Mechanism of traumatic neuroma development

Neuroma-to-Nerve Ratio: Does Size Matter?

BACKGROUND AND OBJECTIVES

Anatomic features of neuromas have been explored in imaging studies. However, there has been limited research into these features using resected, ex vivo human neuroma specimens. The aim of this study was to investigate the influence that time may have on neuroma growth and size, and the clinical significance of these parameters.

METHODS

Patients who underwent neuroma excision between 2022 through 2023 were prospectively included in this study. Neuroma specimens were obtained after operative resection. Standardized neuroma size measurements, expressed as a neuroma-to-nerve ratio (NNR), were conducted with ImageJ software. Pain data (numeric rating scale, 0-10) were prospectively recorded during preoperative evaluation, and patient factors were collected from chart reviews.

RESULTS

Fifty terminal neuroma specimens from 31 patients were included, with 94.0% of the neuromas obtained from individuals with amputations. Most neuromas were excised from the lower extremities (n = 44, 88.0%). The neuromas had a median NNR of 2.45, and the median injury to neuroma excision interval was 6.3 years. Larger NNRs were associated with a longer injury to neuroma excision interval and with a smaller native nerve diameter. In addition, sensory nerves were associated with a larger NNR compared with mixed nerves. NNR was not associated with preoperative pain or with anatomical nerve distribution.

CONCLUSION

This study suggests that neuromas seem to continue to grow over time and that smaller nerves may form relatively larger neuromas. In addition, sensory nerves develop relatively larger neuromas compared with mixed nerves. Neuroma size does not appear to correlate with pain severity. These findings may stimulate future research efforts and contribute to a better understanding of symptomatic neuroma development.

Management of an Early-Onset, Painful Tibial Nerve Neuroma Using an Autologous Nerve Graft

This case report describes the treatment of a postoperative painful neuroma of the tibial nerve using an autologous nerve graft in a dog. The patient presented with sudden non-weight-bearing lameness 10 days after iatrogenic tibial nerve injury during preparation of a reverse saphenous conduit flap. The dog showed severe pain at the surgical site without nerve deficits. A magnetic resonance imaging examination revealed an enlarged tibial nerve at the injury site, consistent with a neuroma. Analgesics were administered over 11 days, but the patient remained in severe pain and non-weight-bearing. Therefore, surgical resection was recommended. The fusiform neuroma was resected microsurgically, and a saphenous nerve graft was transplanted using an epineural nerve repair technique. Histopathological examination was consistent with a neuroma. The dog showed immediate pain relief and weight-bearing the day after surgery with normal motor function. The dog made a full recovery by the last follow-up 6 mo after surgery. If patients develop pain and lameness following surgery or nerve injury, neuroma formation must be considered, even shortly after surgery. Microsurgical resection and autologous nerve transplantation using an epineural nerve repair technique is a viable method to treat painful neuromas and minimize the risk for recurrence in dogs.

Comparative Effectiveness Systematic Review and Meta-analysis of Peripheral Nerve Repair Using Direct Repair and Connector-assisted Repair

Background

This clinical literature systematic review and meta-analysis were performed to assess differences in outcomes between nerves repaired with direct repair (DR) and connector-assisted repair (CAR).

Methods

A systematic literature review for DR and CAR was performed. Studies from 1980 through August 2023 were included if DR or CAR repairs were performed in upper extremities with nerve gaps less than 5 mm and reported sensory Medical Research Council Classification (MRCC) outcomes or equivalent. Comparative analyses were planned for meaningful recovery (MR) rate (at both S3 and S3+ or better), postsurgical neuroma, cold intolerance, altered sensation, pain, and revision rate.

Results

There were significant differences in MR rates for CAR and DR. At the MRCC S3 threshold, 96.1% of CAR and 81.3% of DR achieved MR (P < 0.0001). At the MRCC S3+ threshold, 87.1% of CAR and 54.2% of DR achieved this higher threshold of MR (P < 0.0001). There were no differences in neuroma rate or pain scores in our dataset. Altered sensation (dysesthesia, paresthesia, hyperesthesia, or hypersensitivity) was not discussed in any CAR studies, so no analysis could be performed. The revision rate for both procedures was 0%. The proportion of patients with cold intolerance was 46.2% in the DR studies, which was significantly higher than the 10.7% of patients in the CAR group.

Conclusions

Significantly more patients achieved sensory MR and fewer had cold intolerance when the CAR technique, instead of the DR technique, was performed to repair peripheral nerve injuries.

Strategies for Treating Traumatic Neuromas with Tissue-Engineered Materials

Neuroma, a pathological response to peripheral nerve injury, refers to the abnormal growth of nerve tissue characterized by disorganized axonal proliferation. Commonly occurring after nerve injuries, surgeries, or amputations, this condition leads to the formation of painful nodular structures. Traditional treatment options include surgical excision and pharmacological management, aiming to alleviate symptoms. However, these approaches often offer temporary relief without addressing the underlying regenerative challenges, necessitating the exploration of advanced strategies such as tissue-engineered materials for more comprehensive and effective solutions. In this study, we discussed the etiology, molecular mechanisms, and histological morphology of traumatic neuromas after peripheral nerve injury. Subsequently, we summarized and analyzed current nonsurgical and surgical treatment options, along with their advantages and disadvantages. Additionally, we emphasized recent advancements in treating traumatic neuromas with tissue-engineered material strategies. By integrating biomaterials, growth factors, cell-based approaches, and electrical stimulation, tissue engineering offers a comprehensive solution surpassing mere symptomatic relief, striving for the structural and functional restoration of damaged nerves. In conclusion, the utilization of tissue-engineered materials has the potential to significantly reduce the risk of neuroma recurrence after surgical treatment.

Traumatic Neuroma in the External Auditory Canal

Traumatic neuroma is the reparative proliferation of axons and Schwann cells at the proximal end of a severed nerve following injury or surgery. Traumatic neuromas with or without clinical symptoms have rarely been reported in the external auditory canal. A 50-year-old woman with a history of trauma visited our otorhinolaryngology clinic with a 7 × 5-mm mass localized on the anterior wall of the external auditory canal. The mass was easily removed via surgical excision and was histopathologically diagnosed as a neuroma. No signs of recurrence were observed after excision. Herein, the authors present this case, along with a review of the literature.

Nerve Capping Techniques for Neuroma Management: A Comprehensive Literature Review

BACKGROUND/AIM OF THE STUDY

Nerve capping is a method of neuroma treatment or prevention that consists of the transplantation of a proximal nerve stump into an autograft or other material cap, after surgical removal of the neuroma or transection of the nerve. The aim was to reduce neuroma formation and symptoms by preventing neuronal adhesions and scar tissue. In this narrative literature review, we summarize the studies that have investigated the effectiveness of nerve capping for neuroma management to provide clarity and update the clinician's knowledge on the topic.

