Traumatic injury to peripheral nerves

Effect of tourniquet time and nerve diameter change on nerve damage in upper extremity surgery interventions

Background

Peripheral nerve damage is the most common and most frightening complication after a peripheral nerve block procedure. The purpose of this study was to evaluate the effects of different tourniquet durations on the sensory, motor, and sympathetic functions of peripheral nerves in patients undergoing upper extremity surgery by measuring nerve diameters under ultrasound guidance and performing nerve conduction studies to evaluate the effects on nerve damage in distal forearm.

Methods

This study was conducted on ASA I-III patients between the ages of18 and70 who were scheduled to undergo surgery on the mid and distal forearm. All patients underwent brachial plexus block via an axillary approach using USG and a nerve stimulator Prior to the application of the block, the diameters of the median, radial, ulnar, and musculocutaneous nerves were measured under USG guidance.The same assistant personnel injected 7 ml of bupivacaine and lidocaine mixture into each nerve (median, radial, ulnar). Local anesthetic(LA) to spread along the nerve sheath, the diameters of each nerve sheath were measured and recorded again by USG. Nerve conduction studies using EMG were performed by the same researcher before surgery and 1month after surgery to evaluate for nerve damage.

Results

The study consisted of 61 patients. Of the patients, 42.6 % were aged 40-60 years, and 54.1 % were women. One patient was switched to general anesthesia due to block failure, and the patient was excluded from the study. Three patients experienced complications (prolonged sensory block of 15 h in two patients, and sensory paralysis of one month in one patient. The tourniquet times of the patients were almost equal.There was a statistically significant difference between the first and final measurements of patients' Median Nerve Diameter, Radial Nerve Diameter, Ulnar Nerve Diameter, Median Nerve Sensory Amplitude, Ulnar Nerve Sensory Amplitude, Radial Nerve Sensory Amplitude, Ulnar Nerve Motor Amplitude, Median Sensory Latency, Ulnar Sensory Latency, and Radial Sensory Latency(p < 0.05).). In both patients with and without DM, the difference between the first and last measurements of Median Nerve Diameter, Radial Nerve Diameter, Ulnar Nerve Diameter, Median Sensory Latency, and Radial Sensory Latency was statistically significant (p < 0, 05).

Conclusion

Involuntary intraneural injections can occur with peripheral nerve blocks. When the effect of the increase in nerve diameter due to local anesthesia and appropriate tourniquet duration on nerve damage is evaluated by nerve conduction studies, although it causes partial impairment of nerve function (slowing of nerve conduction, decrease in amplitude), it generally does not cause permanent nerve damage.

Understanding surgical decision-making in patients with traumatic upper extremity peripheral nerve injury: A retrospective cohort study

PURPOSE

Careful patient selection and optimal surgical timing are essential to the success of nerve transfers. It is important to understand what factors contribute to this decision-making. The purpose of this study was to describe the characteristics of patients referred to interdisciplinary peripheral nerve clinics with traumatic upper extremity injuries and compare those who went on to nerve transfer surgery with those who did not.

METHODS

Patient and injury characteristics, preoperative physical examination and electrodiagnostic findings, and patient-reported outcome measures were examined. Inclusion criteria were subjects ≥18 years of age presenting to an interdisciplinary peripheral nerve clinic with traumatic upper extremity peripheral nerve injuries. Subjects were stratified into surgical and non-surgical groups for comparison.

RESULTS

Eighty-three subjects met the inclusion criteria, and 36 subjects received nerve transfer surgery. More male subjects went on to have surgery than female subjects. The surgical group demonstrated a significantly higher ratio of weak and denervated muscle groups than the non-surgical group (p < 0.05). No other statistically significant differences were identified between operative and non-operatively managed subjects.

CONCLUSION

Subjects that received nerve transfer surgery demonstrated a significantly higher ratio of weak and denervated muscles than those managed non-surgically, and males were disproportionately represented in the surgical group. These findings suggest that anticipated motor recovery is the most important factor driving surgical decision-making and that male subjects may be more likely to proceed with surgery. Understanding which patients undergo nerve transfer surgery allows clinicians to interrogate their decision-making, address patient-related barriers to surgery, and better understand surgical outcomes.

Assessment, management, and rehabilitation of traumatic peripheral nerve injuries for non-surgeons

Electrodiagnostic evaluation is often requested for persons with peripheral nerve injuries and plays an important role in their diagnosis, prognosis, and management. Peripheral nerve injuries are common and can have devastating effects on patients' physical, psychological, and socioeconomic well-being; alongside surgeons, electrodiagnostic medicine specialists serve a central function in ensuring patients receive optimal treatment for these injuries. Surgical intervention-nerve grafting, nerve transfers, and tendon transfers-often plays a critical role in the management of these injuries and the restoration of patients' function. Increasingly, nerve transfers are becoming the standard of care for some types of peripheral nerve injury due to two significant advantages: first, they shorten the time to reinnervation of denervated muscles; and second, they confer greater specificity in directing motor and sensory axons toward their respective targets. As the indications for, and use of, nerve transfers expand, so too does the role of the electrodiagnostic medicine specialist in establishing or confirming the diagnosis, determining the injury's prognosis, recommending treatment, aiding in surgical planning, and supporting rehabilitation. Having a working knowledge of nerve and/or tendon transfer options allows the electrodiagnostic medicine specialist to not only arrive at the diagnosis and prognosticate, but also to clarify which nerves and/or muscles might be suitable donors, such as confirming whether the branch to supinator could be a nerve transfer donor to restore distal posterior interosseous nerve function. Moreover, post-operative testing can determine if nerve transfer reinnervation is occurring and progress patients' rehabilitation and/or direct surgeons to consider tendon transfers.

Combat-related peripheral nerve injuries

Active-duty service members (ADSM) and military Veterans represent a population with increased occupational risk for nerve injuries sustained both during training operations and wartime. Mechanisms of war-related nerve injuries have evolved over time, from the musket ball-related traumas described by S.W. Mitchell to complex blast injuries and toxic exposures sustained during Middle East conflicts in the 21st century. Commonly encountered nerve injury etiologies in this population currently include compression, direct trauma, nutritional deficits, traumatic limb amputation, toxic chemical exposures, or blast-related injuries. Expeditious identification and comprehensive, interdisciplinary treatment of combat-associated neuropathies, as well as prevention of these injuries whenever possible is critical to reduce chronic morbidity and disability for service members and to maintain a well-prepared military. However, diagnosis of a combat-associated nerve injury may be particularly challenging due to comorbid battlefield injuries or delayed presentation of neuropathy from military toxic exposures. Advances in imaging for nerve injury, including MRI and ultrasound, provide useful tools to compliment EMG in establishing a diagnosis of combat-associated nerve injury, particularly in the setting of anatomic disruption or edema. Surgical techniques can improve pain control or restoration of function. In all cases, comprehensive interdisciplinary rehabilitation provides the best framework for optimization of recovery. Further work is needed to prevent combat-associated nerve injuries and promote nerve recovery following injury.

