Current issues in nerve repair

Although accepted surgical techniques for peripheral nerve repair remain largely unchanged over the past three decades, much progress has been made toward understanding the mechanisms involved in nerve regeneration, and consequently toward providing adjunctive measures to enhance this regenerative process. We present a comprehensive review of the significant advances made in several aspects of nerve repair over the past decade, and particularly the past few years, and provide a few examples of facial nerve repair using the standard neurorrhaphy techniques recommended today. Several conclusions were drawn after thorough review of the literature. Early repair of injured nerves is preferred, and there appears to be no benefit to waiting for 3 weeks. Severed nerves should be repaired with monofilament 9-0 nylon suture placed in epineurial fashion. Fibrin glue confers no benefit in reattaching injured nerves. Likewise, theoretical advantages of laser neurorrhaphy have not resulted in improved nerve regeneration. Finally, trophic factors, such as apolipoproteins and nerve growth factor, and tubulization both appear to offer promise for future experimental and clinical progress in nerve repair. However, further work must be done to prove their efficacy.     

Myelinated sensory and alpha motor axon regeneration in peripheral nerve neuromas

Histochemical staining for carbonic anhydrase and cholinesterase (CE) activities was used to analyze sensory and motor axon regeneration, respectively, during neuroma formation in transected and tube-encapsulated peripheral nerves. Median-ulnar and sciatic nerves in the rodent model permitted testing whether a 4 cm greater distance of the motor neuron soma from axotomy site or intrinsic differences between motor and sensory neurons influenced regeneration and neuroma formation 10, 30, and 90 days later. Ventral root radiculotomy confirmed that CE-stained axons were 97% alpha motor axons. Distance significantly delayed axon regeneration. When distance was negligible, sensory axons grew out sooner than motor axons, but motor axons regenerated to a greater quantity. These results indicate regeneration differences between axon subtypes and suggest more extensive branching of motor axons within the neuroma. Thus, both distance from injury site to soma and inherent motor and sensory differences should be considered in peripheral nerve repair strategies.     

Alteration to the levels of galanin in uninjured contralateral rat saphenous nerves after unilateral saphenous nerve section

Previous work in this laboratory has demonstrated that unilateral injury to the rat saphenous nerve decreases levels of substance P in the uninjured contralateral saphenous nerve during the subsequent regenerative period. Furthermore this contralateral nerve also has a decreased ability to elicit a neurogenic inflammatory response. In this present study the levels of galanin were investigated under similar experimental conditions. Levels of this peptide were found to be significantly decreased in the uninjured contralateral nerve. No significant changes in the total protein level of these nerves was found as compared to the control uninjured animals. The implications of this, in the context of the other contralateral changes found after peripheral nerve injury, are discussed.     

Separation of chiral polychlorinated biphenyls by micellar electrokinetic chromatography using beta- and gamma-cyclodextrin mixtures in the separation buffer

The present study was designed to compare regenerative potential of normal and degenerated nerve grafts. Peripheral nerves in rats were induced to undergo in situ degeneration for a period of 6 weeks, 3, 6 and 12 months. During early phase of denervation the myelin and axons degenerated and were absorbed. With prolonged denervation (i.e. 12 months), such nerves were reduced in size and exhibited extensive fibrosis. A 2 cm long segment of the degenerated nerve was transplanted in an surgically created gap in the host peroneal nerve to evaluate their regeneration supporting ability. Regeneration of host axons occurred rapidly through nerves degenerated for a period up to 3 months. The extent of regeneration was compromised in 6-month degenerated nerve group, and was significantly reduced in the 12-month degenerated nerve grafts. These results show that with extended degeneration interval, the regeneration supporting ability of nerves is compromised. It is concluded that nerve repair should not be excessively delayed in order to compromise recovery.     

