Evaluation and management of 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.

The role of exercise on peripheral nerve regeneration: from animal model to clinical application

Peripheral nerve injury is a complex condition with a variety of signs and symptoms depending on the severity and nerves involved. Peripheral nerve damage may lead to sensory and motor functions deficits and even lifelong disability, causing important socioeconomic costs worldwide. Despite the increase in knowledge of the mechanisms of injury and regeneration, a full functional recovery is still unsatisfying in the majority of patients. It is well known that exercise promotes physical and psychological well-being, by ameliorating general health. In the last years, there has been a growing interest in evaluating the effects of exercise on the peripheral nervous system. Experimental works with rodent models showed the potential utility of exercise following peripheral nerve injuries, as evinced by increasing axon regeneration, muscle reinnervation, better recovery of strength, muscle mass and higher expression of neurotrophic factors. Moreover, clinical evidence showed positive trends in favour of physical therapy following peripheral nerve damage based on the improvement of range of motion (ROM), muscle power grade and pain. After a brief overview of peripheral nerve anatomy and the different types of nerve injury, the present review aims to summarize the impact of exercise on peripheral nerve regeneration. Some clinical evidence regarding the effect of exercise after peripheral nerve injury will also be discussed.

The Myth of Median Nerve in Forearm and Its Role in Double Crush Syndrome: A Cadaveric Study

Purpose: This study aims to histologically compare the median nerve in the arm, forearm, and wrist, to help understand how cervical radiculopathy in a double crush phenomenon causes distal nerve dysfunction at the carpal tunnel and median nerve with concurrent absence of symptoms at the forearm.

Methods: The study was performed on 12 fresh cadaveric upper limbs free from any injury or operation. Male cadavers in the age range of 35–40 years were used. The dissection of the median nerve and the histological examination of the specimens from the arm, forearm, and wrist were conducted to evaluate variations in the epineurium thickness (μm), perineurium thickness (μm), number of fascicles per nerve trunk, area percent of myelin covering, and area percent of neurolemmal sheath.

Results: Morphometric and statistical results of the cadaveric median nerve trunk revealed that the mean epineurium and perineurium thickness measured in H&E-stained sections in the forearm were significantly greater than those in the arm and wrist specimens. Further, the mean percent area of the myelin covering in the forearm was significantly lower than that in the arm and wrist specimens in the sections stained with osmium oxide (p < 0.001). There were, however, no significant differences in the neurolemmal sheath among the arm, forearm, and wrist specimens in the silver-stained sections.

Conclusion: The histological differences explained the high concomitant occurrence of carpal tunnel syndrome (CTS) and cervical radiculopathy and the concurrent absence of symptoms at the forearm. Hence, we suggest cautious evaluation of patients with upper limb symptoms, since the management of these conditions requires a different approach.

Scapular winging in surgical treatment of breast cancer, prospective study to optimize the follow-up protocol

INTRODUCTION

One of the most common complications of the surgical treatment of breast cancer is limited range-of-motion in the shoulder. Scapular winging is one of the most underdiagnosed shoulder mobility impairments.

OBJECTIVE

The main objective of this study was to determine the incidence of scapular winging in patients who underwent breast cancer surgery as the basis for expanding the protocol to patients who have had a sentinel lymph node biopsy. The secondary objective was to determine the risk factors that lead to the development of a winged scapula presented after breast cancer treatment in our sample.

METHODS

This was a prospective, observational, and multidisciplinary study. Between 2013 and 2018, 214 consecutive patients who had been diagnosed with breast cancer and treated for it surgically were followed by Rehabilitation Department for 3 years. The patients were evaluated in the 1st, 6th, 12th, 18th, 24th and 36th months following surgery. Scapular winging was evaluated at each visit by means of static and dynamic tests.

RESULTS

The cumulative incidence of scapular winging was 3.6% and seven cases of winged scapula were diagnosed. All the cases were diagnosed at the first visit, 1 month after the intervention. In the univariate analysis, the axillary lymph node dissection technique was a more significant risk factor for a winged scapula than sentinel lymph node biopsy.

CONCLUSIONS

The axillary lymph node dissection technique is a risk factor for developing a winged scapula. No evidence was found for any other significant risk factor.

Traumatic Brachial Plexus Injury in Indonesia: An Experience from a Developing Country

Background  Brachial plexus injuries (BPI) cause severe physical disability and major psycho-socioeconomic burden. Although various countries have reported BPI incidence, the data from Indonesia as the fourth most populated country in the world remains unknown. We aim to assess the distribution of traumatic BPI, patients' characteristics, and treatment modalities in Indonesia.

Methods  A retrospective investigation was performed comprising 491 BPI patients at a tertiary referral hospital in Indonesia from January 2003 to October 2019. Demographic and outcomes data were retrieved from medical records.

Results  The average BPI patients' age was 27.3 ± 11.6 years old, with a male/female ratio of 4.6:1. Motorcycle accidents caused the majority (76.1%) of all BPI cases. Concomitant injuries were present in 62.3% of patients, dominated by fractures (57.1%) and brain injuries (25.4%). BPI lesion type was classified into complete (C5-T1, observed in 70% patients), upper (C5-C6, in 15% patients), extended upper (C5-C7, in 14% patients), and lower type (C8-T1, in 1% patients). The average time to surgery was 16.8 months (range 1–120 months), with the majority (76.6%) of the patients was operated on six months after the trauma. Free functional muscle transfer (FFMT) was the most common procedure performed (37%). We also analyzed the functional outcomes (active range of motion (AROM) and muscle power), DASH (Disabilities of the Arm, Shoulder, and Hand) score, and VAS (Visual Analogue Scale) across four most frequent procedures involving nerve reconstruction (FFMT, nerve transfer, external neurolysis, and nerve grafting). We found that FFMT was significantly better than nerve transfer in terms of DASH score and VAS ( p  = 0.000 and p  = 0.016, respectively) in complete BPI (C5-T1). Moreover, we also found that nerve grafting resulted in a significantly better shoulder abduction AROM than nerve transfer and external neurolysis in extended upper BPI (C5-C7) ( p  = 0.033 and p  = 0.033, respectively). Interestingly, no significant differences were observed in other measurements.

Conclusion  This study provides an overview of traumatic BPI patients in a single tertiary trauma center in Indonesia, expressing the profile of their characteristics and functional outcomes after surgical procedures.

Epidemiology of Peripheral Nerve Injuries in Sports, Exercise, and Recreation in the United States, 2009 - 2018

OBJECTIVE

To assess rates of peripheral nerve injuries (PNI) in sport, exercise, and recreational activities.

METHODS

The National Electronic Injury Surveillance System (NEISS) was used to query nerve injuries presenting to emergency departments across the United States. Identified injuries were stratified to those with product codes associated with exercise, sports, or recreation. Injuries only to the upper and lower extremities were included as cranial and spinal cord injuries were excluded. PNI was analyzed by age, sex, sport/recreational activity, race, and evaluated for incidence rates by year and activity. Statistical significance was considered to be P < 0.05.

RESULTS

Between 2009-2018, 551,612 patients presented with PNI from which 120,675 (21.9%) were associated with exercise, sports, or recreation. PNI significantly increased between 2009-2018 (p = 0.002) with an overall incidence rate of 36.9 (95% confidence interval: 28.6, 45.2) per 1,000,000 person-years. A majority of PNI occurred through exercise (n = 56,328, 46.7%). PNI peaked in the fourth and fifth decades in males and females, respectively, with males accounting for significantly more than females (incidence rate ratio: 1.52, 95% confidence interval: 1.18, 1.86; p < 0.0001). White patients had a majority of PNI at 49.3% though African-Americans carried the highest incidence rate at 30.4 (95% confidence interval: 23.8, 36.9) per 1,000,000 person-years. Football had the highest proportion of PNI until age 19 (17.3%) as exercise carried the highest proportion for those 20 and older ranging from 27.9% to 53.8% of PNI.

CONCLUSION

PNIs are rising with participation in exercise, sports, and recreation over this 10-year study period. Injuries predominantly occurred in football for those under 20 and exercise for those 20 and older. Precautions and appropriate training are necessary for individuals participating in high-intensity exercise, sports, or recreation to limit the risk of a devastating neurological injury.

