Pathophysiology of peripheral nerve injury: a brief review

Conductive hydrogel luminal filler for peripheral nerve regeneration

Peripheral nerve injuries impair quality of life due to pain and loss of sensory and motor functions. Current treatments like autografts and nerve guidance conduits (NGCs) have limitations in functional restoration. Luminal fillers can enhance the effectiveness of NGCs by providing beneficial intraneural environments. In this study, we devised a novel injectable conductive luminal filler that allows for electrically active environments and efficient electrical stimulation of nerves. We developed injectable conductive hydrogel as a luminal filler for NGCs, composed of pluronic-coated reduced graphene oxide (rGO) and gelatin-based polymers, that gels spontaneously under physiological conditions. This filler combines nerve-like softness (0.31 ± 0.02 kPa), appropriate conductivity (2.7 ± 0.3 mS/cm), quick gelation (<5 min), and in vivo degradability. In a rat peripheral nerve defect model, the conductive hydrogel filler with electrical stimulation showed promising results in nerve regrowth, myelination, and functional recovery, performing comparably to autografts. This study underscores the potential of conductive fillers in enhancing nerve regeneration therapies.

Neuralgic amyotrophy: An update in evaluation, diagnosis, and treatment approaches

Neuralgic amyotrophy (NA) is an underrecognized peripheral nerve disorder distinguished by severe pain followed by weakness in the distribution of one or more nerves, most commonly in the upper extremity. While classically felt to carry a favorable prognosis, updates in research have demonstrated that patients frequently endure delay in diagnosis and continue to experience long term pain, paresis, and fatigue even years after the diagnosis is made. A transition in therapeutic approach is recommended and described by this review, which emphasizes the necessity to target compensatory abnormal motor control and fatigue by focusing on motor coordination, energy conservation strategies, and behavioral change, rather than strength training which may worsen the symptoms. The development of structural hourglass-like constrictions (HGCs) on imaging can help confirm the suspected clinical diagnosis, and in association with persistent weakness and limited recovery on electrodiagnostic testing may be considered for surgical consultation. Given the complex nature of management, a multidisciplinary approach is described, which can provide an optimal level of care and support for patients with persistent symptoms from NA and allow more unified guidance of rehabilitation and surgical referrals.

An overview of the non-procedural treatment options for peripheral neuropathic pain

Peripheral neuropathic pain is common in patients with peripheral nerve injury and can significantly impact both their function and quality of life. There is a wide variety of non-interventional treatment approaches, including pharmacologic therapy, physical/occupational therapy, modalities (therapeutic, mechanical, thermal, etc.), psychology, and lifestyle modification. First line pharmacologic therapy for peripheral neuropathic pain includes gabapentinoids, tricyclic antidepressants, and serotonin-norepinephrine reuptake inhibitors. Other classes of medications, such as topical treatments, opioids, and cannabinoids, have more limited usefulness in treatment but remain part of a treatment regimen. Physical and occupational therapy, psychological interventions, and lifestyle medicine are important adjuncts in the treatment and prevention of future peripheral neuropathic pain. The strength of the evidence supporting each intervention varies, with that for pharmacologic intervention being the strongest. A combination of these options tailored to the individual needs of the patient likely will result in the best treatment outcome for peripheral neuropathic pain.

Surgical Strategies for Functional Upper Extremity Reconstruction After Spinal Cord Injury

Spinal cord injuries (SCI) can substantially affect independence and quality of life, particularly by limiting upper extremity function. Surgical reconstruction offers the potential to restore motion in the hand, wrist, and elbow for those with deficits following cervical spinal cord injury. Techniques such as tendon transfer, tenodesis, and arthrodesis-often used in combination-are well-established strategies for enhancing upper extremity function. Nerve transfers have more recently been employed and differ from other procedures in that they are often time sensitive and should be performed before permanent muscle atrophy occurs. A comprehensive preoperative evaluation, including clinical examination and electrodiagnostic assessment, is essential to determine the availability and strength of donor tendons and nerves. The International Classification of Surgery for the Hand in Tetraplegia (ICSHT) system is the most utilized surgical classification for determining muscle that can be used for reconstruction. Based on this classification, prioritization is given to restoring elbow extension, wrist extension, pinch, and grasp. Postoperative rehabilitative therapy balances the need for immobilization while preventing joint stiffness and may also incorporate cortical retraining strategies to activate tendon and nerve transfers. Ultimately, a collaborative, interdisciplinary approach is essential for assessing the injury, determining operative candidacy, selecting the optimal treatment strategy, and providing tailored rehabilitation. This article explores the classification of SCI as it pertains to the upper limb, provides an overview of surgical options, describes the preoperative clinical and electrodiagnostic evaluation process, and discusses reconstructive strategies aimed at improving functional outcomes in individuals with SCI.

Clinical evaluation of a novel disposable neurostimulator used to accelerate regeneration of injured peripheral nerves in the hand

BACKGROUND

Preclinical and early clinical evidence demonstrates that electrical stimulation (ES) applied for one hour following surgical nerve intervention enhances axonal regeneration and functional outcomes. Wide clinical implementation however, has been hindered by a lack of suitably designed stimulators. The aim of this pilot study was to investigate sensory recovery, safety, tolerability, and RCT feasibility for the use of a novel single-use stimulator to deliver ES therapy in an acute nerve transection cohort.

METHODS

Patients with complete transection of a proper digital nerve were included in the trial. An investigational version of PeriPulseTM was used with intraoperative electrode implantation and 1-hour ES therapy delivered postoperatively. Patient tolerance was assessed during stimulation and visual-analogue pain scores were collected at the first post-operative visit. At 3- and 6-months post-op, sensory recovery and quality of life were assessed using 2-point discrimination, monofilament tests, and the Disability of Arm, Shoulder, and Hand (DASH) questionnaire, respectively.

RESULTS

A total of 10 patients were enrolled. Intraoperative electrode placement did not impact operating room time, taking less than 5 minutes to implement. There were no related adverse events. Participants reported tolerable stimulation during ES therapy with no reports of pain. At the first post-operative visit patients had a mean visual-analogue pain score of 0.6 (range 0 - 1.9). Pressure threshold detection significantly improved between baseline, 3 months and 6 months. A greater proportion of ES treated patients (87.5%) had improved hand pressure thresholds (diminished light touch or diminished protective sensation) at 6 months compared to a historical comparator group. DASH scores improved over the timeline. Participants treated with ES therapy experienced minimal postoperative functional disability.

CONCLUSIONS

The use of the PeriPulseTM prototype for the delivery of perioperative ES therapy was safe, well-tolerated, and usable. Sensory recovery was demonstrated and a larger RCT is feasible.

TRIAL REGISTRATION

 NCT04732936; 2021 - 01 - 29.

Established and emerging roles of protein kinases in regulating primary sensory neurons in injury-and inflammation-associated pain

INTRODUCTION

Recent seminal neuroscience research has significantly increased our knowledge on cellular and molecular responses of various cells in the pain pathway to peripheral nerve injuries and inflammatory processes. Transcriptomic and epigenetic analysis of primary sensory neurons (PSNs) in animal models of peripheral injuries revealed new insights into altered gene expression profiles and epigenetic modifications, which, via increasing spinal nociceptive input, lead to the development of pain. Among the various classes of molecules involved in driving differential gene expression, protein kinases, the enzymes that catalyze the phosphorylation of molecules, are emerging to control histone modification and chromatin remodeling needed for the alteration in transcriptional activity.

AREAS COVERED

Here, we focused on how protein kinases contribute to transcriptomic changes and pathways of induced reprogramming within PSNs upon peripheral nerve injury and inflammation. We conducted systematic literature search across multiple databases, including PubMed, NIH ClinicalTrials.gov portal and GEOData from 1980 to 2024 and compared protein kinase expression frequencies between publicly available RNA sequencing datasets of PSNs and investigated differences in protein kinase expression levels after peripheral nerve injury.

EXPERT OPINION

Novel findings support a new concept that protein kinases constitute regulatory hubs of reprogramming of PSNs, which offers novel analgesic approaches.

