Pain as a symptom of peripheral nerve sheath tumors: clinical significance and future therapeutic directions

Primary BAP1-absent atypical meningioma arising from median nerve within infraclavicular brachial plexus: illustrative case

BACKGROUND

The authors present the only known case of a World Health Organization grade II ectopic meningioma occurring in the infraclavicular brachial plexus, causing pain within the axilla not associated with a primary malignant meningioma of the central nervous system. Peripheral nerve sheath tumors are rare entities, the majority of which are schwannomas or neurofibromas. Ectopic meningiomas only represent 1%-2% of all meningiomas. To date, there is one other published case specifically of a primary ectopic meningioma located in the brachial plexus.

OBSERVATIONS

Following the dissection of the left axilla, a dominant rubbery tumor involving the median nerve was encountered. The tumor capsule contained areas of hemorrhage and a soft core with nerve fascicles coursing through, which were not compromised during internal tumor debulking. The tumor lacked a clear pseudocapsule that is characteristically seen in schwannomas. Histopathological studies confirmed an atypical epithelioid neoplasm with elevated numbers of mitotic figures and BAP1 gene deletion.

LESSONS

Primary meningiomas arising outside the central nervous system are exceedingly rare. For this unusual higher-grade primary ectopic meningioma located in the distal brachial plexus, surgery with the goal of gross-total resection, adjuvant radiation, additional imaging, and genetics screening were recommended. Close follow-up is warranted. https://thejns.org/doi/10.3171/CASE24226.

A Recurrent Schwannoma in the Left Distal Ulnar Nerve

While peripheral nerve schwannomas have a relatively low incidence, schwannomatosis, the condition in which one forms multiple recurring schwannomas, is an even rarer phenomenon and can be hard to detect given its ability to mimic other conditions. We report a case of a 35-year-old male who presented with a mass in his left wrist and forearm, volar pain in his forearm, and numbness in his fingers. Magnetic resonance imaging (MRI) revealed a bilobed heterogeneous neural sheath tumor in the distal left ulnar nerve. The tumor was resected including extensive internal neurolysis using a Zeiss operative microscope. Post-operative biopsy confirmed an encapsulated schwannoma. The patient did well initially but developed worsening pain in his forearm and weakness. He had persistent paresthesias in the ulnar nerve distribution. He underwent a repeat MRI almost one year later, which showed thickening of the ulnar nerve proximal to the area of resection with an 8.5 mm hyperintense nodule. The patient underwent a subsequent resection with extensive neurolysis, which confirmed that the mass was a benign non-invasive schwannoma. At six weeks post-surgery, the patient's forearm pain was significantly improved and his range of motion returned to baseline. Our case demonstrates the importance of post-operative follow-up in schwannomas with appropriate imaging if symptoms persist or recur.

Peripheral Nerve Sheath Tumor: A Diagnostic and Therapeutic Challenge

INTRODUCTION

Peripheral nerve tumors are a group of rare soft tissue tumors of neuro-ectodermal origin. Although the majority of them are benign in nature, up to 10% can be malignant. The symptoms depend on the site, size, and structures compressed by the tumor.

AIM

To highlight the heterogeneity of signs and symptoms and their presentations, which has often made it difficult for the attending physician to accurately diagnose and direct the patient toward appropriate treatment.

METHODS

Eight patients treated at our tertiary care hospital between 2015 and 2022 were included in this study. They were evaluated in detail. Treatment was surgical. The patients underwent complete excision of the tumor under magnification to help preserve the adjacent neurovascular bundle. All patients were followed up post-operatively to document the status of their symptoms.

RESULTS

The average duration prior to referral to our hospital was 13 months. Seven subjects had pain at presentation, one had neurological deficit. Seven also complained of swelling. Five of the eight lesions were schwannoma, two neurofibroma and one showed malignant histology. Post-operatively, Hoffman Tinel signs improved in all six subjects. five of the seven subjects were completely pain-free, and the other two had a reduction in symptoms.

CONCLUSIONS

Early diagnosis and referral to a specialist center are needed to achieve satisfactory outcomes while treating peripheral nerve tumors. Proliferative lesions should be treated surgically in specialist centers by experienced doctors with appropriate skills and equipment for microsurgical procedures to ensure full recovery.