Natural Polymeric Scaffolds for Tissue Engineering Applications

Natural polymeric scaffolds can be used for tissue engineering applications such as cell delivery and cell-free supporting of native tissues. This is because of their desirable properties such as; high biocompatibility, tunable mechanical strength and conductivity, large surface area, porous- and extracellular matrix (ECM)-mimicked structures. Specifically, their less toxicity and biocompatibility makes them suitable for several tissue engineering applications. For these reasons, several biopolymeric scaffolds are currently being explored for numerous tissue engineering applications. To date, research on the nature, chemistry, and properties of nanocomposite biopolymers are been reported, while the need for a comprehensive research note on more tissue engineering application of these biopolymers remains. As a result, this present study comprehensively reviews the development of common natural biopolymers as scaffolds for tissue engineering applications such as cartilage tissue engineering, cornea repairs, osteochondral defect repairs, and nerve regeneration. More so, the implications of research findings for further studies are presented, while the impact of research advances on future research and other specific recommendations are added as well.

Noninvasive diffusion MRI to determine the severity of peripheral nerve injury

OBJECTIVE

Primary repair of peripheral nerves is recommended following transection; however, patient management following repair is challenged by a lack of biomarkers to nerve regeneration. Previous studies have demonstrated that diffusion magnetic resonance imaging (MRI) may provide viable biomarkers of nerve regeneration in injury models; though, these methods have not been systematically evaluated in graded partial transections and repairs.

METHODS

Ex vivo diffusion MRI was performed in fixed rat sciatic nerve samples 4 or 12 weeks following partial nerve transection and repair (25% cut = 12, 50% cut = 12 and 75% cut = 11), crush injuries (n = 12), and sham surgeries (n = 9). Behavioral testing and histologic evaluation were performed in the same animals and nerve samples for comparison.

RESULTS

Diffusion tractography provided visual characterizations of nerve damage and recovery consistent with the expected degree of injury within each cohort. In addition, quantitative indices from diffusion MRI correlated with both histological and behavioral evaluations, the latter of indicated full recovery for sham and crush nerves and limited recovery in all partially transected/repaired nerves. Nerve recovery between 4 and 12 weeks was statistically significant in partial transections 50% and 75% depth cuts (p = 0.043 and p = 0.022) but not for 25% transections.

INTERPRETATION

Our findings suggest that DTI can i) distinguish different degrees of partial nerve transection following surgical repair and ii) map spatially heterogeneous nerve recovery (e.g., due to collateral sprouting) from 4 to 12 weeks in partially transected nerves.

Characteristics of Upper Extremity Recovery in Acute Flaccid Myelitis: A Case Series

BACKGROUND

Clinical characteristics and timing associated with nonsurgical recovery of upper extremity function in acute flaccid myelitis are unknown.

METHODS

A single-institution retrospective case series was analyzed to describe clinical features of acute flaccid myelitis diagnosed between October of 2013 and December of 2016. Patients were consecutively sampled children with a diagnosis of acute flaccid myelitis who were referred to a hand surgeon. Patient factors and initial severity of paralysis were compared with upper extremity muscle strength outcomes using the Medical Research Council scale every 3 months up to 18 months after onset.

RESULTS

Twenty-two patients with acute flaccid myelitis (aged 2 to 16 years) were studied. Proximal upper extremity musculature was more frequently and severely affected, with 56 percent of patients affected bilaterally. Functional recovery of all muscle groups (≥M3) in an individual limb was observed in 43 percent of upper extremities within 3 months. Additional complete limb recovery to greater than or equal to M3 after 3 months was rarely observed. Extraplexal paralysis, including spinal accessory (72 percent), glossopharyngeal/hypoglossal (28 percent), lower extremity (28 percent), facial (22 percent), and phrenic nerves (17 percent), was correlated with greater severity of upper extremity paralysis and decreased spontaneous recovery. There was no correlation between severity of paralysis or recovery and patient characteristics, including age, sex, comorbidities, prodromal symptoms, or time to paralysis.

CONCLUSIONS

Spontaneous functional limb recovery, if present, occurred early, within 3 months of the onset of paralysis. The authors recommend that patients without signs of early recovery warrant consideration for early surgical intervention and referral to a hand surgeon or other specialist in peripheral nerve injury.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Risk, III.

Neurological complications in COVID-19: a single case study of rehabilitation treatment

Background/aims:

COVID-19 is a global pandemic, which has seen over 198 million cases as of August 2021. This case study highlights the rehabilitation of a young patient with respiratory and neurologic sequalae of COVID-19 across the continuum of care, from the intensive care unit to the inpatient rehabilitation unit.

Case description:

A 45-year-old woman, with past medical history of fibromyalgia and morbid obesity, presented with complaints of shortness of breath. She tested positive for SARS-CoV-2, was transferred to the intensive care unit, and was intubated for 17 days. The day after extubation, she experienced worsened mental status; computed tomography and magnetic resonance imaging scans revealed bilateral strokes. On hospital day 21, she was transferred to the stroke step-down unit. On hospital day 24, she recovered some cognitive ability and movement of her lower extremities. On hospital day 30, she was admitted to the inpatient rehabilitation unit. Examination by occupational and physiotherapists found motor and sensory impairments of multiple peripheral nerves, including musculocutaneous, axillary and radial nerves. Interventions included passive range of motion, sitting balance, transfer training, rigid taping, upper extremity strengthening and functional training (gait, stair, activities of daily living). Her activities of daily living performance was limited by upper extremity weakness, sensory loss and pain.

Conclusions

This case highlights the medical, neurological and functional implications of COVID-19 on patients after prolonged hospitalisation. The plan of care was informed by collaboration between rehabilitation disciplines. Causes of her injuries are unclear but could include positioning, brachial plexus injuries, or post-critical illness syndrome. Further research on the evaluation and care of patients with COVID-19 that result in profound neurological impairments is warranted.

Role of electrodiagnosis in nerve transfers for focal neuropathies and brachial plexopathies

Over the past 2 decades, the surgical treatment of brachial plexus and peripheral nerve injuries has advanced considerably. Nerve transfers have become an important surgical tool in addition to nerve repair and grafting. Electrodiagnosis has traditionally played a role in the diagnosis and localization of peripheral nervous system injuries, but a different approach is needed for surgical decision-making and monitoring recovery. When patients have complete or severe 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 mo after onset. Patients with minimal recovery of voluntary activity are particularly challenging, and the presence of a few motor unit action potentials in these individuals should be interpreted on the basis of timing and evidence of ongoing reinnervation. Evaluation of potential recipient and donor muscles, as well as redundant muscles, for nerve transfers requires an individualized approach to optimize the chances of a successful surgical intervention. Anomalous innervation takes on new importance in these patients. Communication between surgeons and electrodiagnostic medicine specialists (EMSs) is best facilitated by a joint collaborative clinic. Ongoing monitoring of recovery post-operatively is critical to allow for decision making for continued surgical and rehabilitation treatments. Different electrodiagnostic findings are expected with resolution of neurapraxia, distal axon sprouting, and axonal regrowth. As new surgical techniques become available, EMSs will play an important role in the assessment and treatment of these patients with severe nerve injuries.

Nerve Suture Combined With ADSCs Injection Under Real-Time and Dynamic NIR-II Fluorescence Imaging in Peripheral Nerve Regeneration in vivo

Peripheral nerve injury gives rise to devastating conditions including neural dysfunction, unbearable pain and even paralysis. The therapeutic effect of current treatment for peripheral nerve injury is unsatisfactory, resulting in slow nerve regeneration and incomplete recovery of neural function. In this study, nerve suture combined with ADSCs injection was adopted in rat model of sciatic nerve injury. Under real-time visualization of the injected cells with the guidance of NIR-II fluorescence imaging in vivo, a spatio-temporal map displaying cell migration from the proximal injection site (0 day post-injection) of the nerve to the sutured site (7 days post-injection), and then to the distal section (14 days post-injection) was demonstrated. Furthermore, the results of electromyography and mechanical pain threshold indicated nerve regeneration and functional recovery after the combined therapy. Therefore, in the current study, the observed ADSCs migration in vivo, electrophysiological examination results and pathological changes all provided robust evidence for the efficacy of the applied treatment. Our approach of nerve suture combined with ADSCs injection in treating peripheral nerve injury under real-time NIR-II imaging monitoring in vivo added novel insights into the treatment for peripheral nerve injury, thus further enhancing in-depth understanding of peripheral nerve regeneration and the mechanism behind.