Electrodiagnostic Assessment of Peri-Procedural Iatrogenic Peripheral Nerve Injuries and Rehabilitation

Iatrogenic nerve injuries are a significant concern for medical professionals and the patients affected. Peri-procedural nerve injuries result in functional deficits associated with pain and disability. The exact pathophysiology and etiology of peri-procedural nerve injuries are complex and often elude providers. The rates of injury to specific nerves are unclear and relate to both procedural and patient specific risk factors. Initial classification of the nerve injury into neurapraxia, axonotmesis, mixed nerve injury, or possible complete transection (neurotmesis) guides rehabilitation and management. Electrodiagnostic medical consultation at least four weeks post-injury, supplemented with nerve imaging (ultrasound and magnetic resonance imaging), can allow for accurate nerve injury classification. Supplemented with nerve imaging and detailed clinical evaluation, treatment, recovery and rehabilitation can be maximized. Recognizing nerves at risk associated with medical and surgical procedures can facilitate injury avoidance and early diagnosis. If a nerve injury is incomplete, in an optimized physiologic milieu (good glucose control, smoking cessation, etc.), there is a good potential for spontaneous (total or partial) improvement over time. Surgical referral should be considered for severe nerve injuries within 6 months, especially if there is concern for neurotmesis, and/or deteriorating nerve function. This review gives guidance for approaching peri-procedural peripheral nerve injuries, including the timing and the role of electrodiagnostic medical consultation including serial electrodiagnostic studies in management and rehabilitation.

The effects of benzimidazole and electrical stimulation on peripheral nerve regeneration after short- and long-term injury

This research investigated the effects of benzimidazole (BZ) and electrical stimulation (ES) on peripheral nerve regeneration after short- and long-term injury and assessed functional recovery by means of stereological, histological, and electrophysiological analyses. Fifty-four male albino Wistar rats were divided into nine groups of six animals each. No treatment or surgery was applied to the control (CONT) group. The sciatic nerve was crushed for 5 s in the short-term injury (STI) and for 60 s in the long-term injury (LTI) groups. In the STI + BZ group and the LTI + BZ group, the rats received 25 mg/kg/day of BZ via oral gavage for 28 days. In the STI + ES and LTI + ES groups, a 3-V current was applied for 20 min daily for 28 days. In the STI + BZ + ES group and the LTI + BZ + ES groups, 3-V ES was applied for 20 min per day for 28 days following oral administration of BZ at 25 mg/kg/day for 28 days. All groups were subjected to electrophysiological, electron microscopic, stereological, and statistical analyses. The stereological analyses revealed a significant increases in the numbers of myelinated axons in the STI + ES groups compared with the STI (p < 0.01). BZ treatment yielded no significant differences in the numbers of myelinated axons in the groups (p > 0.05). Histological evaluation of the STI and LTI groups showed that ES and BZ treatment positively affect the histological structure of the nerve.

Optimizing Peripheral Nerve Regeneration: Surgical Techniques, Biomolecular and Regenerative Strategies-A Narrative Review

Peripheral nerve injury disrupts the function of the peripheral nervous system, leading to sensory, motor, and autonomic deficits. While peripheral nerves possess an intrinsic regenerative capacity, complete sensory and motor recovery remains challenging due to the unpredictable nature of the healing process, which is influenced by the extent of the injury, age, and timely intervention. Recent advances in microsurgical techniques, imaging technologies, and a deeper understanding of nerve microanatomy have enhanced functional outcomes in nerve repair. Nerve injury initiates complex pathophysiological responses, including Wallerian degeneration, macrophage activation, Schwann cell dedifferentiation, and axonal sprouting. Complete nerve disruptions require surgical intervention to restore nerve continuity and function. Direct nerve repair is the gold standard for clean transections with minimal nerve gaps. However, in cases with larger nerve gaps or when direct repair is not feasible, alternatives such as autologous nerve grafting, vascularized nerve grafts, nerve conduits, allografts, and nerve transfers may be employed. Autologous nerve grafts provide excellent biocompatibility but are limited by donor site morbidity and availability. Vascularized grafts are used for large nerve gaps and poorly vascularized recipient beds, while nerve conduits serve as a promising solution for smaller gaps. Nerve transfers are utilized when neither direct repair nor grafting is possible, often involving re-routing intact regional nerves to restore function. Nerve conduits play a pivotal role in nerve regeneration by bridging nerve gaps, with significant advancements made in material composition and design. Emerging trends in nerve regeneration include the use of 3D bioprinting for personalized conduits, gene therapy for targeted growth factor delivery, and nanotechnology for nanofiber-based conduits and stem cell therapy. Advancements in molecular sciences have provided critical insights into the cellular and biochemical mechanisms underlying nerve repair, leading to targeted therapies that enhance axonal regeneration, remyelination, and functional recovery in peripheral nerve injuries. This review explores the current strategies for the therapeutic management of peripheral nerve injuries, highlighting their indications, benefits, and limitations, while emphasizing the need for tailored approaches based on injury severity and patient factors.

The Influence of Fluoxetine on the Sensorimotor Function of the Sciatic Nerve in Wistar Rats after Axonotmesis: An Experimental Animal Model

BACKGROUND

Fluoxetine, a serotonin reuptake inhibitor antidepressant, raises extracellular serotonin levels and promotes angiogenesis and neurogenesis. Numerous animal models have shown its beneficial effects on recovery from peripheral nerve injury.

PURPOSE

The primary objective of this study was to analyze the influence of fluoxetine on the sensory-motor function recovery of the sciatic nerve in Wistar rats after axonotmesis.

STUDY DESIGN, SETTING, AND SAMPLE

This study utilized an experimental rat model, conducted in the laboratory at the Federal University of Pernambuco. The sample consisted of 40 male Wistar rats.

PREDICTOR VARIABLE

The primary predictor variable was the fluoxetine exposure. The animals were randomly divided into 4 groups (control and 3 experimental groups), with 10 animals in each group. They were injected subcutaneously with saline or fluoxetine 5, 10, and 20 mg/kg/day, respectively.