[Features of course of pain syndrome in patients with schwannomatosis]

OBJECTIVE

To identify the characteristics of pain syndrome in patients with schwannomas depending on genetic predisposition.

MATERIAL AND METHODS

The study included 46 patients with peripheral, spinal and intracranial schwannomas, corresponding to the schwannomatosis phenotype according to the 2022 clinical criteria. All patients underwent sequencing of the LZRT1, Nf2 and SMARCB1 and a copy number study in the NF2.

RESULTS

The most severe widespread pain was observed in patients with pathogenic LZRT1 variants, while patients with mosaic variants may not even have local tumor-related pain. Patients with SMARCB1variants may have no pain or have localized pain that responds well to surgical treatment.

CONCLUSION

Further studies of the molecular features of schwannomatosis and driver mutations in the pathogenesis of pain are necessary to improve the effectiveness of pain therapy in this group of patients. Schwannomatosis is a disease from the group of neurofibromatosis, manifested by the development of multiple schwannomas. Neuropathic pain is one of the main symptoms characteristic of peripheral schwannomas, however, the severity and prevalence of the pain syndrome does not always correlate with the location of the tumors. According to modern concepts, the key factors influencing the characteristics of the pain syndrome are the target gene and the type of pathogenic variant. The most severe widespread pain is observed in patients with pathogenic variants in the LZRT1 gene, while patients with mosaic variants may not even have local pain associated with tumors. Patients with variants in SMARCB1 may have no pain or localized pain that responds well to surgical treatment.

Benign peripheral nerve sheath tumors: an interdisciplinary diagnostic and therapeutic challenge

A benign peripheral nerve sheath tumor (bPNST) is a rare lesion associated with peripheral nerval structures. Symptoms may be heterogeneous, complicating diagnosis finding. Additionally, management concepts of bPNST may vary. In some cases, initial misdiagnosis leads to mistreatment resulting in severe functional deficits and chronic pain syndromes. Therefore, we analyzed patients treated for bPNST in our specialized institution with a primary focus on prior misdiagnosis and possible mistreatment. Patients with bPNSTs (schwannomas, neurofibromas, hybrid nerve sheath tumors, and perineuriomas) treated at the Neurosurgical Department between January 1, 2015, and July 31, 2021, were included. Assessment of demographics, tumor entity, tumor location, symptoms, the interval between the onset of symptoms and surgery, involved medical specialties, and outpatients' treatment, with particular focus on initial misdiagnosis and inappropriate medical treatment, was performed. Eighty-five patients were included in the final analysis with schwannoma being the most prevalent histopathological diagnosis (schwannoma (75.3%, n=64), neurofibroma (12.9%, n=11), hybrid nerve sheath tumor (5.9%, n=5), and perineurioma (5.9%, n=5)). An incorrect primary diagnosis was detected in 44.7% (n=38), leading to suboptimal or insufficient treatment in these cases. Of those, 28.9% (n=11/38) were treated suboptimal, while 18.5% (n=7/38) underwent unnecessary invasive diagnostics. Inappropriate surgery based on prior misdiagnosis, which led to severe neurological deficits in all these cases, was reported in 26.3% (n=10/38). For the first time, our data shows the quantity and impact of incorrect initial diagnosis in bPNST causing a delay in causative treatment or resulting in unnecessary or potentially harmful treatment.

Pleural Schwannoma Presenting As Musculoskeletal Type Pain: A Case Report

Schwannomas are benign peripheral nerve sheath tumors typically found in the neck, flexor surfaces of the extremities, mediastinum, posterior spinal roots, cerebellopontine angle, and retroperitoneum. Pleural schwannomas are a type of neoplasm that arises from autonomic nerve fiber sheaths in the pleura and rarely originate in the thoracic cavity. These schwannomas tend to be asymptomatic, benign, and slow-growing neoplasms. Although pleural schwannomas commonly occur in males, our report highlights a unique presentation of a pleural schwannoma presenting as musculoskeletal-type chest pain in an adult female. Our patient's diagnosis of pleural schwannoma was supported after X-Ray, Computed Tomography (CT) Scan, and Positron Emission Tomography (PET) Scan imaging was complete. All imagining and immunohistochemical staining yielded pleural schwannoma as the final diagnosis. We aim to bring awareness to the necessity of imaging and histopathological staining in atypical clinical cases of pleural schwannoma. Our novel case highlights pleural schwannoma as a differential diagnosis for patients with intermittent, musculoskeletal-type chest pain.