Quantitative Sensory Testing in Women After Surgery for Breast Cancer: A Systematic Review and Narrative Synthesis

OBJECTIVES

Quantitative sensory testing (QST) is a noninvasive technique to evaluate functioning of the somatosensory system. In many women surgically treated for breast cancer (BC), somatosensory functioning is disturbed with high prevalence of sensory loss and/or pain. The aims of this systematic review were (1) to summarize literature about QST methods; (2) to summarize the results within women surgically treated for BC (patients and survivors); (3) to compare QST results between women surgically treated for BC with and without pain; and (4) to compare the results between women surgically treated for BC and women without history of BC.

METHODS

A systematic literature search was conducted up to February 2020. Included studies had to report on QST methods (mechanical or thermal detection-pain thresholds, pressure pain thresholds [PPT], temporal summation [TS], or conditioned pain modulation [CPM]) in women over 18 years with-without pain, who had undergone unilateral surgery for BC.

RESULTS

Twenty-eight studies were included. Discrepancies in QST methods were greatest for TS and CPM. A local disturbance in thermal detection and an increased pain facilitation were found in BC survivors with pain in the surgical area. BC survivors with upper limb pain had significantly lower PPT at the surgical area and PPT were also significantly lower compared with women without history of BC, at affected and nonaffected sides for both local and remote body regions.

DISCUSSION

Standardized QST incorporating assessments of CPM is warranted in order to draw conclusions about neurobiological mechanisms of pain and somatosensory disturbances after surgical treatment for BC and to enhance mechanism-based management of these sequelae.

Iatrogenic lesions of the peripheral nervous system in orthopaedic surgery and traumatology procedures

OBJECTIVE

To describe iatrogenic lesions of the peripheral nervous system and their relationship with different orthopaedic and traumatological procedures, through their assessment by means of electromyographic study.

MATERIAL AND METHODS

Retrospective descriptive study of the electromyographies performed in the clinical neurophysiology service of the Hospital General Universitari de Castelló between July 2015 and March 2019, recovering those in which the aetiology was diagnosed as iatrogenic in relation to surgical procedures and analysing those that were initiated after orthopaedic and traumatological procedures.

RESULTS

Of the total number of electromyographies reviewed, 1.37% corresponded to iatrogenic surgical lesions and 55.1% of these were secondary to orthopaedic surgery and traumatology procedures, the incidence in relation to the procedures performed was 0.65%. The most frequent locations related to injuries were the lumbar spine, hip and hand/wrist. Injuries due to postural causes not directly related to the surgical field are noteworthy.

CONCLUSION

Iatrogenic injuries to the peripheral nervous system after orthopaedic surgery and traumatology procedures are infrequent, but given their mechanism of injury and the high severity of most of them, it would be advisable to implement corrective mechanisms to reduce their incidence.

LEVEL OF EVIDENCE

IV.

Interpretation of Electrodiagnostic Studies: How to Apply It to the Practice of Orthopaedic Surgery

Electrodiagnostic studies may help orthopaedic surgeons to identify and confirm nerve pathology, determine severity of disease, localize the lesion, identify concomitant or alternative pathology, and prognosticate potential outcomes with nonoperative or operative treatment. Surgeons should recognize the indications for electrodiagnostic studies, principles of their performance, and how to assess the primary data generated by the examination and how it can inform their treatment plans.

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.

Low-intensity pulsed ultrasound for regenerating peripheral nerves: potential for penile nerve

Peripheral nerve damage, such as that found after surgery or trauma, is a substantial clinical challenge. Much research continues in attempts to improve outcomes after peripheral nerve damage and to promote nerve repair after injury. In recent years, low-intensity pulsed ultrasound (LIPUS) has been studied as a potential method of stimulating peripheral nerve regeneration. In this review, the physiology of peripheral nerve regeneration is reviewed, and the experiments employing LIPUS to improve peripheral nerve regeneration are discussed. Application of LIPUS following nerve surgery may promote nerve regeneration and improve functional outcomes through a variety of proposed mechanisms. These include an increase of neurotrophic factors, Schwann cell (SC) activation, cellular signaling activations, and induction of mitosis. We searched PubMed for articles related to these topics in both in vitro and in vivo animal research models. We found numerous studies, suggesting that LIPUS following nerve surgery promotes nerve regeneration and improves functional outcomes. Based on these findings, LIPUS could be a novel and valuable treatment for nerve injury-induced erectile dysfunction.

Low-Intensity Pulsed Ultrasound Prompts Both Functional and Histologic Improvements While Upregulating the Brain-Derived Neurotrophic Factor Expression after Sciatic Crush Injury in Rats

The aim of this study was to determine that low-intensity pulsed ultrasound (LIPUS) at an intensity of 140 mW/cm² promotes functional and histologic improvements in sciatic nerve crush injury in a rat model and to investigate changes over time in relevant growth factors and receptors, exploring the mechanism of LIPUS in the recovery process after injury. Toe angle in the toe-off phase, regenerative axonal length, myelinated nerve fiber density, diameter of myelinated nerve fiber, axon diameter and myelin sheath thickness were significantly higher in the LIPUS group than in the sham group. Gene and protein expression of brain-derived neurotrophic factor (BDNF) was upregulated in the LIPUS group. In conclusion, LIPUS contributed to rapid functional and histologic improvement and upregulated BDNF expression after sciatic nerve crush injury in rats.

3D-printed nerve guidance conduits multi-functionalized with canine multipotent mesenchymal stromal cells promote neuroregeneration after sciatic nerve injury in rats

Background

Nerve injuries are debilitating, leading to long-term motor deficits. Remyelination and axonal growth are supported and enhanced by growth factor and cytokines. Combination of nerve guidance conduits (NGCs) with adipose-tissue-derived multipotent mesenchymal stromal cells (AdMSCs) has been performing promising strategy for nerve regeneration.

Methods

3D-printed polycaprolactone (PCL)-NGCs were fabricated. Wistar rats subjected to critical sciatic nerve damage (12-mm gap) were divided into sham, autograft, PCL (empty NGC), and PCL + MSCs (NGC multi-functionalized with 10⁶ canine AdMSCs embedded in heterologous fibrin biopolymer) groups. In vitro, the cells were characterized and directly stimulated with interferon-gamma to evaluate their neuroregeneration potential. In vivo, the sciatic and tibial functional indices were evaluated for 12 weeks. Gait analysis and nerve conduction velocity were analyzed after 8 and 12 weeks. Morphometric analysis was performed after 8 and 12 weeks following lesion development. Real-time PCR was performed to evaluate the neurotrophic factors BDNF, GDNF, and HGF, and the cytokine and IL-10. Immunohistochemical analysis for the p75^NTR neurotrophic receptor, S100, and neurofilament was performed with the sciatic nerve.

Results

The inflammatory environment in vitro have increased the expression of neurotrophins BDNF, GDNF, HGF, and IL-10 in canine AdMSCs. Nerve guidance conduits multi-functionalized with canine AdMSCs embedded in HFB improved functional motor and electrophysiological recovery compared with PCL group after 12 weeks. However, the results were not significantly different than those obtained using autografts. These findings were associated with a shift in the regeneration process towards the formation of myelinated fibers. Increased immunostaining of BDNF, GDNF, and growth factor receptor p75^NTR was associated with the upregulation of BDNF, GDNF, and HGF in the spinal cord of the PCL + MSCs group. A trend demonstrating higher reactivity of Schwann cells and axonal branching in the sciatic nerve was observed, and canine AdMSCs were engrafted at 30 days following repair.

Conclusions

3D-printed NGCs multi-functionalized with canine AdMSCs embedded in heterologous fibrin biopolymer as cell scaffold exerted neuroregenerative effects. Our multimodal approach supports the trophic microenvironment, resulting in a pro-regenerative state after critical sciatic nerve injury in rats.