METHODS

A systematic electronic search following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria was performed in the PubMed database combining "neuroma," "nerve," "capping," "conduit," "treatment," "management," "wrap," "tube," and "surgery" as search terms. English-language clinical studies on humans and animals that described nerve capping as a treatment/prevention technique for neuromas were then selected based on a full-text article review. The data from the included studies were compiled based on the technique and material used for nerve capping, and technique and outcomes were reviewed.

RESULTS

We found 10 applicable human studies from our literature search. Several capping materials were described: epineurium, nerve, muscle, collagen nerve conduit, Neurocap (synthetic copolymer of lactide and caprolactone, which is biocompatible and resorbable), silicone rubber, and collagen. Overall, 146 patients were treated in the clinical studies. After surgery, many patients were completely pain-free or had considerable improvement in pain scores, whereas some patients did not have improvement or were not satisfied after the procedure. Nerve capping was used in 18 preclinical animal studies, using a variety of capping materials including autologous tissues, silicone, and synthetic nanofibers. Preclinical studies demonstrated successful reduction in rates of neuroma formation.

CONCLUSIONS

Nerve capping has undergone major advancements since its beginnings and is now a useful option for the treatment or prevention of neuromas. As knowledge of peripheral nerve injuries and neuroma prevention grows, the criterion standard neuroprotective material for enhancement of nerve regeneration can be identified and applied to produce reliable surgical outcomes.

M2 macrophage-derived cathepsin S promotes peripheral nerve regeneration via fibroblast-Schwann cell-signaling relay

BACKGROUND

Although peripheral nerves have an intrinsic self-repair capacity following damage, functional recovery is limited in patients. It is a well-established fact that macrophages accumulate at the site of injury. Numerous studies indicate that the phenotypic shift from M1 macrophage to M2 macrophage plays a crucial role in the process of axon regeneration. This polarity change is observed exclusively in peripheral macrophages but not in microglia and CNS macrophages. However, the molecular basis of axonal regeneration by M2 macrophage is not yet fully understood. Herein, we aimed to identify the M2 macrophage-derived axon regeneration factor.

METHODS

We established a peripheral nerve injury model by transection of the inferior alveolar nerve (IANX) in Sprague-Dawley rats. Transcriptome analysis was performed on the injured nerve. Recovery from sensory deficits in the mandibular region and histological reconnection of IAN after IANX were assessed in rats with macrophage depletion by clodronate. We investigated the effects of adoptive transfer of M2 macrophages or M2-derived cathepsin S (CTSS) on the sensory deficit. CTSS initiating signaling was explored by western blot analysis in IANX rats and immunohistochemistry in co-culture of primary fibroblasts and Schwann cells (SCs).

RESULTS

Transcriptome analysis revealed that CTSS, a macrophage-selective lysosomal protease, was upregulated in the IAN after its injury. Spontaneous but partial recovery from a sensory deficit in the mandibular region after IANX was abrogated by macrophage ablation at the injured site. In addition, a robust induction of c-Jun, a marker of the repair-supportive phenotype of SCs, after IANX was abolished by macrophage ablation. As in transcriptome analysis, CTSS was upregulated at the injured IAN than in the intact IAN. Endogenous recovery from hypoesthesia was facilitated by supplementation of CTSS but delayed by pharmacological inhibition or genetic silencing of CTSS at the injured site. Adoptive transfer of M2-polarized macrophages at this site facilitated sensory recovery dependent on CTSS in macrophages. Post-IANX, CTSS caused the cleavage of Ephrin-B2 in fibroblasts, which, in turn, bound EphB2 in SCs. CTSS-induced Ephrin-B2 cleavage was also observed in human sensory nerves. Inhibition of CTSS-induced Ephrin-B2 signaling suppressed c-Jun induction in SCs and sensory recovery.

CONCLUSIONS

These results suggest that M2 macrophage-derived CTSS contributes to axon regeneration by activating SCs via Ephrin-B2 shedding from fibroblasts.

Spectrum of ultrasound findings in patients with history of breast conservative treatment

Breast conservative treatment (BCT) is currently accepted as the standard treatment option for breast cancer. Targeted ultrasound helps detect recurrent lesions, postoperative changes, and scarring tissue. In this pictorial essay, we review the ultrasound features of benign (seroma, hematoma, fat necrosis, traumatic neuroma, fibrosis/scarring) and malignant (recurrence, new primary cancer) causes of palpable lumps after BCT and provide images from our patients to illustrate some typical findings of common pathologies. Ultrasound, especially as an adjunct to mammography, can make a specific diagnosis in most cases.

Experimental Study on Repairing Peripheral Nerve Defects with Novel Bionic Tissue Engineering

Peripheral nerve defects are a worldwide problem, and autologous nerve transplantation is currently the gold-standard treatment for them. Tissue-engineered nerve (TEN) grafts are widely considered promising methods for the same, and have attracted much attention. To improve repair, the incorporation of bionics into TEN grafts has become a focus of research. In this study, a novel bionic TEN graft with a biomimetic structure and composition is designed. For this purpose, a chitin helical scaffold is fabricated by means of mold casting and acetylation using chitosan as the raw material, following which a fibrous membrane is electrospun on the outer layer of the chitin scaffold. The lumen of the structure is filled with human bone mesenchymal stem cell-derived extracellular matrix and fibers to provide nutrition and topographic guidance, respectively. The prepared TEN graft is then transplanted to bridge 10 mm sciatic nerve defects in rats. Morphological and functional examination shows that the repair effects of the TEN grafts and autografts are similar. The bionic TEN graft described in this study shows great potential for application and offers a new way to repair clinical peripheral nerve defects.

Biliary tree traumatic neuroma following laparoscopic cholecystectomy: A case report and literature review

Laparoscopic cholecystectomy has been found to be associated with the development of traumatic neuromas on rare occasions. The present study reports a rare case of post-cholecystectomy biliary tree traumatic neuroma. Herein, a 47-year-old female with a history of laparoscopic cholecystectomy presented with upper abdominal pain and anorexia. Upon an examination, a yellow discoloration of the sclera was observed. Magnetic resonance cholangiopancreatography revealed a dilated proximal bile duct and mild dilatation of the intrahepatic biliary tree due to a stricture. Intraoperatively, a hard bile duct mass was observed with multiple enlarged lymph nodes in the peri-hepatic region. The patient was initially suspected to have bile duct cancer; however, a histopathological analysis of the resected mass revealed a bile duct traumatic neuroma. Biliary traumatic neuromas may be underestimated since they often remain asymptomatic. It is unfortunate that, as traumatic neuromas often lack distinguishing characteristics, no particular radiological findings for traumatic neuromas of the bile duct have been described to date, at least to the best of our knowledge. The rarity of this condition, combined with the absence of a standardized diagnostic modality, renders its diagnosis difficult and can even lead to misdiagnosis as biliary cancer.