Basic Pathological Mechanisms in Peripheral Nerve Diseases

Pathological changes and the cellular and molecular mechanisms underlying axonopathy and myelinopathy are key to understanding a wide range of inherited and acquired peripheral nerve disorders. While the clinical indications for nerve biopsy have diminished over time, its diagnostic value remains significant in select conditions, offering a unique window into the pathophysiological processes of peripheral neuropathies. Evidence highlights the symbiotic relationship between axons and myelinating Schwann cells, wherein disruptions in axo-glial interactions contribute to neuropathogenesis. This review synthesizes recent insights into the pathological and molecular underpinnings of axonopathy and myelinopathy. Axonopathy encompasses Wallerian degeneration, axonal atrophy, and dystrophy. Although extensively studied in traumatic nerve injury, the mechanisms of axonal degeneration and Schwann cell-mediated repair are increasingly recognized as pivotal in non-traumatic disorders, including dying-back neuropathies. We briefly outline key transcription factors, signaling pathways, and epigenetic changes driving axonal regeneration. For myelinopathy, we discuss primary segmental demyelination and dysmyelination, characterized by defective myelin development. We describe paranodal demyelination in light of recent findings in nodopathies, emphasizing that it is not an exclusive indicator of demyelinating disorders. This comprehensive review provides a framework to enhance our understanding of peripheral nerve pathology and its implications for developing targeted therapies.

Nerve Recovery in Pediatric Supracondylar Humeral Fractures: Assessing the Impact of Time to Surgery

BACKGROUND

Nerve injuries in pediatric supracondylar humeral (SCH) fractures occur in 2% to 35% of patients. Previous research has suggested that isolated anterior interosseous nerve injuries are not influenced by the time to surgery; however, little is known about other nerve injuries or mixed, motor, and sensory injuries. With this study, we aimed to examine the impact of time to surgery on nerve recovery in patients with traumatic nerve injuries associated with SCH fractures.

METHODS

Patients <18 years of age with SCH fractures stabilized using percutaneous pins during the period of January 2009 to June 2022 were retrospectively reviewed. Patients presenting with any traumatic nerve injury noted preoperatively were included, while those with iatrogenic or postoperative nerve injuries and incomplete documentation were excluded. Demographic data, injury characteristics, time to surgery, and number of days to nerve recovery were collected. Comparisons of nerve recovery time by anatomic distribution and functional deficit using an 8-hour time-to-surgery cutoff were made in bivariate and multivariate analyses.

RESULTS

A total of 2,753 patients with SCH fractures were identified, with 214 of the patients having an associated nerve injury. Documentation of nerve recovery was available for 197 patients (180 patients with complete recovery) with an overall mean age of 6.8 ± 2.1 years. Time to recovery differed significantly when comparing the motor, sensory, and mixed-deficit cohorts (p < 0.001). Early surgery (≤8 hours from injury to surgery) was significantly associated with shorter overall time to nerve recovery (p = 0.002), recovery of multiple nerve distributions (p = 0.011), and recovery of mixed motor and sensory deficits (p = 0.007). On multivariable analysis, mixed nerve deficits (hazard ratio [HR], 0.537 [95% CI, 0.396 to 0.728]; p < 0.001) and time from injury to treatment of >8 hours (HR, 0.542 [95% CI, 0.373 to 0.786]; p = 0.001) were significantly associated with delayed nerve recovery.

CONCLUSIONS

Surgical timing impacts the time to recovery of complex nerve injuries. Early surgical management of patients with mixed motor-sensory deficits may help to reduce the time to complete nerve recovery.

LEVEL OF EVIDENCE

Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

What three years of COVID-19 vaccine administration reveals about the incidence of shoulder injury related to vaccine administration (SIRVA)

BACKGROUND

Shoulder injury related to vaccine administration (SIRVA) has been reported to be a rare but real complication of vaccination. It is considered attributable to an incorrect vaccine administration technique by the vaccinator. To date, evidence about SIRVA is mainly limited to case studies and case series, and the incidence remains unknown. This study aimed to determine the incidence of SIRVA.

METHODS

We conducted a retrospective study of the publicly available Eudravigilance database (pharmacovigilance data). We examined all COVID-19 vaccine case reports administered between January 2020 and December 2022. Reports were analysed to see if they met the Surveillance of Adverse Events Following Vaccination In the Community (SAEFVIC) definition and inclusion criteria for SIRVA. Data was extracted.

FINDINGS

Between January 2020, and December 2022, from 1,172,583,008 administered COVID-19 vaccines, 43,192 cases met the SAEFVIC inclusion criteria for SIRVA. This equals an incidence of 3·7 cases per 100,000 vaccines administered during the three years. Female subjects are disproportionately affected, with 33,828 cases (77.9 %). The incidence was higher with some COVID-19 vaccine formulations than others.

INTERPRETATION

The incidence found in this study is higher than previously reported. The data also reflects that it affects more female subjects than males. While previously considered avoidable using the correct vaccine administration technique, the data challenges this notion as it shows that certain vaccine formulations may be associated with a higher incidence of the condition. The causes of SIRVA are likely multifaceted, with current understanding being further impacted by unclear definitions and reporting requirements.

FUNDING

This project was supported by an ECARD grant from The University of Canberra.

Therapeutic Potential of Growth Hormone in Peripheral Nerve Injury: Enhancing Schwann Cell Proliferation and Migration Through IGF-1R-AKT and ERK Signaling Pathways

Peripheral nerve injury (PNI) represents a prevalent condition characterized by the demyelination of affected nerves. The challenge of remyelinating these nerves and achieving satisfactory functional recovery has long been a persistent issue. The specific contributions of growth hormone (GH) in the aftermath of PNI have remained ambiguous. Our investigations have demonstrated that GH not only enhances neurological function scores but also promotes remyelination within a three-week period. Further in vivo studies corroborated that GH facilitates nerve function improvement by mitigating neuronal apoptosis. In vitro, the ideal concentration of GH for exerting effects on Schwann cells (SCs) has been identified as 80 ng/mL. Subsequent research uncovered GH's profound impact on SCs proliferation, cell cycle progression, and migration. Through RNA sequencing and additional experiments, it was discovered that GH treatment elevates the phosphorylation levels of IGF-1R, AKT, and ERK. Moreover, the GH-induced proliferation and migration of SCs were significantly diminished by the inhibition of the IGF-1R pathway, achieved through pre-treatment with Linsitinib. The outcomes of this investigation suggest that GH can significantly enhance the proliferation and migration of SCs, presenting it as a viable option for PNI repair.

Does halofuginone influence regeneration after peripheral nerve injury?

BACKGROUND

Halofuginone is an antiprotozoal drug with antifibrotic and anti-inflammatory properties. The aim of our study was to determine the effects of halofuginone on nerve recovery in sciatic nerve injury and compare it with steroid treatment.

METHODS

The left sciatic nerves of Sham subjects were exposed without intervention. The nerves of trauma animals were transected and sutured. In the methylprednisolone group and in the trauma group, after nerve transection and repair, 1 mg/kg methylprednisolone per day was administered intraperitoneally for seven days; in the halofuginone group and in the trauma group, after nerve transection and repair, 0.2 mg/kg halofuginone per day was administered orally by gavage for seven days. The rats were functionally evaluated at 4 and 8 weeks through walking path analysis. Pathological-morphometric, immunostaining-quantitative, and muscle weight measurements were performed at 8 weeks.

RESULTS

Compared with the trauma group, the methylprednisolone and the halofuginone groups had better functional outcomes (p < 0.001). Statistically significant difference was found in comparisons of the pathological and immunostaining results of the methylprednisolone and halofuginone groups (Respectively, nerve diameter (p = 0.007) and edema (P = 0.009)).

CONCLUSION

Halofuginone positively contributed to recovery after sciatic nerve injury.

CLINICAL TRIAL NUMBER

Not applicable.

Melatonin and Methylprednisolone Combination Ameliorates Inflammation and Enhances Recovery After Sciatic Nerve Crush Injury

This sham-controlled animal study aimed to investigate the effects of melatonin and methylprednisolone combination on motor function, nerve conduction and histopathological and biochemical findings in rats with sciatic nerve crush injury. Forty-eight male Sprague-Dawley rats were divided into 6 groups (n = 8): CT: control, VEH: sciatic nerve injury, LMP: 15-mg/kg methylprednisolone, high-dose methylprednisolone (HMP): 30-mg/kg methylprednisolone, MEL: 15-mg/kg melatonin, MMP: 15-mg/kg methylprednisolone+15-mg/kg melatonin. The rats were evaluated with Sciatic Functional Index (SFI), nerve conduction study, interleukin-1β (IL-1ß), nerve growth factor (NGF), total antioxidant status (TAS), total oxidant status (TOS) and histopathological scores. There were no significant intergroup differences in baseline tests. SFI significantly improved in all treated groups with no significant intergroup differences. Motor amplitude improved most in MMP, LMP and MEL, respectively. Nerve conduction velocity significantly improved in MMP compared to VEH. There were no significant intergroup differences regarding serum NGF, TAS and TOS. Tissue NGF levels were higher in LMP, HMP and MEL. IL-1ß levels were significantly lower in CT and MMP. Tissue oxidative stress levels were significantly lower in treated groups compared to VEH, with no significant difference among them. MMP showed greater histopathological improvement. Melatonin combination therapy in sciatic nerve crush injury provided adequate functional improvement, superior electrophysiological and histopathological recovery compared to high-dose methylprednisolone and exhibited better anti-inflammatory activity through IL-1ß.