(4-Aminopyridine)-PLGA-PEG as a Novel Thermosensitive and Locally Injectable Treatment for Acute Peripheral Nerve Injury

Traumatic peripheral nerve injury (TPNI) represents a major medical problem that results in loss of motor and sensory function, and in severe cases, limb paralysis and amputation. To date, there are no effective treatments beyond surgery in selective cases. In repurposing studies, we found that daily systemic administration of the FDA-approved drug 4-aminopyridine (4-AP) enhanced functional recovery after acute peripheral nerve injury. This study was aimed at constructing a novel local delivery system of 4-AP using thermogelling polymers. We optimized a thermosensitive (4-AP)-poly(lactide-co-glycolide)-b-poly(ethylene glycol)-b-poly(lactide-co-glycolide) (PLGA-PEG-PLGA) block copolymer formulation. (4-AP)-PLGA-PEG exhibited controlled release of 4-AP both in vitro and in vivo for approximately 3 weeks, with clinically relevant safe serum levels in animals. Rheological investigation showed that (4-AP)-PLGA-PEG underwent a solution to gel transition at 32 °C, a physiologically relevant temperature, allowing us to administer it to an injured limb while subsequently forming an in situ gel. A single local administration of (4-AP)-PLGA-PEG remarkably enhanced motor and sensory functional recovery on post-sciatic nerve crush injury days 1, 3, 7, 14, and 21. Moreover, immunohistochemical studies of injured nerves treated with (4-AP)-PLGA-PEG demonstrated an increased expression of neurofilament heavy chain (NF-H) and myelin protein zero (MPZ) proteins, two major markers of nerve regeneration. These findings demonstrate that (4-AP)-PLGA-PEG may be a promising long-acting local therapeutic agent in TPNI, for which no pharmacologic treatment exists.

Novel Real-time Digital Pressure Sensor Reveals Wide Variations in Current Nerve Crush Injury Models

INTRODUCTION

Peripheral nerve crush injury (PNCI) models are commonly used to study nerve damage and the potential beneficial effects of novel therapeutic strategies. Current models of PNCI rely on inter-device and operator precision to limit the variation with applied pressure. Although the inability to accurately quantify the PNCI pressure may result in reduced reproducibility between animals and studies, there is very limited information on the standardization and quantification of applied pressure with PNCI. To address this deficit, we constructed a novel device comprised of an Arduino UNO microcontroller board and Force Sensitive Resistor capable of reporting the real-time pressure applied to a nerve.

METHODS

Two forceps and two needle drivers were used to perform 30-second PNCIs to the sciatic nerves of mice (n = 5/group). Needle drivers were set to the first notch, and a jig was used to hold the forceps pinch at a reproducible pressure. The Force Sensitive Resistor was interposed in-series between the nerve and instrument during PNCI.

RESULTS

Data collected from these procedures displayed average needle driver pressures an order of multitude greater than forceps pressures. Additionally, needle driver inter- and intra-procedure pressure remained more consistent than forceps pressure, with needle driver coefficient of variation equal to 14.5% vs. a forceps coefficient of variation equal to 45.4%.

CONCLUSIONS

This is the first demonstration of real-time pressure measurements in PNCI models and it reveals that the applied pressures are dependent on the types of device used. The large disparity in pressure represents an inability to apply graded accurate and consistent intermediate pressure gradients in PNCI. These findings indicate a need for documentation of pressure severity as a screening for PNCI in animals, and the real-time pressure sensor could be a useful tool in monitoring and applying consistent pressure, reducing the outcome variability within the same experimental model of PNCI.

4-Aminopyridine: A Single-Dose Diagnostic Agent to Differentiate Axonal Continuity in Nerve Injuries

INTRODUCTION

Traumatic peripheral nerve injuries (TPNIs) are increasingly prevalent in battlefield trauma, and the functional recovery with TPNIs depends on axonal continuity. Although the physical examination is the main tool for clinical diagnosis with diagnostic work up, there is no diagnostic tool available to differentiate nerve injuries based on axonal continuity. Therefore, treatment often relies on "watchful waiting," and this leads to muscle weakness and further reduces the chances of functional recovery. 4-aminopyridine (4-AP) is clinically used in multiple sclerosis patients for walking performance improvement. Preliminary results in conscious mice suggested a diagnostic role of 4-AP in distinguishing axonal continuity. In this study, we thought to evaluate the diagnostic potential of 4-AP on the axonal continuity in unawake/sedated animals.

MATERIALS AND METHODS

Rat sciatic nerve crush and transection injuries were used in this study. Briefly, rats were anesthetized with isoflurane and mechanically ventilated with oxygen-balanced vaporized isoflurane. Sciatic nerve and triceps surae muscles were exposed by blunt dissection, and a stimulating electrode was placed under a sciatic nerve proximal to the crush injury. A force transducer measured muscle tension response to electrical stimulation of sciatic nerve. Muscle response was measured before crush, after crush, and 30 minutes after systemic 4-AP (150 µg/kg) or local (4-AP)-poly(lactide-co-glycolide)-b-poly(ethylene glycol)-b-poly(lactide-co-glycolide) (PLGA-PEG) treatment.

RESULTS

We found that both crush and transection injuries in sciatic nerve completely abolished muscle response to electrical stimulation. Single dose of systemic 4-AP and local (4-AP)-PLGA-PEG treatment with crush injury significantly restored muscle responses to electrical stimulation after 30 minutes of administration. However, systemic 4-AP treatment had no effect on muscle response after nerve transection. These results clearly demonstrate that 4-AP can restore nerve conduction and produce muscle response within minutes of administration only when there is a nerve continuity, even in the sedated animal.

CONCLUSIONS

We conclude that 4-AP could be a promising diagnostic agent in differentiating TPNI based on axonal continuity.

Purposeful Misalignment of Severed Nerve Stumps in a Standardized Transection Model Reveals Persistent Functional Deficit With Aberrant Neurofilament Distribution

BACKGROUND

Functional recovery following primary nerve repair of a transected nerve is often poor even with advanced microsurgical techniques. Recently, we developed a novel sciatic nerve transection method where end-to-end apposition of the nerve endings with minimal gap was performed with fibrin glue. We demonstrated that transected nerve repair with gluing results in optimal functional recovery with improved axonal neurofilament distribution profile compared to the end-to-end micro-suture repair. However, the impact of axonal misdirection and misalignment of nerve fascicles remains largely unknown in nerve-injury recovery. We addressed this issue using a novel nerve repair model with gluing.

METHODS

In our complete "Flip and Transection with Glue" model, the nerve was "first" transected to 40% of its width from each side and distal stump was transversely flipped, then 20 µL of fibrin glue was applied around the transection site and the central 20% nerve was completely transected before fibrin glue clotting. Mice were followed for 28 days with weekly assessment of sciatic function. Immunohistochemistry analysis of both sciatic nerves was performed for neurofilament distribution and angiogenesis. Tibialis anterior muscles were analyzed for atrophy and histomorphometry.

RESULTS

Functional recovery following misaligned repair remained persistently low throughout the postsurgical period. Immunohistochemistry of nerve sections revealed significantly increased aberrant axonal neurofilaments in injured and distal nerve segments compared to proximal segments. Increased aberrant neurofilament profiles in the injured and distal nerve segments were associated with significantly increased nerve blood-vessel density and branching index than in the proximal segment. Injured limbs had significant muscle atrophy, and muscle fiber distribution showed significantly increased numbers of smaller muscle fibers and decreased numbers of larger muscle fibers.

CONCLUSIONS

These findings in a novel nerve transection mouse model with misaligned repair suggest that aberrant neurofilament distributions and axonal misdirections play an important role in functional recovery and muscle atrophy.

Iatrogenic common peroneal nerve injury during harvesting of semitendinosus tendon for anterior cruciate ligament reconstruction

We present a case of iatrogenic injury to the common peroneal nerve (CPN) occurring due to harvesting of a hamstring graft, using a posterior mini-incision technique. A twitch of the foot was noted on retraction of the tendon stripper. After clinically diagnosing a CPN palsy proximal to the knee, the patient was referred to a neurosurgeon within 24 hours. An electromyography (EMG) was not obtained since it cannot accurately differentiate between partial and complete nerve injury in the first week after injury. Because the nerve might have been transacted by the tendon stripper, surgical exploration within 72 hours after injury was indicated. An intraneural haematoma was found and neurolysis was performed to decompress the nerve. Functioning of the anterior cruciate ligament was satisfactory during follow-up. Complete return of motor function of the CPN was observed at 1-year follow-up, with some remaining hypoaesthesia.