MAIN OUTCOME VARIABLES

The main outcome variables were postoperative motor and sensory sciatic nerve function. Sensory nerve function was measured using the withdrawal reflex by thermostimulation. Motor nerve function was measured using the Sciatic Nerve Recovery Index and the Static Sciatic Nerve Index (SSI).

COVARIATES

None.

ANALYSES

Descriptive statistical analysis was performed using mean and SD. Analaysis of variance (ANOVA) was used for comparisons between the groups and Dunnett's multiple comparisons test was used in case of significant differences between the groups. Statistical Analysis System was the software used for statistical analyses.

RESULTS

During the study, 15 animals were lost (3 in the control group and 4 in each experimental group), with no specific cause identified. On day 35, the latency time of the withdrawal reflex was significantly different, with decreased pain perception in the 5 mg/kg/day fluoxetine group (3.80 ± 1.20, P < .05). On day 14, the Sciatic Nerve Recovery Index showed greater deficits in the l0 and 20 mg/kg/day groups (-65.67 ± 7.20 and -63.57 ± 11.59, respectively) compared to the control group (P < .05). The SSI also showed a delay in recovery with the 10 mg/kg/day dose (-62.50 ± 6.72, P < .05).

CONCLUSION

The daily treatment with fluoxetine failed to bring any improvement to motor or sensory recuperation after injury to the sciatic nerve in Wistar rats.

The Role of 70-MHz Ultrahigh-Frequency Ultrasound in the Peripheral Nerve Injury

AIM

High-frequency ultrasound with an 18-MHz probe (18 MHz-HFUS) plays a relevant role in the evaluation of peripheral nerve injury (PNI). Ultrahigh-frequency ultrasound with a 70-MHz probe (70 MHz-UHFUS) offers higher spatial resolution and could allow a better detection of PNI. This study aimed to compare the diagnostic performance of HFUS and UHFUS in PNI detection.

MATERIALS AND METHODS

In this retrospective study, were selected, between July 2022 and April 2024, 61 patients underwent HFUS, UHFUS, and nerve conduction study (NCS) for clinical suspicion of traumatic forearm PNI. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy of HFUS and UHFUS in PNI detection were calculated and compared. NCS was used as the reference standard. Nonparametric statistical tests were used. A p value of < 0.05 was considered statistically significant.

RESULTS

Comparing the diagnostic performance in PNI detection, the 70 MHz-UHFUS showed a sensitivity and diagnostic accuracy significantly higher than 18 MHz-HFUS, respectively, 98.0% versus 82.4% (p = 0.0205) and 95.1% versus 82.0% (p = 0.0468). Otherwise, not significantly difference were in specificity, PPV, and NPV.

CONCLUSIONS

UHFUS compared to HFUS demonstrated a higher sensitivity and diagnostic accuracy in PNI detection.

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.

Tracking adipose-derived stem cell exosomes applied in a mouse crush injury model: insights from fluorescent labeling and spatial transcriptomics - an experimental study

Adipose-derived stem cell exosomes (ADSC-exos) are promising for nerve regeneration; however, their precise mechanisms remain unclear. This study employed fluorescent labeling and spatial transcriptomics to track the effects of ADSC-exos on crushed sciatic nerves in mice. Labeled exosomes were detected in spinal neurons and proximal nerve segments after application. Spatial transcriptomics revealed significant changes in gene expression, with an upregulation of neurons and Schwann cells and the downregulation of oligodendrocytes. The key pathways affected were prosaposin, pleiotrophin, fibroblast growth factor, secreted phosphoprotein 1, SLIT and NTRK-like family, member, vascular endothelial growth factor, and growth arrest-specific protein. ADSC-exo treatment enhanced cell-cell interactions, particularly between Schwann cells and astrocytes, thereby promoting a regenerative environment. Gene ontology analysis suggested improvements in metabolic activity, cell communication, and structural support. This study highlights the complex interplay between multiple cell types and signaling pathways involved in the nerve regeneration response to ADSC-exos. This comprehensive approach offers new perspectives on the role of ADSC-exos in nerve regeneration and paves the way for advanced regenerative strategies for peripheral nerve injuries.

Influences of Variability in Attenuation Compensation on the Estimation of Backscatter Coefficient of Median Nerves in Vivo

OBJECTIVE

Peripheral nerves remain a challenging target for medical imaging, given their size, anatomical complexity, and structural heterogeneity. Quantitative ultrasound (QUS) applies a set of techniques to estimate tissue acoustic parameters independent of the imaging platform. Many useful medical and laboratory applications for QUS have been reported, but challenges remain for deployment in vivo, especially for heterogeneous tissues. Several phenomena introduce variability in attenuation estimates, which may influence the estimation of other QUS parameters. For example, estimating the backscatter coefficient (BSC) requires compensation for the attenuation of overlying tissues between the transducer and the underlying tissue of interest. The purpose of this study is to extend prior studies by investigating the efficacy of several analytical methods of estimating attenuation compensation on QUS outcomes in the human median nerve.

METHODS

Median nerves were imaged at the volar wrist in vivo and beam-formed radiofrequency (RF) data were acquired. Six analytical approaches for attenuation compensation were compared: 1-2) attenuation estimated by applying spectral difference method (SDM) and spectral log difference method (SLDM) independently to regions of interest (ROIs) overlying the nerve and to the nerve ROI itself; 3-4) attenuation estimation by applying SDM and SLDM to ROIs overlying the nerve, and transferring these properties to the nerve ROI; and 5-6) methods that apply previously published values of tissue attenuation to the measured thickness of each overlying tissue. Mean between-subject estimates of BSC-related outcomes as well as within-subject variability of these outcomes were compared among the 6 methods.

RESULTS

Compensating for attenuation using SLDM and values from the literature reduced variability in BSC-based outcomes, compared to SDM. Variability in attenuation coefficients contributes substantially to variability in backscatter measurements.

CONCLUSION

This work has implications for the application of QUS to in vivo diagnostic assessments in peripheral nerves and possibly other heterogeneous tissues.

Platelet-rich plasma (PRP) in nerve repair

Platelet-rich plasma (PRP) has the capability of assisting in the recovery of damaged tissues by releasing a variety of biologically active factors to initiate a hemostatic cascade reaction and promote the synthesis of new connective tissue and revascularization. It is now widely used for tissue engineering repair. In addition, PRP has demonstrated nerve repair and pain relief, and has been studied and applied to the facial nerve, median nerve, sciatic nerve, and central nerve. These suggest that PRP injection therapy has a positive effect on nerve repair. This indicates that PRP has high clinical value and potential application in nerve repair. It is worthwhile for scientists and medical workers to further explore and study PRP to expand its application in nerve repair, and to provide a more reliable scientific basis for the opening of a new approach to nerve repair.

