Nerve injury in severe trauma with upper extremity involvement: evaluation of 49,382 patients from the TraumaRegister DGU® between 2002 and 2015

Biological conduits based on spider silk for reconstruction of extended nerve defects

Objectives

The availability of appropriate conduits remains an obstacle for successful reconstruction of long-distance nerve defects. In previous sheep trials, we were able to bridge 6 cm nerve gaps with nerve conduits based on spider silk fibers with full functional outcomes. Here, we describe the first application of spider silk for nerve repair in humans.

Methods

Four patients with extended nerve defects (>20 cm) underwent nerve reconstruction by interposition of conduits that were composed of spider silk fibers contained in autologous veins. The longitudinal luminal fibers (approx. 2500 fibers per graft) consisted of drag line silk from Trichonephila spiders. All patients were evaluated between 2 and 10 years postreconstruction, clinically, and by neurography.

Results

In all patients, primary wound healing and no adverse reactions to the implanted spider silk material were observed. Patients regained the following relevant functions: protective sensibility, full flexor function with near-normal grasp and powerful function after microvascular gracilis muscle transfer, and key grip function and gross finger flexion after additional tenodesis. One patient with sciatic nerve reconstruction developed protective sensibility of the lower leg, foot, and gait, enabling normal walking and jogging. No neuroma formation or neuropathic or chronic pain occurred in any of the patients.

Conclusions

For patients with extended peripheral nerve defects in the extremities, use of conduits based on spider silk fibers offers the possibility of restoring sensory function and protection from neuroma. This kind of nerve bridges provides new perspectives for the reconstruction of complex and long-distance nerve defects.

Electrical stimulation enhances sciatic nerve regeneration using a silk-based conductive scaffold beyond traditional nerve guide conduits

Despite recent advancements in peripheral nerve regeneration, the creation of nerve conduits with chemical and physical cues to enhance glial cell function and support axonal growth remains challenging. This study aimed to assess the impact of electrical stimulation (ES) using a conductive nerve conduit on sciatic nerve regeneration in a rat model with transection injury. The study involved the fabrication of conductive nerve conduits using silk fibroin and Au nanoparticles (AuNPs). Collagen hydrogel loaded with green fluorescent protein (GFP)-positive adipose-derived mesenchymal stem cells (ADSCs) served as the filling for the conduit. Both conductive and non-conductive conduits were applied with and without ES in rat models. Locomotor recovery was assessed using walking track analysis. Histological evaluations were performed using H&E, luxol fast blue staining and immunohistochemistry. Moreover, TEM analysis was conducted to distinguish various ultrastructural aspects of sciatic tissue. In the ES + conductive conduit group, higher S100 (p < 0.0001) and neurofilament (p < 0.001) expression was seen after 6 weeks. Ultrastructural evaluations showed that conductive scaffolds with ES minimized Wallerian degeneration. Furthermore, the conductive conduit with ES group demonstrated significantly increased myelin sheet thickness and decreased G. ratio compared to the autograft. Immunofluorescent images confirmed the presence of GFP-positive ADSCs by the 6th week. Locomotor recovery assessments revealed improved function in the conductive conduit with ES group compared to the control group and groups without ES. These results show that a Silk/AuNPs conduit filled with ADSC-seeded collagen hydrogel can function as a nerve conduit, aiding in the restoration of substantial gaps in the sciatic nerve with ES. Histological and locomotor evaluations indicated that ES had a greater impact on functional recovery compared to using a conductive conduit alone, although the use of conductive conduits did enhance the effects of ES.

Utilization of the Rat Tibial Nerve Transection Model to Evaluate Cellular and Molecular Mechanisms Underpinning Denervation-Mediated Muscle Injury

Peripheral nerve injury denervates muscle, resulting in muscle paralysis and atrophy. This is reversible if timely muscle reinnervation occurs. With delayed reinnervation, the muscle's reparative ability declines, and muscle-resident fibro-adipogenic progenitor cells (FAPs) proliferate and differentiate, inducing fibro-fatty muscle degradation and thereby physical disability. The mechanisms by which the peripheral nerve regulates FAPs expansion and differentiation are incompletely understood. Using the rat tibial neve transection model, we demonstrated an increased FAPs content and a changing FAPs phenotype, with an increased capacity for adipocyte and fibroblast differentiation, in gastrocnemius muscle post-denervation. The FAPs response was inhibited by immediate tibial nerve repair with muscle reinnervation via neuromuscular junctions (NMJs) and sensory organs (e.g., muscle spindles) or the sensory protection of muscle (where a pure sensory nerve is sutured to the distal tibial nerve stump) with reinnervation by muscle spindles alone. We found that both procedures reduced denervation-mediated increases in glial-cell-line-derived neurotrophic factor (GDNF) in muscle and that GDNF promoted FAPs adipogenic and fibrogenic differentiation in vitro. These results suggest that the peripheral nerve controls FAPs recruitment and differentiation via the modulation of muscle GDNF expression through NMJs and muscle spindles. GDNF can serve as a therapeutic target in the management of denervation-induced muscle injury.

Surgery for mononeuropathies

Advancement in microsurgical techniques and innovative approaches including greater use of nerve and tendon transfers have resulted in better peripheral nerve injury (PNI) surgical outcomes. Clinical evaluation of the patient and their injury factors along with a shift toward earlier time frame for intervention remain key. A better understanding of the pathophysiology and biology involved in PNI and specifically mononeuropathies along with advances in ultrasound and magnetic resonance imaging allow us, nowadays, to provide our patients with a logical and sophisticated approach. While functional outcomes are constantly being refined through different surgical techniques, basic scientific concepts are being advanced and translated to clinical practice on a continuous basis. Finally, a combination of nerve transfers and technological advances in nerve/brain and machine interfaces are expanding the scope of nerve surgery to help patients with amputations, spinal cord, and brain lesions.

Strain-induced bands of Büngner formation promotes axon growth in 3D tissue-engineered constructs

Treatment of peripheral nerve lesions remains a major challenge due to poor functional recovery; hence, ongoing research efforts strive to enhance peripheral nerve repair. In this study, we aimed to establish three-dimensional tissue-engineered bands of Büngner constructs by subjecting Schwann cells (SCs) embedded in fibrin hydrogels to mechanical stimulation. We show for the first time that the application of strain induces (i) longitudinal alignment of SCs resembling bands of Büngner, and (ii) the expression of a pronounced repair SC phenotype as evidenced by upregulation of BDNF, NGF, and p75NTR. Furthermore, we show that mechanically aligned SCs provide physical guidance for migrating axons over several millimeters in vitro in a co-culture model with rat dorsal root ganglion explants. Consequently, these constructs hold great therapeutic potential for transplantation into patients and might also provide a physiologically relevant in vitro peripheral nerve model for drug screening or investigation of pathologic or regenerative processes.

The role of imaging in focal neuropathies

Electrodiagnostic testing (EDX) has been the diagnostic tool of choice in peripheral nerve disease for many years, but in recent years, peripheral nerve imaging has been used ever more frequently in daily clinical practice. Nerve ultrasound and magnetic resonance (MR) neurography are able to visualize nerve structures reliably. These techniques can aid in localizing nerve pathology and can reveal significant anatomical abnormalities underlying nerve pathology that may have been otherwise undetected by EDX. As such, nerve ultrasound and MR neurography can significantly improve diagnostic accuracy and can have a significant effect on treatment strategy. In this chapter, the basic principles and recent developments of these techniques will be discussed, as well as their potential application in several types of peripheral nerve disease, such as carpal tunnel syndrome (CTS), ulnar neuropathy at the elbow (UNE), radial neuropathy, brachial and lumbosacral plexopathy, neuralgic amyotrophy (NA), fibular, tibial, sciatic, femoral neuropathy, meralgia paresthetica, peripheral nerve trauma, tumors, and inflammatory neuropathies.