Corneal neurotization for neurotrophic keratopathy: Review of surgical techniques and outcomes

Neurotrophic keratopathy is a degenerative disease in which damage to the corneal nerves leads to corneal hypoesthesia. Injuries to neurotrophic corneas are notoriously difficult to treat and have traditionally been approached with supportive management. However, recent progress in the field of corneal neurotization has given new direction for addressing nerve loss directly by stimulating new nerve growth onto the cornea from nearby sensory nerves transferred to the perilimbal region. Herein, we review the surgical techniques utilized in corneal neurotization, including direct transfers and the use of nerve grafts. Considerations in surgical approach, as well as factors that influence prognosis and outcomes of the surgical intervention are also discussed.

Effectiveness of electrophysical modalities in the sensorimotor rehabilitation of radial, ulnar, and median neuropathies: A meta-analysis

INTRODUCTION

People with ulnar, radial or median nerve injuries can present significant impairment of their sensory and motor functions. The prescribed treatment for these conditions often includes electrophysical therapies, whose effectiveness in improving symptoms and function is a source of debate. Therefore, this systematic review aims to provide an integrative overview of the efficacy of these modalities in sensorimotor rehabilitation compared to placebo, manual therapy, or between them.

METHODS

We conducted a systematic review according to PRISMA guidelines. We perform a literature review in the following databases: Biomed Central, Ebscohost, Lilacs, Ovid, PEDro, Sage, Scopus, Science Direct, Semantic Scholar, Taylor & Francis, and Web of Science, for the period 1980-2020. We include studies that discussed the sensorimotor rehabilitation of people with non-degenerative ulnar, radial, or median nerve injury. We assessed the quality of the included studies using the Risk of Bias Tool described in the Cochrane Handbook of Systematic Reviews of Interventions and the risk of bias across studies with the GRADE approach described in the GRADE Handbook.

RESULTS

Thirty-eight studies were included in the systematic review and 34 in the meta-analysis. The overall quality of evidence was rated as low or very low according to GRADE criteria. Low-level laser therapy and ultrasound showed favourable results in improving symptom severity and functional status compared to manual therapy. In addition, the low level laser showed improvements in pinch strength compared to placebo and pain (VAS) compared to manual therapy. Splints showed superior results to electrophysical modalities. The clinical significance of the results was assessed by effect size estimation and comparison with the minimum clinically important difference (MCID).

CONCLUSIONS

We found favourable results in pain relief, improvement of symptoms, functional status, and neurophysiological parameters for some electrophysical modalities, mainly when applied with a splint. Our results coincide with those obtained in some meta-analyses. However, none of these can be considered clinically significant.

TRIAL REGISTRATION

PROSPERO registration number CRD42020168792; https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=168792.

Iatrogenic lesions of the peripheral nervous system in orthopaedic surgery and traumatology procedures

OBJECTIVE

To describe iatrogenic lesions of the peripheral nervous system and their relationship with different orthopaedic and traumatological procedures, through their assessment by means of electromyographic study.

MATERIAL AND METHODS

Retrospective descriptive study of the electromyographies performed in the clinical neurophysiology service of the Hospital General Universitari de Castelló between July 2015 and March 2019, recovering those in which the aetiology was diagnosed as iatrogenic in relation to surgical procedures and analysing those that were initiated after orthopaedic and traumatological procedures.

RESULTS

Of the total number of electromyographies reviewed, 1.37% corresponded to iatrogenic surgical lesions and 55.1% of these were secondary to orthopaedic surgery and traumatology procedures, the incidence in relation to the procedures performed was 0.65%. The most frequent locations related to injuries were the lumbar spine, hip and hand/wrist. Injuries due to postural causes not directly related to the surgical field are noteworthy.

CONCLUSION

Iatrogenic injuries to the peripheral nervous system after orthopaedic surgery and traumatology procedures are infrequent, but given their mechanism of injury and the high severity of most of them, it would be advisable to implement corrective mechanisms to reduce their incidence.

LEVEL OF EVIDENCE

IV.

Initial findings in traumatic peripheral nerve injury and repair with diffusion tensor imaging

OBJECTIVE

Management of peripheral nerve injuries requires physicians to rely on qualitative measures from patient history, electromyography, and physical exam. Determining a successful nerve repair can take months to years for proximal injuries, and the resulting delays in clinical decision-making can lead to a negative impact on patient outcomes. Early identification of a failed nerve repair could prevent permanent muscle atrophy and loss of function. This study aims to test the feasibility of performing diffusion tensor imaging (DTI) to evaluate injury and recovery following repair of wrist trauma. We hypothesize that DTI provides a noninvasive and reliable assessment of regeneration, which may improve clinical decision-making and alter the clinical course of surgical interventions.

METHODS

Clinical and MRI measurements from subjects with traumatic peripheral nerve injury, carpal tunnel syndrome, and healthy control subjects were compared to evaluate the relationship between DTI metrics and injury severity.

RESULTS

Fractional anisotropy from DTI was sensitive to differences between damaged and healthy nerves, damaged and compressed nerves, and injured and healthy contralateral nerves. Longitudinal measurements in two injury subjects also related to clinical outcomes. Implications of other diffusion measures are also discussed.

INTERPRETATION

DTI is a sensitive tool for wrist nerve injuries and can be utilized for monitoring nerve recovery. Across three subjects with nerve injuries, this study has shown how DTI can detect abnormalities between injured and healthy nerves, measure recovery, and determine if re-operation was successful. Additional comparisons to carpal tunnel syndrome and healthy nerves show that DTI is sensitive to the degree of impairment.

Impairment of accessory nerves around major pelvic ganglion leading to overflow urinary incontinence in rats

AIMS

To investigate the relationship between lower urinary tract function and the accessory nerve (ACN) arising from the major pelvic ganglion (MPG).

METHODS

Ten-week-old male Wistar/ST rats were randomly divided into eight groups according to the type of treatment (sham or bilateral accessory nerve injury [BACNI]) and the duration of observation (3 days, 1 week, 2 weeks, or 4 weeks: Sham-3d, Sham-1w, Sham-2w, Sham-4w, BACNI-3d, BACNI-1w, BACNI-2ws, and BACNI-4w. BACNI was induced in the following manner: the ACN was crushed for 1 min (2 mm away from the MPG) using reverse-action tweezers. The same procedure was performed on both sides. On the last day of each observation period, the bladder function was measured by awake cystometry, and histological evaluation was performed.

RESULTS

All rats in the Sham groups micturated normally. In the BACNI-3d and BACNI-1w groups, all rats showed symptoms of overflow urinary incontinence (OUI). This OUI improved gradually over time. The bladder's size in the BACNI group was significantly larger than that in the Sham group (p < .01). In addition, fibrosis was observed in the subserosa of the bladder of rats in BACNI groups.

CONCLUSION

The BACNI model rats exhibited OUI, suggesting that ACN is involved in the lower urinary tract function. It might be possible that ACN controls the function of either the bladder, the urethra, or both.

Mesenchymal stem cell treatment for peripheral nerve injury: a narrative review

Peripheral nerve injuries occur as the result of sudden trauma and lead to reduced quality of life. The peripheral nervous system has an inherent capability to regenerate axons. However, peripheral nerve regeneration following injury is generally slow and incomplete that results in poor functional outcomes such as muscle atrophy. Although conventional surgical procedures for peripheral nerve injuries present many benefits, there are still several limitations including scarring, difficult accessibility to donor nerve, neuroma formation and a need to sacrifice the autologous nerve. For many years, other therapeutic approaches for peripheral nerve injuries have been explored, the most notable being the replacement of Schwann cells, the glial cells responsible for clearing out debris from the site of injury. Introducing cultured Schwann cells to the injured sites showed great benefits in promoting axonal regeneration and functional recovery. However, there are limited sources of Schwann cells for extraction and difficulties in culturing Schwann cells in vitro. Therefore, novel therapeutic avenues that offer maximum benefits for the treatment of peripheral nerve injuries should be investigated. This review focused on strategies using mesenchymal stem cells to promote peripheral nerve regeneration including exosomes of mesenchymal stem cells, nerve engineering using the nerve guidance conduits containing mesenchymal stem cells, and genetically engineered mesenchymal stem cells. We present the current progress of mesenchymal stem cell treatment of peripheral nerve injuries.