Regenerative Peripheral Nerve Interface Surgery: Anatomic and Technical Guide

Regenerative peripheral nerve interface (RPNI) surgery has been demonstrated to be an effective tool as an interface for neuroprosthetics. Additionally, it has been shown to be a reproducible and reliable strategy for the active treatment and for prevention of neuromas. The purpose of this article is to provide a comprehensive review of RPNI surgery to demonstrate its simplicity and empower reconstructive surgeons to add this to their armamentarium. This article discusses the basic science of neuroma formation and prevention, as well as the theory of RPNI. An anatomic review and discussion of surgical technique for each level of amputation and considerations for other etiologies of traumatic neuromas are included. Lastly, the authors discuss the future of RPNI surgery and compare this with other active techniques for the treatment of neuromas.

Traumatic neuromas of peripheral nerves: Diagnosis, management and future perspectives

Traumatic neuromas are infrequent in clinical settings but are prevalent following trauma or surgery. A traumatic neuroma is not a true malignancy, rather, it is a hyperplastic, reparative nerve reaction after injury and typically manifests as a nodular mass. The most common clinical manifestations include painful hypersensitivity and the presence of a trigger point that causes neuralgic pain, which could seriously decrease the living standards of patients. While various studies are conducted aiming to improve current diagnosis and management strategies via the induction of emerging imaging tools and surgical or conservative treatment. However, researchers and clinicians have yet to reach a consensus regarding traumatic neuromas. In this review, we aim to start with the possible underlying mechanisms of traumatic neuromas, elaborate on the diagnosis, treatment, and prevention schemes, and discuss the current experiment models and advances in research for the future management of traumatic neuromas.

New techniques and methods for prevention and treatment of symptomatic traumatic neuroma: A systematic review

Generally, axons located at the central end of the nerve system will sprout after injury. Once these sprouts cannot reach the distal end of the severed nerve, they will form a traumatic neuroma. Traumatic neuromas bring a series of complex symptoms to patients, such as neuropathic pain, skin abnormalities, skeletal abnormalities, hearing loss, and visceral damage. To date, the most promising and practical clinical treatments are drug induction and surgery, but both have their limitations. Therefore, it will be the mainstream trend to explore new methods to prevent and treat traumatic neuroma by regulating and remodeling the microenvironment of nerve injury. This work first summarized the pathogenesis of traumatic neuroma. Additionally, the standard methods of prevention and treatment on traumatic neuroma were analyzed. We focused on three essential parts of advanced functional biomaterial therapy, stem cell therapy, and human-computer interface therapy to provide the availability and value of preventing and treating a traumatic neuroma. Finally, the revolutionary development of the prevention and treatment on traumatic neuroma has been prospected. How to transform the existing advanced functional materials, stem cells, and artificial intelligence robots into clinical practical technical means as soon as possible for high-quality nerve repair and prevention of neuroma was further discussed.

Contrast-enhanced ultrasound of a traumatic neuroma of the extrahepatic bile duct: A case report and review of literature

BACKGROUND

Traumatic neuromas result from nerve injury after trauma or surgery but rarely occur in the bile duct. However, it is challenging to diagnose traumatic neuromas correctly preoperatively. Although some previous reports have described the imaging features of traumatic neuroma in the bile duct, no features of traumatic neuromas in the bile duct have been identified by using contrast-enhanced ultrasound (CEUS) imaging before.

CASE SUMMARY

A 55-year-old male patient presented to our hospital with a 3-mo history of abdominal distension and anorexia and history of cholecystectomy 4 years ago. Grayscale ultrasound demonstrated mild to moderate intrahepatic bile duct dilatation. Meanwhile, a hyperechoic nodule was found in the upper extrahepatic bile duct. The lesion approximately 0.8 cm × 0.6 cm with a regular shape and clear margins. The nodule of the bile duct showed slight hyperenhancement in the arterial phase and isoenhancement in the venous phase on CEUS. Laboratory tests showed that alanine aminotransferase and aspartate aminotransferase were increased significantly, while the tumor marker carbohydrate antigen 19-9 was increased slightly. Then, hilar bile duct resection and end-to-end bile ductal anastomosis were performed. The histological examination revealed traumatic neuroma of the extrahepatic bile duct. The patient had an uneventful recovery after surgery.

CONCLUSION

The current report will help enhance the current knowledge regarding identifying traumatic neuromas by CEUS imaging and review the related literature.

Targeted Muscle Reinnervation of the Supraclavicular Nerve to the Motor Branch of the Omohyoid Muscle in Patients Undergoing Thoracic Outlet Syndrome Procedures

Transection of the supraclavicular nerve (SCN) through supraclavicular incisions can lead to debilitating neuroma formation. Targeted muscle reinnervation (TMR) proved to be an effective technique for the prevention and treatment of neuroma. In this case series, we propose the TMR of the SCN to the motor branch of the omohyoid muscle (OM) to prevent the formation of neuroma and avoid chronic pain at the supraclavicular area after thoracic outlet syndrome (TOS) procedures. A total of 10 patients underwent the procedure. Dissection of the SCN and its branches was performed through a supraclavicular incision. The branches were transected close to the clavicle. The inferior belly of the OM was identified and its motor branch isolated. Coaptation of the SCN branches with the motor branch of the OM was performed under the microscope and the wound was closed in layers. All the patients denied pain or hypersensitivity at the supraclavicular area on follow-up. In summary, the motor branch of the OM is a viable recipient for the TMR of the SCN and can prevent and treat painful neuromas at the supraclavicular area with minimal morbidity.

Surgical Approaches for Prevention of Neuroma at Time of Peripheral Nerve Injury

Painful neuroma is a frequent sequela of peripheral nerve injury which can result in pain and decreased quality of life for the patient, often necessitating surgical intervention. End neuromas are benign neural tumors that commonly form after nerve transection, when axons from the proximal nerve stump regenerate in a disorganized manner in an attempt to recreate nerve continuity. Inflammation and collagen remodeling leads to a bulbous end neuroma which can become symptomatic and result in decreased quality of life. This review covers surgical prophylaxis of end neuroma formation at time of injury, rather than treatment of existing neuroma and prevention of recurrence. The current accepted methods to prevent end neuroma formation at time of injury include different mechanisms to inhibit the regenerative response or provide a conduit for organized regrowth, with mixed results. Approaches include proximal nerve stump capping, nerve implantation into bone, muscle and vein, various pharmacologic methods to inhibit axonal growth, and mechanisms to guide axonal growth after injury. This article reviews historical treatments that aimed to prevent end neuroma formation as well as current and experimental treatments, and seeks to provide a concise, comprehensive resource for current and future therapies aimed at preventing neuroma formation.