High-resolution ultrasound of the supra- and infraclavicular levels of the brachial plexus including the axillary nerve: imaging anatomy based on multiplanar reconstructions and technical guide

PURPOSE

The diagnosis of peripheral nerve injuries remains challenging. Electromyography and nerve conduction studies do not allow precise localization of the lesion and differentiation between lesions in continuity and non-continuity in cases with complete axonotmesis. Improved ultrasound technology allows the examination of almost the entire peripheral nervous system. The complex sono-anatomy of the brachial plexus outside of the standard scanning planes makes it difficult to access this region.

METHODS

On the basis of the Visible Human Project of the National Institutes of Health (NIH), multiplanar reconstructions were created with the 3D Slicer open-source software in the various planes of the ultrasound cross-sections. The ultrasound examination itself and the guidance of the ultrasound probe in relation to the patient were recorded as video files and were synchronized through the audio channel. Subsequently, image matching was performed.

RESULTS

Multiplanar reconstructions facilitate visualization of anatomical regions which are challenging to access thereby enabling physicians to evaluate the course of the peripheral nerve of interest in dynamic conditions. Sonographically visible structures could be reproducibly identified in single-frame analysis.

CONCLUSION

With precise knowledge of the ultrasound anatomy, the nerve structures of the brachial plexus can also be dynamically assessed almost in their entire course. An instructional video on ultrasound of the brachial plexus supplements this manuscript and has been published on Vimeo.com.

Unveiling adcyap1 as a protective factor linking pain and nerve regeneration through single-cell RNA sequencing of rat dorsal root ganglion neurons

BACKGROUND

Severe peripheral nerve injury (PNI) often leads to significant movement disorders and intractable pain. Therefore, promoting nerve regeneration while avoiding neuropathic pain is crucial for the clinical treatment of PNI patients. However, established animal models for peripheral neuropathy fail to accurately recapitulate the clinical features of PNI. Additionally, researchers usually investigate neuropathic pain and axonal regeneration separately, leaving the intrinsic relationship between the development of neuropathic pain and nerve regeneration after PNI unclear. To explore the underlying connections between pain and regeneration after PNI and provide potential molecular targets, we performed single-cell RNA sequencing and functional verification in an established rat model, allowing simultaneous study of the neuropathic pain and axonal regeneration after PNI.

RESULTS

First, a novel rat model named spared nerve crush (SNC) was created. In this model, two branches of the sciatic nerve were crushed, but the epineurium remained unsevered. This model successfully recapitulated both neuropathic pain and axonal regeneration after PNI, allowing for the study of the intrinsic link between these two crucial biological processes. Dorsal root ganglions (DRGs) from SNC and naïve rats at various time points after SNC were collected for single-cell RNA sequencing (scRNA-seq). After matching all scRNA-seq data to the 7 known DRG types, we discovered that the PEP1 and PEP3 DRG neuron subtypes increased in crushed and uncrushed DRG separately after SNC. Using experimental design scRNA-seq processing (EDSSP), we identified Adcyap1 as a potential gene contributing to both pain and nerve regeneration. Indeed, repeated intrathecal administration of PACAP38 mitigated pain and facilitated axonal regeneration, while Adcyap1 siRNA or PACAP6-38, an antagonist of PAC1R (a receptor of PACAP38) led to both mechanical hyperalgesia and delayed DRG axon regeneration in SNC rats. Moreover, these effects can be reversed by repeated intrathecal administration of PACAP38 in the acute phase but not the late phase after PNI, resulting in alleviated pain and promoted axonal regeneration.

CONCLUSIONS

Our study reveals that Adcyap1 is an intrinsic protective factor linking neuropathic pain and axonal regeneration following PNI. This finding provides new potential targets and strategies for early therapeutic intervention of PNI.

An Updated Surgical Approach of Using Flap and Cutaneous Nerve in the Lateral Arm to Reconstruct Complex Injuries of the Forearm and Hand: A Case Series Study

BACKGROUND

Complex injuries involving the nerves and other soft tissues in the forearm and hand lead to functional and aesthetic defects. In such situations, multiple types of nerve autografts and flap donor sites are available. However, multiple donor sites cause donor morbidity in different locations and may lead to awkward operational positions. Therefore, based on the anatomical characterization, we aimed to modify the utilization of the lateral arm donor site for reconstruction, which restricts donor morbidity in the affected upper extremity.

METHODS

We report a case series (N = 6) using a lateral arm flap (LAF) to reconstruct complex soft tissue defects in the forearm, palm, and finger. The posterior antebrachial cutaneous nerve (PACN) is the primary option for nerve bridging, whereas the LAF can carry the lower lateral brachial cutaneous nerve (LBCN) as a sensory flap. Once the PACN was insufficient, the LBCN was harvested simultaneously. All the cases included in this study were performed between January 2012 and August 2021. Demographic information, flap and nerve characteristics, complications, and hand function were analyzed.

RESULTS

The LAF plus PACN or plus LBCN as nerve autograft, both successfully repaired 6 complex injuries: 2 cases in the forearm side, 1 in the hand palm, and 3 in the finger defects. Posterior antebrachial cutaneous nerve was the most used (8-15 cm), and LBCN plus PACN was used to bridge nerve defects when necessary (in total, 20 and 21 cm). The average follow-up time was 19.7 months. The disabilities of the arm, shoulder and hand score ranged between 6 and 12, and the mean 2-point discrimination values ranged between 6 and 12. The Semmes-Weinstein monofilament test result was under 5.46. In addition, 2 patients underwent a secondary debulking surgery. The average length of hospital stay was 10.4 days. Hematoma occurred in 2 cases, and all patients reported numbness in the donor nerve innervated areas.

CONCLUSIONS

This surgical refinement can reconstruct complex injuries in the forearm and hand. In addition, this approach restricts donor morbidity in the affected limb, comforts the operational position, and is achieved under brachial plexus anesthesia.

Pulsed Electromagnetic Fields Improved Peripheral Nerve Regeneration After Delayed Repair of One Month

The goal of this study was to determine if postoperative pulsed electromagnetic fields (PEMFs) could improve the neuromuscular rehabilitation after delayed repair of peripheral nerve injuries. Thirty-six Sprague-Dawley rats were randomly divided into sham group, control group, and PEMFs group. The sciatic nerves were transected except for the control group. One month later, the nerve ends of the former two groups were reconnected. PEMFs group of rats was subjected to PEMFs thereafter. Control group and sham group received no treatment. Four and 8 weeks later, morphological and functional changes were measured. Four and eight weeks postoperatively, compared to sham group, the sciatic functional indices (SFIs) of PEMFs group were higher. More axons regenerated distally in PEMFs group. The fiber diameters of PEMFs group were larger. However, the axon diameters and myelin thicknesses were not different between these two groups. The brain-derived neurotrophic factor and vascular endothelial growth factor expressions were higher in PEMFs group after 8 weeks. Semi-quantitative IOD analysis for the intensity of positive staining indicated that there were more BDNF, VEGF, and NF200 in PEMFs group. It's concluded that PEMFs have effect on the axonal regeneration after delayed nerve repair of one month. The upregulated expressions of BDNF and VEGF may play roles in this process. © 2023 Bioelectromagnetics Society.

Functional Electrical Stimulation in Conjunction With Proprioceptive Neuromuscular Facilitation (PNF) Technique to Improve Upper Limb Function in Traumatic Brachial Plexus Injury: A Case Report

Traumatic brachial plexus injuries (TBPIs) in the adult population are primarily a result of road traffic accidents or falls on a shoulder, which mainly affects the young population. Adult TBPI is a serious incapacitating injury that affects young adults. It decreases the function of upper extremity muscles, which affects social participation and quality of life. Physiotherapy intervention demonstrates its effectiveness in enhancing and maintaining the function of the upper extremity, eventually decreasing the participation restriction and improving quality of life. The proprioceptive neuromuscular facilitation (PNF) technique has been selected as a useful therapeutic option to enhance upper limb function after TBPI. The preceding case report proved the effectiveness of six weeks of functional electrical stimulation in addition to the PNF technique in improving upper limb function after TBPI.