Wnt 3a-Modified Scaffolds Improve Nerve Regeneration by Boosting Schwann Cell Function

A pivotal approach in engineering artificial peripheral nerve sheaths encompasses the augmentation of the regenerative microenvironment via the manipulation of Schwann cells (SCs). Our investigation employed single-cell sequencing analysis to elucidate the potential functions of Schwann cells and the Wnt pathway in facilitating peripheral nerve regeneration. In vitro studies showed that activating the Wnt signaling pathway promotes the transition to repair SCs, boosting their growth, movement, and immune functions. To better understand the peripheral nerve regeneration environment, we created a polymer scaffold using ammonization and electrospinning. The Wnt3a protein was incorporated into the polycaprolactone (PCL) electrospun fiber surface. In a rat sciatic nerve defect model, the Wnt3a-modified scaffold showed better nerve repair outcomes than traditional electrospun scaffolds. After a week, the test group showed better immune regulation and angiogenesis, with a significant increase in axon growth rate observed after 3 weeks. Three-month-long animal experiments revealed notable improvements in neuroelectrophysiology, reduced organ atrophy, and enhanced sciatic nerve recovery. In this nerve defect model, Wnt3a-modified neural scaffolds achieved repair effects.

Effect and mechanism of Tetramethylpyrazine in repair of sciatic nerve injury in rats

OBJECTIVE

Observing the effects of Tetramethylpyrazine (TMP) on the expression of Collagen IV and Laminin in neurovascular basement membrane and the apoptosis of vascular endothelial cells, and to study the mechanism of TMP in the treatment of sciatic nerve injury.

RESULTS

Compared with the NS group, the TMP group had a significant increase in the sciatic nerve function index (P < 0.01).The miss times in TMP group was significantly lower than that in NS group (P < 0.01). The HE staining results of the TMP group showed irregular arrangement of some neuronal axons and Schwann cells, and more edema and rupture of cells. The proliferation of glial cells and inflammatory cells was significantly increased in TMP group. The results of immunohistochemistry showed that the expression of type IV collagen and laminin in the TMP group group was distributed around the blood vessels, vascular endothelial cells, basal membrane and glial cells after SNI. The expression of type IV collagen and laminin in TMP group increased significantly(P < 0.05). Immunofluorescence showed that compared with NS group, the apoptosis rate of TMP group was significantly decreased (P < 0.01). Flow cytometry results showed that compared with the NS group, the number of CECs in the TMP group was significantly decreased (P < 0.01).

CONCLUSIONS

TMP can effectively improve the sciatic nerve functional index (SFI) of Sprague Dawley (SD) rats, enhance the proliferation of sciatic nerve vascular endothelial cells, reduce apoptosis, promote the expression of Collagen IV and Laminin in sciatic nerve microvascular basal membrane components, thereby promoting angiogenesis and improving lower limb function in rats.

Combining external physical stimuli and nanostructured materials for upregulating pro-regenerative cellular pathways in peripheral nerve repair

Peripheral nerve repair remains a major clinical challenge, particularly in the pursuit of therapeutic approaches that ensure adequate recovery of patient's activity of daily living. Autografts are the gold standard in clinical practice for restoring lost sensorimotor functions nowadays. However, autografts have notable drawbacks, including dimensional mismatches and the need to sacrifice one function to restore another. Engineered nerve guidance conduits have therefore emerged as promising alternatives. While these conduits show surgical potential, their clinical use is currently limited to the repair of minor injuries, as their ability to reinnervate limiting gap lesions is still unsatisfactory. Therefore, improving patient functional recovery requires a deeper understanding of the cellular mechanisms involved in peripheral nerve regeneration and the development of therapeutic strategies that can precisely modulate these processes. Interest has grown in the use of external energy sources, such as light, ultrasound, electrical, and magnetic fields, to activate cellular pathways related to proliferation, differentiation, and migration. Recent research has explored combining these energy sources with tailored nanostructured materials as nanotransducers to enhance selectivity towards the target cells. This review aims to present the recent findings on this innovative strategy, discussing its potential to support nerve regeneration and its viability as an alternative to autologous transplantation.

Electrodiagnostic Findings Using Radial Motor Segmental Conduction Study and Inching Test in Patients With Radial Neuropathy

OBJECTIVES

The aims of this study were to characterize the electrodiagnostic findings of radial neuropathy using motor segmental conduction study and to determine the utility of subsequent inching test in precise lesion localization.

DESIGN

Twenty-three patients with radial neuropathy were evaluated using radial neuropathy using motor segmental conduction study with three-point stimulation. The pathomechanism of the lesions according to the radial neuropathy using motor segmental conduction study was classified into three groups: conduction block, mixed lesion (combination of conduction block and axonal degeneration), and axonal degeneration. Inching test was performed in patients with conduction block to localize the lesion site, and needle electromyography identified the most proximal radial nerve-innervated muscles affected.

RESULTS

Out of 23 cases, the radial neuropathy using motor segmental conduction study demonstrated probable partial conduction block in 10, mixed lesions in 2, and axonal degeneration in 10. One case could not be categorized with radial neuropathy using motor segmental conduction study alone. As determined by radial neuropathy using motor segmental conduction study and inching test, the most common cause of conduction block was compression, while the most common cause of axonal degeneration was iatrogenic. In the conduction block group, the lesion locations identified by radial neuropathy using motor segmental conduction study and inching test were consistent with needle electromyography localization.

CONCLUSIONS

The combined radial neuropathy using motor segmental conduction study and inching test technique can precisely localize radial motor nerve injuries and provide detailed information on electrodiagnostic characteristics of radial mononeuropathy.

Adipose-derived stem cells modified by TWIST1 silencing accelerates rat sciatic nerve repair and functional recovery

The regeneration of peripheral nerves after injury is often slow and impaired, which may be associated with weakened and denervated muscles subsequently leading to atrophy. Adipose-derived stem cells (ADSCs) are often regarded as cell-based therapeutic candidate due to their regenerative potential. The study aims to assess the therapeutic efficacy of gene-modified ADSCs on sciatic nerve injury. We lentivirally transduced ADSCs with shRNA-TWIST1 and transplanted modified cells to rats undergoing sciatic nerve transection and repair. Results showed that TWIST1 knockdown accelerated functional recovery of rats with sciatic nerve injury as faster nerve conduction velocity and higher wire hang scores obtained by rats transplanted with TWIST1-silenced ADSCs than scramble ADSCs. Although the rats experienced degenerated axons and decreased myelin sheath thickness after sciatic nerve injury 8 weeks after operation, those transplanted with TWIST1-silenced ADSCs exhibited more signs of regenerated nerve fibers surrounded by newly formed myelin sheaths than those with scramble ADSCs. The rats transplanted with TWIST1-silenced ADSCs presented increased expressions of neurotrophic factors including neurotrophin-3 (NT-3), brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and glial cell line-derived neurotrophic factor (GDNF) in the sciatic nerves than those with scramble ADSCs. These results suggest that genetically modifying TWIST1 in ADSCs could facilitate peripheral nerve repair after injury in a more efficient way than that with ADSCs alone.