The role of nerve transfers in chronic nerve compression syndromes

PURPOSE

Compression neuropathy is a common problem that results in impaired axonal conduction, and with time, numbness, tingling and weakness from muscle atrophy. Supercharge reverse end-to-side (SETS) nerve transfers have emerged as a novel approach to augment function in chronic nerve compression syndromes with minimal donor site morbidity. This review answers the question, "What are the indications, surgical techniques, and nuances of SETS nerve transfers for ulnar, axillary, radial, and femoral compression neuropathies?".

METHODS

This article reviews current literature and technical components of the use of SETS in chronic nerve compression syndromes.

RESULTS

SETS nerve transfers improve functional outcomes and reduce disability in chronic nerve compression syndromes with limited donor site morbidity. SETS nerve transfers for ulnar, axillary, and femoral compressive neuropathy improve muscle strength, as demonstrated by increased MRC scores. It has also been shown that SETS transfers decrease clawing in ulnar nerve compression and pain in axillary nerve compression. More research is needed for SETS transfers for radial nerve compression neuropathies.

CONCLUSION

SETs nerve transfers have emerged as a novel approach to restore function and reduce pain and dysfunction in chronic nerve compression syndromes. SETS nerve transfers have minimal donor site morbidity and improve the strength and function of muscles innervated by the effected "recipient" nerve. This review explores the indications and surgical techniques of SETS nerve transfers for ulnar, axillary, radial, and femoral compression neuropathies as well as their reported outcomes.

Adhesive and Conductive Fibrous Hydrogel Bandages for Effective Peripheral Nerve Regeneration

Peripheral nerve injury is a common disease resulting in reversible and irreversible impairments of motor and sensory functions. In addition to conventional surgical interventions such as nerve grafting and neurorrhaphy, nerve guidance conduits are used to effectively support axonal growth without unexpected neuroma formation. However, there are still challenges to secure tissue-mimetic mechanical and electrophysiological properties of the conduit materials. Herein, the phenylborate-tethered hydrogel-assisted doping effect is elucidated on conductive polymers, enhancing peripheral nerve regeneration when used as a sutureless bandage on the injured nerve. The adhesive and conductive nerve bandage consists of biocompatible hyaluronic acid hydrogel microfibers produced by electrospinning, followed by in situ conductive polypyrrole polymerization on the fibrous mat. Particularly, phenylborate groups enable high adsorption of pyrrole without mechanical crack on the hydrogel network and allow tissue-like stretchability and on-nerve adhesiveness. In a rat crushed nerve injury model, the nerve bandage can effectively promote nerve regeneration through stable sutureless wrapping followed by great electrical transmission on the defect region, showing anatomical and functional recovery of the nerve tissues and preventing muscular atrophy. Such hydrogel fibrous bandages will be a promising surgical dressing to be combined with versatile biomedical devices/materials for peripheral nerve repair.

Fenugreek seed extract combined with acellular nerve allografts promotes peripheral nerve regeneration and neovascularization in sciatic nerve defects

Background

Acellular nerve allografts (ANAs) have been confirmed to improve the repair and reconstruction of long peripheral nerve defects. However, its efficacy is not comparable to that of autologous nerve grafts, which are used as the gold standard for treating peripheral nerve defects. Our study investigated whether fenugreek seed extract (FSE) exhibits neuroprotective potential and enhances the therapeutic outcomes of ANA repair in peripheral nerve defects.

Methods

Rat Schwann cells were treated with FSE to assess the effects of FSE on cell proliferation and their secretion function of neurotrophic factors in vitro. Sprague-Dawley rats with a unilateral 15-mm sciatic nerve defect were randomized into the ANA group (the 15-mm defect was replaced by an 18-mm ANA), the ANA + FSE group (the 15-mm defect was repaired with an 18-mm ANA with FSE administration for four weeks), and the Auto group (the 15-mm defect was repaired with an autologous graft). After four weeks post-surgery, various behavioral tests and electrophysiological assays were performed to evaluate the motor and sensory behavior as well as nerve conduction of rats. Then, rats were sacrificed, and the nerve grafts were collected for toluidine blue staining, RT-qPCR, immunofluorescence staining, immunohistochemical staining to evaluate nerve regeneration, neovascularization, and neuroinflammation. Their gastrocnemius was harvested for Masson's trichrome staining to examine gastrocnemius muscle recovery.

Results

FSE treatment promoted Schwann cell proliferation and its secretion of neurotrophic factors in vitro. Compared with ANAs alone, FSE treatment combined with ANAs enhanced axonal regeneration, upregulated S100, NF200, P0, MBP, and GAP43 expression, facilitated angiogenesis, and elevated neurotrophic factor expression in regenerating nerves of rats with sciatic nerve defects. In addition, FSE treatment promoted gastrocnemius muscle recovery, stimulated motor and sensory functional recovery and nerve conduction, and mitigated neuroinflammation in rats with sciatic nerve defects after repair with ANAs.

Conclusion

FSE treatment improves the beneficial effects of ANA repair on sciatic nerve defects.

Repair methods in peripheral nerves after traumatic injuries: a systematic literature review

PURPOSE

To identify and describe the most used surgical repair methods for traumatic injuries to peripheral nerves, as well as highlight the causes of trauma to peripheral nerves and the most prevalent traumatized nerves.

METHODS

This is a systematic literature review using the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The searches were carried out in PubMED, in the time window from January 2018 to December 2022.

RESULTS

In total, 3,687 articles were collected, of which, after applying the inclusion and exclusion filters and analyzing the risk of bias, 34 articles remained. It was observed that the age of the injury and type of nerve repair strongly influence the recovery of patients. The most identified trauma repair procedures were neurolysis, direct suturing, grafting, and nerve transfer. Among these four procedures, direct suturing is currently preferred.

CONCLUSION

Several repair methods can be used in peripheral nerve injuries, with emphasis on direct suturing. However, nerve transfer proves to be a differential in those cases in which repair is delayed or the first treatment options have failed, which shows that each method will be used according to the indication for each case.

The Potential Role of Adipose-Derived Stem Cells in Regeneration of Peripheral Nerves

Peripheral nerve injuries are common complications in surgical and dental practices, often resulting in functional deficiencies and reduced quality of life. Current treatment choices, such as autografts, have limitations, including donor site morbidity and suboptimal outcomes. Adipose-derived stem cells (ADSCs) have shown assuring regenerative potential due to their accessibility, ease of harvesting and propagation, and multipotent properties. This review investigates the therapeutic potential of ADSCs in peripheral nerve regeneration, focusing on their use in bioengineered nerve conduits and supportive microenvironments. The analysis is constructed on published case reports, organized reviews, and clinical trials from Phase I to Phase III that investigate ADSCs in managing nerve injuries, emphasizing both peripheral and orofacial applications. The findings highlight the advantages of ADSCs in promoting nerve regeneration, including their secretion of angiogenic and neurotrophic factors, support for cellular persistence, and supplementing scaffold-based tissue repair. The regenerative capabilities of ADSCs in peripheral nerve injuries offer a novel approach to augmenting nerve repair and functional recovery. The accessibility of adipose tissue and the minimally invasive nature of ADSC harvesting further encourage its prospective application as an autologous cell source in regenerative medicine. Future research is needed to ascertain standardized protocols and optimize clinical outcomes, paving the way for ADSCs to become a mainstay in nerve regeneration.

A pupil called Worry: Mydriasis in orbital surgery

OBJECTIVE

Surgeons routinely check the pupils to assess, in part, the brain stem function and the neural integrity of the visual system. Where a relative afferent pupillary defect is difficult to notice during surgery, an efferent pupillary defect or mydriasis is clearly recognizable. Visual loss in orbital surgery is attributed to compromised perfusion of the optic nerve, retina, or choroid, but an association with mydriasis is generally not assumed. This study investigates the clinical significance of mydriasis in orbital surgery to identify visual threatening situations and prevent operative complications.

METHODS

PubMed search of MEDLINE and OLDMEDLINE databases, and of references in related articles, using the following Mesh and non-Mesh terms: "Mydriasis", "Pupil", "Pupillary defect", "Orbital surgery", "Visual loss", "Ciliary ganglion", "Short ciliary nerves", "Complications", and corresponding keywords of the specific lesions and surgical techniques discussed.