Neuropathic Pain in the Emergency Setting: Diagnosis and Management

Neuropathic pain, traditionally considered a chronic condition, is increasingly encountered in the emergency department (ED), accounting for approximately 20% of patients presenting with pain. Understanding the physiology and key clinical presentations of neuropathic pain is crucial for ED physicians to provide optimal treatment. While diagnosing neuropathic pain can be challenging, emphasis should be placed on obtaining a comprehensive medical history and conducting a thorough clinical examination. Patients often describe neuropathic pain as a burning or shock-like sensation, leading them to seek care in the ED after ineffective relief from common analgesics such as paracetamol and NSAIDs. Collaboration between emergency medicine specialists, neurologists, and pain management experts can contribute to the development of evidence-based guidelines specifically tailored for the emergency department setting. This article provides a concise overview of the common clinical manifestations of neuropathic pain that may prompt patients to seek emergency care.

Evaluation of Processed Nerve Allograft in Peripheral Nerve Surgery: A Systematic Review and Critical Appraisal

Peripheral nerve injuries cause substantial problems when not treated properly. A specific problem is reconstruction of nerve defects, which can be treated in different ways. This study aimed to systematically review whether processed nerve allograft (PNA) is justified in reconstruction of a nerve defect in patients after posttraumatic or iatrogenic peripheral nerve injury and to compare PNA with other established methods.

Methods

A systematic review with a focused question, PICO (patient, intervention, comparison, outcome) and constraints, was performed. A structured literature search, including several databases, was done to evaluate the existing evidence for outcomes and postoperative complications related to PNA. The certainty of evidence was classified according to Grading of Recommendations, Assessment, Development and Evaluations.

Results

No conclusions, concerning differences in outcome of nerve reconstruction using PNA compared with the use of nerve autograft or conduits, could be drawn. The level of certainty for all evaluated outcomes was very low (⊕◯◯◯). Most published studies lack a control group to patients treated with PNA; being only descriptive, making it difficult to compare PNA with established methods without substantial risk of bias. For studies including a control group, the scientific evidence was of very low certainty, due to a low number of included patients, and large, undefined loss of patients during follow-up, rendering a high risk of bias. Finally, the authors often had financial disclosures.

Conclusion

Properly conducted randomized controlled trial studies on the use of PNA in reconstruction of peripheral nerve injuries are needed to establish recommendations in clinical practice.

Traumatic peripheral nerve injuries: a classification proposal

BACKGROUND

Peripheral nerve injuries (PNIs) include several conditions in which one or more peripheral nerves are damaged. Trauma is one of the most common causes of PNIs and young people are particularly affected. They have a significant impact on patients' quality of life and on the healthcare system, while timing and type of surgical treatment are of the utmost importance to guarantee the most favorable functional recovery. To date, several different classifications of PNIs have been proposed, most of them focusing on just one or few aspects of these complex conditions, such as type of injury, anatomic situation, or prognostic factors. Current classifications do not enable us to have a complete view of this pathology, which includes diagnosis, treatment choice, and possible outcomes. This fragmentation sometimes leads to an ambiguous definition of PNIs and the impossibility of exchanging crucial information between different physicians and healthcare structures, which can create confusion in the choice of therapeutic strategies and timing of surgery.

MATERIALS

The authors retrospectively analyzed a group of 24 patients treated in their center and applied a new classification for PNI injuries. They chose (a) five injury-related factors, namely nerve involved, lesion site, nerve type (whether motor, sensory or mixed), surrounding tissues (whether soft tissues were involved or not), and lesion type-whether partial/in continuity or complete. An alphanumeric code was applied to each of these classes, and (b) four prognostic codes, related to age, timing, techniques, and comorbidities.

RESULTS

An alphanumeric code was produced, similar to that used in the AO classification of fractures.

CONCLUSIONS

The authors propose this novel classification for PNIs, with the main advantage to allow physicians to easily understand the characteristics of nerve lesions, severity, possibility of spontaneous recovery, onset of early complications, need for surgical treatment, and the best surgical approach.

LEVEL OF EVIDENCE

according to the Oxford 2011 level of evidence, level 2.

Does Electrical Stimulation through Nerve Conduits Improve Peripheral Nerve Regeneration?—A Systematic Review

Background: Peripheral nerve injuries affect over 2% of trauma patients and can lead to severe functional impairment and permanent disability. Autologous nerve transplantation is still the gold standard in the reconstruction of nerve defects. For small defects, conduits can be considered for bridging. Lately, the combined use of conduits and electrical stimulation has gained attention in the treatment of peripheral nerve injury. This review aimed to present the currently available data on this topic. Methods: PubMed, Embase, Medline and the Cochrane Library were searched for studies on electrical stimulation through nerve conduits for nerve defects in in vivo studies. Results: Fifteen studies fit the inclusion criteria. All of them reported on the application of nerve conduits combined with stimulation for sciatic nerve gaps in rats. Functional, electrophysiological and histological evaluations showed improved nerve regeneration after electrical stimulation. High variation was observed in the treatment protocols. Conclusion: Electrically stimulated conduits could improve peripheral nerve regeneration in rat models. The combined application of nerve guidance conduits and electrical stimulation shows promising results and should be further evaluated under standardized conditions.

Muscle Grafts with Doxorubicin Pretreatment Produce "Empty Tubes" in the Basal Laminae, Promote Contentious Maturation of the Regenerated Axons, and Bridge 20-mm Sciatic Nerve Defects in Rats

BACKGROUND

 We newly developed a muscle graft that employs a doxorubicin pretreatment technique. The aims of this study were to reveal the biological and morphological features of the muscle tissue in the second week (Study I), to reveal the regeneration outcomes of functional and kinematic assessments of longer-term follow-up (16 weeks, Study II), and to make assessments of the muscle graft with doxorubicin pretreatment in the critical-sized nerve defect model (20 mm, Study III).

METHODS

 A total of 26 adult rats were used in this study. Doxorubicin treatment was accomplished by immersion in a doxorubicin solution for 10 minutes followed by a rinsing procedure. The rats were divided into three groups: the muscle graft with and without doxorubicin pretreatment (M-graft-w-Dox and M-graft-w/o-Dox) groups and the autologous nerve graft (N-graft) group. Assays of apoptosis, immunofluorescent histochemistry including CD68 (macrophage marker), scanning electron microscopy (SEM), morphometrical studies of the regenerated axons, nerve conduction studies, and kinematic studies were performed.

RESULTS

 The M-graft-w-Dox group contained significantly larger numbers of apoptotic cells and CD68-positive cells. SEM revealed the existence of the basal lamina, so called "empty tubes," in the M-graft-w-Dox group. Study II showed contentious maturation of the regenerated axons, especially in the compound muscle action potentials. Study III showed that even at 20 mm, the M-graft-w-Dox group promoted axonal regeneration and functional regeneration.

CONCLUSION

 The M-graft-w-Dox group showed superior regeneration results, and this easy and short-term procedure can expand the muscle graft clinical indication for the treatment of peripheral nerve defects.

Primary Repair of Upper Extremity Peripheral Nerve Injuries: An NSQIP Analysis From 2010 to 2016

BACKGROUND

To identify the rate of 30-day complications after primary repair of upper extremity peripheral nerve injuries, associated diagnoses, and postoperative complication rate.