Recent update on craniofacial tissue engineering

The craniofacial region consists of several different tissue types. These tissues are quite commonly affected by traumatic/pathologic tissue loss which has so far been traditionally treated by grafting procedures. With the complications and drawbacks of grafting procedures, the emerging field of regenerative medicine has proved potential. Tissue engineering advancements and the application in the craniofacial region is quickly gaining momentum although most research is still at early in vitro/in vivo stages. We aim to provide an overview on where research stands now in tissue engineering of craniofacial tissue; namely bone, cartilage muscle, skin, periodontal ligament, and mucosa. Abstracts and full-text English articles discussing techniques used for tissue engineering/regeneration of these tissue types were summarized in this article. The future perspectives and how current technological advancements and different material applications are enhancing tissue engineering procedures are also highlighted. Clinically, patients with craniofacial defects need hybrid reconstruction techniques to overcome the complexity of these defects. Cost-effectiveness and cost-efficiency are also required in such defects. The results of the studies covered in this review confirm the potential of craniofacial tissue engineering strategies as an alternative to avoid the problems of currently employed techniques. Furthermore, 3D printing advances may allow for fabrication of patient-specific tissue engineered constructs which should improve post-operative esthetic results of reconstruction. There are on the other hand still many challenges that clearly require further research in order to catch up with engineering of other parts of the human body.

Methylene blue enhances polyethylene glycol-fusion repair of completely severed rat sciatic nerves

Complete transection of peripheral mixed nerves immediately produces loss of sensory perception, muscle contractions and voluntary behavior mediated by the severed distal axons. In contrast to natural regeneration (~1 mm/d) of proximal axons that may eventually reinnervate denervated targets, re-innervation is restored within minutes by PEG-fusion that consists of neurorrhaphy and a sequence of well specified hypo- and isotonic calcium-free or calcium-containing solutions, the anti-oxidant methylene blue (MB) and the membrane fusogen polyethylene glycol (PEG). In this study, we examined the relative efficacy of PEG-fusion with no MB (0%), 0.5% MB, or 1% MB on the recovery of voluntary behaviors by female Sprague-Dawley rats with a complete mid-thigh severance of their sciatic nerve bathed in extracellular fluid or calcium-containing isotonic saline. The recovery of voluntary behaviors is the most relevant measure of success of any technique to repair peripheral nerve injuries. We assessed recovery by the sciatic functional index, a commonly used measure of voluntary hindlimb behaviors following complete sciatic transections. We reported that both 1% MB and 0.5% MB in sterile distilled water in our PEG-fusion protocol with neurorrhaphy significantly increased the rate and extent of behavioral recovery compared to PEG plus neurorrhaphy alone. Furthermore, 0.5% MB was as effective as 1% MB in voluntary behavioral recovery as assessed by the sciatic functional index. Since sterile 1% MB is no longer clinically available, we therefore recommend that 0.5% MB be included in upcoming human clinical trials to evaluate the safety and efficacy of PEG-fusion. All animal procedures were approved by the University of Texas Institutional Animal Care and Use Committee (AUP-2019-00225) on September 9, 2020.

A novel nerve transection and repair method in mice: histomorphometric analysis of nerves, blood vessels, and muscles with functional recovery

Peripheral nerve transection is associated with permanent functional deficit even after advanced microsurgical repair. While it is difficult to investigate the reasons of poor functional outcomes of microsurgical repairs in humans, we developed a novel pre-clinical nerve transection method that allows reliable evaluation of nerve regeneration, neural angiogenesis, muscle atrophy, and functional recovery. Adult male C57BL/6 mice were randomly assigned to four different types of sciatic nerve transection: Simple Transection (ST), Simple Transection & Glue (TG), Stepwise Transection and Sutures (SU), and Stepwise Transection and Glue (STG). Mice were followed for 28 days for sciatic function index (SFI), and sciatic nerves and hind limb muscles were harvested for histomorphological and cellular analyses. Immunohistochemistry revealed more directional nerve fiber growth in SU and STG groups compared with ST and TG groups. Compared to ST and TG groups, optimal neural vessel density and branching index in SU and STG groups were associated with significantly decreased muscle atrophy, increased myofiber diameter, and improved SFI. In conclusion, our novel STG method represents an easily reproducible and reliable model with close resemblance to the pathophysiological characteristics of SU model, and this can be easily reproduced by any lab.

Polyethylene Glycol Fusion of Nerve Injuries: Review of the Technique and Clinical Applicability

Traumatic peripheral nerve injuries present a particular challenge to hand surgeons as mechanisms of nerve-healing pose serious limitations to achieving complete functional recovery. The loss of distal axonal segments through Wallerian degeneration results in the loss of neuromuscular junctions and irreversible muscle atrophy. Current methods of repair depend on the outgrowth of proximal nerve fibers following direct end-to-end repair or gap repair techniques. Investigational techniques in nerve repair using polyethylene glycol (PEG) nerve fusion have been shown to bypass Wallerian degeneration by immediately restoring nerve axonal continuity, thus resulting in a rapid and more complete functional recovery. The purpose of this article is to review the current literature surrounding this novel technique for traumatic nerve repair, paying particular attention to the underlying physiology of nerve healing and the current applications of PEG fusion in the laboratory and clinical setting. This article also serves to identify areas of future investigation to further establish validity and feasibility and encourage the translation of PEG fusion into clinical use.

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.

Characteristics of cytokines in the sciatic nerve stumps and DRGs after rat sciatic nerve crush injury

BACKGROUND

Cytokines are essential cellular modulators of various physiological and pathological activities, including peripheral nerve repair and regeneration. However, the molecular changes of these cellular mediators after peripheral nerve injury are still unclear. This study aimed to identify cytokines critical for the regenerative process of injured peripheral nerves.

METHODS

The sequencing data of the injured nerve stumps and the dorsal root ganglia (DRGs) of Sprague-Dawley (SD) rats subjected to sciatic nerve (SN) crush injury were analyzed to determine the expression patterns of genes coding for cytokines. PCR was used to validate the accuracy of the sequencing data.

RESULTS

A total of 46, 52, and 54 upstream cytokines were differentially expressed in the SNs at 1 day, 4 days, and 7 days after nerve injury. A total of 25, 28, and 34 upstream cytokines were differentially expressed in the DRGs at these time points. The expression patterns of some essential upstream cytokines are displayed in a heatmap and were validated by PCR. Bioinformatic analysis of these differentially expressed upstream cytokines after nerve injury demonstrated that inflammatory and immune responses were significantly involved.

CONCLUSIONS

In summary, these findings provide an overview of the dynamic changes in cytokines in the SNs and DRGs at different time points after nerve crush injury in rats, elucidate the biological processes of differentially expressed cytokines, especially the important roles in inflammatory and immune responses after peripheral nerve injury, and thus might contribute to the identification of potential treatments for peripheral nerve repair and regeneration.

Recovery of sciatic nerve with complete transection in rats treated with leuprolide acetate: A gonadotropin-releasing hormone agonist

It has been reported that the Gonadotropin-releasing hormone (GnRH) and its agonist leuprolide acetate (LA) can act as promoters of nerve regeneration. The aim of this study is to evaluate the effect of LA in a complete transection model. Sciatic nerve injury (SNI) was performed using a complete nerve transection and immediately repaired by epineural sutures. Rats were divided into three groups: SHAM, SNI treated with LA (SNI + LA) or saline solution (SNI + SS) for 5 weeks. Sciatic nerve regeneration was evaluated by kinematic gait analyzes, electrophysiological, morphological and biochemical tests. SNI + LA group had a functional recovery in kinematic gait, an increase in ankle angle value and a faster walking speed, compound muscle action potential amplitude, nerve conduction velocity (NCV). Furthermore, the number of myelinated axons and microtubule-associated protein 2 (MAP-2) expression were also higher compared to SS group. In conclusion, LA treatment improves of gait, walking speed, NCV, axons morphometry and MAP-2 expression in rats with sciatic nerve complete transection. These results suggest that LA can be a potential treatment for peripheral nerve injuries.

