Nerve physiology: mechanisms of injury and recovery

Myelinated peripheral axons are more vulnerable to mechanical trauma in a model of enlarged axonal diameters

The velocity of axonal impulse propagation is facilitated by myelination and axonal diameters. Both parameters are frequently impaired in peripheral nerve disorders, but it is not known if the diameters of myelinated axons affect the liability to injury or the efficiency of functional recovery. Mice lacking the adaxonal myelin protein chemokine-like factor-like MARVEL-transmembrane domain-containing family member-6 (CMTM6) specifically from Schwann cells (SCs) display appropriate myelination but increased diameters of peripheral axons. Here we subjected Cmtm6-cKo mice as a model of enlarged axonal diameters to a mild sciatic nerve compression injury that causes temporarily reduced axonal diameters but otherwise comparatively moderate pathology of the axon/myelin-unit. Notably, both of these pathological features were worsened in Cmtm6-cKo compared to genotype-control mice early post-injury. The increase of axonal diameters caused by CMTM6-deficiency thus does not override their injury-dependent decrease. Accordingly, we did not detect signs of improved regeneration or functional recovery after nerve compression in Cmtm6-cKo mice; depleting CMTM6 in SCs is thus not a promising strategy toward enhanced recovery after nerve injury. Conversely, the exacerbated axonal damage in Cmtm6-cKo nerves early post-injury coincided with both enhanced immune response including foamy macrophages and SCs and transiently reduced grip strength. Our observations support the concept that larger peripheral axons are particularly susceptible toward mechanical trauma.

Types of Short-Duration Electrical Stimulation-Induced Efficiency in the Axonal Regeneration and Recovery: Comparative in Vivo Study in Rat Model of Repaired Sciatic Nerve and its Tibial Branch after Transection Injury

The restoration of adequate function and sensation in nerves following an injury is often insufficient. Electrical stimulation (ES) applied during nerve repair can promote axon regeneration, which may enhance the likelihood of successful functional recovery. However, increasing operation time and complexity are associated with limited clinical use of ES. This study aims to better assess whether short-duration ES types (voltage mode vs. current mode) are able to produce enhanced regenerative activity following peripheral nerve repair in rat models. Wistar rats were randomly divided into 3 groups: no ES (control), 30-minute ES with a current pulse, and 30-minute ES with a voltage pulse. All groups underwent sciatic nerve transection and repair using a silicone tube to bridge the 6-mm gap between the stumps. In the 2 groups other than the control, ES was applied after the surgical repair. Outcomes were evaluated using electrophysiology, histology, and serial walking track analysis. Biweekly walking tracks test over 12 weeks revealed that subjects that underwent ES experienced more rapid functional improvement than subjects that underwent repair alone. Electrophysiological analysis of the newly intratubular sciatic nerve at week 12 revealed strong motor function recovery in rats that underwent 30-minute ES. Histologic analysis of the sciatic nerve and its tibial branch at 12 weeks demonstrated robust axon regrowth in all groups. Both types of short-duration ES applied during nerve repair can promote axon regrowth and enhance the chances of successful functional recovery.

Assessing Survival, Distribution, and Optimal Loading Technique of Schwann Cell-Derived Exosomes Into Second-generation Axon Guidance Channels

INTRODUCTION

Peripheral nerve injury (PNI) occurs in approximately 3% of all trauma patients and can be challenging to treat, particularly when injury is severe such as with a long-segmental gap. Although peripheral nerves can regenerate after injury, functional recovery is often insufficient, leading to deficits in the quality of life of patients with PNI. Although nerve autografts are the gold standard of care, there are several disadvantages to their use, namely a lack of autologous nerve material for repair. This has led to the pursuit of alternative treatment methods such as axon guidance channels (AGCs). Second-generation AGCs have been shown to be able to deliver growth-enhancing substrates for nerve repair directly to the injury site. Although our laboratory has had success with second-generation AGCs filled with Schwann cells (SCs), SCs have their own set of issues clinically. Because of this, we have begun to utilize SC-derived exosomes as an alternative, as they have the appropriate protein markers, associate to axons in high concentrations, and are able to improve nerve regeneration. However, it is unknown how SC-derived exosomes may react within second-generation AGCs; thus, the aim of the present study was to assess the ability of SC-derived exosomes to be loaded into a second-generation AGC and how they would distribute within it.

MATERIALS AND METHODS

A total of 4 dry second-generation AGCs were loaded with SC-derived exosomes that were derived from green fluorescent protein (GFP)-labeled SCs. They were subsequently frozen and sliced before imaging.

RESULTS

Here, we present findings that SC-derived exosomes can be loaded into second-generation AGCs through our established loading method utilizing negative pressure and are able to survive and equally distribute along the length of the AGC.

CONCLUSIONS

Although only 4 second-generation AGCs were utilized, these findings indicate a potential use for SC-derived exosomes within second-generation AGCs to treat severe PNI. Future research should focus on exploring this in greater detail and in different contexts to assess the ability of SC-derived exosomes to survive at the site of injury and treat PNI.

Repetitive magnetic stimulation prevents dorsal root ganglion neuron death and enhances nerve regeneration in a sciatic nerve injury rat model

Peripheral nerve injury (PNI) often leads to retrograde cell death in the spinal cord and dorsal root ganglia (DRG), hindering nerve regeneration and functional recovery. Repetitive magnetic stimulation (rMS) promotes nerve regeneration following PNI. Therefore, this study aimed to investigate the effects of rMS on post-injury neuronal death and nerve regeneration. Seventy-two rats underwent autologous sciatic nerve grafting and were divided into two groups: the rMS group, which received rMS and the control (CON) group, which received no treatment. Motor neuron, DRG neuron, and caspase-3 positive DRG neuron counts, as well as DRG mRNA expression analyses, were conducted at 1-, 4-, and 8-weeks post-injury. Functional and axon regeneration analyses were performed at 8-weeks post-injury. The CON group demonstrated a decreased DRG neuron count starting from 1 week post-injury, whereas the rMS group exhibited significantly higher DRG neuron counts at 1- and 4-weeks post-injury. At 8-weeks post-injury, the rMS group demonstrated a significantly greater myelinated nerve fiber density in autografted nerves. Furthermore, functional analysis showed significant improvements in latency and toe angle in the rMS group. Overall, these results suggest that rMS can prevent DRG neuron death and enhance nerve regeneration and motor function recovery after PNI.

Upper limb peripheral nerve injuries in patients with ARDS requiring prone positioning: A systematic review with proportion meta-analysis

OBJECTIVE

To investigate the prevalence of upper limb peripheral nerve injuries (PNI) in adult patients admitted to the intensive care unit (ICU) with acute respiratory distress syndrome (ARDS) undergoing prone positioning.

METHODS

This systematic review with meta-analysis was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Meta-analysis of Observational Studies in Epidemiology (MOOSE) reporting guidelines. Four electronic databases including PubMed, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), The Cochrane Library, and EMBASE were searched from inception to January 2024. The quality of the included studies was evaluated according to the Joanna Briggs Institute Critical Appraisal Tools. A proportion meta-analysis was conducted to examine the combined prevalence of upper limb PNI among patients requiring prone positioning.

RESULTS

A total of 8 studies (511 patients) were pooled in the quantitative analysis. All studies had a low or moderate risk of bias in methodological quality. The overall proportion of patients with upper limb PNI was 13% (95%CI: 5% to 29%), with large between-study heterogeneity (I2 = 84.6%, P<0.001). Both ulnar neuropathy and brachial plexopathy were described in 4 studies.

CONCLUSION

During the COVID-19 pandemic, prone positioning has been used extensively. Different approaches among ICU teams and selective reporting by untrained staff may be a factor in interpreting the large variability between studies and the 13% proportion of patients with upper limb PNI found in the present meta-analysis. Therefore, it is paramount to stress the importance of patient assessment both after discharge from the ICU and during subsequent follow-up evaluations.

IMPLICATIONS FOR CLINICAL PRACTICE

Specialized training is essential to ensure safe prone positioning, with careful consideration given to arms and head placement to mitigate potential nerve injuries. Therefore, healthcare protocols should incorporate preventive strategies, with patient assessments conducted by expert multidisciplinary teams.