RESULTS

During an orbital procedure mydriasis regularly occurs and emerges in different shapes. The variants in mydriasis follow distinct types of injury. With surgery near the optic nerve and apex, classical circular mydriasis reflects ischemic injury involving the parasympathetic ciliary ganglion. Located deep in the orbit, the ciliary ganglion is nourished by ultrafine arteries directly or indirectly originating from the ophthalmic artery. In a varied amount of cases the ischemic event includes critical arteries for vision with resultant operative visual loss. On the other hand, oval mydriasis is related to structural injury to the short ciliary nerves. These are situated in the anterior two third of the orbit, and their injury is not associated with operative visual loss.

CONCLUSION

In orbital surgery circular mydriasis may portend visual loss whereas an oval pupil has no prognostic visual functional significance.

Biomechanical modelling infers that collagen content within peripheral nerves is a greater indicator of axial Young's modulus than structure

The mechanical behaviour of peripheral nerves is known to vary between different nerves and nerve regions. As the field of nerve tissue engineering advances, it is vital that we understand the range of mechanical regimes future nerve implants must match to prevent failure. Data on the mechanical behaviour of human peripheral nerves are difficult to obtain due to the need to conduct mechanical testing shortly after removal from the body. In this work, we adapt a 3D multiscale biomechanical model, developed using asymptotic homogenisation, to mimic the micro- and macroscale structure of a peripheral nerve. This model is then parameterised using experimental data from rat peripheral nerves and used to investigate the effect of varying the collagen content, the fibril radius and number density, and the macroscale cross-sectional geometry of the peripheral nerve on the effective axial Young's moduli of the whole nerve. Our results indicate that the total amount of collagen within a cross section has a greater effect on the axial Young's moduli compared to other measures of structure. This suggests that the amount of collagen in a cross section of a peripheral nerve, which can be measured through histological and imaging techniques, is one of the key metrics that should be recorded in the future experimental studies on the biomechanical properties of peripheral nerves.

Cryoneurolysis for Post Operative Pain Following Chest Surgery: Contemporary Evidence and Future Directions

Management of acute and chronic pain following surgery remains a critical patient management challenge, with poor pain management associated with negative patient satisfaction, increased opioid consumption and a high incidence of adverse events. Chest surgery specifically carries a high incidence of significant early and chronic post operative pain. The high incidence, prolonged duration of pain, and adverse effects associated with chronic opioid analgesia, has given rise to the need for non-opioid pain management strategies. Cryoneurolysis, also known as cryoanalgesia, has emerged as a promising option for both acute and chronic pain management. While cryoneurolysis was first developed over fifty years ago, its utilization was limited by technical implementation challenges and limitations in identifying target structures percutaneously. Advances both in cryoneurolysis delivery devices as well as ultrasound have reinvigorated interest in the technique, with recent studies highlighting the advantages of cryoneurolysis, including its favorable side effect profile, long duration of efficacy and relative technical simplicity. The purpose of this review is to examine techniques for cryoneurolysis, and explore recent evidence for safety and efficacy of the technique following different surgical procedures.

The Effect of Surgical Timing on Upper Extremity Nerve Repair

BACKGROUND

The purpose of this study was to evaluate the association between timing of nerve repair and the ability to perform a primary nerve repair versus a bridge repair requiring the use of allograft, autograft, or a conduit in lacerated upper extremity peripheral nerve injuries.

METHODS

This is a retrospective case-control study of patients who underwent upper extremity nerve repair for lacerated peripheral nerves identified by Current Procedural Terminology codes. Timing of injury and surgery, as well as other information such as demographic information, mechanism of injury, site of injury, and type of nerve repair, was recorded. The odds of a patient requiring bridge repair based on the duration of time between injury and surgery was evaluated using logistic regression.

RESULTS

A total of 403 nerves in 335 patients (mean age 35.87 ± 15.33 years) were included. In all, 241 nerves were primarily repaired and 162 required bridge repair. Patients requiring bridge repair had a greater duration between injury and surgery compared with patients who underwent primary repair. Furthermore, the nerves requiring bridge repair were associated with a greater gap compared with the nerves repaired primarily. Based on logistic regression, each 1-day increase in duration between injury and surgery was associated with a 3% increase in the odds of requiring bridge repair.

CONCLUSIONS

There is no defined critical window to achieve a primary nerve repair following injury. This study demonstrated that nerve injuries requiring bridge repair were associated with a significantly greater delay to surgery.

Treatment Strategies for Painful Pelvic Floor Conditions: A Focus on the Potential Benefits of Cannabidiol

Painful conditions of the pelvic floor include a set of disorders of the pelvic region, discreetly prevalent in the female population, in which pain emerges as the predominant symptom. Such disorders have a significant impact on quality of life as they impair couple relationships and promote states of anxiety and irascibility in affected individuals. Although numerous treatment approaches have been proposed for the management of such disorders, there is a need to identify strategies to promote muscle relaxation, counter pelvic pain, and reduce inflammation. The endocannabinoid system (ECS) represents a complex system spread throughout the body and is involved in the regulation of numerous physiological processes representing a potential therapeutic target for mood and anxiety disorders as well as pain management. Cannabidiol (CBD), acting on the ECS, can promote relief from hyperalgesia and allodynia typical of disorders affecting the pelvic floor and promote muscle relaxation by restoring balance to this delicate anatomical region. However, its use is currently limited due to a lack of evidence supporting its efficacy and harmlessness, and the mechanism of action on the ECS remains partially unexplored to this day. This comprehensive review of the literature examines the impact of pain disorders affecting the pelvic floor and major treatment approaches and brings together the main evidence supporting CBD in the management of such disorders.

A Novel Approach to Peripheral Nerve Regeneration: Local FK-506 Delivery Using a Reservoir Flap Model

PURPOSE

Peripheral nerve injuries can lead to lasting functional impairments, impacting movement and quality of life. FK-506, a widely used immunosuppressant, has demonstrated potential in promoting nerve regeneration in addition to its immunosuppressive effects. This study investigates the use of a local reservoir flap to deliver FK-506 directly to the nerve injury site, aiming to enhance nerve regeneration while minimizing systemic immunosuppression.

MATERIALS AND METHODS

Sciatic nerve injuries were surgically induced in 24 rats, which were divided into control, 0.5 mg/kg FK-506 (Exp 1), and 2.0 mg/kg FK-506 (Exp 2) groups. A superficial inferior epigastric artery flap served as a reservoir for FK-506, allowing direct delivery to the injury site. FK-506 was administered intermittently over a 4-week period. Outcomes included the Sciatic Functional Index (SFI), muscle recovery (width and weight), nerve morphology, expression of neurogenic markers such as GDNF, immune cell counts, and body weight.

RESULTS

Exp 1 (0.5 mg/kg) demonstrated significant improvements in SFI, GDNF expression, and muscle width compared to the control and high-dose groups. These findings suggest that FK-506 administration via a reservoir flap, particularly at a lower dose, supports effective nerve regeneration. Additionally, FK-506 treatment did not result in significant changes in immune cell profiles or body weight, indicating minimal systemic effects.

CONCLUSION

Localized FK-506 administration via a reservoir flap effectively enhances peripheral nerve regeneration and minimizes systemic immunosuppression, making it a promising approach for clinical application in treating peripheral nerve injuries.

In Vitro Models for Peripheral Nerve Regeneration

Peripheral nerve injury (PNI) resulting in lesions is highly prevalent clinically, but current therapeutic approaches fail to provide satisfactory outcomes in many patients. While peripheral nerves have intrinsic regenerative capacity, the regenerative capabilities of peripheral nerves are often insufficient to restore full functionality. This highlights an unmet need for developing more effective strategies to repair damaged peripheral nerves and improve regenerative success. Consequently, researchers are actively exploring a variety of therapeutic strategies, encompassing the local delivery of trophic factors or bioactive molecules, the design of advanced biomaterials that interact with regenerating axons, and augmentation with nerve guidance conduits or complex prostheses. However, clinical translation of these technologies remains limited, emphasizing the need for continued research on peripheral nerve regeneration modalities that can enhance functional restoration. Experimental models that accurately recapitulate key aspects of peripheral nerve injury and repair biology can accelerate therapeutic development by enabling systematic testing of new techniques. Advancing regenerative therapies for PNI requires bridging the gap between basic science discoveries and clinical application. This review discusses different in vitro models of peripheral nerve injury and repair, including their advantages, limitations, and potential applications.