Prognostic value of male diagnostic profiles in intracytoplasmic sperm injection (ICSI)

This reported investigation was designed to determine the role of a new synthetic conduit-expanded polytetrafluoroethylene (ePTFE) tube--in clinical repair of median and ulnar nerves in the upper extremities. The main goals of this study were: to determine the effectiveness of the ePTFE conduit in clinical nerve reconstruction; to evaluate the potential of this technique in reconstruction of various nerve gaps (1.5 to 6 cm); and to analyze the results of repair with the ePTFE tube regarding different mechanisms of injury. Forty-three patients were evaluated. They had upper-extremity peripheral-nerve injuries (21 injuries to the median nerve, and 22 ulnar nerve injuries) located at the various levels of the upper extremities. All surgical procedures described in the study were secondary reconstructions, and the average delay from injury to repair was 4.2 months. With regard to the nerve-gap lengths, patients were categorized in two groups. Group 1 (gaps from 1.5 to 4 cm) included 28 patients (17 median nerve injuries and 11 ulnar nerve injuries), and Group 2 (gaps from 4.1 to 6 cm) comprised 15 patients (4 median nerve injuries and 11 ulnar nerve injuries). Results showed that 78.6 percent of patients from Group 1 demonstrated functional motor and sensory recovery, while reconstruction of only 13.3 percent of peripheral nerves from Group 2 resulted in useful reinnervation. According to published results, ePTFE conduit is a reliable and successful surgical procedure for nerve repair in reconstruction of nerve gaps up to 4 cm between the ends of median and ulnar nerves in various levels of the upper extremity. Because of its properties, ePTFE conduit has the advantages of promoting better nerve regeneration, compared to other synthetic tubes, especially in reconstruction of proximal nerve injuries, larger nerve gaps, and in cases with unfavorable mechanisms of nerve injury.     

c-Jun expression in adult rat dorsal root ganglion neurons: differential response after central or peripheral axotomy

The response of the mature central nervous system (CNS) to injury differs significantly from the response of the peripheral nervous system (PNS). Axotomized PNS neurons generally regenerate following injury, while CNS neurons do not. The mechanisms that are responsible for these differences are not completely known, but both intrinsic neuronal and extrinsic environmental influences are likely to contribute to regenerative success or failure. One intrinsic factor that may contribute to successful axonal regeneration is the induction of specific genes in the injured neurons. In the present study, we have evaluated the hypothesis that expression of the immediate early gene c-jun is involved in a successful regenerative response. We have compared c-Jun expression in dorsal root ganglion (DRG) neurons following central or peripheral axotomy. We prepared animals that received either a sciatic nerve (peripheral) lesion or a dorsal rhizotomy in combination with spinal cord hemisection (central lesion). In a third group of animals, several dorsal roots were placed into the hemisection site along with a fetal spinal cord transplant. This intervention has been demonstrated to promote regrowth of severed axons and provides a model to examine DRG neurons during regenerative growth after central lesion. Our results indicated that c-Jun was upregulated substantially in DRG neurons following a peripheral axotomy, but following a central axotomy, only 18% of the neurons expressed c-Jun. Following dorsal rhizotomy and transplantation, however, c-Jun expression was upregulated dramatically; under those experimental conditions, 63% of the DRG neurons were c-Jun-positive. These data indicate that c-Jun expression may be related to successful regenerative growth following both PNS and CNS lesions.     

Interferon or corticosteroid: treatment of patients with chronic hepatitis C positive for serum markers of autoimmune diseases

From 1979 to 1994, reparative and reconstructive surgery were used to repair the war injuries of skins, bones, blood vessels and nerves of the limbs in 800 cases. A systematic clinical study was carried out. Many new operative methods were used and the results of treatment were good. Innovations and modifications were made in technique. In 120 cases of war injuries having soft tissues defects including skin and muscles, various tissue transplantations were used with the hope to accomplish one-staged repair of the defect and reconstruction of motor function of muscle. To those infections of bone and joint in war injuries, following early eradication of infected focus, transplantation of musculo-cutaneous flap or omental graft was immediately carried out with the aim to obtain primary healing of the wound. In the treatment of bone defects from war wounds with loss of skin and muscles, the vascularized skeleto-cutaneous graft was used. In the treatment of 150 cases of injury of peripheral nerve from forearms, the result of good to fair rated 68.8 percent for upper extremity and that for lower extremity, it was 62.2 percent. Following the early repair of 500 cases of injury of peripheral blood vessels, the patency rate of the blood vessel was 90 percent. The result following by pass vascular graft in the treatment of forearms injury of blood vessels even with very poor local condition was still very successful.     