Electrospun PAN/PANI/CNT scaffolds and electrical pulses: a pathway to stem cell-derived nerve regeneration

Biocompatible polymer-based scaffolds hold great promise for neural repair, especially when they are coupled with electrostimulation to induce neural differentiation. In this study, a combination of polyacrylonitrile/polyaniline (PAN/PANI) and Carbon Nanotubes (CNTs) were used to fabricate three different biomimetic electrospun scaffolds (samples 1, 2 and 3 containing 0.26 wt%, 1 wt% and 2 wt% of CNTs, respectively). These scaffolds underwent thorough characterization for assessing electroconductivity, tensile strength, wettability, degradability, swelling, XRD, and FTIR data. Notably, scanning electron microscopy (SEM) images revealed a three-dimensional scaffold morphology with aligned fibers ranging from 60 nm to 292 nm in diameter. To comprehensively investigate the impact of electrical stimulation on the nervous differentiation of the stem cells seeded on these scaffolds, cell morphology and adhesion were assessed based on SEM images. Additionally, scaffold biocompatibility was studied through MTT assay. Importantly, Real-Time PCR results indicated the expression of neural markers-Nestin,β-tubulin III, and MAP2-by the cells cultured on these samples. In comparison with the control group, samples 1 and 2 exhibited significant increases in Nestin marker expression, indicating early stages of neuronal differentiation, whileβ-tubulin III expression was significantly reduced and MAP2 expression remained statistically unchanged. In contrast, sample 3 did not display a statistically significant upturn in Nestin maker expression, while showcasing remarkable increases in the expression of both MAP2 andβ-tubulin III, as markers of the end stages of differentiation, leading to postmitotic neurons. These results could be attributed to the higher electroconductivity of S3 compared to other samples. Our findings highlight the biomimetic potential of the prepared scaffolds for neural repair, illustrating their effectiveness in guiding stem cell differentiation toward a neural lineage.

Opioid Prescriptions at Discharge After Minimally Invasive Repair of Pectus Excavatum Are Reduced With Cryoablation

BACKGROUND

The minimally invasive repair of pectus excavatum (MIRPE) is associated with significant postoperative pain and opioid use. The objective of this study was to determine the effect of intercostal nerve cryoablation (Cryo) on inpatient and post-hospital opioid prescription practices following MIPRE.

METHODS

A retrospective review at a single pediatric center was conducted of patients ≤21 years old who underwent MIRPE. Oral morphine equivalents (OME) of inpatient and discharge opioids were compared between Cryo and no-Cryo cohorts.

RESULTS

579 patients were identified (82.8% male, mean age 15.4 ± 2.0 years). Cryo was performed in 73.5% of patients. The total inpatient OME use was less in the Cryo group (0.89 ± 0.68 vs. 1.6 ± 0.5 OME/kg/day; p < 0.001). Patients who underwent Cryo were prescribed significantly less OME at discharge compared to the no-Cryo group (3.9 ± 1.7 vs. 10.0 ± 4.1 OME mg/kg, p < 0.001). There was no statistically significant difference in the proportion of patients who required an opioid prescription refill (Cryo 12.4% vs. no-Cryo 11.5%, p = 0.884) or were readmitted (Cryo 5.3% vs. no-Cryo 4.6%, p = 0.833).

CONCLUSION

Patients who underwent cryoablation during MIRPE were prescribed significantly less opioid at the time of discharge without increasing the need for opioid refills or hospital readmissions.

LEVEL OF EVIDENCE

Treatment study; Level III evidence.

GCPII Inhibition Promotes Remyelination after Peripheral Nerve Injury in Aged Mice

Peripheral nerve injuries (PNIs) represent a significant clinical challenge, particularly in elderly populations where axonal remyelination and regeneration are impaired. Developing therapies to enhance these processes is crucial for improving PNI repair outcomes. Glutamate carboxypeptidase II (GCPII) is a neuropeptidase that plays a pivotal role in modulating glutamate signaling through its enzymatic cleavage of the abundant neuropeptide N-acetyl aspartyl glutamate (NAAG) to liberate glutamate. Within the PNS, GCPII is expressed in Schwann cells and activated macrophages, and its expression is amplified with aging. In this study, we explored the therapeutic potential of inhibiting GCPII activity following PNI. We report significant GCPII protein and activity upregulation following PNI, which was normalized by the potent and selective GCPII inhibitor 2-(phosphonomethyl)-pentanedioic acid (2-PMPA). In vitro, 2-PMPA robustly enhanced myelination in dorsal root ganglion (DRG) explants. In vivo, using a sciatic nerve crush injury model in aged mice, 2-PMPA accelerated remyelination, as evidenced by increased myelin sheath thickness and higher numbers of remyelinated axons. These findings suggest that GCPII inhibition may be a promising therapeutic strategy to enhance remyelination and potentially improve functional recovery after PNI, which is especially relevant in elderly PNI patients where this process is compromised.

Optimizing Surgical Outcomes and the Role of Preventive Surgery: A Scoping Review

BACKGROUND

 Plastic and reconstructive surgeons are often presented with reconstructive challenges as a sequela of complications in high-risk surgical patients, ranging from exposure of hardware, lymphedema, and chronic pain after amputation. These complications can result in significant morbidity, recovery time, resource utilization, and cost. Given the prevalence of surgical complications managed by plastic and reconstructive surgeons, developing novel preventative techniques to mitigate surgical risk is paramount.

METHODS

 Herein, we aim to understand efforts supporting the nascent field of Preventive Surgery, including (1) enhanced risk stratification, (2) advancements in postoperative care. Through an emphasis on four surgical cohorts who may benefit from preventive surgery, two of which are at high risk of morbidity from wound-related complications (patients undergoing sternotomy and spine procedures) and two at high risk of other morbidities, including lymphedema and neuropathic pain, we aim to provide a comprehensive and improved understanding of preventive surgery. Additionally, the role of risk analysis for these procedures and the relationship between microsurgery and prophylaxis is emphasized.

RESULTS

 (1) medical optimization and prehabilitation, (2) surgical mitigation techniques.

CONCLUSION

 Reconstructive surgeons are ideally placed to lead efforts in the creation and validation of accurate risk assessment tools and to support algorithmic approaches to surgical risk mitigation. Through a paradigm shift, including universal promotion of the concept of "Preventive Surgery," major improvements in surgical outcomes may be achieved.

Are There Hidden Adverse Events in Hypoglossal Nerve Stimulation: Comparing Social Media and a Federal Database

OBJECTIVE

Hypoglossal nerve stimulation (HNS) can be an effective treatment for moderate to severe obstructive sleep apnea (OSA) in positive airway pressure (PAP) intolerant patients. To better understand patient experiences with HNS therapy, we explored reported events from HNS-related Facebook groups and the Manufacturer and User Facility Device Experience (MAUDE) database.

METHODS

A retrospective analysis of HNS-related Facebook posts from three groups pertaining to HNS therapy, from October 1, 2022 to October 1, 2023, was performed. Posts were analyzed for patient-reported adverse events. Concurrently, the MAUDE database was reviewed for HNS-related events during the same timeframe.

RESULTS

From 737 Facebook posts, 132 (17.55%) adverse events were identified. Adverse events included pain (34.85%), stimulation discomfort (14.39%), lip weakness (6.82%) and issues related to lead tethering or tight leads around the neck (3.79%). Analysis of the MAUDE database found 428 adverse events, including pain (24.07%), lip weakness (0.44%), and lead tethering (1.64%).

CONCLUSION

Facebook group members reported higher rates of lip weakness and lead tethering than recorded in the MAUDE database. These findings illustrate how diverse data sources, such as social media, can enhance our understanding of patient experiences and identify gaps in patient education with HNS therapy.

LEVEL OF EVIDENCE

NA Laryngoscope, 2024.