Nerve guide conduits promote nerve regeneration under a combination of electrical stimulation and RSCs combined with stem cell differentiation

Nerve guide conduits (NGCs) offer a promising alternative to traditional tools for regenerating peripheral nerves. The efficacy of nerve regeneration and functional recovery is heavily dependent on the electrical, chemical, and physical properties of NGCs. A bionic melt electrowriting (MEW) NGC loaded with placental derived mesenchymal stem cells (PDMSCs) has been developed. Our study introduces a novel approach by utilizing Schwann cells induced from placental mesenchymal stem cells (PDMSCs), showcasing their potential in enhancing nerve regeneration when integrated with conductive nerve guidance conduits. Schwann cells (SCs) are crucial for nerve regeneration, and while various stem cells, including bone marrow stromal cells (BMSCs), have been investigated as sources of SCs for NGC loading, they are often limited by ethical concerns and restricted availability. PDMSCs, however, offer the advantages of widespread sourcing and unique ability to differentiate into SCs, making them an attractive alternative for NGC applications. This NGC utilizes an electrostatic direct writing technique employing polycaprolactone (PCL) for the sheath and a crimped fiber scaffold made of polypyrrole (PPY) incorporated with PDMSCs for its internal structure. The bionic PC-NGC loaded with PDMSCs exhibits favorable characteristics including permeability, mechanical stability, and electrical conductivity. The PPY component effectively transmits physiological nerve signals, thereby promoting nerve regeneration, while the PDMSCs differentiate into Schwann cells, creating a conducive environment for nerve regeneration. This research innovatively combines PDMSCs, known for their wide availability and SC differentiation potential, with a bionic NGC to enhance the treatment of peripheral nerve injuries (PNIs). In vitro evaluations have confirmed the excellent biocompatibility of the materials used. Animal experiments using a rat model with sciatic nerve injury demonstrated that the PC-NGC significently facilitated peripheral nerve regeneration. This was evidenced by improvements in axonal myelination, increased muscle mass, enhanced sciatic nerve function index, and positive electrophysiological findings. These outcomes are comparable to those achieved through autologous transplantation. Characterized by its layered oriented fibers, the bionic PC-NGC integrates multi-scale and multifunctional biomaterials with PDMSCs to effectively address peripheral nerve injuries (PNIs). The use of this printed NGC stimulates neuronal cell growth, thereby accelerating nerve regeneration. This innovative approach in tissue engineering presents a promising clinical treatment strategy for PNIs.

Psychology of nerve injury, repair, and recovery: a systematic review

Background

Peripheral nerve injuries (PNIs) are associated with significant physical and psychological challenges, impacting both functional recovery and quality of life. Despite the physical focus of traditional treatments, psychological factors play a crucial role in the outcomes of PNI repair and recovery.

Objectives

This systematic review aims to evaluate the impact of psychological and social factors on the repair and recovery of peripheral nerve injuries.

Methods

A comprehensive literature search was conducted in PubMed/Medline, EMBASE, and Cochrane databases, covering studies from January 1985 to December 2022. A total of 36,190 records were identified, and after screening with Rayyan AI and applying inclusion criteria, 111 articles were selected for review.

Results

The review highlights that pre-existing psychological conditions, as well as psychological responses to the injury and treatment, significantly influence recovery outcomes in PNI patients. Psychological interventions, when integrated into standard care, may improve functional recovery and quality of life.

Conclusions

Psychosocial factors are critical in the management of PNIs and should be incorporated into treatment algorithms to enhance patient outcomes. Future research should focus on developing and integrating psychological support strategies in PNI treatment protocols.

Molecular mechanisms of neuropathic pain

Peripheral neuropathic pain, which occurs after a lesion or disease affecting the peripheral somatosensory nervous system, is a complex and challenging condition to treat. This chapter will cover molecular mechanisms underlying the pathophysiology of peripheral neuropathic pain, focusing on (1) sensitization of nociceptors, (2) neuro-immune crosstalk, and (3) axonal degeneration and regeneration. The chapter will also emphasize the importance of identifying novel therapeutic targets in non-neuronal cells. A comprehensive understanding of how changes at both neuronal and non-neuronal levels contribute to peripheral neuropathic pain may significantly improve pain management and treatment options, expanding to topical application that bypass the side effects associated with systemic administration.

Delayed-onset vocal cord palsy after thyroidectomy occurring despite normal initial post-operative endoscopy

BACKGROUND

Recurrent laryngeal nerve (RLN) injury is a known complication of thyroidectomy. Most cases manifest immediately and are promptly recognized. Rarely, some patients experience delayed-onset vocal cord palsy. This can occur despite normal findings on intra-operative nerve monitoring and initial post-operative endoscopy. This can cause considerable distress for patients, and its incidence and prognosis should be recognized.

METHODOLOGY

We report seven patients experiencing delayed-onset RLN palsy (RLNP) after thyroidectomy. All had normal findings on pre-operative flexible nasoendoscopy (FNE), intra-operative nerve monitoring at conclusion of surgery, and initial post-operative FNE. All diagnoses of RLNP were confirmed on endoscopy. Serial FNE examinations were performed to evaluate recovery.

RESULTS

Of seven patients (43% male, median age 65 years), the median timing of delayed-onset RLNP was 12 (range 9-35) days. RLNP was diagnosed on the unilateral side of surgery in six out of seven patients (86%). All received conservative management, including referral to voice therapy. All seven patients recovered vocal cord function after a median duration of 24 weeks (range 8-52 weeks), and six within ~6 months (28 weeks). The incidence of this complication was 0.1% (among 6607 thyroidectomies).

CONCLUSION

We report the first Australian series of delayed-onset vocal cord palsy after thyroidectomy. We explore its prognosis, discussing different pathophysiological mechanisms and the timeframe for recovery compared to most other RLN injuries. This may assist recognition of a rare complication, reassure patients, and facilitate early intervention to improve a patient's quality of life.

The Role of Length of Nerve Grafts in Combination with Free Functional Muscle Transplantation for Brachial Plexus Injury: A Single-Center Experience

PURPOSE

Extensive lesions of the brachial plexus, or late cases, require free functional muscle grafts because the expected recovery time exceeds the critical threshold of 1.5 years, beyond which irreversible damage may be expected in the distal nerve stump and in the muscle. The reconstructive concept consists of a two-stage procedure where, in the first step, a nerve transfer is performed (from ipsi- or contralateral donor nerves). In the second step, after successful axonal regeneration within the graft has been confirmed, a free muscle transfer is performed. These grafts often exceed 40 cm in length, particularly for contralateral transfers. The purpose of this study was to assess whether robust motor recovery could be supported by such long nerve grafts.

METHODS

From April 2004 to April 2023, a total of 327 free functional muscle transfers were performed, the nerve graft length ranging from 0 cm (direct coaptation) to 90 cm (serial grafts). Motor recovery was evaluated 1.5 years after surgery according to the MRC scale.

RESULTS

A total of 208 patients were available for follow up. Direct coaptation yielded the best results, with 83% of patients reaching an M3 or M4 level of muscle strength. With the application of long (30-60 cm) grafts, 73% of the patients were classified as M3 or M4. The application of serial nerve grafts, however, only resulted in 18% of patients achieving a motor recovery rating of M3.

CONCLUSIONS

These findings demonstrate that robust motor regeneration is supported by long (30-60 cm) nerve grafts, whereas serial nerve grafting results in a marked reduction in the quality of regeneration.

Nerve Injury Following Regional Nerve Block: A Literature Review of Its Etiologies, Risk Factors, and Prevention

PURPOSE OF REVIEW

Postoperative nerve injury after nerve block is complex and multifactorial. The mechanisms, etiologies, and risk factors are explored. This review article conducts a literature search and summarizes current evidence and best practices in prevention of nerve injury.

RECENT FINDINGS

Emerging technology such as ultrasound, injection pressure monitors, and nerve stimulators for peripheral nerve block have been incorporated into regular practice to reduce the rate of nerve injury. Studies show avoidance of intrafascicular injection, limiting concentrations/volumes of local anesthetic, and appropriate patient selection are the most significant controllable factors in limiting the negative consequences of nerve block. Peripheral nerve injury is an uncommon occurrence after nerve block and is obscured by surgical manipulation, positioning, and underlying neural integrity. Underlying neural integrity is not always evident despite an adequate history and physical exam. Surgical stress, independently of nerve block, may exacerbate these neurologic disease processes and make diagnosing a postoperative nerve injury more challenging. Prevention of nerve injury by surgical teams, care with positioning, and avoidance of intrafascicular injection with nerve block are the most evidence-based practices.