Rare Tumors Causing Median Nerve Compression in Adults-A Narrative Review

The median nerve can be compressed due to a tumor along the course of the median nerve, causing typical compression symptoms or even persistence or recurrence after an operation. The aim of this review is to provide a comprehensive overview of rare tumors described in recent publications that cause median nerve compression and to evaluate treatment options. The PubMed, Embase, and Web of Science databases were searched for studies describing median nerve compression due to a tumor in adults, published from the year 2000 and written in English. From 94 studies, information of approximately 100 patients have been obtained. Results  The rare tumors causing compression were in 32 patients located at the carpal tunnel, in 21 cases in the palm of the hand, and 28 proximal from the carpal tunnel. In the other cases the compression site extended over a longer trajectory. There were 37 different histological types of lesions. Complete resection of the tumor was possible in 58 cases. A total of 8 patients presented for the second time after receiving initial therapy. During follow-up, three cases of recurrence were reported with a mean follow-up period of 11 months. The most common published cause of median nerve compression is the lipofibromatous hamartoma. Besides the typical sensory and motor symptoms of median nerve compression, a thorough physical examination of the complete upper extremity is necessary to find any swelling or triggering that might raise suspicion of the presence of a tumor.

Neuropathic pain after spinal intradural benign tumor surgery: an underestimated complication?

Neuropathic pain presents a burdening and impairing condition which may occasionally occur after spinal tumor surgery. While it has been described in peripheral nerve sheath tumors, data on other intradural tumor patients is sparse. We hereby present a large cohort population undergoing different intradural spinal tumor surgery with assessment of early postoperative and follow-up outcomes, focusing on the occurrence of neuropathic pain. We performed a retrospective monocentric study including all patients treated for intradural spinal tumors between 2009 and 2020. We extracted surgical aspects as well as pre- and postoperative clinical courses from the records. Statistical analysis of potential contributing prognostic factors was performed including matched pair analysis. In total, 360 patients were included for analysis. At a median follow-up of 2 years, 26/360 patients complained of a neuropathic pain syndrome (7.2%) requiring continuous medication. Of these patients only 50% complained preoperatively of pain. Tumor entity did not significantly influence the incidence of postoperative neuropathic pain (p = 0.91). Sacrifice of the tumor carrying nerve root and tumor recurrence also did not increase the risk for this condition. Persistent neuropathic pain requiring continuous treatment occurred in 7.2% of patients undergoing intradural spinal surgery in our cohort. This frequently underestimated postoperative adverse event represents a disabling condition leading to a substantial impairment in the quality of life among the affected patients.

Difficulty Breathing or Just a Case of the Nerves? Incidental Finding of Primary Pleural Schwannoma in a COVID-19 Survivor

Schwannoma is a rare tumor that arises from the Schwann cells, which are specialized, myelin-producing cells of the peripheral nerve sheaths. As anatomic logic would dictate, these masses commonly occur in the skull base, cerebellopontine angle, and posterior spinal roots. Of this already rare entity, rarer still are the pleural schwannomas, representing approximately 1-2% of thoracic tumors. These tumors commonly affect adults with a propensity for the third and sixth decades of life and a comparative male predilection. Schwannomas are benign, indolent, and follow an asymptomatic course. As such, they often come to light incidentally. Here we report a case of primary pleural schwannomas in a 68-year-old female, found incidentally on a CT scan of the chest. To the best of our knowledge and literature review, no other similar case has been reported in our country, Pakistan. Around three weeks before her presentation, she was diagnosed with COVID-19. Her infection had run a mild course with quick recovery without the need for any hospitalization. Therefore, the manifestation of shortness of breath after resolution of all other symptoms prompted a further workup. Radiographic chest x-ray revealed an incidental finding of a large right upper lobe lung mass, slightly impinging on the trachea. This was followed by a chest CT scan at our radiological imaging facility, which showed a large, well-encapsulated, right upper lobe lung mass in the paraspinal apical location. She then underwent an image-guided biopsy of the aforementioned mass, pathological analysis of which was suggestive of a benign peripheral nerve sheath tumor (PNST) arising from the pleura (pleural schwannoma). She underwent right posterolateral thoracotomy with uneventful complete surgical removal of the pleural-based lung mass. Postoperative investigations included a chest x-ray that showed interval complete resection of the mass. Currently, she is asymptomatic and her clinical condition has improved with the successful resumption of her daily routine. Physicians thus need to keep pleural schwannomas in mind as a probable diagnosis of intrathoracic tumors. Indolent and asymptomatic, they are very amenable to surgical resection with little to no chances of recurrence in the long term. However, these patients should be closely followed with repeat imaging studies when symptomatic.