A morphofunctional validation of the use of electrostimulation by paired impulses combined with vibromassage for the treatment of patients with trauma to the peripheral nerves of the extremities

The exposure to paired electric impulses and vibromassage promotes completeness of repair in the treatment of injured peripheral nerves of the limb. The effect is achieved due to marked stimulation of myelinization and differentiation of the nerve fibers, regeneration of the nerve system in the denervated muscle.     

Surgical indications in lesions of the brachial plexus

The development of microsurgery and the improved technique of nerve grafting brought new hope in cases of brachial plexus injury. Especially the Tinnel-Hofmann sign is a very helpful parameter in preoperative examination. Cases without any regeneration or no advancement should be operated between 3 and 6 months after the injury. Neurolysis or nerve grafting should be performed. In cases of avulsion of the roots a reneurotisation by nerve transfer is the technique of choice. The intercostal nerves are connected with important parts of the brachial plexus. Also in late cases (after 6 months) an epineurectomy and neurolysis may help to encourage further regeneration. Useful recovery could be achieved in a fairly high number of patients by restoration of continuity by nerve grafts or neurolysis. The functional results can further be improved by exploiting all available reconstructive techniques.     

Histological identification of Lugaro cells in the cat cerebellum

Segmental loss of a peripheral nerve has been a challenging reconstructive problem. Management of the nerve gap has been accomplished classically with nerve grafting. However, autogenous nerve grafts are not always available for bridging large nerve gaps, and clinical results of large nerve cable grafts have been disappointing. Newer techniques concentrate on nerve lengthening with different methods. Tissue expansion of peripheral nerves has been producing promising results. Since the introduction of the Ilizarov external fixator, much attention has turned to limb-lengthening techniques and studies investigating the results of nerve and soft tissues lengthened during the course of this procedure. Primary nerve distraction may be an alternative to nerve elongation, by expansion or nerve grafting to repair the peripheral nerve gap. This study describes a device and a model for peripheral nerve distraction in a rat. Primary nerve distraction will need to be subjected to vigorous studies before clinical application.     

Regulating the balance between differentiation and apoptosis: role of CREM in the male germ cells

Axon regeneration fails in the CNS because the glial environment is inhibitory, and because the regenerative response of CNS is poor. Regeneration can therefore be induced by removing the inhibitory effect of CNS glial molecules, by increasing the regenerative in animal models of spinal cord injury has recently been achieved by several strategies that apply these principles. The successful techniques have been to block inhibitory molecules made by astrocytes, to implant peripheral nerve grafts embedded in a bFGF-containing fibrin gel, to implant olfactory ensheathing cells, to graft embryonic spinal cord tissue, and to implant trophic factor-secreting fibroblasts. The next challenge is to prepare to apply these types of treatment to human patients with spinal cord injuries.     

Treatments of leprosy at the Ryukyu University Hospital

The competence of neurons to regenerate depends on their ability to initiate a program of gene expression supporting growth and on the growth-permissive properties of glial cells in the distal stump of the injured nerve. Most studies on intrinsic molecular mechanisms governing peripheral nerve regeneration have focussed on the lesion-induced expression of proteins promoting growth cone motility, neurite extension, and adhesion. However, little is known about the expression of intrinsic chemorepulsive proteins and their receptors, after peripheral nerve injury and during nerve regeneration. Here we report the effect of peripheral nerve injury on the expression of the genes encoding sema III/coll-1 and its receptor neuropilin-1, which are known to be expressed in adult sensory and/or motor neurons. We have shown that peripheral nerve crush or transection results in a decline in sema III/coll-1 mRNA expression in injured spinal and facial motor neurons. This decline was paralleled by an induction in the expression of the growth-associated protein B-50/GAP-43. As sema III/coll-1 returned to normal levels following nerve crush, B-50/GAP-43 returned to precrush levels. Thus, the decline in sema III/coll-1 mRNA coincided with sensory and motor neuron regeneration. A sustained decline in sema III/coll-1 mRNA expression was found when regeneration was blocked by nerve transection and ligation. No changes were observed in neuropilin-1 mRNA levels after injury to sensory and motor neurons, suggesting that regenerating peripheral neurons continue to be sensitive to sema III/coll-1. Therefore we propose that a decreased expression of sema III/coll-1, one of the major ligands for neuropilin-1, during peripheral nerve regeneration is an important molecular event that is part of the adaptive response related to the success of regenerative neurite outgrowth occurring following peripheral nerve injury.     