Case Report: Idiopathic Traumatic Neuroma of the Gallbladder Without Previous Surgery

Traumatic neuroma mostly results from nerve injury caused by surgery or trauma. Traumatic neuroma of the gallbladder without prior abdominal surgery is extremely rare, and we termed it “idiopathic traumatic neuroma of the gallbladder.” Due to its rarity and a lack of specific clinical and radiological features, it is most commonly misdiagnosed. In our case, the patient was admitted to our hospital for cholangiocarcinoma. Repeated abdominal contrast-enhanced computed tomography scans preoperatively indicated hilar cholangiocarcinoma. Due to insufficient future liver remnant, we planned preoperative percutaneous transhepatic cholangiodrainage and percutaneous transhepatic portal vein embolization based on multidisciplinary team consultation. The patient was then admitted 1 month later for surgery. We performed a laparoscopic cholecystectomy and an extensive laparoscopic right hepatectomy as gallbladder carcinoma was strongly suspected intraoperatively. However, the final diagnosis was traumatic neuroma of the gallbladder confirmed by pathological examination. Traumatic neuroma of the gallbladder is very rare, and we hope to provide some references for diagnosis by reporting our case and reviewing the literature on this topic so that extensive treatment can be avoided, thus improving patients’ quality of life. To the best of our knowledge, this is the first reported case of traumatic neuroma without prior surgery in the English literature since 1996.

Trigeminal Traumatic Neuroma: a Comprehensive Review of the Literature Based On a Rare Case

PURPOSE OF REVIEW

Traumatic neuromas in general, and trigeminal traumatic neuromas in particular, are relatively rare entities originating from a damage to a corresponding nerve or its branches. This manuscript is a comprehensive review of the literature on trigeminal traumatic neuromas based on an interesting and challenging case of bilateral intraoral lesions.

RECENT FINDINGS

The diagnosis for this patient was bilateral trigeminal traumatic neuromas. It is possible that these patients have a genetic predisposition to the development of these lesions. It is a neuropathic pain condition and may mimic dental and other trigeminal pain entities. Topical treatment with lidocaine gel, utilizing a custom-made neurosensory stent, rendered the patient significant and sustained pain relief. Trigeminal traumatic neuromas present a diagnostic challenge even to a seasoned clinician, due to the complex clinical features that may mimic other entities. Topical medications such as local anesthetics may be a good viable alternative to systemic medications to manage the pain associated with the condition. Early identification of the lesion and the associated pain helps in the succinct management of symptomatic trigeminal traumatic neuromas.

The Role of Biomaterials in Peripheral Nerve and Spinal Cord Injury: A Review

Peripheral nerve and spinal cord injuries are potentially devastating traumatic conditions with major consequences for patients’ lives. Severe cases of these conditions are currently incurable. In both the peripheral nerves and the spinal cord, disruption and degeneration of axons is the main cause of neurological deficits. Biomaterials offer experimental solutions to improve these conditions. They can be engineered as scaffolds that mimic the nerve tissue extracellular matrix and, upon implantation, encourage axonal regeneration. Furthermore, biomaterial scaffolds can be designed to deliver therapeutic agents to the lesion site. This article presents the principles and recent advances in the use of biomaterials for axonal regeneration and nervous system repair.

Traumatic neuroma at the mastectomy site, unusual benign lesion, mimicking tumor recurrence: A report of two cases

Traumatic neuroma is not a true neoplasm but a reparative proliferation of axons, Schwann cells, and fibroblasts at the proximal end of transected or injured nerves resulting from trauma or surgery. Breast traumatic neuroma after breast surgery, with or without clinical symptoms, has rarely been reported. Once found, it should be differentiated from tumor recurrence, and tissue confirmation is necessary, although it is small in size and demonstrates a benign appearance in imaging studies. Herein, we present two cases of traumatic neuroma at the mastectomy site. They were incidentally encountered during ultrasound evaluation of mastectomy beds given concerns for potential recurrence or malignancy, and pathologic confirmation by ultrasound-guided core needle biopsy was sufficient for the diagnosis.

Bilateral intraoral traumatic neuroma: Case report of a diagnostic challenge

Oral traumatic neuromas (TrNs) are relatively rare lesions and they originate from a damaged nerve. They present a diagnostic challenge, due to the complex clinical features that may mimic odontogenic, musculoskeletal, and other neuropathic pain conditions. We describe an interesting and challenging case of painful bilateral intraoral lesions in a 56-year-old South Indian female patient who presented with clinical features consistent with TrN lesions bilaterally, in relation to different branches of the trigeminal nerve. The patient had undergone numerous aggressive dental treatments and interventions over the past three decades, with little or no pain relief. Topical treatment with lidocaine gel utilizing a custom-made neurosensory stent rendered the patient significant and sustained pain relief.

Myelin-associated glycoprotein combined with chitin conduit inhibits painful neuroma formation after sciatic nerve transection

Studies have shown that myelin-associated glycoprotein (MAG) can inhibit axon regeneration after nerve injury. However, the effects of MAG on neuroma formation after peripheral nerve injury remain poorly understood. In this study, local injection of MAG combined with nerve cap made of chitin conduit was used to intervene with the formation of painful neuroma after sciatic nerve transfection in rats. After 8 weeks of combined treatment, the autotomy behaviors were reduced in rats subjected to sciatic nerve transfection, the mRNA expression of nerve growth factor, a pain marker, in the proximal nerve stump was decreased, the density of regenerated axons was decreased, the thickness of the myelin sheath was increased, and the ratio of unmyelinated to myelinated axons was reduced. Moereover, the percentage of collagen fiber area and the percentage of fibrosis marker alpha-smooth muscle actin positive staining area in the proximal nerve stump were decreased. The combined treatment exhibited superior effects in these measures to chitin conduit treatment alone. These findings suggest that MAG combined with chitin conduit synergistically inhibits the formation of painful neuroma after sciatic nerve transection and alleviates neuropathic pain. This study was approved by the Animal Ethics Committee of Peking University People’s Hospital (approval No. 2019PHE027) on December 5, 2019.

Aligned nanofiber nerve conduits inhibit alpha smooth muscle actin expression and collagen proliferation by suppressing TGF-β1/SMAD signaling in traumatic neuromas

Transforming growth factor-beta 1 (TGF-β1) is a powerful activator of connective tissue synthesis that is strongly associated with the pathophysiology of traumatic neuroma. Previous studies have demonstrated that aligned nanofiber conduits made from silk fibroin and poly (L-lactic acid-co-ε-caprolactone; PLCL) could prevent traumatic neuromas. In the present study, the possible mechanisms of conduits in treating traumatic neuromas were investigated to provide theoretical basis for procedures. Aligned nanofiber conduits were used for nerve capping. Sciatic nerves of Sprague-Dawley rats were used to create an animal model. The present study contains two parts, each including four experimental groups. SB-431542/SRI-011381 hydrochloride was used to suppress/enhance TGF-β1/SMAD signaling. Part I discussed the connections between traumatic neuroma and the proliferation of alpha smooth muscle actin (α-SMA) and collagen; it also investigated the therapeutic effect of conduits. Part II hypothesized that conduits suppressed TGF-β1/SMAD signaling. Histological characteristics, quantitative analysis of α-SMA, collagens and signaling-related parameters were assessed and compared among groups one month postoperatively. Results from Part I demonstrated that aligned nanofiber conduits suppressed the expression of α-SMA and collagens; and results from Part II revealed the downregulation of pathway-related proteins, suggesting that the suppression was mediated by TGF-β1/SMAD signaling. Aligned nanofiber conduits may be effective nerve capping biomaterials. One of the mechanisms involves suppressing TGF-β1/SMAD signaling. Novel treatments using aligned nanofiber conduits could be developed to manage traumatic neuromas.