Traumatic peripheral nerve injuries in young Korean soldiers: a recent 10-year retrospective study

PURPOSE

Traumatic peripheral nerve injury (PNI), which occurs in up to 3% of trauma patients, is a devastating condition that often leads to permanent disability. However, knowledge of traumatic PNI is limited. We describe epidemiology and clinical characteristics of traumatic PNI in Korea and identify the predictors of traumatic complete PNI.

METHODS

A list of enlisted soldier patients who were discharged from military service due to PNI over a 10-year period (2012-2021) was obtained, and their medical records were reviewed. Patients were classified according to the causative events (traumatic vs. nontraumatic) and injury severity (complete vs. incomplete). Of traumatic PNIs, we compared the clinical variables between the incomplete and complete PNI groups and identified predictors of complete PNI.

RESULTS

Of the 119 young male patients who were discharged from military service due to PNI, 85 (71.4%) were injured by a traumatic event; among them, 22 (25.9%) were assessed as having a complete injury. The most common PNI mechanism (n=49, 57.6%), was adjacent fractures or dislocations. Several injury-related characteristics were significantly associated with complete PNI: laceration or gunshot wound, PNI involving the median nerve, PNI involving multiple individual nerves (multiple PNI), and concomitant muscular or vascular injuries. After adjusting for other possible predictors, multiple PNI was identified as a significant predictor of a complete PNI (odds ratio, 3.583; P=0.017).

CONCLUSIONS

In this study, we analyzed the characteristics of enlisted Korean soldiers discharged due to traumatic PNI and found that the most common injury mechanism was adjacent fracture or dislocation (57.6%). Patients with multiple PNI had a significantly increased risk of complete injury. The results of this study contribute to a better understanding of traumatic PNI, which directly leads to a decline in functioning in patients with trauma.

Advanced nerve regeneration enabled by neural conformal electronic stimulators enhancing mitochondrial transport

Addressing peripheral nerve defects remains a significant challenge in regenerative neurobiology. Autografts emerged as the gold-standard management, however, are hindered by limited availability and potential neuroma formation. Numerous recent studies report the potential of wireless electronic system for nerve defects repair. Unfortunately, few has met clinical needs for inadequate electrode precision, poor nerve entrapment and insufficient bioactivity of the matrix material. Herein, we present an advanced wireless electrical nerve stimulator, based on water-responsive self-curling silk membrane with excellent bioabsorbable and biocompatible properties. We constructed a unique bilayer structure with an oriented pre-stretched inner layer and a general silk membrane as outer layer. After wetting, the simultaneous contraction of inner layer and expansion of outer layer achieved controllable super-contraction from 2D flat surface to 3D structural reconfiguration. It enables shape-adaptive wrapping to cover around nerves, overcomes the technical obstacle of preparing electrodes on the inner wall of the conduit, and prevents electrode breakage caused by material expansion in water. The use of fork capacitor-like metal interface increases the contact points between the metal and the regenerating nerve, solving the challenge of inefficient and rough electrical stimulation methods in the past. Newly developed electronic stimulator is effective in restoring 10 mm rat sciatic nerve defects comparable to autologous grafts. The underlying mechanism involves that electric stimulation enhances anterograde mitochondrial transport to match energy demands. This newly introduced device thereby demonstrated the potential as a viable and efficacious alternative to autografts for enhancing peripheral nerve repair and functional recovery.

Adipose Tissue Derivatives in Peripheral Nerve Regeneration after Transection: A Systematic Review

INTRODUCTION

Peripheral nerve injury (PNI) is increasingly prevalent and challenging to treat despite advances in microsurgical techniques. In this context, adipose tissue derivatives, such as adipose-derived stem cells, nanofat, and stromal vascular fraction have been gaining attention as potential allies in peripheral nerve regeneration.

OBJECTIVES

This study aims to explore the use of adipose tissue derivatives in nerve regeneration following peripheral nerve transection in murine models. Thus, we assess and synthesize the key techniques and methods used for evaluating the obtained nerve regeneration to guide future experimental research and clinical interventions.

METHODOLOGY

A systematic review was conducted in February 2024, adhering to the Cochrane and PRISMA 2020 guidelines, using the PubMed, SciELO, and LILACS databases. The focus was on experimental studies involving adipose tissue derivatives in nerve regeneration in animal models post-transection. Only experimental trials reporting nerve regeneration outcomes were included; studies lacking a comparator group or evaluation methods were excluded.

RESULTS

Out of 273 studies initially identified from MEDLINE, 19 were selected for detailed analysis. The average study included 32.5 subjects, with about 10.2 subjects per intervention subgroup. The predominant model was the sciatic nerve injury with a 10 mm gap. The most common intervention involved unprocessed adipose-derived stem cells, utilized in 14 articles.

CONCLUSIONS

This review underscores the significant potential of current methodologies in peripheral nerve regeneration, particularly highlighting the use of murine models and thorough evaluation techniques.

Updates in diagnostic tools for diagnosing nerve injury and compressions

Predicting prognosis after nerve injury and compression can be challenging, even for the experienced clinician. Although thorough clinical assessment can aid diagnosis, we cannot always be precise about long-term functional recovery of either motor or sensory nerves. To evaluate the severity of nerve injury, surgical exploration remains the gold standard, particularly after iatrogenic injury and major nerve injury from trauma, such as brachial plexus injury. Recently, advances in imaging techniques (ultrasound, magnetic resonance imaging [MRI] and MR neurography) along with multimodality assessment, including electrodiagnostic testing, have allowed us to have a better preoperative understanding of nerve continuity and prediction of nerve health and possible recovery. This article outlines the current and potential roles for clinical assessment, exploratory surgery, electrodiagnostic testing ultrasound and MRI in entrapment neuropathies, inflammatory neuritis and trauma. Emphasis is placed on those modalities that are improving in diagnostic accuracy of nerve assessment before any surgical intervention.