Regeneration of Rat Sciatic Nerve Using PLGA Conduit Containing Rat ADSCs with Controlled Release of BDNF and Gold Nanoparticles

Implantation of a nerve guidance conduit (NGC) carrying neuroprotective factors is promising for repairing peripheral nerve injury. Here, we developed a novel strategy for repairing peripheral nerve injury by gold nanoparticles (AuNPs) and brain-derived neurotrophic factor (BDNF)-encapsulated chitosan in laminin-coated nanofiber of Poly(l-lactide-co-glycolide) (PLGA) conduit and transplantation of rat adipose-derived stem cells (r-ADSCs) suspended in alginate. Then, the beneficial effect of AuNPs, BDNF, and r-ADSCs on nerve regeneration was evaluated in rat sciatic nerve transection model. In vivo experiments showed that the combination of AuNPs- and BDNF-encapsulated chitosan nanoparticles in laminin-coated nanofiber of PLGA conduit with r-ADSCs could synergistically facilitate nerve regeneration. Furthermore, the in vivo histology, immunohistochemistry, and behavioral results demonstrated that the AuNPs- and BDNF-encapsulated chitosan nanoparticles in NGC could significantly reinforce the repair performance of r-ADSCs, which may also contribute to the therapeutic outcome of the AuNPs, BDNF, and r-ADSCs strategies. In this study, we found that the combination of AuNPs and BDNF releases in NGC with r-ADSCs may represent a new potential strategy for peripheral nerve regeneration.

Coding transcriptome analyses reveal altered functions underlying immunotolerance of PEG-fused rat sciatic nerve allografts

BACKGROUND

Current methods to repair ablation-type peripheral nerve injuries (PNIs) using peripheral nerve allografts (PNAs) often result in poor functional recovery due to immunological rejection as well as to slow and inaccurate outgrowth of regenerating axonal sprouts. In contrast, ablation-type PNIs repaired by PNAs, using a multistep protocol in which one step employs the membrane fusogen polyethylene glycol (PEG), permanently restore sciatic-mediated behaviors within weeks. Axons and cells within PEG-fused PNAs remain viable, even though outbred host and donor tissues are neither immunosuppressed nor tissue matched. PEG-fused PNAs exhibit significantly reduced T cell and macrophage infiltration, expression of major histocompatibility complex I/II and consistently low apoptosis. In this study, we analyzed the coding transcriptome of PEG-fused PNAs to examine possible mechanisms underlying immunosuppression.

METHODS

Ablation-type sciatic PNIs in adult Sprague-Dawley rats were repaired using PNAs and a PEG-fusion protocol combined with neurorrhaphy. Electrophysiological and behavioral tests confirmed successful PEG-fusion of PNAs. RNA sequencing analyzed differential expression profiles of protein-coding genes between PEG-fused PNAs and negative control PNAs (not treated with PEG) at 14 days PO, along with unoperated control nerves. Sequencing results were validated by quantitative reverse transcription PCR (RT-qPCR), and in some cases, immunohistochemistry.

RESULTS

PEG-fused PNAs display significant downregulation of many gene transcripts associated with innate and adaptive allorejection responses. Schwann cell-associated transcripts are often upregulated, and cellular processes such as extracellular matrix remodeling and cell/tissue development are particularly enriched. Transcripts encoding several potentially immunosuppressive proteins (e.g., thrombospondins 1 and 2) also are upregulated in PEG-fused PNAs.

CONCLUSIONS

This study is the first to characterize the coding transcriptome of PEG-fused PNAs and to identify possible links between alterations of the extracellular matrix and suppression of the allorejection response. The results establish an initial molecular basis to understand mechanisms underlying PEG-mediated immunosuppression.

A tissue engineering approach for repairing craniofacial volumetric muscle loss in a sheep following a 2, 4, and 6-month recovery

Volumetric muscle loss (VML) is the loss of skeletal muscle that results in significant and persistent impairment of function. The unique characteristics of craniofacial muscle compared trunk and limb skeletal muscle, including differences in gene expression, satellite cell phenotype, and regenerative capacity, suggest that VML injuries may affect craniofacial muscle more severely. However, despite these notable differences, there are currently no animal models of craniofacial VML. In a previous sheep hindlimb VML study, we showed that our lab’s tissue engineered skeletal muscle units (SMUs) were able to restore muscle force production to a level that was statistically indistinguishable from the uninjured contralateral muscle. Thus, the goals of this study were to: 1) develop a model of craniofacial VML in a large animal model and 2) to evaluate the efficacy of our SMUs in repairing a 30% VML in the ovine zygomaticus major muscle. Overall, there was no significant difference in functional recovery between the SMU-treated group and the unrepaired control. Despite the use of the same injury and repair model used in our previous study, results showed differences in pathophysiology between craniofacial and hindlimb VML. Specifically, the craniofacial model was affected by concomitant denervation and ischemia injuries that were not exhibited in the hindlimb model. While clinically realistic, the additional ischemia and denervation likely created an injury that was too severe for our SMUs to repair. This study highlights the importance of balancing the use of a clinically realistic model while also maintaining control over variables related to the severity of the injury. These variables include the volume of muscle removed, the location of the VML injury, and the geometry of the injury, as these affect both the muscle’s ability to self-regenerate as well as the probability of success of the treatment.

Anisotropically Conductive Biodegradable Scaffold with Coaxially Aligned Carbon Nanotubes for Directional Regeneration of Peripheral Nerves

Fascicular rearrangement of an injured peripheral nerve requires reconnection of nerve sprouts from anterior and Büngner bands from distal sides of the lesion, failing to which leads to inefficient regeneration of the injured nerve. However, existing neural scaffolds have limited neuroregeneration efficiency because of either the lack of alignment of fibers and a conductive second phase, leading to compromised electrical conductivity, or the lack of extracellular matrix components and in vivo validation. The present study reports a biocompatible, multiwall carbon nanotube (MWCNT)-reinforced, anisotropically conductive, electrospun, aligned nanofibrous scaffold, ensuring maximal peripheral nerve regeneration. Electrospinning parameters were modulated to deposit random and parallel fibers in separate scaffolds for comparative analysis on the effect of fiber alignment on regeneration. Both types of scaffolds were reinforced with MWCNTs to impart electrical conductivity. Nonreinforced scaffolds were nonconductive. In this comparative study, MWCNT-reinforced, aligned scaffolds showed better tensile property with increased conductivity along the direction of alignment, thereby ensuring an escalated neural-regeneration rate. Collectively, in vitro studies established the scaffolds to be highly biocompatible, promoting cell growth and proliferation. With 85% more anisotropic conductivity in the direction of the alignment and the degradation kinetics tuned to the regeneration regime, the MWCNT-reinforced, aligned scaffold efficiently healed injured sciatic nerves in rats within 30 days. Rigorous revivification of the tissue was due to coordinated Wallerian degeneration and expedited guided axonal regeneration. Structural and functional analysis of nerves in vivo showed the aligned, MWCNT-reinforced scaffold to be very efficient in peripheral sciatic nerve regeneration. This study notes the efficacy of the coaxially aligned, MWCNT-reinforced neural scaffold, with a capability of establishing remarkable advancement in the field of peripheral neural regeneration.

Polyethylene glycol-fusion repair of sciatic allografts in female rats achieves immunotolerance via attenuated innate and adaptive responses

Ablation/segmental loss peripheral nerve injuries (PNIs) exhibit poor functional recovery due to slow and inaccurate outgrowth of regenerating axons. Viable peripheral nerve allografts (PNAs) as growth-guide conduits are immunologically rejected and all anucleated donor/host axonal segments undergo Wallerian degeneration. In contrast, we report that ablation-type sciatic PNIs repaired by neurorrhaphy of viable sciatic PNAs and a polyethylene glycol (PEG)-fusion protocol using PEG immediately restored axonal continuity for many axons, reinnervated/maintained their neuromuscular junctions, and prevented much Wallerian degeneration. PEG-fused PNAs permanently restored many sciatic-mediated behaviors within 2-6 weeks. PEG-fused PNAs were not rejected even though host/donors were neither immunosuppressed nor tissue-matched in outbred female Sprague Dawley rats. Innate and adaptive immune responses to PEG-fused sciatic PNAs were analyzed using electron microscopy, immunohistochemistry, and quantitative reverse transcription polymerase chain reaction for morphological features, T cell and macrophage infiltration, major histocompatibility complex (MHC) expression, apoptosis, expression of cytokines, chemokines, and cytotoxic effectors. PEG-fused PNAs exhibited attenuated innate and adaptive immune responses by 14-21 days postoperatively, as evidenced by (a) many axons and cells remaining viable, (b) significantly reduced infiltration of cytotoxic and total T cells and macrophages, (c) significantly reduced expression of inflammatory cytokines, chemokines, and MHC proteins, (d) consistently low apoptotic response. Morphologically and/or biochemically, PEG-fused sciatic PNAs often resembled sciatic autografts or intact sciatic nerves. In brief, PEG-fused PNAs are an unstudied, perhaps unique, example of immune tolerance of viable allograft tissue in a nonimmune-privileged environment and could greatly improve the clinical outcomes for PNIs relative to current protocols.