METHODS

The American College of Surgeons National Surgical Quality Improvement Program database was reviewed from 2010 to 2016. Current Procedural Terminology codes consistent with primary nerve repair of the upper extremity were identified and included in the analysis. Patient demographics, comorbidities, type of procedure (elective/emergent), wound class, operative time, and 30-day complications were recorded. Patients with isolated upper extremity nerve injuries (isolated) were compared with those with peripheral nerve injuries in addition to bone, tendon, or soft tissue injuries (multiple).

RESULTS

In all, 785 patients were identified as having upper extremity nerve repairs (0.16%). Of them, 64% were men and 36% were women; the average patient age was 40 years. The most common indication for surgery was injury to the digits (54% of cases). Thirty-day adverse events occurred in 3% of all cases. Isolated nerve injury occurred in 43% of patients, whereas 57% had additional injuries. The multiple injury group had a significantly higher complication rate compared with the isolated group (1% vs 4.5%) (P = .007). Repair of tendon at forearm or wrist was the most common concurrent procedure performed.

CONCLUSIONS

Thirty-day complications among upper extremity peripheral nerve injuries are low, accounting for 3% of cases. Return to the operating room accounted for nearly half of all complications. Patients in the multiple injury group accounted for more than half of these and had a significantly higher complication rate compared with patients with isolated nerve injuries.

[Post-traumatic pain mononeuropathies]

Neuropathic pain syndrome (NPS) caused by peripheral nerve (PN) injury is a serious clinical problem due to its prevalence, complexity of pathogenesis, significant impact on the quality of life of patients. The issues of epidemiology, pathogenesis and treatment of patients with NBS with PN injury are considered. Modern possibilities of invasive treatment of such patients are discussed.

The Effect of Electrical Stimulation on Nerve Regeneration Following Peripheral Nerve Injury

Peripheral nerve injuries (PNI) are common and often result in lifelong disability. The peripheral nervous system has an inherent ability to regenerate following injury, yet complete functional recovery is rare. Despite advances in the diagnosis and repair of PNIs, many patients suffer from chronic pain, and sensory and motor dysfunction. One promising surgical adjunct is the application of intraoperative electrical stimulation (ES) to peripheral nerves. ES acts through second messenger cyclic AMP to augment the intrinsic molecular pathways of regeneration. Decades of animal studies have demonstrated that 20 Hz ES delivered post-surgically accelerates axonal outgrowth and end organ reinnervation. This work has been translated clinically in a series of randomized clinical trials, which suggest that ES can be used as an efficacious therapy to improve patient outcomes following PNIs. The aim of this review is to discuss the cellular physiology and the limitations of regeneration after peripheral nerve injuries. The proposed mechanisms of ES protocols and how they facilitate nerve regeneration depending on timing of administration are outlined. Finally, future directions of research that may provide new perspectives on the optimal delivery of ES following PNI are discussed.

Epidemiology of upper extremity peripheral nerve injury in South Korea, 2008 to 2018

Peripheral nerve injuries (PNIs) in the upper extremities is an important medical problem, causing significant morbidity at a relatively young age. The epidemiology of PNI in South Korea has not been comprehensively evaluated. The purpose of our study was to examine the incidence of upper extremity PNI in South Korea based on an analysis of nationwide data and to investigate the association between PNI and patients' demographic characteristics. Patient claims data from the Health Insurance Review and Assessment Service from 2008 to 2018 were collected. Demographic characteristics, such as the age, sex, region, admission route, length of hospital stay, healthcare facility level, and cost were evaluated. Annual incidence, body sites affected, damaged nerves, accompanying injuries, and surgical procedures were analyzed. Annual incidence trends, injured anatomical area, seasonal injury trends, and injury trend according to sex were also evaluated. A total of 57,209 cases were identified during the study period. Mean age was 39.7 ± 16.3 years. Of these cases, 51,651 (90.28%) were surgically treated. About 79% of accompanying injuries occurred in the hand area (hand lacerations, 69.5%; fractures or joint dislocations of the hands, 6.86%; crushing injuries of the hands, 2.67%). Overall, injuries to the digital nerve showed the greatest frequency (62.7%). In the upper arm and forearm, the ulnar nerve was most frequently injured; however, in the hand, radial nerve injuries were most common. The annual incidence rate per 100,000 persons decreased from 10.67 in 2008 to 7.88 in 2018. The annual incidence decreased by 0.98 times per year. PNI occurred 33.91 times more frequently in the finger than in the upper arm, and there were 1.16 times more PNIs in the summer and 2.14 times more in men. We investigated the incidence trend and epidemiologic characteristics of upper extremity peripheral nerve injury in South Korea from 2008 to 2018. A decreasing tendency of annual incidence was observed from 2013 onwards. Finger and digital nerve were most commonly injured, and the incidence of PNI was higher in the summer and in men.

Traumatic injury to peripheral nerves

This article reviews the epidemiology, classification, localization, prognosis, and mechanisms of recovery of traumatic peripheral nerve injuries (PNIs). Electrodiagnostic (EDx) assessments are critical components of treating patients with PNIs. In particular, motor and sensory nerve conduction studies, needle electromyography, and other electrophysiological methods are useful for localizing peripheral nerve injuries, detecting and quantifying the degree of axon loss, and contributing toward treatment decisions as well as prognostication. It is critical that EDx medical consultants are aware of the timing of these changes as well as limitations in interpretations. Mechanisms of recovery may include recovery from conduction block, muscle fiber hypertrophy, distal axonal sprouting, and axon regrowth from the site of injury. Motor recovery generally reaches a plateau at 18 to 24 months postinjury. When patients have complete or severe nerve injuries they should be referred to surgical colleagues early after injury, as outcomes are best when nerve transfers are performed within the first 3 to 6 months after onset.

Sex-related differences in experimental pain sensitivity in subjects with painful or painless neuropathy after surgical repair of traumatic nerve injuries

Higher pain intensities at all experimental stimuli but a tendency to faster recovery after cold conditioning stimuli were seen in women with neuropathy in comparison with men.

Introduction:

Sex-related influences represent a contributor to greater pain sensitivity and have a higher prevalence of many chronic pain conditions, including neuropathic pain (NP), among women.

Objectives:

The aim was to analyze how differences in ongoing pain, experimental pain intensity, and conditioned pain modulation (CPM) relate to sex in subjects with neuropathy after traumatic nerve injuries.

Methods:

Endogenous pain modulation was compared between male (n = 77) and female (n = 55) subjects and between subjects with NP (female = 31, male = 39) and pain-free subjects with posttraumatic neuropathy (female = 24, male = 38). Conditioned pain modulation was assessed by pain ratings to pressure stimuli before and after a noxious conditioning stimulus (CS) conducted with one arm submerged in cold water (4°C) for 1 minute. Time of recovery (Time off) of pain intensity from peak VAS_maxc after CS was recorded and compared between male and female patients.

Results:

Greater ongoing pain intensity was found among female patients compared with male patients and more experimental pain after pressure and cold induced pain. Summing all groups together, women had 0.8 times higher odds (20%) of recovering sooner than men after CS (95% CI = 0.65–2.9). No differences in CPM, time off, and psychosocial variables were seen between female and male patients (P < 0.05).

Conclusion:

Our hypothesis for sex differences in endogenous pain modulation was only supported by a shorter after-sensation time after cold CS in female patients. No sex differences in the magnitude of CPM effect were identified. Increased pain intensity for experimental pain, in both neuropathic pain and neuropathy without pain, was found in female patients.