Evolution of nerve development in frogs. I. The development of the peripheral nervous system in Discoglossus pictus (Discoglossidae)

The gross anatomical development of the peripheral nervous system (PNS) during embryogenesis and metamorphosis in the frog Discoglossus pictus is described based on whole-mount immunostaining for nerves and muscles. In the head, neurite outgrowth starts with the mandibular ramus of the trigeminal nerve at the tailbud stage. Cranial muscles are innervated as soon as they differentiate, beginning at mid-embryonic stages. During late embryonic stages, the course of the trigeminal and facial nerves becomes greatly distorted and changes again drastically during metamorphosis accompanying the reorganization of the jaw muscles. Two occipital somites and nerves develop transitorily but degenerate at late embryonic stages. The hypoglossal nerve develops by fusion of the first and second spinal nerves and receives a transitory contribution of the third and fourth spinal nerve at embryonic stages. In the trunk, several classes of Rohon-Beard neurites could be identified at embryonic stages, one of which forms intersegmental sensory nerves that prefigure the course of the sensory rami of spinal nerves at later stages. We give detailed schedules of PNS and cranial muscle development which, in comparison with data on other frog species described in a companion paper, will serve as a basis to evaluate heterochronic shift during evolution of PNS development in frogs.     

A tissue-engineered conduit for peripheral nerve repair

BACKGROUND: Peripheral nerve repair using autograft material has several shortcomings, including donor site morbidity, inadequate return of function, and aberrant regeneration. Recently, peripheral nerve research has focused on the generation of synthetic nerve guidance conduits that might overcome these phenomena to improve regeneration. In our laboratory, we use the unique chemical and physical properties of synthetic polymers in conjunction with the biological properties of Schwann cells to create a superior prosthesis for the repair of multiply branched peripheral nerves, such as the facial nerve. OBJECTIVES: To create a polymeric facial nerve analog approximating the fascicular architecture of the extratemporal facial nerve, to introduce a population of Schwann cells into the analog, and to implant the prosthesis into an animal model for assessment of regeneration. RESULTS: Tubes of poly-L-lactic acid (molecular weight, 100000) or polylactic-co-glycolic acid copolymer were formed using a dip-molding technique. They were created containing 1, 2, 4, or 5 sublumina, or "fascicular analogs." Populations of Schwann cells were isolated, expanded in culture, and plated onto these polymer films, where they demonstrated excellent adherence to the polymer surfaces. Regeneration was demonstrated through several constructs. CONCLUSIONS: A tubular nerve guidance conduit possessing the macroarchitecture of a polyfascicular peripheral nerve was created. The establishment of resident Schwann cells onto poly-L-lactic acid and polylactic-co-glycolic acid surfaces was demonstrated, and the feasibility of in vivo regeneration through the conduit was shown. It is hypothesized that these tissue-engineered devices, composed of widely used biocompatible, biodegradable polymer materials and adherent Schwann cells, will be useful in promoting both more robust and more precisely directed peripheral nerve regeneration.     