Management of "Long" Nerve Gaps

Long-gap nerve injuries offer unique physiological and logistical treatment challenges to the reconstructive surgeon. Options include nerve autograft, processed nerve allograft, nerve transfers, and tendon transfers. This review provides an evidence-framed discussion regarding the pros and cons of these diverse approaches.

The Physiologic Basis of Molecular Therapeutics for Peripheral Nerve Injury: A Primer

Peripheral nerve injuries affect a significant number of patients who experience trauma affecting the hand and upper extremity. Improving unsatisfactory outcomes from repair of these injuries remains a clinical challenge despite advancements in microsurgical repair. Imperfections of the nerve regeneration process, including imprecise reinnervation, distal axon degradation, and muscular atrophy, complicate the repair process. However, the capacity for peripheral nerves to regenerate offers an avenue for therapeutic advancement. Regeneration is a temporally and spatially dynamic process coordinated by Schwann cells and neurons among other cell types. Neurotrophic factors are a primary means of controlling cell growth and differentiation in the repair setting. Sustained axon survival and regrowth and consequently functional outcomes of nerve repair in animal models are improved by the administration of neurotrophic factors, including glial cell-derived neurotrophic factor, nerve growth factor, sterile alpha and TIR motif containing 1, and erythropoietin. Targeted and sustained delivery of neurotrophic factors through gelatin-based nerve conduits, multiluminal conduits, and hydrogels have been shown to enhance the innate roles of these factors to promote expedient and accurate peripheral nerve regeneration in animal models. These delivery methods may help address the practical limitations to clinical use of neurotrophic factors, including systemic side effects and the need for carefully timed, precisely localized release schedules. In addition, tacrolimus has also improved peripheral nerve regrowth in animal models and has recently shown promise in addressing human disease. Ultimately, this realm of adjunct pharmacotherapies provides ample promise to improve patient outcomes and advance the field of peripheral nerve repair.

Therapeutic Electrical Stimulation for Surgeons: How it Works and How to Apply it

Electrical stimulation (ES) enhances peripheral nerve inherent regeneration capacity by promoting accelerated axonal outgrowth and selectivity toward appropriate motor and sensory targets. These effects lead to significantly improved functional outcomes and shorter recovery time. Electrical stimulation can be applied intra-operatively or immediately post-operatively. Active clinical trials are looking into additional areas of application, length of stimulation, and functional outcomes.

Therapeutic Potential of Mesenchymal Stem Cell-Derived Exosomes as Nanomedicine for Peripheral Nerve Injury

Peripheral nerve injury (PNI) is a complex and protracted process, and existing therapeutic approaches struggle to achieve effective nerve regeneration. Recent studies have shown that mesenchymal stem cells (MSCs) may be a pivotal choice for treating peripheral nerve injury. MSCs possess robust paracrine capabilities, and exosomes, as the primary secretome of MSCs, are considered crucial regulatory mediators involved in peripheral nerve regeneration. Exosomes, as nanocarriers, can transport various endogenous or exogenous bioactive substances to recipient cells, thereby promoting vascular and axonal regeneration while suppressing inflammation and pain. In this review, we summarize the mechanistic roles of exosomes derived from MSCs in peripheral nerve regeneration, discuss the engineering strategies for MSC-derived exosomes to improve therapeutic potential, and explore the combined effects of MSC-derived exosomes with biomaterials (nerve conduits, hydrogels) in peripheral nerve regeneration.

Inflammation in the Peripheral Nervous System after Injury

Nerve injury is a common condition that occurs as a result of trauma, iatrogenic injury, or long-lasting stimulation. Unlike the central nervous system (CNS), the peripheral nervous system (PNS) has a strong capacity for self-repair and regeneration. Peripheral nerve injury results in the degeneration of distal axons and myelin sheaths. Macrophages and Schwann cells (SCs) can phagocytose damaged cells. Wallerian degeneration (WD) makes the whole axon structure degenerate, creating a favorable regenerative environment for new axons. After nerve injury, macrophages, neutrophils and other cells are mobilized and recruited to the injury site to phagocytose necrotic cells and myelin debris. Pro-inflammatory and anti-inflammatory factors involved in the inflammatory response provide a favorable microenvironment for peripheral nerve regeneration and regulate the effects of inflammation on the body through relevant signaling pathways. Previously, inflammation was thought to be detrimental to the body, but further research has shown that appropriate inflammation promotes nerve regeneration, axon regeneration, and myelin formation. On the contrary, excessive inflammation can cause nerve tissue damage and pathological changes, and even lead to neurological diseases. Therefore, after nerve injury, various cells in the body interact with cytokines and chemokines to promote peripheral nerve repair and regeneration by inhibiting the negative effects of inflammation and harnessing the positive effects of inflammation in specific ways and at specific times. Understanding the interaction between neuroinflammation and nerve regeneration provides several therapeutic ideas to improve the inflammatory microenvironment and promote nerve regeneration.

Enhancing neuroinduction activity of PLCL-based nerve conduits through native epineurium integration

Autologous nerve grafts have been considered the gold standard for peripheral nerve grafts. However, due to drawbacks such as functional loss in the donor area and a shortage of donor sources, nerve conduits are increasingly being considered as an alternative approach. Polymer materials have been widely studied as nerve repair materials due to their excellent processing performance. However, their limited biocompatibility has restricted further clinical applications. The epineurium is a natural extra-neural wrapping structure. After undergoing decellularization, the epineurium not only reduces immune rejection but also retains certain bioactive components. In this study, decellularized epineurium (DEP) derived from the sciatic nerve of mammals was prepared, and a bilayer nerve conduit was created by electrospinning a poly (l-lactide-co-ε-caprolactone) (PLCL) membrane layer onto the outer surface of the DEP. Components of the DEP were examined; the physical properties and biosafety of the bilayer nerve conduit were evaluated; and the functionality of the nerve conduit was evaluated in rats. The results demonstrate that the developed bilayer nerve conduit exhibits excellent biocompatibility and mechanical properties. Furthermore, this bilayer nerve conduit shows significantly superior therapeutic effects for sciatic nerve defects in rats compared to the pure PLCL nerve conduit. In conclusion, this research provides a novel strategy for the design of nerve regeneration materials and holds promising potential for further clinical translation.

Nano-pulling stimulates axon regeneration in dorsal root ganglia by inducing stabilization of axonal microtubules and activation of local translation

Introduction

Axonal plasticity is strongly related to neuronal development as well as regeneration. It was recently demonstrated that active mechanical tension, intended as an extrinsic factor, is a valid contribution to the modulation of axonal plasticity.

Methods

In previous publications, our team validated a the "nano-pulling" method used to apply mechanical forces to developing axons of isolated primary neurons using magnetic nanoparticles (MNP) actuated by static magnetic fields. This method was found to promote axon growth and synaptic maturation. Here, we explore the use of nano-pulling as an extrinsic factor to promote axon regeneration in a neuronal tissue explant.

Results

Whole dorsal root ganglia (DRG) were thus dissected from a mouse spinal cord, incubated with MNPs, and then stretched. We found that particles were able to penetrate the ganglion and thus become localised both in the somas and in sprouting axons. Our results highlight that nano-pulling doubles the regeneration rate, and this is accompanied by an increase in the arborizing capacity of axons, an accumulation of cellular organelles related to mass addition (endoplasmic reticulum and mitochondria) and pre-synaptic proteins with respect to spontaneous regeneration. In line with the previous results on isolated hippocampal neurons, we observed that this process is coupled to an increase in the density of stable microtubules and activation of local translation.

Discussion

Our data demonstrate that nano-pulling enhances axon regeneration in whole spinal ganglia exposed to MNPs and external magnetic fields. These preliminary data represent an encouraging starting point for proposing nano-pulling as a biophysical tool for the design of novel therapies based on the use of force as an extrinsic factor for promoting nerve regeneration.

Vibrational spectroscopy and multiphoton microscopy for label-free visualization of nervous system degeneration and regeneration

Neurological disorders, including spinal cord injury, peripheral nerve injury, traumatic brain injury, and neurodegenerative diseases, pose significant challenges in terms of diagnosis, treatment, and understanding the underlying pathophysiological processes. Label-free multiphoton microscopy techniques, such as coherent Raman scattering, two-photon excited autofluorescence, and second and third harmonic generation microscopy, have emerged as powerful tools for visualizing nervous tissue with high resolution and without the need for exogenous labels. Coherent Raman scattering processes as well as third harmonic generation enable label-free visualization of myelin sheaths, while their combination with two-photon excited autofluorescence and second harmonic generation allows for a more comprehensive tissue visualization. They have shown promise in assessing the efficacy of therapeutic interventions and may have future applications in clinical diagnostics. In addition to multiphoton microscopy, vibrational spectroscopy methods such as infrared and Raman spectroscopy offer insights into the molecular signatures of injured nervous tissues and hold potential as diagnostic markers. This review summarizes the application of these label-free optical techniques in preclinical models and illustrates their potential in the diagnosis and treatment of neurological disorders with a special focus on injury, degeneration, and regeneration. Furthermore, it addresses current advancements and challenges for bridging the gap between research findings and their practical applications in a clinical setting.