Deciphering the molecular landscape of human peripheral nerves: implications for diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) is a prevalent complication of diabetes mellitus that is caused by metabolic toxicity to peripheral axons. We aimed to gain deep mechanistic insight into the disease process using bulk and spatial RNA sequencing on tibial and sural nerves recovered from lower leg amputations in a mostly diabetic population. First, our approach comparing mixed sensory and motor tibial and purely sensory sural nerves shows key pathway differences in affected nerves, with distinct immunological features observed in sural nerves. Second, spatial transcriptomics analysis of sural nerves reveals substantial shifts in endothelial and immune cell types associated with severe axonal loss. We also find clear evidence of neuronal gene transcript changes, like PRPH, in nerves with axonal loss suggesting perturbed RNA transport into distal sensory axons. This motivated further investigation into neuronal mRNA localization in peripheral nerve axons generating clear evidence of robust localization of mRNAs such as SCN9A and TRPV1 in human sensory axons. Our work gives new insight into the altered cellular and transcriptomic profiles in human nerves in DPN and highlights the importance of sensory axon mRNA transport as an unappreciated potential contributor to peripheral nerve degeneration.

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.

Histopathologic Study of the Effects of Surgically Applied Cryoanalgesia on Intercostal Nerves in a Live Porcine Model

Background/Objectives: The aim of this study was to establish a histologic baseline for cryoanalgesia of 2 min duration and evaluate the effects of different freeze durations. Methods: A porcine model was used in which the application of bilateral cryoanalgesia from intercostal spaces T3-T7 was completed via partial median sternotomy. The animals were kept alive for 7 days and the ribcages were sent to a specialized center for histopathologic analysis of the freezing injury. Results: Forty freezing lesions were completed and analyzed histologically. Thirty-eight (95%) of the cryo-lesions presented 100% nerve fiber degeneration at or distal to the ablation site, with preservation of the perineural connective tissue, as intended. The two unaffected nerves were found to be physically located outside of the freezing area. Conclusions: The complete axonal degeneration with preservation of the perineural tissue opens the possibility to shorter freezing times than the recommended 2 min. Visualization of the nerve and positioning of the probe is important in ensuring the proper effect on the nerve. This histologic analysis confirms the process triggered by cryoanalgesia that, until now, had only been assumed.

Foot drop in critically ill patients: a narrative review of an elusive complication with intricate implications for recovery and rehabilitation

Foot drop is a condition characterized by the inability to lift the foot upwards towards the shin bone. This condition may affect a proportion of critically ill patients, impacting on their recovery after the acute phase of the illness. The occurrence of foot drop in critical care patients may result from various underlying causes, including neurological injuries, muscular dysfunction, nerve compression, or vascular compromise. Understanding the etiology and assessing the severity of foot drop in these patients is essential for implementing appropriate management strategies and ensuring better patient outcomes. In this comprehensive review, we explore the complexities of foot drop in critically ill patients. We search for the potential risk factors that contribute to its development during critical illness, the impact it has on patients' functional abilities, and the various diagnostic techniques adopted to evaluate its severity. Additionally, we discuss current treatment approaches, rehabilitation strategies, and preventive measures to mitigate the adverse effects of foot drop in the critical care setting. Furthermore, we explore the roles of critical care physical therapists, neurologists, and other healthcare professionals in the comprehensive care of patients with foot drop syndrome and in such highlighting the importance of a multidisciplinary approach.

A wirelessly programmable, skin-integrated thermo-haptic stimulator system for virtual reality

Sensations of heat and touch produced by receptors in the skin are of essential importance for perceptions of the physical environment, with a particularly powerful role in interpersonal interactions. Advances in technologies for replicating these sensations in a programmable manner have the potential not only to enhance virtual/augmented reality environments but they also hold promise in medical applications for individuals with amputations or impaired sensory function. Engineering challenges are in achieving interfaces with precise spatial resolution, power-efficient operation, wide dynamic range, and fast temporal responses in both thermal and in physical modulation, with forms that can extend over large regions of the body. This paper introduces a wireless, skin-compatible interface for thermo-haptic modulation designed to address some of these challenges, with the ability to deliver programmable patterns of enhanced vibrational displacement and high-speed thermal stimulation. Experimental and computational investigations quantify the thermal and mechanical efficiency of a vertically stacked design layout in the thermo-haptic stimulators that also supports real-time, closed-loop control mechanisms. The platform is effective in conveying thermal and physical information through the skin, as demonstrated in the control of robotic prosthetics and in interactions with pressure/temperature-sensitive touch displays.

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.

Delayed repair of the facial nerve and its negative impacts on nerve and muscle regeneration

Background

In this experimental protocol, we evaluated the immediate and delayed repair of the buccal branch of the facial nerve (BBFN) with heterologous fibrin biopolymer (HFB) as a coaptation medium and the use of photobiomodulation (PBM), performing functional and histomorphometric analysis of the BBFN and perioral muscles.

Methods

Twenty-eight rats were divided into eight groups using the BBFN bilaterally (the left nerve was used for PBM), namely: G1 - control group, right BBFN (without injury); G2 - control group, left BBFN (without injury + PBM); G3 - Denervated right BBFN (neurotmesis); G4 - Denervated left BBFN (neurotmesis + PBM); G5 - Immediate repair of right BBFN (neurotmesis + HFB); G6 - Immediate repair of left BBFN (neurotmesis + HFB + PBM); G7 - Delayed repair of right BBFN (neurotmesis + HFB); G8 - Delayed repair of left BBFN (neurotmesis + HFB + PBM). Delayed repair occurred after two weeks of denervation. All animals were sacrificed after six weeks postoperatively.

Results

In the parameters of the BBFN, we observed inferior results in the groups with delayed repair, in relation to the groups with immediate repair, with a significant difference (p < 0.05) in the diameter of the nerve fiber, the axon, and the thickness of the myelin sheath of the group with immediate repair with PBM compared to the other experimental groups. In measuring the muscle fiber area, groups G7 (826.4 ± 69.90) and G8 (836.7 ± 96.44) were similar to G5 (882.8 ± 70.51). In the functional analysis, the G7 (4.10 ± 0.07) and G8 (4.12 ± 0.08) groups presented normal parameters.

Conclusion

We demonstrated that delayed repair of BBFN is possible with HFB, but with worse results compared to immediate repair, and that PBM has a positive influence on nerve regeneration results in immediate repair.

Mesenchymal stem cells' "garbage bags" at work: Treating radial nerve injury with mesenchymal stem cell-derived exosomes

Unlike central nervous system injuries, peripheral nerve injuries (PNIs) are often characterized by more or less successful axonal regeneration. However, structural and functional recovery is a senile process involving multifaceted cellular and molecular processes. The contemporary treatment options are limited, with surgical intervention as the gold-standard method; however, each treatment option has its associated limitations, especially when the injury is severe with a large gap. Recent advancements in cell-based therapy and cell-free therapy approaches using stem cell-derived soluble and insoluble components of the cell secretome are fast-emerging therapeutic approaches to treating acute and chronic PNI. The recent pilot study is a leap forward in the field, which is expected to pave the way for more enormous, systematic, and well-designed clinical trials to assess the therapeutic efficacy of mesenchymal stem cell-derived exosomes as a bio-drug either alone or as part of a combinatorial approach, in an attempt synergize the best of novel treatment approaches to address the complexity of the neural repair and regeneration.

Carpal tunnel syndrome

Carpal tunnel syndrome (CTS) is the most common nerve entrapment disorder worldwide. The epidemiology and risk factors, including family burden, for developing CTS are multi-factorial. Despite much research, its intricate pathophysiological mechanism(s) are not fully understood. An underlying subclinical neuropathy may indicate an increased susceptibility to developing CTS. Although surgery is often performed for CTS, clear international guidelines to indicate when to perform non-surgical or surgical treatment, based on stage and severity of CTS, remain to be elucidated. Neurophysiological examination, using electrophysiology or ultrasonography, performed in certain circumstances, should correlate with the history and findings in clinical examination of the person with CTS. History and clinical examination are particularly relevant globally owing to lack of other equipment. Various instruments are used to assess CTS and treatment outcomes as well as the effect of the disorder on quality of life. The surgical treatment options of CTS - open or endoscopic - offer an effective solution to mitigate functional impairments and pain. However, there are risks of post-operative persistent or recurrent symptoms, requiring meticulous diagnostic re-evaluation before any additional surgery. Health-care professionals should have increased awareness about CTS and all its implications. Future considerations of CTS include use of linked national registries to understand risk factors, explore possible screening methods, and evaluate diagnosis and treatment with a broader perspective beyond surgery, including psychological well-being.