Three-dimensional dynamic behaviour of the human knee joint under impact loading

Over the past 50 years, we have made remarkable advances in the use of bionic devices and solid organ transplants as replacement parts for failing tissues and organs. These approaches to tissue restoration, however, have a number of drawbacks. Thus, a new approach, regenerative biology and engineering, has been developed, consisting of the strategies of cell transplantation, bioartificial tissue constructs, and stimulation of regeneration in vivo. Cell transplants have been successfully used to restore articular cartilage and to treat Parkinson's disease in humans. In rats, transplanted fetal and embryonic stem cell line-derived cardiomyocytes have been shown to differentiate and integrate well with the ventricular myocardium, suggesting the feasibility of using such transplants to restore damaged cardiac muscle. Diabetic symptoms in humans have been alleviated by implanting a bioartificial pancreas consisting of islet cells microencapsulated in alginate. Hydroxyapatite matrixes can stimulate the regeneration of bone across large gaps. Collagenous artificial matrixes can stimulate the regeneration of dermis, and peripheral nerve grafts embedded in a fibrin clot containing fibroblast growth factor-1 stimulate some regeneration of spinal cord axons in adult rats. Future research in regenerative biology will focus on several issues: (1) providing adequate sources of cells for transplantation and bioartificial tissue construction and determining ways to prevent these cells from coming under attack by the immune system, (2) developing new and better materials to build better bionic devices and bioartificial constructs and to stimulate regeneration in vivo, (3) determining how many tissues of the body might contain reserve cells for regeneration in vivo, (4) analyzing the molecular differences between cells and environments of regenerating versus nonregenerating tissues, and (5) understanding the factors and mechanisms involved in the proliferation and patterning of regenerating tissues.     

International Microsurgical Society Thirteenth Congress: some historical highlights

Functional recovery following motor nerve injury and repair is directly related to the degree of muscle atrophy that takes place during the period of nerve regeneration. The extent of this muscle atrophy is related to a number of factors including the accuracy of nerve repair; the distance through which the nerve must regenerate; the age of the patient; and the type of nerve injury and other associated tendon and soft tissue and bony damage. Atrophy of muscle that is always associated with nerve injury is a combination of disuse and degeneration. Our hypothesis proposed the following question: "Would continuous electrical stimulation of the denervated muscle during the period of nerve regeneration maintain the integrity of the muscle fibers and hence their potential functional capacity?" We have completed a series of animal studies (rabbit and canine models) in our laboratory using a completely implantable system to provide continuous muscle stimulation following nerve injury and microsurgical repair. In several different experiments, the nerves under study were cut and repaired at 4 and 12 cm from the muscles to study the effects of short- and long-term recovery. In all experiments, a beneficial effect was demonstrated with improved morphology and functional capacity of the reinnervated stimulated muscles when compared with nonstimulated controls. In addition, electrical stimulation using this implantable system could be applied for extended periods without evidence of discomfort in the experimental animals.     

The retroperitoneal incision. An evaluation of postoperative flank 'bulge'

OBJECTIVES: To determine if intercostal nerve injury is related to postoperative flank "bulge" and to determine whether the extent of the retroperitoneal incision is related to the incidence of flank bulge following abdominal aortic aneurysm repair. DESIGN: Bilateral dissection of the 11th intercostal nerve on seven cadavers; neurophysiological evaluation of five patients, three with a flank bulge and two without; and retrospective analysis of the extent of retroperitoneal incision and incidence of postoperative flank bulge in 63 consecutive patients. SETTING: Urban academic medical center. PATIENTS: Sixty-three consecutive patients who underwent retroperitoneal repair of an abdominal aortic aneurysm and neurophysiological evaluation of five volunteer patients. INTERVENTIONS: Retroperitoneal repair of abdominal aortic aneurysms. MAIN OUTCOME MEASURE: Reduction of injury to the 11th intercostal nerve by avoiding extension of the retroperitoneal incision into the intercostal space. RESULTS: Of 14 dissections of 11th intercostal nerves, there were bifurcations of the main trunk within the intercostal space in four, at the tip of the 11th rib in seven, and at least 2 cm distal to the tip of the rib in three. Neurophysiological evaluation revealed iterative discharges, polyphasia, fibrillation potentials, and altered recruitment patterns compatible with intercostal nerve injury in patients with a bulge but not in the opposite abdominal wall musculature or in patients without a bulge. Seven (11.11%) of 63 patients had a bulge. Thirty-one of 63 patients had incisions into the 11th intercostal space in which a bulge developed in six (19.35%). Thirty-two patients had incisions that avoided extension into the intercostal space; a bulge developed in one (0.03%) (P = .53). CONCLUSIONS: Postoperative bulge is related to intercostal nerve injury with subsequent paralysis of abdominal wall musculature. Intercostal nerve injury can be reduced by avoiding extension of the incision into the 11th intercostal space.     