The Role of 3D Exoscope Systems in Neurosurgery: An Optical Innovation

The development of the three-dimensional (3D) exoscope is a marvel of technological innovation in modern surgical practice. While its predecessor, the operating microscope (OM), has long been the gold-standard surgical visualization modality, its particular limitations in terms of accessibility and ergonomic demand have led to the development of a more sophisticated, 3D model. Specifically, the 3D exoscope allows for an enhanced image quality of the surgical field, while also being more ergonomically favorable. Moreover, this device's ability to handle delicate microsensitve procedures, along with its alleviation of surgeon fatigue, indicates great potential for neurosurgical application. For this narrative review, the authors queried PubMed database using the keyword "exoscope" to identify relevant studies involving the specialty of neurosurgery that were published in English language full text. The search yielded full-text English language-related articles regarding neurosurgical exoscope, its applications and limitations. The 3D exoscope uniquely allows for enhanced surgeon comfort and superior imaging of the patient's real-time anatomy. However, the OM was described to having a slight image favorability with fusion and decompression surgery. Cost analysis is highlighted for its potential disparity. 3D exoscopes will potentially be incorporated with intelligent carriers and robotic surgical systems. Ultimately, with further studies highlighting its use, the 3D exoscope is expected to continue to imprint its status as one of the most efficient technological visualization tools in the future of neurosurgical practice.

Unusual Pain Disorders - What Can Be Learned from Them?

Pain is common in many different disorders and leads to a significant reduction in quality of life in the affected patients. Current treatment options are limited and often result in insufficient pain relief, partly due to the incomplete understanding of the underlying pathophysiological mechanisms. The identification of these pathomechanisms is therefore a central object of current research. There are also a number of rare pain diseases, that are generally little known and often undiagnosed, but whose correct diagnosis and examination can help to improve the management of pain disorders in general. In some of these unusual pain disorders like sodium-channelopathies or sensory modulation disorder the underlying pathophysiological mechanisms have only recently been unravelled. These mechanisms might serve as pharmacological targets that may also play a role in subgroups of other, more common pain diseases. In other unusual pain disorders, the identification of pathomechanisms has already led to the development of new drugs. A completely new therapeutic approach, the gene silencing, can even stop progression in hereditary transthyretin amyloidosis and porphyria, ie in pain diseases that would otherwise be rapidly fatal if left untreated. Thus, pain therapists and researchers should be aware of these rare and unusual pain disorders as they offer the unique opportunity to study mechanisms, identify new druggable targets and finally because early diagnosis might save many patient lives.

Clinical Significance of Pain in Differential Diagnosis between Spinal Meningioma and Schwannoma

While common MRI characteristics for schwannomas exist, diagnosis by imaging alone remains challenging. Detailed analysis of symptoms reported by the patient is very important in the differential diagnosis between meningioma and schwannoma in cases where MRI images are not sufficient for determining the tumor type. The pain, its classification of the character, and the timing seem to be an important predictive symptom in the differential diagnosis of spinal schwannoma.