Outcomes of complete neurotomy and immediate repair of the musculocutaneous nerve for treatment of elbow spasticity

Neurotomy interrupts the stretch reflex and can be used for the treatment of spasticity. We hypothesized that neurotomy with nerve repair reduces spasticity while preserving motor function due to the preferential recovery of efferent over afferent fibres. This study reports the 1-year outcomes of neurotomy and immediate repair of the musculocutaneous nerve in the proximal arm for treatment of elbow flexor spasticity, comparing these to outcomes in the literature for neurectomy without nerve repair. A total of 10 adult patients with spasticity of the elbow flexors from stroke or traumatic brain injury who had undergone neurotomy and immediate repair of the musculocutaneous nerve were prospectively studied. The results suggest that this procedure effectively reduces elbow flexor spasticity, improves elbow resting position, active elbow extension and is useful for achieving patient goals with effects lasting at least 12 months.Level of evidence: IV (therapeutic).

Traumatic and iatrogenic sciatic nerve injury in 38 dogs and 10 cats: Clinical and electrodiagnostic findings

BACKGROUND

Reports describing sciatic nerve injuries (SNI) and their outcome are scarce in veterinary medicine.

HYPOTHESIS

Describe the causes of traumatic and iatrogenic SNI and evaluate which clinical and electrodiagnostic findings predict outcome.

ANIMALS

Thirty-eight dogs and 10 cats with confirmed SNI referred for neurologic and electrodiagnostic evaluation.

METHODS

Clinical and electrodiagnostic examination results, including electromyography (EMG), motor nerve conduction studies, muscle-evoked potential (MEP), F-waves, sensory nerve conduction studies, and cord dorsum potential (CDP), were retrospectively evaluated. Quality of life (QoL) was assessed based on owner interviews.

RESULTS

Surgery (42%) and trauma (33%) were the most common causes of SNI; in dogs, 24% were caused by bites from wild boars. Ability to flex and extend the tarsus was significantly associated with positive outcome in dogs. Mean time from onset of clinical signs until electrodiagnostic evaluation was 67 ± 65 (range, 7-300) days and 65 ± 108 (range, 7-365) days for dogs and cats, respectively. A cut-off amplitude of 1.45 mV for compound motor action potentials (CMAP) was predictive of positive outcome in dogs (P = .01), with sensitivity of 58% and specificity of 100%.

CONCLUSIONS AND CLINICAL IMPORTANCE

Clinical motor function predicts recovery better than sensory function. Electrodiagnostic findings also may play a role in predicting the outcome of SNI. Application of the proposed CMAP cut-off amplitude may assist clinicians in shortening the time to reassessment or for earlier suggestion of salvage procedures. Owners perceived a good quality of life (QoL), even in cases of hindlimb amputation.

Incidence and clinical outcome of lateral femoral cutaneous nerve injury after periacetabular osteotomy

Aims

Lateral femoral cutaneous nerve (LFCN) injury is a complication after periacetabular osteo-tomy (PAO) using an anterior approach, which might adversely affect the outcome. However, no prospective study has assessed the incidence and severity of this injury and its effect on the clinical outcomes over a period of time for longer than one year after PAO. The aim of this study was to assess the incidence and severity of the symptoms of LFCN injury for ≥ three years after PAO and report its effect on clinical outcomes.

Methods

A total of 40 hips in 40 consecutive patients who underwent PAO between May 2016 and July 2018 were included in the study, as further follow-up of the same patients from a previous study. We prospectively evaluated the incidence, severity, and area of symptoms following LFCN injury. We also recorded the clinical scores at one year and ≥ three years postoperatively using the 36-Item Short Form Health Survey (SF-36) and Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire (JHEQ) scores.

Results

A total of 20 patients (50%) had symptoms of a LFCN injury at one year after PAO. At ≥ three years postoperatively, the symptoms had completely resolved in seven of these patients and 13 (33%) had persistent symptoms. The severity and area of symptoms did not significantly differ between one and ≥ three years postoperatively. The JHEQ showed significant differences in the patient satisfaction and mental scores between those with and those without sypmtoms of LFCN injury at ≥ three years postoperatively, while there was no significant difference in the mean SF-36 scores.

Conclusion

The incidence of LFCN injury after PAO using an anterior approach is high. The outcome of PAO, ≥ three years postoperatively, is poorer in patients with persistent symptoms from a perioperative LFCN injury, in that patient satisfaction and mental health scores are adversely affected.

Enhancing nerve regeneration in infraorbital nerve injury rat model: effects of vitamin B complex and photobiomodulation

Orofacial nerve injuries may result in temporary or long-term loss of sensory function and decreased quality of life in patients. B vitamins are required for DNA synthesis and the repair and maintenance of phospholipids. In particular, vitamins B1, B6, and B12 are essential for neuronal function. Deficiency in vitamin B complex (VBC) has been linked to increased oxidative stress, inflammation and demyelination. Photobiomodulation (PBM) has antioxidant activity and is neuroprotective. In addition, a growing literature attests to the positive effects of PBM on nerve repair. To assess the effect of PBM and VBC on regenerative process we evaluated the expression of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), myelin basic protein (MBP), laminin and neurofilaments (NFs) using Western blotting to identify regenerative pattern after chronic constriction injury of the infraorbital nerve (CCI IoN) treated by PBM, VBC or its combination. After CCI IoN, the rats were divided into six groups naive, sham, injured (CCI IoN), treated with photobiomodulation (904 nm, 6.23 J/cm2, CCI IoN + PBM), treated with VBC (containing B1, B6 and B12) 5 times, CCI IoN + VBC) and treated with PBM and VBC (CCI IoN + VBC + PBM). The treatments could revert low expression of BDNF, MBP and laminin. Also reverted the higher expression of neurofilaments and enhanced expression of NGF. PBM and VBC could accelerate injured infraorbital nerve repair in rats through reducing the expression of neurofilaments, increasing the expression of BDNF, laminin and MBP and overexpressing NGF. These data support the notion that the use of PBM and VBC may help in the treatment of nerve injuries. This finding has potential clinical applications.

Bone-nerve crosstalk: a new state for neuralizing bone tissue engineering-A mini review

Neuro bone tissue engineering is a multidisciplinary field that combines both principles of neurobiology and bone tissue engineering to develop innovative strategies for repairing and regenerating injured bone tissues. Despite the fact that regeneration and development are considered two distinct biological processes, yet regeneration can be considered the reactivation of development in later life stages to restore missing tissues. It is noteworthy that the regeneration capabilities are distinct and vary from one organism to another (teleost fishes, hydra, humans), or even in the same organism can vary dependent on the injured tissue itself (Human central nervous system vs. peripheral nervous system). The skeletal tissue is highly innervated, peripheral nervous system plays a role in conveying the signals and connecting the central nervous system with the peripheral organs, moreover it has been shown that they play an important role in tissue regeneration. Their regeneration role is conveyed by the different cells' resident in it and in its endoneurium (fibroblasts, microphages, vasculature associated cells, and Schwann cells) these cells secrete various growth factors (NGF, BDNF, GDNF, NT-3, and bFGF) that contribute to the regenerative phenotype. The peripheral nervous system and central nervous system synchronize together in regulating bone homeostasis and regeneration through neurogenic factors and neural circuits. Receptors of important central nervous system peptides such as Serotonin, Leptin, Semaphorins, and BDNF are expressed in bone tissue playing a role in bone homeostasis, metabolism and regeneration. This review will highlight the crosstalk between peripheral nerves and bone in the developmental stages as well as in regeneration and different neuro-bone tissue engineering strategies for repairing severe bone injuries.