An Epidemiological and Etiological Analysis of 5026 Peripheral Nerve Lesions from a European Level I Trauma Center

Background: Peripheral nerve lesions are associated with debilitating long-term consequences. Albeit being essential for evidence-based clinical decision making, epidemiological and etiological data are scarce. We therefore aimed to comprehensively analyze epidemiological and etiological factors of peripheral nerve lesions in one of the largest cohorts. Methods: We screened a total of 110,667 patients treated at our level I trauma center between January 2012 and July 2020 for nerve lesions. Subsequently, demographics, etiologies, concomitant injuries, and lesion characteristics were analyzed. Results: A total of 5026 patients, predominantly young males suffering from non-work-related nerve injuries, were treated. Proximal levels of injury were more likely to be accompanied by fractures, whereas more distal injuries with concomitant vessel or tendon injury. Main causes were 54.6% lacerations. Acute traumatic nerve injury was treated within 24 h in 55.9% of cases. Conclusions: Given the young age of affected patients, early diagnosis and treatment in specialized centers may facilitate their early return to work and improve long-term functional outcomes. The data show the importance of a special attention on nerve injuries, which may be masked by large accompanying injuries. New findings on lesion characteristics of selected subgroups and accompanying circumstances can support a change in treatment strategies.

Blockage of neuromuscular glutamate receptors impairs reinnervation following nerve crush in adult mice

Motor axons in peripheral nerves are capable of regeneration following injury. However, complete recovery of motor function is rare, particularly when reinnervation is delayed. We have previously found that glutamate receptors play a crucial role in the successful innervation of muscle during mouse development. In particular, blocking N-methyl-D-aspartate (NMDA) receptor activity delays the normal elimination of excess innervation of each neuromuscular junction. Here, we use behavioral, immunohistochemical, electrophysiological, and calcium imaging methods to test whether glutamate receptors play a similar role in the transition from polyneuronal to mono-innervation and in recovery of function following peripheral nerve injury in mature muscle.

The impact of physical, biochemical, and electrical signaling on Schwann cell plasticity

Peripheral nervous system (PNS) injuries are an ongoing health care concern. While autografts and allografts are regarded as the current clinical standard for traumatic injury, there are inherent limitations that suggest alternative remedies should be considered for therapeutic purposes. In recent years, nerve guidance conduits (NGCs) have become increasingly popular as surgical repair devices, with a multitude of various natural and synthetic biomaterials offering potential to enhance the design of conduits or supplant existing technologies entirely. From a cellular perspective, it has become increasingly evident that Schwann cells (SCs), the primary glia of the PNS, are a predominant factor mediating nerve regeneration. Thus, the development of severe nerve trauma therapies requires a deep understanding of how SCs interact with their environment, and how SC microenvironmental cues may be engineered to enhance regeneration. Here we review the most recent advancements in biomaterials development and cell stimulation strategies, with a specific focus on how the microenvironment influences the behavior of SCs and can potentially lead to functional repair. We focus on microenvironmental cues that modulate SC morphology, proliferation, migration, and differentiation to alternative phenotypes. Promotion of regenerative phenotypic responses in SCs and other non-neuronal cells that can augment the regenerative capacity of multiple biomaterials is considered along with innovations and technologies for traumatic injury.

ESWT Diminishes Axonal Regeneration following Repair of the Rat Median Nerve with Muscle-In-Vein Conduits but Not after Autologous Nerve Grafting

Investigations reporting positive effects of extracorporeal shockwave therapy (ESWT) on nerve regeneration are limited to the rat sciatic nerve model. The effects of ESWT on muscle-in-vein conduits (MVCs) have also not been investigated yet. This study aimed to evaluate the effects of ESWT after repair of the rat median nerve with either autografts (ANGs) or MVCs. In male Lewis rats, a 7 mm segment of the right median nerve was reconstructed either with an ANG or an MVC. For each reconstructive technique, one group of animals received one application of ESWT while the other rats served as controls. The animals were observed for 12 weeks, and nerve regeneration was assessed using computerized gait analysis, the grasping test, electrophysiological evaluations and histological quantification of axons, blood vessels and lymphatic vasculature. Here, we provide for the first time a comprehensive analysis of ESWT effects on nerve regeneration in a rat model of median nerve injury. Furthermore, this study is among the first reporting the quantification of lymphatic vessels following peripheral nerve injury and reconstruction in vivo. While we found no significant direct positive effects of ESWT on peripheral nerve regeneration, results following nerve repair with MVCs were significantly inferior to those after ANG repair.

Incidence of Nerve Injury After Extremity Trauma in the United States

BACKGROUND

Traumatic peripheral nerve injuries cause chronic pain, disability, and long-term reductions in quality of life. However, their incidence after extremity trauma remains poorly understood.

METHODS

The IBM® MarketScan® Commercial Database from 2010 to 2015 was used to identify patients aged 18 to 64 who presented to emergency departments for upper and/or lower extremity traumas. Cumulative incidences were calculated for nerve injuries diagnosed within 2 years of trauma. Cox regression models were developed to evaluate the associations between upper extremity nerve injury and chronic pain, disability, and use of physical therapy or occupational therapy.

RESULTS

The final cohort consisted of 1 230 362 patients with employer-sponsored health plans. Nerve injuries were diagnosed in 2.6% of upper extremity trauma patients and 1.2% of lower extremity trauma patients. Only 9% and 38% of nerve injuries were diagnosed by the time of emergency department and hospital discharge, respectively. Patients with nerve injuries were more likely to be diagnosed with chronic pain (hazard ratio [HR]: 5.9, 95% confidence interval [CI], 4.3-8.2), use physical therapy services (HR: 10.7, 95% CI, 8.8-13.1), and use occupational therapy services (HR: 19.2, 95% CI, 15.4-24.0) more than 90 days after injury.

CONCLUSIONS

The incidence of nerve injury in this national cohort was higher than previously reported. A minority of injuries were diagnosed by emergency department or hospital discharge. These findings may improve practitioner awareness and inform public health interventions for injury prevention.

Preclinical Evidence for the Role of Botulinum Neurotoxin A (BoNT/A) in the Treatment of Peripheral Nerve Injury

Traumatic peripheral nerve injuries tend to be more common in younger, working age populations and can lead to long-lasting disability. Peripheral nerves have an impressive capacity to regenerate; however, successful recovery after injury depends on a number of factors including the mechanism and severity of the trauma, the distance from injury to the reinnervation target, connective tissue sheath integrity, and delay between injury and treatment. Even though modern surgical procedures have greatly improved the success rate, many peripheral nerve injuries still culminate in persistent neuropathic pain and incomplete functional recovery. Recent studies in animals suggest that botulinum neurotoxin A (BoNT/A) can accelerate nerve regeneration and improve functional recovery after injury to peripheral nerves. Possible mechanisms of BoNT/A action include activation or proliferation of support cells (Schwann cells, mast cells, and macrophages), increased angiogenesis, and improvement of blood flow to regenerating nerves.

Role of Electrical Stimulation in Peripheral Nerve Regeneration: A Systematic Review

Functional recovery after peripheral nerve injury is often suboptimal despite the intrinsic permissive growth environment of the peripheral nervous system. The objective of this systematic review is to explore the use of electrical stimulation (ES) for peripheral nerve regeneration.

Risk for Persistent Peripheral Neuropathy After Repair of Brachial Artery Injuries

Background

Brachial artery lacerations are limb-threatening injuries requiring emergent repair. Concomitant peripheral nerve symptoms are often only identified postoperatively. This study evaluated the prevalence of peripheral nerve deficits among this population as the indications for early nerve exploration have not been definitively established.

Methods

We reviewed all patients sustaining a brachial artery injury at one pediatric and two adult Level I Trauma Centers between January 1, 2007, and December 31, 2017. We recorded patient demographics, comorbidities, intoxication status, injury mechanism, concomitant injuries, type of repair, and intraoperative peripheral nerve exploration findings. Pre-and post-operative and long-term peripheral nerve function examination findings were analyzed. Differences between categorical variables were determined with Chi-square and Fisher’s exact tests.

