomosis was performed in the proximal lesion. Sixteen months later, wrist and finger extension was grade 3, and reinnervation signs in the radial-innervated muscles except extensor indicis muscle were observed. The complementary relationship between electrophysiologic and ultrasonographic examinations is very important for precise lesion location and decision making for treatment of peripheral nerve injury.

Pedicled Instep Flap and Tibial Nerve Reconstruction in a Cynomolgus Monkey [Macaca fascicularis]

A male cynomolgus monkey experienced extensive soft tissue trauma to the right caudal calf area. Some weeks after complete healing of the original wounds, the monkey developed a chronic pressure sore on plantar surface of the heel of its right foot. A loss of sensitivity in the sole of the foot was hypothesized. The skin defect was closed by a medial sensate pedicled instep flap followed by counter transplantation of a full thickness graft from the interdigital webspace. The integrity of the tibial nerve was revised and reconstructed by means of the turnover flap technique. Both procedures were successful. This is an uncommon case in an exotic veterinary patient as it demonstrates a reconstructive skin flap procedure for the treatment of a chronic, denervated wound in combination with the successful reconstruction of 2.5 cm gap in the tibial nerve.

Intraneural Ganglion Cyst of the Ulnar Nerve at the Elbow Masquerading as a Malignant Peripheral Nerve Sheath Tumor

BACKGROUND

Ulnar neuropathy at the elbow (UNE) is the second most common mononeuropathy of the upper extremity. One rare cause of UNE is nerve mass lesions, including intraneural ganglion cysts (IGCs). IGC imaging studies provide important information that may determine the nature of a peripheral nerve mass lesion.

CASE DESCRIPTION

We present the case of a 73-year-old woman who presented with rapid deterioration of left hand function over 2 months with weakness of fine motor control, grip strength, and dysesthesia in the ulnar nerve distribution. Preoperative imaging studies, including magnetic resonance imaging (MRI) of the elbow, postcontrast studies, diffusion-weighted imaging, and apparent diffusion coefficient measurements, suggested a highly cellular tumor. Diffusion tensor tractography also revealed imaging features suggestive of a malignant peripheral nerve sheath tumor. During the operation, a sample of the lesion was sent for frozen section. There were no features of malignancy, and the pathologist could not determine a diagnosis based on the tissue sample sent. An intraoperative decision was made not to divide the ulnar nerve above and below the lesion. The IGC was successfully managed by identifying a suitable plane of dissection and cyst resection.

CONCLUSIONS

This case demonstrates that MRI studies indicating malignant peripheral nerve sheath tumor must be considered with some caution and corroborated with supportive features on operative inspection and biopsy before radical resection is undertaken. Furthermore, for any nerve mass lesion immediately adjacent to a joint, the differential diagnosis of an IGC should be considered.

Nerve regeneration techniques respecting the special characteristics of the inferior alveolar nerve

PURPOSE

The aim of this study was to examine the in situ regeneration of the inferior alveolar nerve (IAN) in its bony channel, using autologous tissue in combination with a recombinant human nerve growth factor (rhNGF).

MATERIALS AND METHODS

A total of 20 New Zealand rabbits were randomly divided into five groups. Following dissection of the IAN, the animals underwent reconstruction either with muscle tissue (groups 1 and 2) or with fat tissue (groups 3 and 4). In group 5 (control), the dissected nerve was resected and reconstructed by placement of the reversed autologous segment. After 2 and 4 weeks, 1 mL rhNGF was locally injected in groups 1 and 3. Nerve function was monitored by measuring the jaw-opening reflex using electromyography for a period of 24 weeks.

RESULTS

Regeneration of the nerve was achieved in all groups, but preoperative threshold values were not achieved. Comparing the experimental groups to the control, there was a significant difference in favor of the autologous nerve reconstruction. Differences between the experimental groups remained statistically not significant.

CONCLUSION

Regeneration of the IAN with autologous tissue is possible, but without achieving preoperative thresholds. Additional injection of a growth factor seems to improve the speed of regeneration for fat and muscle grafts.

The Role of Current Techniques and Concepts in Peripheral Nerve Repair

Patients with peripheral nerve injuries, especially severe injury, often face poor nerve regeneration and incomplete functional recovery, even after surgical nerve repair. This review summarizes treatment options of peripheral nerve injuries with current techniques and concepts and reviews developments in research and clinical application of these therapies.

Dual Inhibition of Activin/Nodal/TGF-β and BMP Signaling Pathways by SB431542 and Dorsomorphin Induces Neuronal Differentiation of Human Adipose Derived Stem Cells

Damage to the nervous system can cause devastating diseases or musculoskeletal dysfunctions and transplantation of progenitor stem cells can be an excellent treatment option in this regard. Preclinical studies demonstrate that untreated stem cells, unlike stem cells activated to differentiate into neuronal lineage, do not survive in the neuronal tissues. Conventional methods of inducing neuronal differentiation of stem cells are complex and expensive. We therefore sought to determine if a simple, one-step, and cost effective method, previously reported to induce neuronal differentiation of embryonic stem cells and induced-pluripotent stem cells, can be applied to adult stem cells. Indeed, dual inhibition of activin/nodal/TGF-β and BMP pathways using SB431542 and dorsomorphin, respectively, induced neuronal differentiation of human adipose derived stem cells (hADSCs) as evidenced by formation of neurite extensions, protein expression of neuron-specific gamma enolase, and mRNA expression of neuron-specific transcription factors Sox1 and Pax6 and matured neuronal marker NF200. This process correlated with enhanced phosphorylation of p38, Erk1/2, PI3K, and Akt1/3. Additionally, in vitro subcutaneous implants of SB431542 and dorsomorphin treated hADSCs displayed significantly higher expression of active-axonal-growth-specific marker GAP43. Our data offers novel insights into cell-based therapies for the nervous system repair.