Insights on the Choice and Preparation of the Donor Nerve in Corneal Neurotization for Neurotrophic Keratopathy: A Narrative Review

The article introduces neurotrophic keratopathy (NK), a condition resulting from corneal denervation due to various causes of trigeminal nerve dysfunctions. Surgical techniques for corneal neurotization (CN) have evolved, aiming to restore corneal sensitivity. Initially proposed in 1972, modern approaches offer less invasive options. CN can be performed through a direct approach (DCN) directly suturing a sensitive nerve to the affected cornea or indirectly (ICN) through a nerve auto/allograft. Surgical success relies on meticulous donor nerve selection and preparation, often involving multidisciplinary teams. A PubMed research and review of the relevant literature was conducted regarding the surgical approach, emphasizing surgical techniques and the choice of the donor nerve. The latter considers factors like sensory integrity and proximity to the cornea. The most used are the contralateral or ipsilateral supratrochlear (STN), and the supraorbital (SON) and great auricular (GAN) nerves. Regarding the choice of grafts, the most used in the literature are the sural (SN), the lateral antebrachial cutaneous nerve (LABCN), and the GAN nerves. Another promising option is represented by allografts (acellularized nerves from cadavers). The significance of sensory recovery and factors influencing surgical outcomes, including nerve caliber matching and axonal regeneration, are discussed. Future directions emphasize less invasive techniques and the potential of acellular nerve allografts. In conclusion, CN represents a promising avenue in the treatment of NK, offering tailored approaches based on patient history and surgical expertise, with new emerging techniques warranting further exploration through basic science refinements and clinical trials.

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

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

Nerve Transfer After Cervical Spinal Cord Injury: Who Has a "Time Sensitive" Injury Based on Electrodiagnostic Findings?

OBJECTIVE

To use the ulnar compound muscle action potential (CMAP) to abductor digiti minimi (ADM) to identify the proportion of individuals with cervical spinal cord injury (SCI) who have lower motor neuron (LMN) abnormalities involving the C8-T1 spinal nerve roots, within 3-6 months, and thus may influence the response to nerve transfer surgery.

DESIGN

Retrospective analysis of prospectively collected data. Data were analyzed from European Multicenter Study About SCI database.

SETTING

Multi-center, academic hospitals.

PARTICIPANTS

We included 79 subjects (age=41.4±17.7, range:16-75; 59 men; N=79), who were classified as cervical level injuries 2 weeks after injury and who had manual muscle strength examinations that would warrant consideration for nerve transfer (C5≥4, C8<3).

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

The ulnar nerve CMAP amplitude to ADM was used as a proxy measure for C8-T1 spinal segment health. CMAP amplitude was stratified into very abnormal (<1.0 mV), sub-normal (1.0-5.9 mV), and normal (>6.0 mV). Analysis took place at 3 (n=148 limbs) and 6 months (n=145 limbs).

RESULTS

At 3- and 6-month post-injury, 33.1% and 28.3% of limbs had very abnormal CMAP amplitudes, respectively, while in 54.1% and 51.7%, CMAPs were sub-normal. Median change in amplitude from 3 to 6 months was 0.0 mV for very abnormal and 1.0 mV for subnormal groups. A 3-month ulnar CMAP <1 mV had a positive predictive value of 0.73 (95% CI 0.69-0.76) and 0.78 (95% CI 0.75-0.80) for C8 and T1 muscle strength of 0 vs 1 or 2.

CONCLUSION

A high proportion of individuals have ulnar CMAPs below the lower limit of normal 3- and 6-month post cervical SCI and may also have intercurrent LMN injury. Failure to identify individuals with LMN denervation could result in a lost opportunity to improve hand function through timely nerve transfer surgeries.

Optimal examination for traumatic nerve/muscle injuries in earthquake survivors: a retrospective observational study

BACKGROUND

Physiatrists are facing with survivors from disasters in both the acute and chronic phases of muscle and nerve injuries. Similar to many other clinical conditions, neuromusculoskeletal ultrasound can play a key role in the management of such cases (with various muscle/nerve injuries) as well. Accordingly, in this article, a recent single-center experience after the Turkey-Syria earthquake will be rendered.

METHODS

Ultrasound examinations were performed for various nerve/muscle lesions in 52 earthquake victims referred from different cities. Demographic features, type of injuries, and applied treatment procedures as well as detailed ultrasonographic findings are illustrated.

RESULTS

Of the 52 patients, 19 had incomplete peripheral nerve lesions of the brachial plexus (n=4), lumbosacral plexus (n=1), and upper and lower limbs (n=14).

CONCLUSION

The ultrasonographic approach during disaster relief is paramount as regards subacute and chronic phases of rehabilitation. Considering technological advances (e.g., portable machines), the use of on-site ultrasound examination in the (very) early phases of disaster response also needs to be on the agenda of medical personnel.

Gene-environment interaction elicits dystonia-like features and impaired translational regulation in a DYT-TOR1A mouse model

DYT-TOR1A dystonia is the most common monogenic dystonia characterized by involuntary muscle contractions and lack of therapeutic options. Despite some insights into its etiology, the disease's pathophysiology remains unclear. The reduced penetrance of about 30% suggests that extragenetic factors are needed to develop a dystonic phenotype. In order to systematically investigate this hypothesis, we induced a sciatic nerve crush injury in a genetically predisposed DYT-TOR1A mouse model (DYT1KI) to evoke a dystonic phenotype. Subsequently, we employed a multi-omic approach to uncover novel pathophysiological pathways that might be responsible for this condition. Using an unbiased deep-learning-based characterization of the dystonic phenotype showed that nerve-injured DYT1KI animals exhibited significantly more dystonia-like movements (DLM) compared to naive DYT1KI animals. This finding was noticeable as early as two weeks following the surgical procedure. Furthermore, nerve-injured DYT1KI mice displayed significantly more DLM than nerve-injured wildtype (wt) animals starting at 6 weeks post injury. In the cerebellum of nerve-injured wt mice, multi-omic analysis pointed towards regulation in translation related processes. These observations were not made in the cerebellum of nerve-injured DYT1KI mice; instead, they were localized to the cortex and striatum. Our findings indicate a failed translational compensatory mechanisms in the cerebellum of phenotypic DYT1KI mice that exhibit DLM, while translation dysregulations in the cortex and striatum likely promotes the dystonic phenotype.

Differentiated mesenchymal stem cells-derived exosomes immobilized in decellularized sciatic nerve hydrogels for peripheral nerve repair

Peripheral nerve injury (PNI) and the limitations of current treatments often result in incomplete sensory and motor function recovery, which significantly impact the patient's quality of life. While exosomes (Exo) derived from stem cells and Schwann cells have shown promise on promoting PNI repair following systemic administration or intraneural injection, achieving effective local and sustained Exo delivery holds promise to treat local PNI and remains challenging. In this study, we developed Exo-loaded decellularized porcine nerve hydrogels (DNH) for PNI repair. We successfully isolated Exo from differentiated human adipose-derived mesenchymal stem cells (hADMSC) with a Schwann cell-like phenotype (denoted as dExo). These dExo were further combined with polyethylenimine (PEI), and DNH to create polyplex hydrogels (dExo-loaded pDNH). At a PEI content of 0.1%, pDNH showed cytocompatibility for hADMSCs and supported neurite outgrowth of dorsal root ganglions. The sustained release of dExos from dExo-loaded pDNH persisted for at least 21 days both in vitro and in vivo. When applied around injured nerves in a mouse sciatic nerve crush injury model, the dExo-loaded pDNH group significantly improved sensory and motor function recovery and enhanced remyelination compared to dExo and pDNH only groups, highlighting the synergistic regenerative effects. Interestingly, we observed a negative correlation between the number of colony-stimulating factor-1 receptor (CSF-1R) positive cells and the extent of PNI regeneration at the 21-day post-surgery stage. Subsequent in vitro experiments demonstrated the potential involvement of the CSF-1/CSF-1R axis in Schwann cells and macrophage interaction, with dExo effectively downregulating CSF-1/CSF-1R signaling.

The weepy cry - short neural signal bursts in intraoperative neuromonitoring

PURPOSE

This study aimed to establish an in-vitro alternative to existing in-vivo systems to analyze nerve dysfunction using continuous neuromonitoring (C-IONM).