Results

Thirty-four patients sustained traumatic brachial artery lacerations requiring operative repair. Injury mechanisms included tidy (clean cut) laceration (n=11, 32%), gunshot wound (n=9, 26%), blunt trauma (n=8, 24%), and untidy laceration (n=6, 18%). Preoperatively, 15% had a normal peripheral nerve examination, 26% had localizable symptoms, 38% had non-localizable symptoms, and 21% were taken to the operating room without formal nerve assessment. Thirty-two percent underwent formal nerve exploration, and 81% underwent nerve repair. At an average follow-up of 2.5 years, 27% of patients underwent exploration, and 39% did not have localizable peripheral nerve deficits (p=0.705).

Conclusions

Brachial artery injuries are associated with a clinically significant risk for long-term peripheral nerve symptoms. Early nerve exploration in patients with peripheral nerve symptoms after a brachial artery injury may be warranted, although there is no statistically significant likelihood for improved peripheral neurological outcomes.

Validation of a Cleanroom Compliant Sonication-Based Decellularization Technique: A New Concept in Nerve Allograft Production

Defects of the peripheral nervous system are extremely frequent in trauma and surgeries and have high socioeconomic costs. If the direct suture of a lesion is not possible, i.e., nerve gap > 2 cm, it is necessary to use grafts. While the gold standard is the autograft, it has disadvantages related to its harvesting, with an inevitable functional deficit and further morbidity. An alternative to autografting is represented by the acellular nerve allograft (ANA), which avoids disadvantages of autograft harvesting and fresh allograft rejection. In this research, the authors intend to transfer to human nerves a novel technique, previously implemented in animal models, to decellularize nerves. The new method is based on soaking the nerve tissues in decellularizing solutions while associating ultrasounds and freeze-thaw cycles. It is performed without interrupting the sterility chain, so that the new graft may not require post-production γ-ray irradiation, which is suspected to affect the structural and functional quality of tissues. The new method is rapid, safe, and inexpensive if compared with available commercial ANAs. Histology and immunohistochemistry have been adopted to evaluate the new decellularized nerves. The study shows that the new method can be applied to human nerve samples, obtaining similar, and, sometimes better, results compared with the chosen control method, the Hudson technique.

The efficacy of wrapping the neurorrhaphy site utilizing dura substitute: A case series

BACKGROUND

Different procedures have been developed to improve the surgical outcome of peripheral nerve injuries. The purpose of this study was to evaluate the efficacy of wrapping the neurorrhaphy site utilizing dura substitute graft as an alternative conduit in the management of peripheral nerve injury.

METHODS

This retrospective clinical case series included 42 patients with a single peripheral nerve injury. The mean age was 26.8 ± 11 years, and the mean duration of symptoms was 3 ± 1.8 months. The visual analogue score (VAS) for pain and the Medical Research Council's (MRC) grading for motor power were used to evaluate the functional outcome among our patients. All patients were operated on for primary microscopic end-to-end repair, followed by wrapping the neurorrhaphy site with dura substitute graft as a conduit. Patients were followed in the outpatient clinic with regular visits for average of 6 months.

RESULTS

Thirty-seven patients (83%), showed functional improvement in all aspects, the VAS for pain and the MRC for motor power, as well as the functional state. One patient (2.3%) developed a postoperative hematoma collection, which needed immediate evacuation. Superficial wound infection, reported in two patients (4.7%), was treated conservatively. No postoperative neuroma was observed among our patients during the follow-up period.

CONCLUSION

Wrapping the neurorrhaphy site utilizing dura substitute as conduit appears to be safe and might prove effective in managing peripheral nerve injury.

Volumetric MRI is a promising outcome measure of muscle reinnervation

The development of outcome measures that can track the recovery of reinnervated muscle would benefit the clinical investigation of new therapies which hope to enhance peripheral nerve repair. The primary objective of this study was to assess the validity of volumetric Magnetic Resonance Imaging (MRI) as an outcome measure of muscle reinnervation by testing its reproducibility, responsiveness and relationship with clinical indices of muscular function. Over a 3-year period 25 patients who underwent nerve transfer to reinnervate elbow flexor muscles were assessed using intramuscular electromyography (EMG) and MRI (median post-operative assessment time of 258 days, ranging from 86 days pre-operatively to 1698 days post- operatively). Muscle power (Medical Research Council (MRC) grade) and Stanmore Percentage of Normal Elbow Assessment (SPONEA) assessment was also recorded for all patients. Sub-analysis of peak volitional force (PVF), muscular fatigue and co-contraction was performed in those patients with MRC > 3. The responsiveness of each parameter was compared using Pearson or Spearman correlation. A Hierarchical Gaussian Process (HGP) was implemented to determine the ability of volumetric MRI measurements to predict the recovery of muscular function. Reinnervated muscle volume per unit Body Mass Index (BMI) demonstrated good responsiveness (R² = 0.73, p < 0.001). Using the temporal and muscle volume per unit BMI data, a HGP model was able to predict MRC grade and SPONEA with a mean absolute error (MAE) of 0.73 and 1.7 respectively. Muscle volume per unit BMI demonstrated moderate to good positive correlations with patient reported impairments of reinnervated muscle; co- contraction (R² = 0.63, p = 0.02) and muscle fatigue (R² = 0.64, p = 0.04). In summary, volumetric MRI analysis of reinnervated muscle is highly reproducible, responsive to post-operative time and demonstrates correlation with clinical indices of muscle function. This encourages the view that volumetric MRI is a promising outcome measure for muscle reinnervation which will drive advancements in motor recovery therapy.

Beyond the Knife-Reviewing the Interplay of Psychosocial Factors and Peripheral Nerve Lesions

Peripheral nerve injuries are a common clinical problem. They not only affect the physical capabilities of the injured person due to loss of motor or sensory function but also have a significant impact on psychosocial aspects of life. The aim of this work is to review the interplay of psychosocial factors and peripheral nerve lesions. By reviewing the published literature, we identified several factors to be heavily influenced by peripheral nerve lesions. In addition to psychological factors like pain, depression, catastrophizing and stress, social factors like employment status and worker's compensation status could be identified to be influenced by peripheral nerve lesions as well as serving as predictors of functional outcome themselves, respectively. This work sheds a light not only on the impact of peripheral nerve lesions on psychosocial aspects of life, but also on the prognostic values of these factors of functional outcome. Interdisciplinary, individualized treatment of patients is required to identify patient at risk for adverse outcomes and provide them with emotional support when adapting to their new life situation.

Efficacy of low-level laser therapy in nerve injury repair-a new era in therapeutic agents and regenerative treatments

BACKGROUND

Traumatic nerve injuries may result in severe motor dysfunctions. Although the microenvironment of peripheral axons favors their regeneration, regenerative process is not always successful.

PURPOSE

We reviewed and discussed the main findings obtained with low-level laser therapy (LLLT), a therapeutic intervention that has been employed in order to achieve an optimized regeneration process in peripheral axons.

SCOPE

Disseminating the best available evidence for the effectiveness of this therapeutic strategy can potentially improve the statistics of success in the clinical treatment of nerve injuries. We found evidence that LLLT optimizes the regeneration of peripheral axons, improving motor function, especially in animal models. Nonetheless, further clinical evidence is still needed before LLLT can be strongly recommended. Although the results are promising, the elucidation of the mechanisms of action and safety assessment are necessary to support highquality clinical studies.

CONCLUSION

The present careful compilation of findings with consistent pro-regenerative evidence and published in respected scientific journals can be valuable for health professionals and researchers in the field, possibly contributing to achieve more promising results in future randomized controlled trials and interventions, providing better prognosis for clinical practice.