The cellular and molecular basis of peripheral nerve regeneration

Functional recovery from peripheral nerve injury and repair depends on a multitude of factors, both intrinsic and extrinsic to neurons. Neuronal survival after axotomy is a prerequisite for regeneration and is facilitated by an array of trophic factors from multiple sources, including neurotrophins, neuropoietic cytokines, insulin-like growth factors (IGFs), and glial-cell-line-derived neurotrophic factors (GDNFs). Axotomized neurons must switch from a transmitting mode to a growth mode and express growth-associated proteins, such as GAP-43, tubulin, and actin, as well as an array of novel neuropeptides and cytokines, all of which have the potential to promote axonal regeneration. Axonal sprouts must reach the distal nerve stump at a time when its growth support is optimal. Schwann cells in the distal stump undergo proliferation and phenotypical changes to prepare the local environment to be favorable for axonal regeneration. Schwann cells play an indispensable role in promoting regeneration by increasing their synthesis of surface cell adhesion molecules (CAMs), such as N-CAM, Ng-CAM/L1, N-cadherin, and L2/HNK-1, by elaborating basement membrane that contains many extracellular matrix proteins, such as laminin, fibronectin, and tenascin, and by producing many neurotrophic factors and their receptors. However, the growth support provided by the distal nerve stump and the capacity of the axotomized neurons to regenerate axons may not be sustained indefinitely. Axonal regenerations may be facilitated by new strategies that enhance the growth potential of neurons and optimize the growth support of the distal nerve stump in combination with prompt nerve repair.     

Humoral and cell-mediated immune responses of beef and dairy cattle experimentally infested with Psoroptes ovis

Relatively little is known about the effects of chronic transection on human peripheral nerves. In this study intraoperative biopsies were obtained from proximal and distal nerve stumps and intervening neuromas resected before peripheral nerve reconstruction. Biopsies were collected from ten patients following differing types of nerve injury, with delays to repair ranging from 8 to 53 months. Nerves were examined by light and electron microscopy. In general, reinnervation was poor, although even following the most severe injuries, all of the distal stumps contained some regrowing axons, which were always associated with Schwann cells. Denervated Schwann cells, arranged in typical bands of Büngner were consistently present in each distal stump. Our findings confirm that the morphology of chronically denervated human peripheral nerves is essentially similar to that described in experimental models.     

The effect of bipolar electrocautery on peripheral nerves

Although bipolar cautery was designed to minimize trauma to the central nervous system, little is known about the effects of bipolar cautery on peripheral nerve tissue. This experiment was designed to study the effect of direct bipolar cautery on a peripheral nerve and the muscles innervated by that nerve. Lewis rats (n = 200) were assigned to five different groups: control, sham, and three cautery groups (duration of either 0.5, 1.0, or 1.5 seconds). The hind limb tibial nerves were isolated in the sham group and isolated and cauterized in the cautery groups. Assessments performed at 2 hours, 2 weeks, 4 weeks, and 8 weeks postoperatively included isometric contractile function studies of both a fast- and a slow-twitch muscle, muscle weights, and nerve histology/morphometry. Significant muscle weight loss and reduced muscle function were found in the cautery groups at 2, 4, and 8 weeks (p < 0.05). Histologically, the nerves of the cautery groups showed nerve damage consistent with Sunderland's type 4 nerve injury when examined at 2 weeks and showed nerve regeneration at 4 and 8 weeks. Both the fast-twitch muscle and the shorter duration cautery were associated with faster recovery relative to the slow-twitch muscles and longer duration cautery, respectively. Bipolar cautery, as administered to rat tibial nerves in this experiment, is associated with a significant injury to the nerve and loss of function of the muscles innervated by the nerve.