METHODS

Three hundred sixty-three recurrent laryngeal nerves (RLN) (N(pigs) = 304, N(cattle) = 59) from food industry cadavers were exposed by microsurgical dissection following euthanasia. After rinsing with Ringer's lactate, they were tempered at 22 °C. Signal evaluation using C-IONM was performed for 10 min at 2 min intervals, and traction forces of up to 2N were applied for a median time of 60 s. Based on their post-traumatic electrophysiological response, RLNs were classified into four groups: Group A: Amplitude ≥ 100%, Group B: loss of function (LOS) 0-25%, Group C: ≥ 25-50%, and Group D: > 50%.

RESULTS

A viable in-vitro neuromonitoring system was established. The median post-traumatic amplitudes were 112%, 88%, 59%, and 9% in groups A, B, C, and D, respectively. A time-dependent further dynamic LOS was observed during the 10 min after cessation of strain. Surprisingly, following initial post-traumatic hyperconductivity, complete LOS occurred in up to 20% of the nerves in group A. The critical threshold for triggering LOS was 2N in all four groups, resulting in immediate paralysis of up to 51.4% of the nerves studied.

CONCLUSION

Consistent with in-vivo studies, RLN exhibit significant intrinsic electrophysiological variability in response to tensile forces. Moreover, nerve damage progresses even after the complete cessation of strain. Up to 20% of nerves with transiently increased post-traumatic amplitudes above 100% developed complete LOS, which we termed the "weepy cry." This time-delayed response must be considered during the interpretation of C-IONM signals.

Post-COVID-19 Unilateral Upper Lip Numbness: A Case Report

This is a case of a 63-year-old female with post-COVID-19 unilateral upper lip pain and numbness. Neurologic examination did not reveal any deficits other than deficits on pinprick in the maxillary division (V2) of the left trigeminal nerve. Brain neuroimaging showed signs of acute inflammation of the left maxillary sinus. Neuropraxia of the infraorbital nerve, a branch of the trigeminal nerve, was the diagnosis considered. Reports on trigeminal neurosensory changes following acute sinusitis are few, and isolated trigeminal neuropathy is rare except in cases of dental disorders. Up to this writing, there have been no reports on post-COVID-19 unilateral upper lip numbness and pain. This study will also serve as a concise review on the correlative neuroanatomy of the trigeminal nerve.

Emerging role of extracellular vesicles and exogenous stimuli in molecular mechanisms of peripheral nerve regeneration

Peripheral nerve injuries lead to significant morbidity and adversely affect quality of life. The peripheral nervous system harbors the unique trait of autonomous regeneration; however, achieving successful regeneration remains uncertain. Research continues to augment and expedite successful peripheral nerve recovery, offering promising strategies for promoting peripheral nerve regeneration (PNR). These include leveraging extracellular vesicle (EV) communication and harnessing cellular activation through electrical and mechanical stimulation. Small extracellular vesicles (sEVs), 30-150 nm in diameter, play a pivotal role in regulating intercellular communication within the regenerative cascade, specifically among nerve cells, Schwann cells, macrophages, and fibroblasts. Furthermore, the utilization of exogenous stimuli, including electrical stimulation (ES), ultrasound stimulation (US), and extracorporeal shock wave therapy (ESWT), offers remarkable advantages in accelerating and augmenting PNR. Moreover, the application of mechanical and electrical stimuli can potentially affect the biogenesis and secretion of sEVs, consequently leading to potential improvements in PNR. In this review article, we comprehensively delve into the intricacies of cell-to-cell communication facilitated by sEVs and the key regulatory signaling pathways governing PNR. Additionally, we investigated the broad-ranging impacts of ES, US, and ESWT on PNR.

Long-Term Sensory Function 3 years after Minimally Invasive Repair of Pectus Excavatum with Cryoablation

INTRODUCTION

Minimally invasive repair of pectus excavatum (MIRPE) with intercostal nerve cryoablation (Cryo) decreases length of hospitalization and opioid use, but long-term recovery of sensation has been poorly described. The purpose of this study was to quantify long-term hypoesthesia and neuropathic pain after MIRPE with Cryo.

METHODS

A prospective cohort study was conducted single-institution of patients ≤21 years who presented for bar removal. Consented patients underwent chest wall sensory testing and completed neuropathic pain screening. Chest wall hypoesthesia to cold, soft touch, and pinprick were measured as the percent of the treated anterior chest wall surface area (TACWSA); neuropathic pain was evaluated by questionnaire.

RESULTS

The study enrolled 47 patients; 87% male; median age 18.4 years. The median bar dwell time was 2.9 years. A median of 2 bars were placed; 80.9% were secured with pericostal sutures. At enrollment, 46.8% of patients had identifiable chest wall hypoesthesia. The mean percentage of TACWSA with hypoesthesia was 4.7 ± 9.3% (cold), 3.9 ± 7.7% (soft touch), and 5.9 ± 11.8% (pinprick). Hypoesthesia to cold was found in 0 dermatomes in 62%, 1 dermatome in 11%, 2 dermatomes in 17% and ≥3 dermatomes in 11%. T5 was the most common dermatome with hypoesthesia. Neuropathic symptoms were identified by 13% of patients; none required treatment.

CONCLUSION

In long-term follow up after MIRPE with Cryo, 46.8% of patients experienced some chest wall hypoesthesia; the average TACWSA with hypoesthesia was 4-6%. Hypoesthesia was mostly limited to 1-2 dermatomes, most commonly T5. Chronic symptomatic neuropathic pain was rare.

LEVEL OF EVIDENCE

Level IV.

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.

Ortner syndrome as a presenting symptom of severe chronic mitral regurgitation in heart failure: A case report

Ortner's syndrome or cardiovocal syndrome is a clinical condition associated with hoarseness due to left recurrent laryngeal nerve palsy from compression of surrounding cardiovascular structures. Atrial enlargement, commonly caused by chronic mitral regurgitation (MR) may be a source of compression. We present a case of a 53-year-old man with decompensated heart failure (HF) with a new onset of hoarseness. Chest radiograph showed cardiomegaly with evidence of fluid overload; transthoracic echocardiography showed bi-atrial enlargement secondary to severe chronic mitral regurgitation and moderate pulmonary hypertension. As a result, the diagnosis of Ortner's syndrome was made. For patients with new onset hoarseness with a history of severe cardiovascular disease, Ortner's syndrome should be considered and early initiation of therapy can help reduce the incidence.

Neural dependency in wound healing and regeneration

In response to injury, humans and many other mammals form a fibrous scar that lacks the structure and function of the original tissue, whereas other vertebrate species can spontaneously regenerate damaged tissues and structures. Peripheral nerves have been identified as essential mediators of wound healing and regeneration in both mammalian and nonmammalian systems, interacting with the milieu of cells and biochemical signals present in the post-injury microenvironment. This review examines the diverse functions of peripheral nerves in tissue repair and regeneration, specifically during the processes of wound healing, blastema formation, and organ repair. We compare available evidence in mammalian and nonmammalian models, identifying critical nerve-mediated mechanisms for regeneration and providing future perspectives toward integrating these mechanisms into a therapeutic framework to promote regeneration.

The Role of Early Rehabilitation and Functional Electrical Stimulation in Rehabilitation for Cats with Partial Traumatic Brachial Plexus Injury: A Pilot Study on Domestic Cats in Portugal

This prospective observational cohort pilot study included 22 cats diagnosed with partial traumatic brachial plexus injury (PTBPI), aiming to explore responses to an early intensive neurorehabilitation protocol in a clinical setting. This protocol included functional electrical stimulation (FES), locomotor treadmill training and kinesiotherapy exercises, starting at the time with highest probability of nerve repair. The synergetic benefits of this multimodal approach were based on the potential structural and protective role of proteins and the release of neurotrophic factors. Furthermore, FES was parametrized according to the presence or absence of deep pain. Following treatment, 72.6% of the cats achieved ambulation: 9 cats within 15 days, 2 cats within 30 days and 5 cats within 60 days. During the four-year follow-up, there was evidence of improvement in both muscle mass and muscle weakness, in addition to the disappearance of neuropathic pain. Notably, after the 60 days of neurorehabilitation, 3 cats showed improved ambulation after arthrodesis of the carpus. Thus, early rehabilitation, with FES applied in the first weeks after injury and accurate parametrization according to the presence or absence of deep pain, may help in functional recovery and ambulation, reducing the probability of amputation.