C-Fiber Loss as a Possible Cause of Neuropathic Pain in Schwannomatosis

Schwannomatosis is the third form of neurofibromatosis and characterized by the occurrence of multiple schwannomas. The most prominent symptom is chronic pain. We aimed to test whether pain in schwannomatosis might be caused by small-fiber neuropathy. Twenty patients with schwannomatosis underwent neurological examination and nerve conduction studies. Levels of pain perception as well as anxiety and depression were assessed by established questionnaires. Quantitative sensory testing (QST) and laser-evoked potentials (LEP) were performed on patients and controls. Whole-body magnetic resonance imaging (wbMRI) and magnetic resonance neurography (MRN) were performed to quantify tumors and fascicular nerve lesions; skin biopsies were performed to determine intra-epidermal nerve fiber density (IENFD). All patients suffered from chronic pain without further neurological deficits. The questionnaires indicated neuropathic symptoms with significant impact on quality of life. Peripheral nerve tumors were detected in all patients by wbMRI. MRN showed additional multiple fascicular nerve lesions in 16/18 patients. LEP showed significant faster latencies compared to normal controls. Finally, IENFD was significantly reduced in 13/14 patients. Our study therefore indicates the presence of small-fiber neuropathy, predominantly of unmyelinated C-fibers. Fascicular nerve lesions are characteristic disease features that are associated with faster LEP latencies and decreased IENFD. Together these methods may facilitate differential diagnosis of schwannomatosis.

Pediatric peripheral nerve tumors: clinical and surgical aspects

PURPOSE

Pediatric peripheral nerve tumors (PNTs) are rare. Most are related to neurofibromatosis type 1 (NF1) with the potential for malignancy. An ongoing debate occurs about the best approach to such patients. This study describes a cohort of pediatric patients with PNTs and discusses clinical characteristics and surgical treatment.

METHODS

We retrospectively reviewed the charts of seven pediatric patients with eight PNTs surgically treated from 2007 to 2018. Information concerning patient demographics, clinical presentation, PNTs characteristics, treatment choice, and outcome were recorded.

RESULTS

All children presented with intense pain and a palpable mass. Three of the eight tumors were associated with a neurological deficit. Among the four patients with NF1, two had a neurofibroma and two a malignant peripheral nerve sheath tumor (MPNST). Histologically, three of the lesions were a benign peripheral nerve sheath tumor (BPNST), three a MPNST, and one each a desmoid tumor and Ewing's sarcoma. Two of the eight tumors underwent partial tumor excision and six gross total excisions.

CONCLUSIONS

Intense pain at rest, day, and/or night, preventing normal activities; a palpable, hard, immobile mass; an intense Tinel's sign related to the lump; clinical evidence of NF1; and high-speed growth of a tumor in the trajectory of the nerve or plexus should alert the clinician to the potential for malignancy. Preoperative biopsy is not indicated when clinical and imaging findings suggest a benign tumor. The surgical management of PNTs must be to achieve total resection, including wide margins with malignant tumors, though this is not always possible.

Somatic Mutations of lats2 Cause Peripheral Nerve Sheath Tumors in Zebrafish

The cellular signaling pathways underlying peripheral nerve sheath tumor (PNST) formation are poorly understood. Hippo signaling has been recently implicated in the biology of various cancers, and is thought to function downstream of mutations in the known PNST driver, NF2. Utilizing CRISPR-Cas9 gene editing, we targeted the canonical Hippo signaling kinase Lats2. We show that, while germline deletion leads to early lethality, targeted somatic mutations of zebrafish lats2 leads to peripheral nerve sheath tumor formation. These peripheral nerve sheath tumors exhibit high levels of Hippo effectors Yap and Taz, suggesting that dysregulation of these transcriptional co-factors drives PNST formation in this model. These data indicate that somatic lats2 deletion in zebrafish can serve as a powerful experimental platform to probe the mechanisms of PNST formation and progression.

The Somatostatin Receptor-4 Agonist J-2156 Alleviates Mechanical Hypersensitivity in a Rat Model of Breast Cancer Induced Bone Pain