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.

Hand function outcomes following surgical treatment of complete neonatal brachial plexus palsy

PURPOSE

Although re-innervation of the hand is considered a priority in the treatment of infants with complete brachial plexus injury, there is currently a paucity of publications investigating hand function outcomes following primary nerve reconstruction in infants with neonatal brachial plexus palsy (NBPP). This study therefore aimed to evaluate hand function outcomes in a series of patients with complete NBPP.

METHODS

This retrospective case series included all patients who underwent primary nerve surgery for complete neonatal brachial plexus palsy over an 8-year period. Outcomes were assessed using the Raimond Hand Scale. Classification of grade 3 or higher indicates a functional hand (assistance in bimanual activity).

RESULTS

Nineteen patients with a complete NBPP underwent primary nerve reconstruction at a mean age of 3.7 months. Periodic clinical evaluations were performed until at least 4 years of age. According to the Raimondi hand scale, one patient did not recover (grade 0), three patients attained grade 1, four grade 2, ten grade 3, and in one grade 4. Overall hand functional recovery was achieved in 57.8% (11/19) of patients.

CONCLUSION

Sufficient recovery of hand function to perform bimanual activity tasks in patients with complete NBPP lesions is possible and should be a priority in the surgical treatment of these infants.

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.

The impact of SARS-Covid-19 pandemic on peripheral nerve surgery - A single centre report

OBJECTIVE

SARS-Cov-19 pandemic totally changed daily routine work in German hospitals. As hospital capacity was reduced, many surgeries were postponed or even cancelled. On March 25th 2020 the German Society of Neurosurgery (DGNC) published a statement in which urgent non-elective surgeries were defined for each neurosurgical domain, whereas elective interventions were deferred. The present work examines the impact of these Covid strategies focusing on patients with peripheral lesions who were conducted to our department during this period of time.

METHODS

All patients who underwent any peripheral nerve surgery at our department from January 2018 until December 2022, were included. The complete range of surgeries including peripheral nerve lesions was examined encompassing compression syndromes, traumatic lesions of brachial plexus, traumatic lesions and tumors of single peripheral nerves. The numbers of surgical procedures were compared before, during and after pandemic. Pearson correlation coefficient was analysed.

RESULTS

From 2018 to 2022 the total number of surgical procedures involving peripheral nerves included 2422 procedures. Compression syndromes made up the largest proportion (1433 operations, 59%), followed by peripheral nerve lesions (445 operations, 18%), peripheral nerve tumors (344 operations, 14%) and lesions of the brachial plexus (142 operations, 6%). The average was 40,5 interventions per month, the range was 7-63. Two declines in the number of peripheral nerve surgeries were noted during this period. The first was in April and May 2020 with an average drop of 65% and 41% respectively. In these months the average number of operations was 37. The second decrease was from October 2021 until January 2022, where number of surgeries was reduced by 16%, 36%, 83% and 18% with an average number of 50 operations. Both declines showed a significant and strong correlation with the lower number of compression syndrome treatments (r = 0.952, p < 0.001 and r = 0.968, p < 0.001), while no drop and no significant correlation was found in the treatment of traumatic peripheral nerve injuries (p = 0.769, r = 0.095 and p = 0.243, r = 0.366) and traumatic brachial plexus injuries (p = 0.787, r = 0.088 and p = 0.780, r = 0.09). A weak significant correlation was seen in the treatment numbers of peripheral nerve tumors (p = 0.017, r = 0.672 and p = 0.015, r = 0.67).

CONCLUSION

Covid-19 pandemic lead to a significant decrease in the number of nerve decompressions, since, according to the German Society of Neurosurgery, those were considered as elective surgeries.

Entrapment of median nerve after elbow fracture dislocations: expected surgical time frame based on cadaver study

INTRODUCTION

Median nerve injuries occur in approximately 3% of pediatric elbow fracture dislocations. These rare injuries can be difficult to diagnose, and the results are poor in delay cases. Surgical timing is one of the most important prognostic factors. We aimed to present three patients with median nerve palsy who were referred to our clinic late, and according to these cases, we emphasized the expected time frame for exploration based on our anatomical cadaver study.

MATERIALS AND METHODS

Between 2008 and 2010, three patients were referred to our clinic because of median nerve paralysis after a treated elbow dislocation. The mean interval between injury and referral was 15 (min: 13-max: 18) months, and the mean age of the patients was 15 (13-18) years. Neurolysis was performed in two patients, and for the third patent, after neurolysis, axonal continuity was observed to be disrupted so sural nerve grafting was performed with four cables. Tendon transfers were performed in all patients. A total number of 20 upper extremities of 10 cadavers were dissected. Due to its proximal innervation and ease of assessment, the muscle innervation of the flexor pollicis longus (FPL) was planned to be evaluated. The distance from the medial epicondyle is calculated in the cadaver study where the nerve injury is found.

RESULTS

The mean length from the medial epicondyle to the motor innervation of FPL was calculated in each specimen and found to be 101.99 millimeters (mm) (range: 87.5-134.2). The mean longest innervation of FPL was 110.83 mm from (range 87.5-148.1) the medial epicondyle calculated by including each specimens longest nerve length. Knowing that the healing time of a nerve lesion is 1 mm per day, we calculated that the recovery of FPL would take approximately 4 months.

CONCLUSION

When nerve healing is expected to be 1 mm a day in axonotmesis type injury, after the median nerve palsy following elbow dislocation, thumb flexion should be achieved in the following 4 months generally if the nerve was not entrapped in the joint. This cadaver-based study objectively defined how long to wait for the innervation of the FPL in median nerve injuries in elbow fracture dislocations.