Regenerative Peripheral Nerve Interfaces for the Treatment and Prevention of Neuromas and Neuroma Pain

A neuroma occurs when a regenerating transected peripheral nerve has no distal target to reinnervate. This situation can result in a hypersensitive free nerve ending that causes debilitating pain to affected patients. No techniques to treat symptomatic neuromas have shown consistent results. One novel physiologic solution is the regenerative peripheral nerve interface (RPNI). RPNI consists of a transected peripheral nerve that is implanted into an autologous free skeletal muscle graft. Early clinical studies have shown promising results in the use of RPNIs to treat and prevent symptomatic neuromas. This review article describes the rationale behind the success of RPNIs and its clinical applications.

Palpable Lumps after Mastectomy: Radiologic-Pathologic Review of Benign and Malignant Masses

Patients who have undergone mastectomy, with or without reconstruction, are not universally screened with mammography or US. Therefore, clinical breast examination by the physician and patient-detected palpable abnormalities are crucial for detecting breast cancer or recurrence. Diagnostic US is the first-line modality for evaluation of postmastectomy palpable masses, with occasional adjunct use of diagnostic mammography for confirming certain benign masses. In the setting of a negative initial imaging evaluation with continued clinical concern, diagnostic MRI may aid in improving sensitivity. Knowledge of the typical multimodality imaging appearances and locations of malignant palpable abnormalities-such as invasive carcinoma recurrence, cancer in residual breast tissue, radiation-induced sarcoma, and metastatic disease-is crucial in diagnosis and treatment of these entities. In addition, familiarity with the range of benign palpable postmastectomy processes-including fat necrosis, fat graft, seroma, granuloma, neuroma, fibrosis, and infection-may help avoid unnecessary biopsies and reassure patients. The authors review common and rare benign and malignant palpable masses in mastectomy patients, describe multimodality diagnostic imaging evaluation of each entity, review radiologic and pathologic correlation, and acquaint the radiologist with management when these findings are encountered. ^©RSNA, 2021.

Covering the proximal nerve stump with chondroitin sulfate proteoglycans prevents traumatic painful neuroma formation by blocking axon regeneration after neurotomy in Sprague Dawley rats

OBJECTIVE

Neuropathic pain caused by traumatic neuromas is an extremely intractable clinical problem. Disorderly scar tissue accumulation and irregular and immature axon regeneration around the injury site mainly contribute to traumatic painful neuroma formation. Therefore, successfully preventing traumatic painful neuroma formation requires the effective inhibition of irregular axon regeneration and disorderly accumulation of scar tissue. Considering that chondroitin sulfate proteoglycans (CSPGs) can act on the growth cone and effectively inhibit axon regeneration, the authors designed and manufactured a CSPG-gelatin blocker to regulate the CSPGs' spatial distribution artificially and applied it in a rat model after sciatic nerve neurectomy to evaluate its effects in preventing traumatic painful neuroma formation.

METHODS

Sixty female Sprague Dawley rats were randomly divided into three groups (positive group: no covering; blank group: covering with gelatin blocker; and CSPG group: covering with the CSPG-gelatin blocker). Pain-related factors were evaluated 2 and 8 weeks postoperatively (n = 30). Neuroma growth, autotomy behavior, and histological features of the neuromas were assessed 8 weeks postoperatively (n = 30).

RESULTS

Eight weeks postoperatively, typical bulb-shaped neuromas did not form in the CSPG group, and autotomy behavior was obviously better in the CSPG group (p < 0.01) than in the other two groups. Also, in the CSPG group the regenerated axons showed a lower density and more regular and improved myelination (p < 0.01). Additionally, the distribution and density of collagenous fibers and the expression of α-smooth muscle actin were significantly lower in the CSPG group than in the positive group (p < 0.01). Regarding pain-related factors, c-fos, substance P, interleukin (IL)-17, and IL-1β levels were significantly lower in the CSPG group than those in the positive and blank groups 2 weeks postoperatively (p < 0.05), while substance P and IL-17 remained lower in the CSPG group 8 weeks postoperatively (p < 0.05).

CONCLUSIONS

The authors found that CSPGs loaded in a gelatin blocker can prevent traumatic neuroma formation and effectively relieve pain symptoms after sciatic nerve neurotomy by blocking irregular axon regeneration and disorderly collagenous fiber accumulation in the proximal nerve stump. These results indicate that covering the proximal nerve stump with CSPGs may be a new and promising strategy to prevent traumatic painful neuroma formation in the clinical setting.

MRI features of symptomatic amputation neuromas

OBJECTIVES

To demonstrate the magnetic resonance imaging (MRI) features of amputation neuromas in lower extremity amputees and investigate independent predictive MRI features for symptomatic neuromas.

METHODS

This retrospective study included 45 amputation neuromas in 44 lower extremity amputees. Two radiologists assessed the imaging features, including shape, size, type (end-bulb or spindle), signal intensity (SI), heterogeneity, margins, enlarged fascicles, dark outer rim, tail sign, target sign, enhancement, perilesional fibrosis, and muscle denervation. The neuromas were categorized into symptomatic (n = 24) or asymptomatic (n = 21). Symptomatic neuromas were determined based on neuropathic pain characteristics, the presence of Tinel's sign or tenderness, and response to local anesthetic injection. Univariate and multivariate analyses were performed to identify independent predictive MRI features.

RESULTS

Of 45 neuromas, 80% (36/45) were end-bulb neuromas and 20% (9/45) were spindle-type neuromas. Eighty percent of the neuromas (36/45) were heterogeneous on T2-weighted images (WIs). Enlarged fascicles were present in 42% (19/45) and dark outer rims in 27% (12/45) of the neuromas. Among the 23 neuromas with enhanced images, 78% (18/23) showed enhancement. Heterogeneity on T2-WIs and enhancement ratios were significantly different between the asymptomatic and symptomatic neuroma groups (p < 0.05). The multivariate analyses indicated that heterogeneity on T2-WIs was an independent factor associated with symptomatic neuromas (p < 0.001).

CONCLUSIONS

Heterogeneity on T2-WIs could be a predictive indicator for symptomatic neuromas in lower extremity amputees.

KEY POINTS

• Amputation neuromas are classified as either end-bulb or spindle-type. They can show enlarged fascicles, dark outer rims, and enhancement. • Heterogeneity on T2-weighted images could be a predictive indicator for symptomatic neuromas. • Predicting the symptomatic neuroma on MRI would help in effective management of stump pain.