In the majority of patients with breast cancer in the advanced stages, skeletal metastases are common, which may cause excruciating pain. Currently available drug treatments for relief of breast cancer-induced bone pain (BCIBP) include non-steroidal anti-inflammatory drugs and strong opioid analgesics along with inhibitors of osteoclast activity such as bisphosphonates and monoclonal antibodies such as denosumab. However, these medications often lack efficacy and/or they may produce serious dose-limiting side effects. In the present study, we show that J-2156, a somatostatin receptor type 4 (SST4 receptor) selective agonist, reverses pain-like behaviors in a rat model of BCIBP induced by unilateral intra-tibial injection of Walker 256 breast cancer cells. Following intraperitoneal administration, the ED₅₀ of J-2156 for the relief of mechanical allodynia and mechanical hyperalgesia in the ipsilateral hindpaws was 3.7 and 8.0 mg/kg, respectively. Importantly, the vast majority of somatosensory neurons in the dorsal root ganglia including small diameter C-fibers and medium-large diameter fibers, that play a crucial role in cancer pain hypersensitivities, expressed the SST4 receptor. J-2156 mediated pain relief in BCIBP-rats was confirmed by observations of a reduction in the levels of phosphorylated extracellular signal-regulated kinase (pERK), a protein essential for central sensitization and persistent pain, in the spinal dorsal horn. Our results demonstrate the potential of the SST4 receptor as a pharmacological target for relief of BCIBP and we anticipate the present work to be a starting point for further mechanism-based studies.

Radiologic manifestation of the malignant peripheral nerve sheet tumor involving the brachial plexus

A 63-year-old African American female with history of bilateral breast cancer status after lumpectomy and radiation therapy presented with right hand, wrist, and arm pain. She was found to have a right axillary mass and a large lesion in the right brachial plexus. A biopsy of the brachial plexus mass came back as a malignant peripheral nerve sheath tumor. This case report illustrates the critical value of multiple imaging modalities in definitive diagnosis of this rare pathologic entity.

Tumors and tumor-like lesions mimicking carpal tunnel syndrome

INTRODUCTION

Tumors and tumor-like lesions in or around the median nerve are uncommon causes of carpal tunnel syndrome (CTS). The purpose of the present study is to highlight the diagnostic approach and point out the profile of patients with CTS and potential underlying pathology.

MATERIALS AND METHODS

Twenty-eight patients with 32 affected hands had CTS correlated to a mass in or around the nerve. In 20 hands a palpable mass was present. Diagnostic workup included nerve conduction studies, ultrasound and/or MRI. Pre- and postoperative examination included two-point discrimination (2PD), grip strength, visual analogue scale (for pain) (VAS) and disabilities of the arm, shoulder and hand (DASH) scores.

RESULTS

Twelve of 28 patients were young (range 9-38 years) and 10 were male. Nerve compression was due to 27 extraneural lesions (8 abnormal muscles, 5 lipomas, 7 tenosynovitis, 4 vascular tumors, 2 ganglia, 1 Dupuytren's fibromatosis) and five intraneural tumors (three schwannomas, one neurofibroma, one sarcoma). Nerve decompression and excision of extraneural lesions were performed in all cases whereas in intraneural tumors, decompression was followed by excision in most cases and nerve grafting in one. Mean follow-up was 22 months (12-105 months). Extraneural masses were associated with a better outcome than nerve tumors. The mean postoperative VAS/DASH scores were 0.3/16.2 in extraneural lesions and 2.5/22 in intraneural lesions. The 2PD improved gradually in all patients (mean pre- and postoperative 12 and 5 mm). The mean grip strength increased from 28 to 31.3 kg postoperatively.

CONCLUSIONS

Although rare, the surgeon should include in the differential diagnosis of CTS the unusual cause of tumors and tumor-like lesions, especially when the patients' profile is not typical (young, male, no repetitive stress or manual labor). In addition, the presence of a palpable mass at the distal forearm or palm dictates the need for imaging studies. The extent, location and aggressiveness of the mass will determine the approach and type of procedure.

[Schwannoma of the femoral nerve: a rare differential diagnosis of leg pain]

BACKGROUND

Schwannomas (neurinomas) are among the most frequent peripheral nerve tumors. Nevertheless, these are seldom located in the lower extremities in association with the femoral nerve.

CLINICAL PRESENTATION

In this case, the occurrence of a schwannoma adjacent to the femoral nerve is described in a patient presenting with nonspecific pain in the thigh accompanied by a palpable mass. Sensory and motor deficits were not present. Further examinations by MRI and biopsy followed by histopathology, revealed the diagnosis of a schwannoma. The tumor was completely excised.

CONCLUSION

Although schwannomas of the lower extremities are rare, they should be included in the differential diagnosis. Knowing the typical clinical symptoms, radiological signs, and histopathological findings, diagnosis should be straight forward.