Intramuscular injection of skeletal muscle derived extracellular matrix mitigates denervation atrophy after sciatic nerve transection

Peripheral nerve injury and the associated muscle atrophy has an estimated annual healthcare burden of $150 billion dollars in the United States. When considering the total annual health-related spending of $3.5 trillion, these pathologies alone occupy about 4.3%. The prevalence of these ailments is rooted, at least in part, in the lack of specific preventative therapies that can be administered to muscle while it remains in the denervated state. To address this, skeletal muscle-derived ECM (skECM) was injected directly in denervated muscle with postoperative analysis performed at 20 weeks, including gait analysis, force production, cytokine quantification, and histological analysis. skECM was shown to be superior against non-injected muscle controls showing no difference in contraction force to uninjured muscle at 20 weeks. Cytokines IL-1β, IL-18, and IFNγ appeared to mediate regeneration with statistical regression implicating these cytokines as strong predictors of muscle contraction, showing significant linear correlation.

[The use of intraoperative fascicle-topographic electromyography in peripheral nerve surgery: review of the literature and clinical experience]

The intraoperative assessment of a pathological nerve segment is crucial in peripheral nerve surgery. Based on different techniques the function of a peripheral nerve is analyzed and either a neurolysis alone or a resection with subsequent nerve reconstruction is performed. Beside the morphological and histological assessment or the use of a nerve stimulator, intraoperative electrophysiology is highly useful. The aim of this diagnostic tool is the recording of objective parameters, documenting the function of peripheral nerves. Intraoperative electroneurography allows the assessment of a nerve action potential over a pathological nerve segment and has been used for decades. In contrast, additional needle electromyography is rarely used even though this technique is characterized by interesting advantages: It is very helpful for the selection of donor fascicles during neurotization surgeries and for the electrophysiological assessment of neuromata in continuity. In the present review, we discuss the value of intraoperative electromyography in the treatment of peripheral nerve trauma as well as peripheral nerve tumors.

[Functional reconstruction in traumatic paralysis]

BACKGROUND

Traumatic nerve injuries are associated with a high morbidity and long rehabilitation times. The extent of a nerve lesion and the related regeneration potential can often only be estimated during the course, whereby the time window for successful surgical interventions is limited.

OBJECTIVE

The incidence and distribution of traumatic nerve lesions are reported. Algorithms for treatment decisions are presented.

MATERIAL AND METHODS

Statistics from the German TraumaRegister DGU® as well as international registers were evaluated. The results of basic research and expert recommendations for diagnostics and treatment are discussed.

RESULTS AND CONCLUSION

A strategic approach to conservative and surgical treatment of traumatic nerve injuries depending on the extent of injury and resulting regeneration potential is recommended. In conjunction with the clinical course, electrophysiology and imaging diagnostics, e.g. nerve sonography, can help to differentiate between neurapraxia, axonotmesis and neurotmesis.

Preclinical study of peripheral nerve regeneration using nerve guidance conduits based on polyhydroxyalkanaotes

Nerve guidance conduits (NGCs) are used as an alternative to the "gold standard" nerve autografting, preventing the need for surgical intervention required to harvest autologous nerves. However, the regeneration outcomes achieved with the current NGCs are only comparable with autografting when the gap is short (less than 10 mm). In the present study, we have developed NGCs made from a blend of polyhydroxyalkanoates, a family of natural resorbable polymers. Hollow NGCs made from a 75:25 poly(3-hydroxyoctanoate)/poly(3-hydroxybutyrate) blend (PHA-NGCs) were manufactured using dip-molding. These PHA-NGCs showed appropriate flexibility for peripheral nerve regeneration. In vitro cell studies performed using RT4-D6P2T rat Schwann cell line confirmed that the material is capable of sustaining cell proliferation and adhesion. PHA-NGCs were then implanted in vivo to repair 10 mm gaps of the median nerve of female Wistar rats for 12 weeks. Functional evaluation of the regenerated nerve using the grasping test showed that PHA-NGCs displayed similar motor recovery as the autograft, starting from week 7. Additionally, nerve cross-sectional area, density and number of myelinated cells, as well as axon diameter, fiber diameter, myelin thickness and g-ratio obtained using the PHA-NGCs were found comparable to an autograft. This preclinical data confirmed that the PHA-NGCs are indeed highly promising candidates for peripheral nerve regeneration.

The Role of Dietary Nutrients in Peripheral Nerve Regeneration

Peripheral nerves are highly susceptible to injuries induced from everyday activities such as falling or work and sport accidents as well as more severe incidents such as car and motorcycle accidents. Many efforts have been made to improve nerve regeneration, but a satisfactory outcome is still unachieved, highlighting the need for easy to apply supportive strategies for stimulating nerve growth and functional recovery. Recent focus has been made on the effect of the consumed diet and its relation to healthy and well-functioning body systems. Normally, a balanced, healthy daily diet should provide our body with all the needed nutritional elements for maintaining correct function. The health of the central and peripheral nervous system is largely dependent on balanced nutrients supply. While already addressed in many reviews with different focus, we comprehensively review here the possible role of different nutrients in maintaining a healthy peripheral nervous system and their possible role in supporting the process of peripheral nerve regeneration. In fact, many dietary supplements have already demonstrated an important role in peripheral nerve development and regeneration; thus, a tailored dietary plan supplied to a patient following nerve injury could play a non-negotiable role in accelerating and promoting the process of nerve regeneration.

Risk Factors for a False-Negative Examination in Complete Upper Extremity Nerve Lacerations

Background: Many patients with complete nerve lacerations after upper extremity trauma have a documented normal peripheral nerve examination at the time of initial evaluation. The purpose of this study was to determine whether physician-, patient-, and injury-related factors increase the risk of false-negative nerve examinations. Methods: A statewide health information exchange was used to identify complete upper extremity nerve lacerations subsequently confirmed by surgical exploration at 1 pediatric and 2 adult level I trauma centers in a single city from January 2013 to January 2017. Charts were manually reviewed to build a database that included Glasgow Coma Scale score, urine drug screen results, blood alcohol level, presence of concomitant trauma, type of injury, level of injury, laterality, initial provider examination, and initial specialist examination. Bivariate and multivariable analyses were performed to evaluate risk factors for a false-negative examination. Results: Two hundred eighty-eight patients met inclusion criteria. The overall false-negative examination rate was 32.5% at initial encounter, which was higher among emergency medicine physicians compared with extremity subspecialists (P < .001) and among trauma surgeons compared with surgical subspecialists (P = .002). The false-negative rate decreased to 8% at subsequent encounter (P < .001). Risk factors for a false-negative nerve examination included physician specialty, a gunshot wound mechanism of injury, injury at the elbow, and age greater than 71 years. Conclusion: There is a high false-negative rate among upper extremity neurotmesis injuries. Patients with an injury pattern that may lead to nerve injury warrant prompt referral to an upper extremity specialist in an effort to optimize outcomes.

Electrical stimulation of human neural stem cells via conductive polymer nerve guides enhances peripheral nerve recovery

Severe peripheral nerve injuries often result in permanent loss of function of the affected limb. Current treatments are limited by their efficacy in supporting nerve regeneration and behavioral recovery. Here we demonstrate that electrical stimulation through conductive nerve guides (CNGs) enhances the efficacy of human neural progenitor cells (hNPCs) in treating a sciatic nerve transection in rats. Electrical stimulation strengthened the therapeutic potential of NPCs by upregulating gene expression of neurotrophic factors which are critical in augmenting synaptic remodeling, nerve regeneration, and myelination. Electrically-stimulated hNPC-containing CNGs are significantly more effective in improving sensory and motor functions starting at 1-2 weeks after treatment than either treatment alone. Electrophysiology and muscle assessment demonstrated successful re-innervation of the affected target muscles in this group. Furthermore, histological analysis highlighted an increased number of regenerated nerve fibers with thicker myelination in electrically-stimulated hNPC-containing CNGs. The elevated expression of tyrosine kinase receptors (Trk) receptors, known to bind to neurotrophic factors, indicated the long-lasting effect from electrical stimulation on nerve regeneration and distal nerve re-innervation. These data suggest that electrically-enhanced stem cell-based therapy provides a regenerative rehabilitative approach to promote peripheral nerve regeneration and functional recovery.