Cut wires: The Electrophysiology of Regenerated Tissue

When nerves are damaged by trauma or disease, they are still capable of firing off electrical command signals that originate from the brain. Furthermore, those damaged nerves have an innate ability to partially regenerate, so they can heal from trauma and even reinnervate new muscle targets. For an amputee who has his/her damaged nerves surgically reconstructed, the electrical signals that are generated by the reinnervated muscle tissue can be sensed and interpreted with bioelectronics to control assistive devices or robotic prostheses. No two amputees will have identical physiologies because there are many surgical options for reconstructing residual limbs, which may in turn impact how well someone can interface with a robotic prosthesis later on. In this review, we aim to investigate what the literature has to say about different pathways for peripheral nerve regeneration and how each pathway can impact the neuromuscular tissue’s final electrophysiology. This information is important because it can guide us in planning the development of future bioelectronic devices, such as prosthetic limbs or neurostimulators. Future devices will primarily have to interface with tissue that has undergone some natural regeneration process, and so we have explored and reported here what is known about the bioelectrical features of neuromuscular tissue regeneration.

Resolution of persistent traumatic supraorbital pain after neuroma excision

We describe a case of an 18-year-old male who developed a supraorbital neuroma following facial trauma that occurred 2 years earlier. He presented with complaints of persistent facial pain and migraines despite successful laceration repair and removal of foreign bodies at the time of injury. A non-contrast computed tomography (CT) scan of the orbits revealed an enlarged supraorbital nerve with remodeling and expansion of the supraorbital notch, suggesting a neuroma. The patient underwent orbitotomy with excision of neuroma (confirmed histologically) and experienced a complete resolution of periorbital pain.

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

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

Excision of Rare Intraosseous Traumatic Neuroma of the Mandible

Traumatic neuroma is a non-neoplastic proliferative disorder of the nerve sheath in response to injury or surgery. Traumatic neuroma most frequently occurs in soft tissues and intraosseous involvement is uncommon. In this paper, we present a rare case of intraosseous traumatic neuroma of the inferior alveolar nerve leading to pain and paresthesia of the lower lip on the left side.

Evidence-Based Strategies for the Prevention of Chronic Post-Intensive Care and Acute Care-Related Pain

Chronic pain is prevalent in intensive care survivors and in patients who require acute care treatments. Many adverse consequences have been associated with chronic post-intensive care and acute care-related pain. Hence, interest in interventions to prevent these pain disorders has grown. To improve the understanding of the mechanisms of action of these interventions and their potential impacts, this article outlines the pathophysiology involved in the transition from acute to chronic pain, the epidemiology and consequences of chronic post-intensive care and acute care- related pain, and risk factors for the development of chronic pain. Pharmacological, nonpharmacological, and multimodal preventive interventions specific to the targeted populations and their levels of evidence are presented. Nursing implications for preventing chronic pain in patients receiving critical and acute care are also discussed.

Repairing Volumetric Muscle Loss in the Ovine Peroneus Tertius Following a 3-Month Recovery

Much effort has been made to fabricate engineered tissues on a scale that is clinically relevant to humans; however, scale-up remains one of the most significant technological challenges of tissue engineering to date. To address this limitation, our laboratory has developed tissue-engineered skeletal muscle units (SMUs) and engineered neural conduits (ENCs), and modularly scaled them to clinically relevant sizes for the treatment of volumetric muscle loss (VML). The goal of this study was to evaluate the SMUs and ENCs in vitro, and to test the efficacy of our SMUs and ENCs in restoring muscle function in a clinically relevant large animal (sheep) model. The animals received a 30% VML injury to the peroneus tertius muscle and were allowed to recover for 3 months. The animals were divided into three experimental groups: VML injury without a repair (VML only), repair with an SMU (VML+SMU), or repair with an SMU and ENC (VML+SMU+ENC). We evaluated the SMUs before implantation and found that our single scaled-up SMUs were characterized by the presence of contracting myotubes, linearly aligned extracellular matrix proteins, and Pax7⁺ satellite cells. Three months after implantation, we found that the repair groups (VML+SMU and VML+SMU+ENC) had restored muscle mass and tetanic force production to a level that was statistically indistinguishable from the uninjured contralateral muscle after 3 months in vivo. Furthermore, we demonstrated the ability of our ENCs to effectively bridge the gap between native nerve and the repair site by eliciting a muscle contraction through direct electrical stimulation of the re-routed nerve. Impact statement The fabrication of tissues of clinically relevant sizes is one of the largest obstacles preventing engineered tissues from achieving widespread use in the clinic. This study aimed to combat this limitation by developing a fabrication method to scale-up tissue-engineered skeletal muscle for the treatment of volumetric muscle loss in a large animal (sheep) model and evaluating the efficacy of the tissue-engineered constructs after a 3-month recovery.

Application of a Porcine Small Intestine Submucosa Nerve Cap for Prevention of Neuromas and Associated Pain

Painful neuroma formation is a common and debilitating sequela of traumatic or oncologic nerve amputations. Studies suggest that isolating transected nerve stumps within protective caps during amputation surgery or revision procedures may assist in preventing symptomatic nerve-end neuroma formation. This study evaluated the local effects of two porcine small intestine submucosa (pSIS) nerve caps of differing configurations on a terminal nerve end in an animal model. The tibial nerves of 57 Sprague Dawley rats were transected and transposed to the lateral hind leg. The nerves were treated with one of three SIS materials, including (i) a nerve cap with spiraling chambering, termed spiral nerve cap (SNC), (ii) a nerve cap with bifurcated chambers termed chambered nerve cap (CNC), or (iii) an open tube. The surgical control consisted of nerve stumps that were not treated. Overall tissue response, axonal swirling, optical density of axons, and behavioral pain response were quantified at 8 and 12 weeks postoperatively. There were no notable differences between the performance of the SNC and CNC groups. The pSIS nerve caps mitigated aberrant axonal regeneration and decreased neuroma formation and associated pain response. These findings suggest that nerve caps with internal chambers for axonal outgrowth may improve axonal alignment, therefore reducing the likelihood of symptomatic neuroma formation.

Methodology for creating a chronic osseointegrated neural interface for prosthetic control in rabbits

BACKGROUND

Chronic stability and high degrees of selectivity are both essential but somewhat juxtaposed components for creating an implantable bi-directional PNI capable of controlling of a prosthetic limb. While the more invasive implantable electrode arrays provide greater specificity, they are less stable over time due to compliance mismatch with the dynamic soft tissue environment in which the interface is created.

NEW METHOD

This paper takes the surgical approach of transposing nerves into bone to create neural interface within the medullary canal of long bones, an osseointegrated neural interface, to provide greater stability for implantable electrodes. In this context, we describe the surgical model for transfemoral amputation with transposition of the sciatic nerve into the medullary canal in rabbits. We investigate the capacity to create a neural interface within the medullary canal histolomorphologically. In a separate proof of concept experiment, we quantify the chronic physiological capacity of transposed nerves to conduct compound nerve action potentials evoked via an Osseointegrated Neural Interface.

COMPARISON WITH EXISTING METHOD(S)

The rabbit serves as an important animal model for both amputation neuroma and osseointegration research, but is underutilized for the exploration neural interfacing in an amputation setting.