Chronic neuropathic pain after traumatic peripheral nerve injuries in the upper extremity: prevalence, demographic and surgical determinants, impact on health and on pain medication

Background and aims Aside from the long term side effects of a nerve injury in the upper extremity with devastating consequences there is often the problem of chronic neuropathic pain. The studies concerning the prevalence of persistent pain of neuropathic origin after peripheral nerve injuries are sparse. The prevalence and risk factors associated with chronic neuropathic pain after nerve injuries in the upper extremity were assessed. Methods A standardized data collection template was employed prospectively and retrospectively for all patients with traumatic nerve injuries accepted at the Hand Surgery Department, Uppsala, Sweden between 2010 and 2018. The template included demographic data, pain diagnosis, type of injured nerve, level of injury, date of the lesion and repair, type of procedure, reoperation, time since the procedure, S-LANSS questionnaire (Self report-Leeds Assessment of Neuropathic Symptoms and Signs), RAND-36 (Item short form health survey), QuickDASH (Disability of Shoulder, Arm and Hand) and additional questionnaires concerned medication, pain intensity were sent to 1,051 patients with nerve injuries. Partial proportional odds models were used to investigate the association between persistent pain and potential predictors. Results More than half of the patients undergoing a surgical procedure developed persistent pain. Prevalence of neuropathic pain was 73% of the patients with pain (S-LANSS ≥ 12 or more). Multivariate analysis indicated that injury of a major nerve OR 1.6 (p = 0.013), years from surgery OR 0.91 (p = 0.01), younger age OR 0.7 (p < 0.001), were the main factors for predicting pain after surgery. The type of the nerve injured was the strongest predictor for chronic pain with major nerves associated with more pain (p = 0.019). Conclusions A high prevalence of chronic pain and neuropathic pain with a negative impact on quality of life and disability were found in patients after traumatic nerve injury. Major nerve injury, younger age and less time from surgery were predictors for chronic pain.

Protein phosphorylation profiling of peripheral nerve regeneration after autologous nerve grafting

Autologous nerve grafting is the golden standard therapeutic approach of peripheral nerve injury. However, the clinical effect of autologous nerve grafting is still unsatisfying. To achieve better clinical functional recovery, it is of an impending need to expand our understanding of the dynamic cellular and molecular changes after nerve transection and autologous nerve transplantation. To address this aim, in the current study, rats were subjected to sciatic nerve transection and autologous nerve grafting. Rat sciatic nerve segments were collected at 4, 7, and 14 days after surgery and subjected to antibody array analysis to determine phosphoprotein profiling patterns. Compared with rats that underwent sham surgery, a total of 48, 19, and 75 differentially expressed phosphoproteins with fold changes > 2 or < -2 were identified at 4, 7, and 14 days after autologous nerve grafting, respectively. Several phosphoproteins, including STAM2 (Phospho-Tyr192) and Tau (Phospho-Ser422), were found to be differentially expressed at multiple time points, suggesting the importance of the phosphorylation of these proteins. Western blot validation of the expression patterns of STAM2 (Phospho-Tyr192) indicated the accuracy of antibody array assay. Bioinformatic analysis of these differentially expressed proteins suggested that cellular behavior and organ morphology were significantly involved biological functions while cell behavior and immune response-related signaling pathways were significantly involved canonical signaling pathways. These outcomes contributed to the illumination of the molecular mechanisms underlying autologous nerve grafting from the phosphoprotein profiling perspective.

Quantitative Assessment of Traumatic Upper-Limb Peripheral Nerve Injuries Using Surface Electromyography

Background

There is a great demand for convenient and quantitative assessment of upper-limb traumatic peripheral nerve injuries (PNIs) beyond their clinical routine. This would contribute to improved PNI management and rehabilitation.

Objective

The aim of this study was to develop a novel surface EMG examination method for quantitatively evaluating traumatic upper-limb PNIs.

Methods

Experiments were conducted to collect surface EMG data from forearm muscles on both sides of seven male subjects during their performance of eight designated hand and wrist motion tasks. All participants were clinically diagnosed as unilateral traumatic upper-limb PNIs on the ulnar nerve, median nerve, or radial nerve. Ten healthy control participants were also enrolled in the study. A novel framework consisting of two modules was also proposed for data analysis. One module was first used to identify whether a PNI occurs on a tested forearm using a machine learning algorithm by extracting and classifying features from surface EMG data. The second module was then used to quantitatively evaluate the degree of injury on three individual nerves on the examined arm.

Results

The evaluation scores yielded by the proposed method were highly consistent with the clinical assessment decisions for three nerves of all 34 examined arms (7 × 2 + 10 × 2), with a sensitivity of 81.82%, specificity of 98.90%, and significate linear correlation (p < 0.05) in quantitative decision points between the proposed method and the routine clinical approach.

Conclusion

This study offers a useful tool for PNI assessment and helps to promote extensive clinical applications of surface EMG.

Controlling the Release of Neurotrophin-3 and Chondroitinase ABC Enhances the Efficacy of Nerve Guidance Conduits

Nerve guidance conduits (NGCs) have the potential to replace autografts in repairing peripheral nerve injuries, but their efficacy still needs to be improved. The efficacy of NGCs is augmented by neurotrophic factors that promote axon growth and by enzymes capable of degrading molecules that inhibit axon growth. In the current study, two types of NGCs loaded with factors (both neurotrophin-3 and chondroitinase ABC) are constructed and their abilities to repair an 8 mm gap in the rat sciatic nerve are examined. The factors are encapsulated in microparticles made of a phase-change material (PCM) or collagen and then sandwiched between two layers of electrospun fibers. The use of PCM allows to achieve pulsed release of the factors upon irradiation with a near-infrared laser. The use of collagen enables slow, continuous release via diffusion. The efficacy is evaluated by measuring compound muscle action potentials (CMAP) in the gastrocnemius muscle and analyzing the nerve histology. Continuous release of the factors from collagen results in enhanced CMAP amplitude and increased axon counts in the distal nerve relative to the plain conduit. In contrast, pulsed release of the same factors from PCM shows a markedly adverse impact on the efficacy, possibly by inhibiting axon growth.

Ultrasound Stimulation Increases Neurite Regeneration in Injured Dorsal Root Ganglion Neurons through Mammalian Target of Rapamycin Activation

Ultrasound stimulation (US) is reported to be a safe and useful technology for improving injured nerve regeneration. However, the intracellular mechanisms underlying its stimulatory effects are only partially understood. Mammalian target of rapamycin (mTOR) signaling is involved in neuronal survival and axonal outgrowth. In this study, we investigated the effect of US on regeneration of injured dorsal root ganglion (DRG) neurons and activation of the mTOR pathway. We showed that US significantly increased neurite regeneration and enhanced mTOR activation. Moreover, the expression of growth-associated protein-43 (GAP-43), a crucial factor for axonal outgrowth and regeneration in neurons, was significantly increased by US. These data suggest that US-induced neurite regeneration is mediated by upregulation of mTOR activity, which promotes the regeneration of injured DRG neurons.

Perioperative Automated Noninvasive Blood Pressure- (NIBP-) Related Peripheral Nerve Injuries: An Anesthetist's Dilemma-A Case Report and Review of the Literature

Peripheral nerve injury following regional or general anesthesia is a relatively uncommon entity but, potentially, a serious complication of anesthesia. Most nerve injuries are related to either regional anesthesia or position-related complications, and they are rarely seen in association with the use of automated blood pressure monitoring. We describe a patient who developed neurological dysfunction of all the three major nerves, median, ulnar, and radial, after general anesthesia. The distribution of sensory motor deficit along with the nerve conduction study demonstrated the location of the anatomical nerve lesions coinciding with the automatic noninvasive blood pressure (NIBP) cuff. No other cause of nerve injury was identified except for the use of the NIBP cuff. In the absence of another identifiable cause, we strongly suspected the NIBP cuff compression as a possible cause for the nerve injuries. In this article, we will discuss the possible risk factors, mechanisms, diagnosis, and prevention of perioperative nerve injury.