Bioactive Nanofiber-Based Conduits in a Peripheral Nerve Gap Management-An Animal Model Study

The aim was to examine the efficiency of a scaffold made of poly (L-lactic acid)-co-poly(ϵ-caprolactone), collagen (COL), polyaniline (PANI), and enriched with adipose-derived stem cells (ASCs) as a nerve conduit in a rat model. P(LLA-CL)-COL-PANI scaffold was optimized and electrospun into a tubular-shaped structure. Adipose tissue from 10 Lewis rats was harvested for ASCs culture. A total of 28 inbred male Lewis rats underwent sciatic nerve transection and excision of a 10 mm nerve trunk fragment. In Group A, the nerve gap remained untouched; in Group B, an excised trunk was used as an autograft; in Group C, nerve stumps were secured with P(LLA-CL)-COL-PANI conduit; in Group D, P(LLA-CL)-COL-PANI conduit was enriched with ASCs. After 6 months of observation, rats were sacrificed. Gastrocnemius muscles and sciatic nerves were harvested for weight, histology analysis, and nerve fiber count analyses. Group A showed advanced atrophy of the muscle, and each intervention (B, C, D) prevented muscle mass decrease (p < 0.0001); however, ASCs addition decreased efficiency vs. autograft (p < 0.05). Nerve fiber count revealed a superior effect in the nerve fiber density observed in the groups with the use of conduit (D vs. B p < 0.0001, C vs. B p < 0.001). P(LLA-CL)-COL-PANI conduits with ASCs showed promising results in managing nerve gap by decreasing muscle atrophy.

Three-Dimensional Engineered Peripheral Nerve: Toward a New Era of Patient-Specific Nerve Repair Solutions

Reconstruction of peripheral nerve injuries (PNIs) with substance loss remains challenging because of limited treatment solutions and unsatisfactory patient outcomes. Currently, nerve autografting is the first-line management choice for bridging critical-sized nerve defects. The procedure, however, is often complicated by donor site morbidity and paucity of nerve tissue, raising a quest for better alternatives. The application of other treatment surrogates, such as nerve guides, remains questionable, and it is inefficient in irreducible nerve gaps. More importantly, these strategies lack customization for personalized patient therapy, which is a significant drawback of these nerve repair options. This negatively impacts the fascicle-to-fascicle regeneration process, critical to restoring the physiological axonal pathway of the disrupted nerve. Recently, the use of additive manufacturing (AM) technologies has offered major advancements to the bioengineering solutions for PNI therapy. These techniques aim at reinstating the native nerve fascicle pathway using biomimetic approaches, thereby augmenting end-organ innervation. AM-based approaches, such as three-dimensional (3D) bioprinting, are capable of biofabricating 3D-engineered nerve graft scaffolds in a patient-specific manner with high precision. Moreover, realistic in vitro models of peripheral nerve tissues that represent the physiologically and functionally relevant environment of human organs could also be developed. However, the technology is still nascent and faces major translational hurdles. In this review, we spotlighted the clinical burden of PNIs and most up-to-date treatment to address nerve gaps. Next, a summarized illustration of the nerve ultrastructure that guides research solutions is discussed. This is followed by a contrast of the existing bioengineering strategies used to repair peripheral nerve discontinuities. In addition, we elaborated on the most recent advances in 3D printing and biofabrication applications in peripheral nerve modeling and engineering. Finally, the major challenges that limit the evolution of the field along with their possible solutions are also critically analyzed.

The Role of the IL-4 Signaling Pathway in Traumatic Nerve Injuries

Following traumatic peripheral nerve injury, adequate restoration of function remains an elusive clinical goal. Recent research highlights the complex role that the immune system plays in both nerve injury and regeneration. Pro-regenerative processes in wounded soft tissues appear to be significantly mediated by cytokines of the type 2 immune response, notably interleukin (IL)-4. While IL-4 signaling has been firmly established as a critical element in general tissue regeneration during wound healing, it has also emerged as a critical process in nerve injury and regeneration. In this context of peripheral nerve injury, endogenous IL-4 signaling has recently been confirmed to influence more than leukocytes, but including also neurons, axons, and Schwann cells. Given the role IL-4 plays in nerve injury and regeneration, exogenous IL-4 and/or compounds targeting this signaling pathway have shown encouraging preliminary results to treat nerve injury or other neuropathy in rodent models. In particular, the exogenous stimulation of the IL-4 signaling pathway appears to promote postinjury neuron survival, axonal regeneration, remyelination, and thereby improved functional recovery. These preclinical data strongly suggest that targeting IL-4 signaling pathways is a promising translational therapy to augment treatment approaches of traumatic nerve injury. However, a better understanding of the type 2 immune response and associated signaling networks functioning within the nerve injury microenvironment is still needed to fully develop this promising therapeutic avenue.

Comparison between optical coherence tomography imaging and histological sections of peripheral nerves

OBJECTIVE

Optical coherence tomography (OCT) is an imaging technique that uses the light-backscattering properties of different tissue types to generate an image. In an earlier feasibility study the authors showed that it can be applied to visualize human peripheral nerves. As a follow-up, this paper focuses on the interpretation of the images obtained.

METHODS

Ten different short peripheral nerve specimens were retained following surgery. In a first step they were examined by OCT during, or directly after, surgery. In a second step the nerve specimens were subjected to histological examination. Various steps of image processing were applied to the OCT raw data acquired. The improved OCT images were compared with the sections stained by H & E. The authors assigned the structures in the images to the various nerve components including perineurium, fascicles, and intrafascicular microstructures.

RESULTS

The results show that OCT is able to resolve the myelinated axons. A weighted averaging filter helps in identifying the borders of structural features and reduces artifacts at the same time. Tissue-remodeling processes due to injury (perineural fibrosis or neuroma) led to more homogeneous light backscattering. Anterograde axonal degeneration due to sharp injury led to a loss of visible axons and to an increase of light-backscattering tissue as well. However, the depth of light penetration is too small to allow generation of a complete picture of the nerve.

CONCLUSIONS

OCT is the first in vivo imaging technique that is able to resolve a nerve's structures down to the level of myelinated axons. It can yield information about focal and segmental pathologies.

Nerve Ultrasound in Traumatic and Iatrogenic Peripheral Nerve Injury

Peripheral nerve injury is a potentially debilitating disorder that occurs in an estimated 2–3% of all patients with major trauma, in a similar percentage of medical procedures. The workup of these injuries has traditionally been clinical, combined with electrodiagnostic testing. However, this has limitations, especially in the acute phase of the trauma or lack of any recovery, when it is very important to determine nerve continuity and perform surgical exploration and repair in the case of the complete transection or intraneural fibrosis. Ultrasound can help in those situations. It is a versatile imaging technique with a high sensitivity of 93% for detecting focal nerve lesions. Ultrasound can assess the structural integrity of the nerve, neuroma formation and other surrounding abnormalities of bone or foreign bodies impeding the nerve. In addition, this can help to prevent iatrogenic nerve injury by marking the nerve before the procedure. This narrative review gives an overview of why and how nerve ultrasound can play a role in the detection, management and prevention of peripheral nerve injury.

Traumatic Injuries to the Spinal Cord and Peripheral Nervous System

Both blunt and penetrating trauma can cause injuries to the peripheral and central nervous systems. Emergency providers must maintain a high index of suspicion, especially in the setting of polytrauma. There are 2 major classifications of peripheral nerve injuries (PNIs). Some PNIs are classically associated with certain traumatic mechanisms. Most closed PNIs are managed conservatively, whereas sharp nerve transections require specialist consultation for urgent repair. Spinal cord injuries almost universally require computed tomography imaging; some require emergent magnetic resonance imaging. Providers should work to minimize secondary injury. Surgical specialists are needed for closed reduction, surgical decompression, or stabilization.