RESULTS

Our findings demonstrate that transposed nerves remain stable over 12 weeks. Creating a neural interface within the medullary canal is possible and does not impede nerve regeneration or physiological capacity.

CONCLUSIONS

This article represents the first evidence that an Osseointegrated Neural Interface can be surgically created, capable of chronic stimulation/recording from amputated nerves required for future prosthetic control.

Neuromas at the castration site in geldings

Background

Inguinal pain, unexplained hind limb lameness, back pain or behavioural problems in geldings could be attributable to painful neuromas that develop as a consequence of crushing and severing the testicular nerves during castration. The presence of neuroma in this anatomical location has never been reported, hence the knowledge of possible clinical relevance is limited. The aim of this study was to histologically investigate the testicular nerves at the castration site in geldings for the presence of neuromas. Proximal spermatic cord remnants were collected from 20 geldings admitted to routine post mortem examination for various reasons. The time of castration was unknown, but it had not been performed during the last year. Spermatic cord specimens were immersed in 10% formalin, trimmed, dehydrated, embedded in paraffin, sectioned and stained with haematoxylin and eosin (HE) for light microscopy. Identification of nerve tissue was done by immuno-localization of nerve specific enolase (NSE).

Results

Neuromas were found in 21 spermatic cords from 13 geldings and were bilateral in eight of the horses. The neuromas consisted of areas with small groups of non-neoplastic proliferations of peripheral neural tissue. The tissue included neurofilaments and Schwann cells, intermingled or surrounded with, epineural, perineural and endoneural fibrous tissue. The neural tissue immunostained positive with NSE.

Conclusions

This study showed neuromas of the remnant testicular nerves at the site of castration. Further studies are required to establish if these neuromas in the castration site are painful and if certain castration methods promote their formation. Future studies should also investigate the clinical consequence of these neuromas for the individual horse.

Traumatic neuroma of the posterior tibial nerve due to previous surgery presenting as a massive tumor in the midfoot: A case report

A case report of traumatic neuroma, a benign non-neoplastic tumor of the posterior tibial nerve is presented. The soft tissue mass in the midfoot region was likely a sequela of previous nerve decompression surgery that the patient underwent five years previously in the same region and on the same nerve. Physical examination and history taking, along with an MRI, were important steps in reaching a definitive diagnosis of traumatic neuroma based on the findings of an interventional radiologist and histopathological evaluation of the biopsy by a pathologist. The lesion was subsequently surgically removed utilizing a multidisciplinary management approach. The patient recovered uneventfully and no symptom recurrence was noted at the 30-month follow-up. The tumor was the largest reported in the literature at the time. This case was also unique in that the patient was relieved of pronation and regained tactile sensation in the midfoot.

Traumatic neuroma in mastectomy scar: Two case reports and review of the literature

RATIONALE

Traumatic neuroma is a reparative proliferative response of the nerve after trauma or surgery, which rarely occurs in the breast. However, it must be distinguished from tumor recurrence.

PATIENT CONCERNS

A 78-year-old woman underwent left-sided modified radical mastectomy for invasive carcinoma, 7 years before this case. Two painless nodules near the mastectomy scar were discovered in regular follow-up physical examination. A 62-year-old woman had received right-sided modified radical mastectomy for intraductal carcinoma, 4 years before this case. An asymptomatic nodule near the mastectomy scar was detected during follow-up ultrasound (US) examination.

DIAGNOSIS

The lesions in both patients were diagnosed as traumatic neuroma.

INTERVENTIONS

The first patient underwent excisional biopsy. The second patient underwent US guided core-needle aspiration, followed by conservative therapy.

OUTCOMES

Neither patient complained of any discomfort, nor both exhibited normal physical and US findings during follow-up examinations.

LESSONS

Newly discovered nodules with the benign imaging features near the mastectomy site of a patient, especially with the tail sign, traumatic neuromas should be taken into consideration. Routine US examination is important for follow-up of breast cancer patients who have undergone mastectomy.

Can phantom limb pain be reduced/eliminated solely by techniques applied to peripheral nerves?

About 0.5% of the US population (1.7 million) is living with a lost limb and this number is expected to double by 2050. This number is much higher in other parts of the world. Within days to weeks of an extremity amputation, up to 80% of these individuals develop neuropathic pain presenting as phantom limb pain (PLP). The level of PLP increases significantly by one year and remains chronic and severe for about 10% of individuals. PLP has a serious negative impact on individuals’ lives. Current pain treatment therapies, such pharmacological approaches provide limited to no pain relief, some other techniques applied to the central nervous system (CNS) and peripheral nervous system (PNS) reduce or block PLP, but none produces long-term pain suppression. Therefore, new drugs or novel analgesic methods must be developed that prevent PLP from developing, or if it develops, to reduce the level of pain. This paper examines the potential causes of PLP, and present techniques used to prevent the development of PLP, or if it develops, to reduce the level of pain. Finally it presents a novel technique being developed that eliminates/reduces chronic neuropathic pain and which may induce the long-term reduction/elimination of PLP.

Traumatic neuroma as a rare cause of intractable neuropathic breast pain following cancer surgery: Management and review of the literature

Traumatic neuroma of the breast after cancer surgery is a very rare clinical entity with only a few cases having been reported to date. We herein present a very rare case of traumatic breast neuroma in a postmenopausal patient with a history of breast-conserving surgery, who presented with a four-month history of intractable neuropathic breast pain. Diagnostic evaluation and management are discussed along with a review of the literature. Traumatic breast neuromas are very rare benign lesions that have been reported mainly after mastectomy. Our literature review yielded only 35 cases of traumatic breast neuromas in 28 patients, reported so far. Although imaging features may be indicative of a benign lesion, surgical excision is necessary to obtain a definitive diagnosis and to rule out a recurrent breast cancer. Conservative treatment is feasible in properly selected cases with asymptomatic neuromas after an accurate tissue sampling. The case presented herein underlines the necessity to consider traumatic neuroma in the differential diagnosis in patients with a history of breast surgery presenting with refractory neuropathic breast pain. A high index of suspicion is required because the lesion may be too small and can be missed on imaging investigations.

Time course of traumatic neuroma development

This study was designed to characterize morphologic stages during neuroma development post amputation with an eye toward developing better treatment strategies that intervene before neuromas are fully formed. Right forelimbs of 30 Sprague Dawley rats were amputated and limb stumps were collected at 3, 7, 28, 60 and 90 Days Post Amputation (DPA). Morphology of newly formed nerves and neuromas were assessed via general histology and neurofilament protein antibody staining. Analysis revealed six morphological characteristics during nerve and neuroma development; 1) normal nerve, 2) degenerating axons, 3) axonal sprouts, 4) unorganized bundles of axons, 5) unorganized axon growth into muscles, and 6) unorganized axon growth into fibrotic tissue (neuroma). At early stages (3 & 7 DPA) after amputation, normal nerves could be identified throughout the limb stump and small areas of axonal sprouts were present near the site of injury. Signs of degenerating axons were evident from 7 to 90 DPA. From day 28 on, variability of nerve characteristics with signs of unorganized axon growth into muscle and fibrotic tissue and neuroma formation became visible in multiple areas of stump tissue. These pathological features became more evident on days 60 and 90. At 90 DPA frank neuroma formation was present in all stump tissue. By following nerve regrowth and neuroma formation after amputation we were able to identify 6 separate histological stages of nerve regrowth and neuroma development. Axonal regrowth was observed as early as 3 DPA and signs of unorganized axonal growth and neuroma formation were evident by 28 DPA. Based on these observations we speculate that neuroma treatment and or prevention strategies might be more successful if targeted at the initial stages of development and not after 28 DPA.