Distal Entrapment of Regenerating Peripheral Nerves After a Proximal Injury: A Case Series and Review of the Literature

A complication of peripheral nerve injuries, of which there exists limited discourse, is the entrapment of the nerve as it regenerates from the site of injury to its end target, resulting in the arrest of axon regeneration and a consequent reduction of functional recovery. This proof-of-concept paper reports a review of the relevant literature alongside a case series of patients who presented with this phenomenon and who were treated with targeted peripheral nerve decompression. Three cases were identified prospectively. The baseline function was recorded pre-and post-operatively. Recovery was assessed using various tools, including the Medical Research Council (MRC) motor grading, ten-test sensory testing, Tinel's sign progression, a visual analogue scale (VAS) for pain, and the Impact of Hand Nerve Disorders (I-HaND) patient-reported outcome measure (PROM). The first case sustained a brachial plexus injury and received decompression at the pronator fascia, carpal tunnel, cubital tunnel, and Guyon's canal. The second case sustained a sciatic nerve injury and was managed with peroneal and tarsal tunnel decompressions. The final case sustained a suprascapular nerve injury and underwent decompression at the suprascapular ligament. In all these cases, motor function, sensory function, and pain (depending on the nerve's original components) improved following decompression. A literature review revealed seven relevant studies, including four case reports, two cohort studies, and a pre-clinical animal study. These cases, and those identified in our review of the literature, suggest that targeted decompressive surgery can be an appropriate treatment for patients who display signs of stalled neural regeneration. This study adds to the limited evidence of this phenomenon and highlights the challenges in proving the efficacy of decompressive surgery for this specific complication. This study is limited by the number of cases included, the heterogeneity of nerve injuries presented, and its observational nature. There is a clear need for further research into this phenomenon, and the authors are working towards developing a prospective study that will investigate the indications, value, predictors of success, and practicality of decompression surgery for this complication of peripheral nerve injury.

Google Trends Analysis of Peripheral Nerve Disease and Surgery

BACKGROUND

Despite advances in the surgical management of peripheral nerve pathologies over the past several decades, it is unknown how public awareness of these procedures has changed. We hypothesize that Google searches for peripheral nerve surgery have increased over time.

METHODS

Google Trends was queried for search volumes of a list of 40 keywords related to the following topics in peripheral nerve surgery: spasticity, nerve injury, prosthetics, and nerve pain. Monthly relative search volume over the first 5 years of the study period (2010-2014) was compared with that of the last 5 years (2018-2022) of the study period.

RESULTS

Search volumes for keywords "nerve injury," "nerve laceration," "peripheral nerve injury," "nerve repair," "nerve transfer", "neuroma," "neuroma pain," "nerve pain," "nerve pain surgery," and "neuroma pain surgery" all increased more than 10% points in relative search volume over the study period (P < 0.0001 for each keyword). In contrast, searches for "rhizotomy," "spasticity surgery," "targeted muscle reinnervation," "bionic arm," and "myoelectric prosthesis" either decreased or remained stable. Technical terms such as "selective neurectomy," "hyperselective neurectomy," "regenerative peripheral nerve interface," and "regenerative peripheral nerve interface surgery" did not have adequate search volume to be reported by Google Trends.

CONCLUSIONS

The increase in Google searches related to nerve injury and pain between 2010 and 2022 may reflect increasing public recognition of these clinical entities and surgical techniques addressing them. Technical terms relating to nerve pain are infrequently searched, surgeons should use plain English terms for online discovery. Interest in spasticity and myoelectric prosthetics remains stable, indicating an opportunity for better public outreach.

Assessment, patient selection, and rehabilitation of nerve transfers

Peripheral nerve injuries are common and can have a devastating effect on physical, psychological, and socioeconomic wellbeing. Peripheral nerve transfers have become the standard of care for many types of peripheral nerve injury due to their superior outcomes relative to conventional techniques. As the indications for, and use of, nerve transfers expand, the importance of pre-operative assessment and post-operative optimization increases. There are two principal advantages of nerve transfers: (1) their ability to shorten the time to reinnervation of muscles undergoing denervation because of peripheral nerve injury; and (2) their specificity in ensuring proximal motor and sensory axons are directed towards appropriate motor and sensory targets. Compared to conventional nerve grafting, nerve transfers offer opportunities to reinnervate muscles affected by cervical spinal cord injury and to augment natural reinnervation potential for very proximal injuries. This article provides a narrative review of the current scientific knowledge and clinical understanding of nerve transfers including peripheral nerve injury assessment and pre- and post-operative electrodiagnostic testing, adjuvant therapies, and post-operative rehabilitation for optimizing nerve transfer outcomes.

Nerve Regeneration with a Scaffold Incorporating an Absorbable Zinc-2% Iron Alloy Filament to Improve Axonal Guidance

Peripheral nerve damage that results in lost segments requires surgery, but currently available hollow scaffolds have limitations that could be overcome by adding internal guidance support. A novel solution is to use filaments of absorbable metals to supply physical support and guidance for nerve regeneration that then safely disappear from the body. Previously, we showed that thin filaments of magnesium metal (Mg) would support nerve regeneration. Here, we tested another absorbable metal, zinc (Zn), using a proprietary zinc alloy with 2% iron (Zn-2%Fe) that was designed to overcome the limitations of both Mg and pure Zn metal. Non-critical-sized gaps in adult rat sciatic nerves were repaired with silicone conduits plus single filaments of Zn-2%Fe, Mg, or no metal, with autografts as controls. After seventeen weeks, all groups showed equal recovery of function and axonal density at the distal end of the conduit. The Zn alloy group showed some improvements in early rat health and recovery of function. The alloy had a greater local accumulation of degradation products and inflammatory cells than Mg; however, both metals had an equally thin capsule (no difference in tissue irritation) and no toxicity or inflammation in neighboring nerve tissues. Therefore, Zn-2%Fe, like Mg, is biocompatible and has great potential for use in nervous tissue regeneration and repair.

Mathematical modelling with Bayesian inference to quantitatively characterize therapeutic cell behaviour in nerve tissue engineering

Cellular engineered neural tissues have significant potential to improve peripheral nerve repair strategies. Traditional approaches depend on quantifying tissue behaviours using experiments in isolation, presenting a challenge for an overarching framework for tissue design. By comparison, mathematical cell-solute models benchmarked against experimental data enable computational experiments to be performed to test the role of biological/biophysical mechanisms, as well as to explore the impact of different design scenarios and thus accelerate the development of new treatment strategies. Such models generally consist of a set of continuous, coupled, partial differential equations relying on a number of parameters and functional forms. They necessitate dedicated in vitro experiments to be informed, which are seldom available and often involve small datasets with limited spatio-temporal resolution, generating uncertainties. We address this issue and propose a pipeline based on Bayesian inference enabling the derivation of experimentally informed cell-solute models describing therapeutic cell behaviour in nerve tissue engineering. We apply our pipeline to three relevant cell types and obtain models that can readily be used to simulate nerve repair scenarios and quantitatively compare therapeutic cells. Beyond parameter estimation, the proposed pipeline enables model selection as well as experiment utility quantification, aimed at improving both model formulation and experimental design.