Nerve Wrap for Local Delivery of FK506/Tacrolimus Accelerates Nerve Regeneration

Peripheral nerve injuries (PNIs) occur frequently and can lead to devastating and permanent sensory and motor function disabilities. Systemic tacrolimus (FK506) administration has been shown to hasten recovery and improve functional outcomes after PNI repair. Unfortunately, high systemic levels of FK506 can result in adverse side effects. The localized administration of FK506 could provide the neuroregenerative benefits of FK506 while avoiding systemic, off-target side effects. This study investigates the utility of a novel FK506-impregnated polyester urethane urea (PEUU) nerve wrap to treat PNI in a previously validated rat infraorbital nerve (ION) transection and repair model. ION function was assessed by microelectrode recordings of trigeminal ganglion cells responding to controlled vibrissae deflections in ION-transected and -repaired animals, with and without the nerve wrap. Peristimulus time histograms (PSTHs) having 1 ms bins were constructed from spike times of individual single units. Responses to stimulus onsets (ON responses) were calculated during a 20 ms period beginning 1 ms after deflection onset; this epoch captures the initial, transient phase of the whisker-evoked response. Compared to no-wrap controls, rats with PEUU-FK506 wraps functionally recovered earlier, displaying larger response magnitudes. With nerve wrap treatment, FK506 blood levels up to six weeks were measured nearly at the limit of quantification (LOQ ≥ 2.0 ng/mL); whereas the drug concentrations within the ION and muscle were much higher, demonstrating the local delivery of FK506 to treat PNI. An immunohistological assessment of ION showed increased myelin expression for animals assigned to neurorrhaphy with PEUU-FK506 treatment compared to untreated or systemic-FK506-treated animals, suggesting that improved PNI outcomes using PEUU-FK506 is mediated by the modulation of Schwann cell activity.

The Effect of Liraglutide on Axon Regeneration and Functional Recovery after Peripheral Nerve Lesion

Peripheral nerve injuries inflict severe consequences, necessitating innovative therapeutic strategies. This study investigates the potential of liraglutide, a glucagon-like peptide-1 receptor agonist, in mitigating the consequences of peripheral nerve injury. The existing treatment methods for such injuries underscore the importance of ongoing translational research efforts. Thirty adult Wistar rats underwent sciatic nerve dissection and repair surgery. The nerves were surgically transected using micro scissors at a precise location located 1.5 cm proximal to the trifurcation site. The study included a control group and two experimental groups, one treated with saline (placebo group) and the other with liraglutide (experimental group) for 12 weeks. Motor function, electromyography (EMG), and biochemical and histopathological analyses were performed after 12 weeks of treatment. Electrophysiological assessments revealed that liraglutide improved the compound muscle action potential (CMAP) amplitude and motor function compared to the saline-treated group. Histological and immunohistochemical analyses demonstrated increased NGF expression, total axon number, and diameter and reduced fibrosis in the liraglutide group. Biochemical analyses illustrated liraglutide's antioxidative properties, evidenced by reduced malondialdehyde (MDA) levels. Galectin-3 levels were suppressed and GDF-11 levels were modulated by liraglutide, indicating anti-inflammatory and anti-apoptotic effects. Liraglutide is a promising therapeutic intervention for peripheral nerve injuries, promoting functional recovery and histopathological improvement. Its multifaceted positive impact, beyond glycemic control, suggests constructive effects on the acute and chronic inflammatory processes associated with peripheral neuropathy. These findings warrant further research to elucidate molecular mechanisms and facilitate clinical translation. The study contributes valuable insights to the growing understanding of GLP-1 receptor agonists' neuroprotective properties in the context of peripheral nerve injuries.

A Prospective Study of Sensory Changes in Pediatric Patients After Minimally Invasive Repair of Pectus Excavatum With Cryoablation

BACKGROUND

Cryoablation during minimally invasive repair for pectus excavatum (MIRPE) reduces opioid use and hospital length of stay. Skin hypoesthesia of the chest wall also occurs. This study sought to determine the frequency, onset, duration, and location of sensory changes and neuropathic pain after cryoablation.

METHODS

A prospective study was conducted on patients aged ≤21 years undergoing MIRPE with cryoablation of T3 to T7 dermatomes bilaterally for 120 s at a single institution between March 2021 to December 2022. Patients underwent sensory testing of the chest wall and neuropathic pain surveys (S-LANSS) preoperatively and then postoperatively for 6 months. Incidence and duration of hypoesthesia and neuropathic pain were evaluated.

RESULTS

Of 61 patients enrolled in the study, 45 completed evaluations at six months postoperatively. All patients had skin hypoesthesia on postoperative day (POD)1. The mean percentage of the treated anterior chest wall surface area (TACWSA) with hypoesthesia to cold stimulus was 52% (±29.3) on POD 0 and 55% (±19.7) on POD 1. Sensation returned over time, with hypoesthesia affecting 11.1% (±15.5) TACWSA at 6 months. At study completion 58% of patients (26/45) had complete return of sensation; hypoesthesia was found at: 1 dermatome 13% (2/45), 2 dermatomes 22% (11/45), and 3 dermatomes 4% (2/45). Neuropathic pain (S-LANSS ≥12) was documented in 16% (9/55) of patients at hospital discharge but decreased to 6.7% of patients at 6 months.

CONCLUSION

Onset of skin hypoesthesia after cryoablation occurred on POD0 and affected 52% of the TACWSA. All patients experienced return of sensation to varying degrees, with 58% experiencing normal sensation in all dermatomes by 6 months. The etiology of persistent hypoesthesia to select dermatomes is unknown but may be related to operative technique or cryoablation. Chronic neuropathic pain is uncommon.

LEVEL OF EVIDENCE

II.

TYPE OF STUDY

Prognosis Study.

Safety and Effectiveness of Stellate Ganglion Cryoablation in Complex Regional Pain Syndrome

This was a retrospective, observational, descriptive study to evaluate the safety and 6-month effectiveness of percutaneous cryoablation of the stellate ganglion for the treatment of complex regional pain syndrome (CRPS). Eight patients with CRPS diagnosed by Budapest criteria were treated with this procedure. CRPS symptom severity was assessed prior to the procedure and at 3-month intervals after the procedure using a novel CRPS scoring system-the Budapest score-created by the authors. The mean Budapest score prior to and 6 months (187 days, SD ± 43) after stellate ganglion cryoablation was 7.0 (SD ± 2.0) (n = 6) and 3.8 (SD ± 2.3) (n = 6), respectively, showing a decrease of 3.2 (SD ± 1.7) (n = 6; P = .006). There were no major adverse events due to the procedure, and there was only 1 minor adverse event. Stellate ganglion cryoablation is a feasible, safe, and minimally invasive procedure that may represent an efficacious adjunct treatment option for select patients with CRPS.

Prospect of Mesenchymal Stem Cells in Enhancing Nerve Regeneration in Brachial Plexus Injury in Animals: A Systematic Review

Objectives

Brachial plexus injuries (BPI), although rare, often results in significant morbidity. Stem cell was thought to be one of BPI treatment modalities because of their nerve-forming regeneration potential. Although there is a possibility for the use of mesenchymal stem cells as one of BPI treatment, it is still limited on animal studies. Therefore, this systematic review aimed to analyze the role of mesenchymal stem cells in nerve regeneration in animal models of brachial plexus injury.

Method

This study is a systematic review with PROSPERO registration number CRD4202128321. Literature searching was conducted using keywords experimental, animal, brachial plexus injury, mesenchymal stem cell implantation, clinical outcomes, electrophysiological outcomes, and histologic outcomes. Searches were performed in the PubMed, Scopus, and ScienceDirect databases. The risk of bias was assessed using SYRCLE's risk of bias tool for animal studies. The data obtained were described and in-depth analysis was performed.