Early Intensive Neurorehabilitation in Traumatic Peripheral Nerve Injury-State of the Art

Traumatic nerve injuries are common lesions that affect several hundred thousand humans, as well as dogs and cats. The assessment of nerve regeneration through animal models may provide information for translational research and future therapeutic options that can be applied mutually in veterinary and human medicine, from a One Health perspective. This review offers a hands-on vision of the non-invasive and conservative approaches to peripheral nerve injury, focusing on the role of neurorehabilitation in nerve repair and regeneration. The peripheral nerve injury may lead to hypersensitivity, allodynia and hyperalgesia, with the possibility of joint contractures, decreasing functionality and impairing the quality of life. The question remains regarding how to improve nerve repair with surgical possibilities, but also considering electrical stimulation modalities by modulating sensory feedback, upregulation of BDNF, GFNF, TrKB and adenosine monophosphate, maintaining muscle mass and modulating fatigue. This could be improved by the positive synergetic effect of exercises and physical activity with locomotor training, and other physical modalities (low-level laser therapy, ultrasounds, pulsed electromagnetic fields, electroacupuncture and others). In addition, the use of cell-based therapies is an innovative treatment tool in this field. These strategies may help avoid situations of permanent monoplegic limbs that could lead to amputation.

Occupational Nerve Injuries due to Metallic Foreign Bodies: A Case Series of Eighteen Patients

Introduction

Peripheral nerve injuries (PNIs) remain an important health problem. PNIs mostly affect young men as this age group is mostly involved in road traffic accidents and other injuries at workplace. PNI can occur from foreign bodies like metal chips while working in industries using lathe machines. Among PNI's, injuries to the ulnar nerve, the brachial plexus and the median nerve are the most frequent lesions encountered.

Materials and methods

This presentation is on a series of 18 cases of nerve injuries among industrial workers located from finger level up to the arm excluding the brachial plexus due to metallic foreign bodies entering while operating lathe machines over a period of two years with patients being followed-up over a one year period.

Results

Mean age in this series was 31.3 years with age range 16-40 years and all were males. Two patients had more than one nerve involvement and one patient had associated vascular injury. All the patients showed functional improvement. Most common nerve injured was median nerve. Most common site for nerve injury was forearm. Combined lesions most commonly involved the ulnar and median nerves.

Conclusion

Social cost of traumatic peripheral nerve injuries is significant since it has a higher incidence in young, previously healthy, and economically active people.

Biology and pathophysiology of symptomatic neuromas

ABSTRACT

Neuromas are a substantial cause of morbidity and reduction in quality of life. This is not only caused by a disruption in motor and sensory function from the underlying nerve injury but also by the debilitating effects of neuropathic pain resulting from symptomatic neuromas. A wide range of surgical and therapeutic modalities have been introduced to mitigate this pain. Nevertheless, no single treatment option has been successful in completely resolving the associated constellation of symptoms. While certain novel surgical techniques have shown promising results in reducing neuroma-derived and phantom limb pain, their effectiveness and the exact mechanism behind their pain-relieving capacities have not yet been defined. Furthermore, surgery has inherent risks, may not be suitable for many patients, and may yet still fail to relieve pain. Therefore, there remains a great clinical need for additional therapeutic modalities to further improve treatment for patients with devastating injuries that lead to symptomatic neuromas. However, the molecular mechanisms and genetic contributions behind the regulatory programs that drive neuroma formation-as well as the resulting neuropathic pain-remain incompletely understood. Here, we review the histopathological features of symptomatic neuromas, our current understanding of the mechanisms that favor neuroma formation, and the putative contributory signals and regulatory programs that facilitate somatic pain, including neurotrophic factors, neuroinflammatory peptides, cytokines, along with transient receptor potential, and ionotropic channels that suggest possible approaches and innovations to identify novel clinical therapeutics.

Effects of Physical Cues on Stem Cell-Derived Extracellular Vesicles toward Neuropathy Applications

The peripheral nervous system undergoes sufficient stress when affected by diabetic conditions, chemotherapeutic drugs, and personal injury. Consequently, peripheral neuropathy arises as the most common complication, leading to debilitating symptoms that significantly alter the quality and way of life. The resulting chronic pain requires a treatment approach that does not simply mask the accompanying symptoms but provides the necessary external environment and neurotrophic factors that will effectively facilitate nerve regeneration. Under normal conditions, the peripheral nervous system self-regenerates very slowly. The rate of progression is further hindered by the development of fibrosis and scar tissue formation, which does not allow sufficient neurite outgrowth to the target site. By incorporating scaffolding supplemented with secretome derived from human mesenchymal stem cells, it is hypothesized that neurotrophic factors and cellular signaling can facilitate the optimal microenvironment for nerve reinnervation. However, conventional methods of secretory vesicle production are low yield, thus requiring improved methods to enhance paracrine secretions. This report highlights the state-of-the-art methods of neuropathy treatment as well as methods to optimize the clinical application of stem cells and derived secretory vesicles for nerve regeneration.

Autophagy-modulating biomaterials: multifunctional weapons to promote tissue regeneration

Autophagy is a self-renewal mechanism that maintains homeostasis and can promote tissue regeneration by regulating inflammation, reducing oxidative stress and promoting cell differentiation. The interaction between biomaterials and tissue cells significantly affects biomaterial-tissue integration and tissue regeneration. In recent years, it has been found that biomaterials can affect various processes related to tissue regeneration by regulating autophagy. The utilization of biomaterials in a controlled environment has become a prominent approach for enhancing the tissue regeneration capabilities. This involves the regulation of autophagy in diverse cell types implicated in tissue regeneration, encompassing the modulation of inflammatory responses, oxidative stress, cell differentiation, proliferation, migration, apoptosis, and extracellular matrix formation. In addition, biomaterials possess the potential to serve as carriers for drug delivery, enabling the regulation of autophagy by either activating or inhibiting its processes. This review summarizes the relationship between autophagy and tissue regeneration and discusses the role of biomaterial-based autophagy in tissue regeneration. In addition, recent advanced technologies used to design autophagy-modulating biomaterials are summarized, and rational design of biomaterials for providing controlled autophagy regulation via modification of the chemistry and surface of biomaterials and incorporation of cells and molecules is discussed. A better understanding of biomaterial-based autophagy and tissue regeneration, as well as the underlying molecular mechanisms, may lead to new possibilities for promoting tissue regeneration. Video Abstract.

Role of Oxygen and Its Radicals in Peripheral Nerve Regeneration: From Hypoxia to Physoxia to Hyperoxia

Oxygen is compulsory for mitochondrial function and energy supply, but it has numerous more nuanced roles. The different roles of oxygen in peripheral nerve regeneration range from energy supply, inflammation, phagocytosis, and oxidative cell destruction in the context of reperfusion injury to crucial redox signaling cascades that are necessary for effective axonal outgrowth. A fine balance between reactive oxygen species production and antioxidant activity draws the line between physiological and pathological nerve regeneration. There is compelling evidence that redox signaling mediated by the Nox family of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases plays an important role in peripheral nerve regeneration. Further research is needed to better characterize the role of Nox in physiological and pathological circumstances, but the available data suggest that the modulation of Nox activity fosters great therapeutic potential. One of the promising approaches to enhance nerve regeneration by modulating the redox environment is hyperbaric oxygen therapy. In this review, we highlight the influence of various oxygenation states, i.e., hypoxia, physoxia, and hyperoxia, on peripheral nerve repair and regeneration. We summarize the currently available data and knowledge on the effectiveness of using hyperbaric oxygen therapy to treat nerve injuries and discuss future directions.