In vivo evaluation of nerve guidance channels of PTMC/PLLA porous biomaterial

INTRODUCTION

Peripheral nerve disruptions, frequently occurring during limb injuries, give rise to serious complications of patients recovery resulting from limitations in neural tissue regeneration capabilities. To overcome this problem bridging techniques utilizing guidance channels gain their importance. Biodegradable polymeric tubes seem to be more prospective then non-degradable materials - no necessity of implant removal and possibilities of release of incorporated drugs or biologically active agents that may support nerve regeneration process are the main advantages.

MATERIAL AND METHODS

Polymer blend of commercial poly(L-lactic acid) (PLLA) and in-house synthesized poly(trimethylene carbonate) (PTMC) were processed in an organic solvent - phase inversion process on a supporting rod - to form a guidance porous tube of 1.1 mm inner diameter. In vivo experiments on rat's cut femoral nerve by using either the tubes or end-to-end suturing (control group) involved 22 and 19 rats, respectively. Motor recovery of operated limbs, neuroma occurrence and histopathology of explanted nerves were evaluated after 30, 60 and 90 days of implantation.

RESULTS

Motor recovery of the limbs was of similar rate for the two animal groups. The neuroma formation was evident in over 90% control specimens, while for the bridging group it was less than 40% of all evaluable samples (p = 0.0022). Biocompatibility of applied materials was affirmed by moderate tissue response.

CONCLUSIONS

Application of the biodegradable PLLA/PTMC polymeric tubes effectively supports regeneration of discontinued nerves. The applied material prevents neuroma formation, by reducing the scar tissue formation time and, thus, accelerating the process of neural tissue restoration.

Extra-osseous Ewing's sarcoma of sciatic nerve masquerading as an infected hemangioma: A rare case report

Extra-osseous Ewing's Sarcoma (EES) arising from the peripheral nerve is rarely reported in children. Here, we report an instance of EES arising from the left sciatic nerve mimicking an infected hemangioma. This case highlights the need for a high index of suspicion and early histological diagnosis to avoid diagnostic delay.

Bladder reinnervation using a primarily motor donor nerve (femoral nerve branches) is functionally superior to using a primarily sensory donor nerve (genitofemoral nerve)

PURPOSE

We determined whether transfer of a primarily motor nerve (femoral) to the anterior vesicle branch of the pelvic nerve would allow for more effective bladder reinnervation than transfer of a primarily sensory nerve (genitofemoral).

MATERIALS AND METHODS

A total of 41 female mongrel dogs underwent bladder decentralization and then bilateral nerve transfer, or served as sham operated or unoperated controls. Decentralization was achieved by bilateral transection of all sacral roots that induced bladder contraction upon electrical stimulation. Retrograde neuronal labeling dye was injected in the bladder 3 weeks before sacrifice.

RESULTS

Increased detrusor pressure after direct stimulation of the transferred nerve, lumbar spinal cord or spinal root was observed in 12 of 17 dogs with genitofemoral nerve transfer and in 9 of 10 with femoral nerve transfer (mean ± SEM 7.6 ± 1.4 and 11.7 ± 3.1 cm H2O, respectively). Mean detrusor pressure after direct electrical stimulation of transferred femoral nerves was statistically significantly greater than after stimulation of transferred genitofemoral nerves. Retrograde labeled neurons from the bladder observed in upper lumbar cord segments after genitofemoral and femoral nerve transfer confirmed bladder reinnervation, as did labeled axons at the nerve transfer site.

CONCLUSIONS

While transfer of a mixed sensory and motor nerve (genitofemoral) or a primarily motor nerve (femoral) can reinnervate the bladder, using the primarily motor nerve provided greater return of nerve evoked detrusor contraction. This surgical approach may be useful to achieve bladder emptying in patients with lower motor spinal cord injury.

Nerve repair: toward a sutureless approach

Peripheral nerve repair for complete section injuries employ reconstructive techniques that invariably require sutures in their application. Sutures are unable to seal the nerve, thus incapable of preventing leakage of important intraneural fluids from the regenerating nerve. Furthermore, sutures are technically demanding to apply for direct repairs and often induce detrimental scarring that impedes healing and functional recovery. To overcome these limitations, biocompatible and biodegradable glues have been used to seal and repair peripheral nerves. Although creating a sufficient seal, they can lack flexibility and present infection risks or cytotoxicity. Other adhesive biomaterials have recently emerged into practice that are usually based on proteins such as albumin and collagen or polysaccharides like chitosan. These adhesives form their union to nerve tissue by either photothermal (tissue welding) or photochemical (tissue bonding) activation with laser light. These biomaterial adhesives offer significant advantages over sutures, such as their capacity to unite and seal the epineurium, ease of application, reduced invasiveness and add the potential for drug delivery in situ to facilitate regeneration. This paper reviews a number of different peripheral nerve repair (or reconstructive) techniques currently used clinically and in experimental procedures for nerve injuries with or without tissue deficit.