Painful Terminal Neuroma Prevention by Capping PRGD/PDLLA Conduit in Rat Sciatic Nerves

Neuroma formation after amputation as a long-term deficiency leads to spontaneous neuropathic pain that reduces quality of life of patients. To prevent neuroma formation, capping techniques are implemented as effective treatments. However, an ideal, biocompatible material covering the nerves is an unmet clinical need. In this study, biocompatible characteristics presented by the poly(D,L-lactic acid)/arginylglycylaspartic acid (RGD peptide) modification of poly{(lactic acid)-co- [(glycolic acid)-alt-(L-lysine)]} (PRGD/PDLLA) are evaluated as a nerve conduit. After being capped on the rat sciatic nerve stump in vivo, rodent behaviors and tissue structures are compared via autotomy scoring and histological analyses. The PRGD/PDLLA capped group gains lower autotomy score and improves the recovery, where inflammatory infiltrations and excessive collagen deposition are defeated. Transmission electron microscopy images of the regeneration of myelin sheath in both groups show that abnormal myelination is only present in the uncapped rats. Changes in related genes (MPZ, MBP, MAG, and Krox20) are monitored quantitative real-time polymerase chain reaction (qRT-PCR) for mechanism investigation. The PRGD/PDLLA capping conduits not only act as physical barriers to inhibit the invasion of inflammatory infiltration in the scar tissue but also provide a suitable microenvironment for promoting nerve repairing and avoiding neuroma formation during nerve recovery.

A case of traumatic infraorbital neuroma

A 53-year-old Afghan man presented with a 12-month history of left proptosis, diplopia and facial swelling 20 years after a bomb blast injury. Magnetic resonance and computed tomography imaging revealed a well-circumscribed lesion centred within the left inferior orbit/superior maxillary sinus along with left orbital fracture. Histopathology and immunostaining of the debulked lesion were consistent with traumatic neuroma of the infraorbital nerve. Infraorbital neuromas have developed following orbital decompression surgeries but have not been reported previously following non-surgical trauma.

Local Administration of Methylprednisolone Laden Hydrogel Enhances Functional Recovery of Transected Sciatic Nerve in Rat

Objective

To determine the effects of methylprednisolone-laden hydrogel loaded into a chitosan conduit on the functional recovery of peripheral nerve using a rat sciatic nerve regeneration model was assessed.

Methods

10-mm sciatic nerve defect was bridged using a chitosan conduit (CHIT/CGP-Hydrogel) filled with CGP-hydrogel. In authograft group (AUTO) a segment of sciatic nerve was transected and reimplanted reversely. In methylprednisolone treated group (CHIT/MP) the conduit was filled with methylprednisolone-laden CGP-hydrogel. The regenerated fibers were studied within 16 weeks after surgery.

Results

The behavioral, functional and electrophysiological studies confirmed faster recovery of the regenerated axons in methylprednisolone treated group compared to CHIT/Hydrogel group (p<0.05). The mean ratios of gastrocnemius muscles weight were measured. There was statistically significant difference between the muscle weight ratios of CHIT/MP and CHIT/Hydrogel groups (p<0.05). Morphometric indices of regenerated fibers showed number and diameter of the myelinated fibers were significantly higher in CHIT/MP than in CHIT/Hydrogel group.

Conclusion

Methylprednisolone-laden hydrogel when loaded in a chitosan conduit resulted in improvement of functional recovery and quantitative morphometric indices of sciatic nerve.

Determination of stable reference genes for RT-qPCR expression data in mechanistic pain studies on pig dorsal root ganglia and spinal cord

RNA expression levels for genes of interest must be normalised with appropriate reference or "housekeeping" genes that are stably expressed across samples and treatments. This study determined the most stable reference genes from a panel of 6 porcine candidate genes: beta actin (ACTB), beta-2-microglobulin (B2M), eukaryotic elongation factor 1 gamma-like protein (eEF-1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), succinate dehydrogenase complex subunit A (SDHA), Ubiquitin C (UBC) in sacral dorsal root ganglia and spinal cord samples collected from 16 tail docked pigs (2/3rds of tail amputated) 1, 4, 8 and 16weeks after tail injury (4 pigs/time point). Total RNA from pooled samples was measured by SYBRgreen real-time quantitative PCR. Cycle threshold values were analysed using geNorm, BestKeeper and NormFinder PCR analysis software. Average expression stability and pairwise variation values were calculated for each candidate reference gene. GeNorm analysis identified the most stable genes for normalisation of gene expression data to be GAPDH>eEF-1>UBC>B2M>ACTB>SDHA for dorsal root ganglia and ACTB>SDHA>UBC>B2M>GAPDH>eEF-1 for spinal cord samples. Expression stability estimates were verified by BestKeeper and NormFinder analysis. Expression stability varied between genes within and between tissues. Validation of most stably expressed reference genes was performed by normalisation of calcitonin gene related polypeptide beta (CALCB). The results show similar patterns of CALCB expression when the best reference genes selected by all three programs were used. GAPDH, eEF-1 and UBC are suitable reference genes for porcine dorsal root ganglia samples, whereas ACTB, SDHA and UBC are more appropriate for spinal cord samples.

Characterization of short- and long-term mechanical sensitisation following surgical tail amputation in pigs

Commercial pigs are frequently exposed to tail mutilations in the form of preventive husbandry procedures (tail docking) or as a result of abnormal behaviour (tail biting). Although tissue and nerve injuries are well-described causes of pain hypersensitivity in humans and in rodent animal models, there is no information on the changes in local pain sensitivity induced by tail injuries in pigs. To determine the temporal profile of sensitisation, pigs were exposed to surgical tail resections and mechanical nociceptive thresholds (MNT) were measured in the acute (one week post-operatively) and in the long-term (either eight or sixteen weeks post-surgery) phase of recovery. The influence of the degree of amputation on MNTs was also evaluated by comparing three different tail-resection treatments (intact, ‘short tail’, ‘long tail’). A significant reduction in MNTs one week following surgery suggests the occurrence of acute sensitisation. Long-term hypersensitivity was also observed in tail-resected pigs at either two or four months following surgery. Tail amputation in pigs appears to evoke acute and sustained changes in peripheral mechanical sensitivity, which resemble features of neuropathic pain reported in humans and other species and provides new information on implications for the welfare of animals subjected to this type of injury.