Brain injury drives optic glioma formation through neuron-glia signaling

Tissue injury and tumorigenesis share many cellular and molecular features, including immune cell (T cells, monocytes) infiltration and inflammatory factor (cytokines, chemokines) elaboration. Their common pathobiology raises the intriguing possibility that brain injury could create a tissue microenvironment permissive for tumor formation. Leveraging several murine models of the Neurofibromatosis type 1 (NF1) cancer predisposition syndrome and two experimental methods of brain injury, we demonstrate that both optic nerve crush and diffuse traumatic brain injury induce optic glioma (OPG) formation in mice harboring Nf1-deficient preneoplastic progenitors. We further elucidate the underlying molecular and cellular mechanisms, whereby glutamate released from damaged neurons stimulates IL-1β release by oligodendrocytes to induce microglia expression of Ccl5, a growth factor critical for Nf1-OPG formation. Interruption of this cellular circuit using glutamate receptor, IL-1β or Ccl5 inhibitors abrogates injury-induced glioma progression, thus establishing a causative relationship between injury and tumorigenesis.

Effects of exosomes from mesenchymal stem cells on functional recovery of a patient with total radial nerve injury: A pilot study

BACKGROUND

Peripheral nerve injury can result in significant clinical complications that have uncertain prognoses. Currently, there is a lack of effective pharmacological interventions for nerve damage, despite the existence of several small compounds, peptides, hormones, and growth factors that have been suggested as potential enhancers of neuron regeneration. Despite the objective of achieving full functional restoration by surgical intervention, the persistent challenge of inadequate functional recovery remains a significant concern in the context of peripheral nerve injuries.

AIM

To examine the impact of exosomes on the process of functional recovery following a complete radial nerve damage.

METHODS

A male individual, aged 24, who is right-hand dominant and an immigrant, arrived with an injury caused by a knife assault. The cut is located on the left arm, specifically below the elbow. The neurological examination and electrodiagnostic testing reveal evidence of left radial nerve damage. The sural autograft was utilized for repair, followed by the application of 1 mL of mesenchymal stem cell-derived exosome, comprising 5 billion microvesicles. This exosome was split into four equal volumes of 0.25 mL each and delivered microsurgically to both the proximal and distal stumps using the subepineural pathway. The patient was subjected to a period of 180 d during which they had neurological examination and electrodiagnostic testing.

RESULTS

The duration of the patient's follow-up period was 180 d. An increasing Tinel's sign and sensory-motor recovery were detected even at the 10th wk following nerve grafting. Upon the conclusion of the 6-mo post-treatment period, an evaluation was conducted to measure the extent of improvement in motor and sensory functions of the nerve. This assessment was based on the British Medical Research Council scale and the Mackinnon-Dellon scale. The results indicated that the level of improvement in motor function was classified as M5, denoting an excellent outcome. Additionally, the level of improvement in sensory function was classified as S3+, indicating a good outcome. It is noteworthy that these assessments were conducted in the absence of physical therapy. At the 10th wk post-injury, despite the persistence of substantial axonal damage, the nerve exhibited indications of nerve re-innervation as evidenced by control electromyography (EMG). In contrast to the preceding. EMG analysis revealed a significant electrophysiological enhancement in the EMG conducted at the 6th-mo follow-up, indicating ongoing regeneration.

CONCLUSION

Enhanced comprehension of the neurobiological ramifications associated with peripheral nerve damage, as well as the experimental and therapy approaches delineated in this investigation, holds the potential to catalyze future clinical progress.

The Muscle Shortening Maneuver: a noninvasive approach to the treatment of peroneal nerve injury. A case report

BACKGROUND

The treatment of peripheral nerve injuries is a debated topic. The Muscle Shortening Maneuver (MSM), a physiotherapy approach, is noninvasive and free of side effects; it consists of a muscle shortening and a solicitation in traction applied simultaneously.

OBJECTIVE

The focus of this report is to describe the effects of the MSM combined with walking retraining in a patient with incomplete injury of the peroneal nerve.

DESCRIPTION

The patient was a 17-year-old man, who underwent osteotomy surgery of the proximal two-thirds of the fibula, due to an Ewing sarcoma that caused a partial injury of the left peroneal nerve. Our assessment plan of the left ankle movement ability comprised range of movement, muscle strength, and surface electromyography (EMG); and a gait analysis was conducted by using an iPhone application. MSM and walking retraining were administered twice and once a week, respectively, for 4 weeks.

OUTCOMES

The active range of movement substantially improved in dorsiflexion (≥15°), whereas slightly decreased in plantar flexion (-5°). Aside from the tibialis anterior, an increase in muscle strength was detected. Surface EMG showed an increased activation, particularly in the peroneus longus. A decrease in gait speed and step length was recorded from the gait analysis, with a better bilateral symmetry.

CONCLUSIONS

Positive outcomes were reported without evidence of risk or adverse events for the participant.

Dynamic three-dimensional coculture model: The future of tissue engineering applied to the peripheral nervous system

Traumatic injuries to the peripheral nervous system (PNI) can lead to severe consequences such as paralysis. Unfortunately, current treatments rarely allow for satisfactory functional recovery. The high healthcare costs associated with PNS injuries, worker disability, and low patient satisfaction press for alternative solutions that surpass current standards. For the treatment of injuries with a deficit of less than 30 mm to bridge, the use of synthetic nerve conduits (NGC) is favored. However, to develop such promising therapeutic strategies, in vitro models that more faithfully mimic nerve physiology are needed. The absence of a clinically scaled model with essential elements such as a three-dimension environment and dynamic coculture has hindered progress in this field. The presented research focuses on the development of an in vitro coculture model of the peripheral nervous system (PNS) involving the use of functional biomaterial which microstructure replicates nerve topography. Initially, the behavior of neuron-derived cell lines (N) and Schwann cells (SC) in contact with a short section of biomaterial (5 mm) was studied. Subsequent investigations, using fluorescent markers and survival assays, demonstrated the synergistic effects of coculture. These optimized parameters were then applied to longer biomaterials (30 mm), equivalent to clinically used NGC. The results obtained demonstrated the possibility of maintaining an extended coculture of SC and N over a 7-day period on a clinically scaled biomaterial, observing some functionality. In the long term, the knowledge gained from this work will contribute to a better understanding of the PNS regeneration process and promote the development of future therapeutic approaches while reducing reliance on animal experimentation. This model can be used for drug screening and adapted for personalized medicine trials. Ultimately, this work fills a critical gap in current research, providing a transformative approach to study and advance treatments for PNS injuries.

Histological Comparison of Porcine Small Intestine Submucosa and Bovine Type-I Collagen Conduit for Nerve Repair in a Rat Model

Purpose

After nerve injury, macrophages and Schwann cells remove axon and myelin debris. We hypothesized that nerves repaired with different conduit materials will result in varying levels of these cell populations, which impacts Wallerian degeneration and axonal regeneration.

Methods

We performed a unilateral sciatic nerve transection in 18 rats. The nerves were repaired with small intestine submucosa (SIS, n = 9) or isolated type-I collagen (CLC, n = 9) conduits. Rats were monitored for 4 weeks. Histology samples were obtained from the proximal nerve, mid-implant, and distal nerve regions. Samples were stained for total macrophages, M2 macrophages, foamy phagocytes, Schwann cells, vascular components, axon components, and collagen density.

Results

Distal nerve analyses showed higher populations of total macrophages and M2 macrophages in SIS-repaired nerves and higher density of foamy phagocytes in CLC-repaired nerves. Proximal nerve, mid-implant, and distal nerve analyses showed higher Schwann cell and vascular component densities in SIS-repaired nerves. Axon density was higher in the mid-implant region of SIS-repaired nerves. Collagen staining in the mid-implant was scant, but less collagen density was observed in SIS-repaired versus CLC-repaired nerves.

Conclusions

In the distal nerve, the following were observed: (1) lower total macrophages in CLC-repaired nerves, suggesting lower overall inflammation versus SIS-repaired nerves; (2) higher M2 macrophages in SIS-repaired versus CLC-repaired nerves, a driving factor for higher total macrophages and indicative of an inflammation resolution response in SIS-repaired nerves; and (3) a lower foamy phagocyte density in SIS-repaired nerves, suggesting earlier resolution of Wallerian degeneration versus CLC-repaired nerves. In the proximal nerve, mid-implant, and distal nerve, higher Schwann cell and vascular component densities were noted in SIS-repaired nerves. In the mid-implant, a higher axon component density and a lower collagen density of the SIS-repaired nerves versus CLC-repaired nerves were noted. These results indicate more robust nerve regeneration with less collagen deposition.

Clinical relevance

This in vivo study evaluated two common conduit materials that are used in peripheral nerve repair. Clinical outcomes of nerves repaired with conduits may be impacted by the response to different conduit materials. These nerve repair responses include Wallerian degeneration, nerve regeneration, and nerve scarring. This study evaluated Wallerian degeneration using total macrophages, M2 macrophages, and foamy phagocytes. Nerve regeneration was evaluated using Schwann cells and axons. Nerve scarring was evaluated using vascular and collagen density.