Result

Four studies were included in this study involving 183 animals from different species those are rats and rabbits. There was an increase in muscle weight and shortened initial onset time of muscle contraction in the group treated with stem cells. Electrophysiological results showed that mesenchymal stem cells exhibited higher (Compound muscle action potential) CMAP amplitude and shorter CMAP latency than control but not better than autograft. Histological outcomes showed an increase in axon density, axon number, and the formation of connections between nerve cells and target muscles.

Conclusion

Mesenchymal stem cell implantation to animals with brachial plexus injury showed its ability to regenerate nerve cells as evidenced by clinical, electrophysiological, and histopathological results. However, this systematic study involved experimental animals from various species so that the results cannot be uniformed, and conclusion should be drawn cautiously.

The Relationship Between Elbow Flexion Postures and Overhead Reaching in Birth Brachial Plexus Injuries

PURPOSE

The aim of this study was to investigate the effect of alterations in muscle length of the biceps in various elbow postures during shoulder elevation and muscle activation.

METHODS

Participants aged 5 years and older with a birth brachial plexus injury were asked to perform elevation shoulder (abduction and flexion) in 7 elbow conditions. Surface electromyography was applied to bilateral biceps and triceps.

RESULTS

Peak shoulder elevation was present in the immobilized 20° elbow posture. Muscle activity of the triceps and biceps was impacted by the elbow posture via immobilization.

CONCLUSIONS

Elbow postures in elongated postures, via immobilization, may result in higher shoulder elevation due to increased passive forces when there is an altered muscle state of the biceps in this population. Clinicians should consider the optimal elbow joint posture (<30°) to improve overhead reaching in this population.

Forearm Lipoma Causing PIN Compression: Literature Review and Meta-Analysis of Predictors for Motor Recovery

BACKGROUND

Lipomas are a rare cause of posterior interosseous nerve (PIN) compression. A systematic review of predictors for motor recovery has not been performed. This study sought to evaluate whether patient or lipoma characteristics are associated with motor recovery and could be used to determine when immediate tendon transfers at the time of excision should be performed.

METHODS

Articles describing patients with forearm lipomas resulting in PIN compression with motor weakness were included. Patient age, gender, symptom duration, laterality and largest dimension of lipoma, surgical intervention, and motor recovery were identified. Article quality was assessed via the Methodological Index for Non-Randomized Studies criteria.

RESULTS

Thirty articles reporting on 34 patients were identified. Average age was 58.2 years. Average largest lipoma dimension was 5.7 cm. All patients underwent lipoma removal, and 2 had concomitant tendon transfers. In all, 73.5% of patients had complete motor recovery at an average of 9.7 months. Patient age and largest dimension of lipoma, and duration of symptoms were not significant predictors of motor recovery. Symptom duration was a significant predictor of motor recovery in binary regression, particularly if < 18 months.

CONCLUSIONS

The majority of patients with PIN weakness secondary to lipoma are likely to have complete motor recovery after excision alone. Concomitant tendon transfers should be considered for patients symptomatic for greater than 18 months. Further, adequately powered, studies are required to stratify risk factors and evaluate other modalities to identify the minority of patients who would benefit from immediate tendon transfer.

Innervation of an Ultrasound-Mediated PVDF-TrFE Scaffold for Skin-Tissue Engineering

In this work, electrospun polyvinylidene-trifluoroethylene (PVDF-TrFE) was utilized for its biocompatibility, mechanics, and piezoelectric properties to promote Schwann cell (SC) elongation and sensory neuron (SN) extension. PVDF-TrFE electrospun scaffolds were characterized over a variety of electrospinning parameters (1, 2, and 3 h aligned and unaligned electrospun fibers) to determine ideal thickness, porosity, and tensile strength for use as an engineered skin tissue. PVDF-TrFE was electrically activated through mechanical deformation using low-intensity pulsed ultrasound (LIPUS) waves as a non-invasive means to trigger piezoelectric properties of the scaffold and deliver electric potential to cells. Using this therapeutic modality, neurite integration in tissue-engineered skin substitutes (TESSs) was quantified including neurite alignment, elongation, and vertical perforation into PVDF-TrFE scaffolds. Results show LIPUS stimulation promoted cell alignment on aligned scaffolds. Further, stimulation significantly increased SC elongation and SN extension separately and in coculture on aligned scaffolds but significantly decreased elongation and extension on unaligned scaffolds. This was also seen in cell perforation depth analysis into scaffolds which indicated LIPUS enhanced perforation of SCs, SNs, and cocultures on scaffolds. Taken together, this work demonstrates the immense potential for non-invasive electric stimulation of an in vitro tissue-engineered-skin model.

From Conservative Measures to Surgical Interventions, Treatment Approaches for Cubital Tunnel Syndrome: A Comprehensive Review

Cubital tunnel syndrome (CuTS) is a neuropathic condition characterized by the compression or irritation of the ulnar nerve at the elbow, resulting in a wide spectrum of symptoms ranging from pain and numbness to muscle weakness and impaired hand function. This comprehensive review delves into the diverse landscape of CuTS treatment approaches, emphasizing the importance of early intervention. The review explores how these strategies aim to alleviate symptoms and enhance patient well-being by beginning with conservative measures encompassing rest, splinting, medications, physical therapy, and lifestyle adjustments. Non-surgical medical interventions, including nerve gliding exercises, ultrasound-guided nerve injections, and orthotic devices, are considered alternative therapies for symptom relief. Surgical interventions, such as decompression procedures and emerging techniques, are discussed in detail, highlighting their indications and expected outcomes. Throughout this review, the critical role of patient-centered care is underscored, emphasizing the need for tailored treatment plans that respect individual preferences and goals. Recognizing the unique nature of each CuTS case, shared decision-making between patients and healthcare providers is advocated, ensuring that interventions align with specific patient needs. As research advances, promising developments in diagnosis, surgical techniques, and drug therapies offer hope for more effective management of CuTS, paving the way for improved symptom relief and enhanced nerve function.

Ten steps for proper peripheral nerve handling during inguinal hernia surgery

INTRODUCTION

Post-inguinal pain after a hernia surgery is prevalent and can be quite frustrating for the surgeon and patient alike. There are several sources for possible post-operative inguinal pain after a successful hernia repair; however, in the setting where a recurrent inguinal hernia is not present, it is likely related to the nerves in the inguinal canal or pelvis. Chronic inguinal groin pain after hernia repairs have been reported in a high percentage of patients following inguinal hernia surgery despite being one of the most common procedures performed annually in the USA and worldwide.

MATERIALS AND METHODS

We present ten of the basic concepts utilized by peripheral nerve surgeons to limit nerve injury, which can easily be applied to open inguinal hernia surgery with or without mesh, starting with the firm understanding of the inguinal anatomy to addressing the nerves, meticulous placement of the mesh and the active revision of the surrounding structures and nerve position before closure.

CONCLUSIONS

Understanding the proper handling of the inguinal nerves during hernia surgery can decrease the incidence of post-operative chronic pain by employing microsurgical concepts to day-to-day surgical procedures and prevent complications in an extensive set of patients.

Hybrid Bionic Nerve Interface for Application in Bionic Limbs

Intuitive and perceptual neuroprosthetic systems require a high degree of neural control and a variety of sensory feedback, but reliable neural interfaces for long-term use that maintain their functionality are limited. Here, a novel hybrid bionic interface is presented, fabricated by integrating a biological interface (regenerative peripheral nerve interface (RPNI)) and a peripheral neural interface to enhance the neural interface performance between a nerve and bionic limbs. This interface utilizes a shape memory polymer buckle that can be easily implanted on a severed nerve and make contact with both the nerve and the muscle graft after RPNI formation. It is demonstrated that this interface can simultaneously record different signal information via the RPNI and the nerve, as well as stimulate them separately, inducing different responses. Furthermore, it is shown that this interface can record naturally evoked signals from a walking rabbit and use them to control a robotic leg. The long-term functionality and biocompatibility of this interface in rabbits are evaluated for up to 29 weeks, confirming its promising potential for enhancing prosthetic control.