"Knowing It Before Blocking It," the ABCD of the Peripheral Nerves: Part B (Nerve Injury Types, Mechanisms, and Pathogenesis)

Selander emphatically said, "Handle these nerves with care," and those words still echo, conveying a loud and clear message that, however rare, peripheral nerve injury (PNI) remains a perturbing possibility that cannot be ignored. The unprecedented nerve injuries associated with peripheral nerve blocks (PNBs) can be most tormenting for the unfortunate patient and a nightmare for the anesthetist. Possible justifications for the seemingly infrequent occurrences of PNB-related PNIs include a lack of documentation/reporting, improper aftercare, or associated legal implications. Although they make up only a small portion of medicolegal claims, they are sometimes difficult to defend. The most common allegations are attributed to insufficient informed consent; preventable damage to a nerve(s); delay in diagnosis, referral, or treatment; misdiagnosis, and inappropriate treatment and follow-up care. Also, sufficient prospective studies or randomized trials have not been conducted, as exploring such nerve injuries (PNB-related) in living patients or volunteers may be impractical or unethical. Understanding the pathophysiology of various types of nerve injury is vital to dealing with them further. Processes like degeneration, regeneration, remyelination, and reinnervation can influence the findings of electrophysiological studies. Events occurring in such a process and their impact during the assessment determine the prognosis and the need for further interventions. This educational review describes various types of PNB-related nerve injuries and their associated pathophysiology.

Functional attachment of primary neurons and glia on radiopaque implantable biomaterials for nerve repair

Repairing peripheral nerve injuries remains a challenge, even with use of auxiliary implantable biomaterial conduits. After implantation the location or function of polymeric devices cannot be assessed via clinical imaging modalities. Adding nanoparticle contrast agents into polymers can introduce radiopacity enabling imaging using computed tomography. Radiopacity must be balanced with changes in material properties impacting device function. In this study radiopaque composites were made from polycaprolactone and poly(lactide-co-glycolide) 50:50 and 85:15 with 0-40 wt% tantalum oxide (TaOx) nanoparticles. To achieve radiopacity, ≥5 wt% TaOx was required, with ≥20 wt% TaOx reducing mechanical properties and causing nanoscale surface roughness. Composite films facilitated nerve regeneration in an in vitro co-culture of adult glia and neurons, measured by markers for myelination. The ability of radiopaque films to support regeneration was driven by the properties of the polymer, with 5-20 wt% TaOx balancing imaging functionality with biological response and proving that in situ monitoring is feasible.

Design of IKVAV peptide/gold nanoparticle decorated, micro/nano-channeled PCL/PLGA film scaffolds for neuronal differentiation and neurite outgrowth

In the field of neural tissue engineering, intensive efforts are being made to develop tissue scaffolds that can support an effective functional recovery and neural development by guiding damaged axons and neurites. Micro/nano-channeled conductive biomaterials are considered a promising approach for repairing the injured neural tissues. Many studies have demonstrated that the micro/nano-channels and aligned nanofibers could guide the neurites to extend along the direction of alignment. However, an ideal biocompatible scaffold containing conductive arrays that could promote effective neural stem cell differentiation and development, and also stimulate high neurite guidance has not been fully developed. In the current study, we aimed to fabricate micro/nano-channeled polycaprolactone (PCL)/Poly-d,l-lactic-co-glycolic acid (PLGA) hybrid film scaffolds, decorate their surfaces with IKVAV pentapeptide/gold nanoparticles (AuNPs), and investigate the behavior of PC12 cells and neural stem cells (NSCs) on the developed biomaterial under static/bioreactor conditions. Here we show that channeled groups decorated with AuNPs highly promote neurite outgrowth and neuronal differentiation along linear lines in the presence of electrical stimulation, compared with the polypyrrole (PPy) coating, which has been used traditionally for many years. Hopefully, this newly developed channeled scaffold structure (PCL/PLGA-AuNPs-IKVAV) could help to support long-distance axonal regeneration and neuronal development after different neural damages.

Electrical stimulation therapy for peripheral nerve injury

Peripheral nerve injury is common and frequently occurs in extremity trauma patients. The motor and sensory impairment caused by the injury will affect patients' daily life and social work. Surgical therapeutic approaches don't assure functional recovery, which may lead to neuronal atrophy and hinder accelerated regeneration. Rehabilitation is a necessary stage for patients to recover better. A meaningful role in non-pharmacological intervention is played by rehabilitation, through individualized electrical stimulation therapy. Clinical studies have shown that electrical stimulation enhances axon growth during nerve repair and accelerates sensorimotor recovery. According to different effects and parameters, electrical stimulation can be divided into neuromuscular, transcutaneous, and functional electrical stimulation. The therapeutic mechanism of electrical stimulation may be to reduce muscle atrophy and promote muscle reinnervation by increasing the expression of structural protective proteins and neurotrophic factors. Meanwhile, it can modulate sensory feedback and reduce neuralgia by inhibiting the descending pathway. However, there are not many summary clinical application parameters of electrical stimulation, and the long-term effectiveness and safety also need to be further explored. This article aims to explore application methodologies for effective electrical stimulation in the rehabilitation of peripheral nerve injury, with simultaneous consideration for fundamental principles of electrical stimulation and the latest technology. The highlight of this paper is to identify the most appropriate stimulation parameters (frequency, intensity, duration) to achieve efficacious electrical stimulation in the rehabilitation of peripheral nerve injury.

Radiopaque Implantable Biomaterials for Nerve Repair

Repairing peripheral nerve injuries remains a clinical challenge. To enhance nerve regeneration and functional recovery, the use of auxiliary implantable biomaterial conduits has become widespread. After implantation, there is currently no way to assess the location or function of polymeric biomedical devices, as they cannot be easily differentiated from surrounding tissue using clinical imaging modalities. Adding nanoparticle contrast agents into polymer matrices can introduce radiopacity and enable imaging using computed tomography (CT), but radiopacity must be balanced with changes in material properties that impact device function and biological response. In this study radiopacity was introduced to porous films of polycaprolactone (PCL) and poly(lactide-co-glycolide) (PLGA) 50:50 and 85:15 with 0-40wt% biocompatible tantalum oxide (TaO x ) nanoparticles. To achieve radiopacity, at least 5wt% TaO x was required, with ≥ 20wt% TaO x leading to reduced mechanical properties and increased nano-scale surface roughness of films. As polymers used for peripheral nerve injury devices, films facilitated nerve regeneration in an in vitro co-culture model of glia (Schwann cells) and dorsal root ganglion neurons (DRG), measured by expression markers for myelination. The ability of radiopaque films to support nerve regeneration was determined by the properties of the polymer matrix, with a range of 5-20wt% TaO x balancing both imaging functionality with biological response and proving that in situ monitoring of nerve repair devices is feasible.

[Post-traumatic pain mononeuropathies]

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