Intraneural perineurioma: a systematic review with illustrative cases

Treatment of childhood intraneural perineurioma: A case report and literature review

Background

Intraneural perineurioma is a rare, benign slow-growing lesion that usually involves a single main trunk nerve during childhood and young adulthood. The treatment of intraneural perineurioma is still a subject of controversy, especially in fast-growing children. To date, there was no systemic analysis of intraneural perineurioma in children.

Method

A case of Intraneural perineurioma affecting the left sciatic nerve with 2 years of follow-up was presented. A systematic review was performed on literature published before June 2023, focusing on intraneural perineurioma diagnosed at no older than 18 years old.

Result

A 9-year-old boy presented with progressive left foot-drop and abnormal gait for 2 years. The electromyography and magnetic resonance neurography study confirmed neuropathy involving the left sciatic nerves and its branches. Pathological investigation of the left sural nerve confirmed the diagnosis of intraneural perineurioma. The boy received physical therapy, and the disease was stable during the 2 years of follow-up. Fifty-seven childhood cases were identified in literature. Five patients with oral intraneural perineurioma underwent excision of the mass with good outcomes. In the other 52 patients with peripheral nerve involvement, 25 of them received surgical treatment, with different outcomes according to different operations. Out of 33 cases with precise lesion sizes, the length of the lesion in patients without nerve resection was significantly longer than that in patients with nerve resection (12.86 ± 7.44 cm vs 4.57 ± 4.5 cm. p < 0.05).

Conclusions

Intraneural perineuriomas are rare benign tumors with slow progression. The options for surgery should be cautiously considered in childhood patients with long segmental peripheral nerve involvement.

Case report: Intraneural perineurioma in dogs: a case series and brief literature review

Intraneural perineurioma is an exceptionally rare neoplasm in animals. This case study comprises a series of three cases and a brief literature review focusing on canine intraneural perineurioma. The pathological and immunohistochemical findings are documented, revealing that canine intraneural perineurioma frequently affects adult dogs aged between 3 and 10 years old, with a male predominance. Clinical signs associated with intraneural perineurioma in dogs include spinal pain, lameness, and paresis, resulting from the involvement of spinal nerve roots of the pelvic limbs, brachial plexus, or distal part of the median nerve. Most neoplasms had characteristic pseudo-onion bulb patterns on histopathology. Neoplastic perineurial cells, in most cases, expressed laminin and claudin-1, and NF200 consistently highlighted the central axon. While the immunohistochemical (IHC) profile of intraneural perineurioma in veterinary medicine remains incompletely characterized, the available IHC data from all reported cases suggest that a combination of laminin and claudin-1 immunomarkers, along with distinctive histological features, can assist in establishing a definitive diagnosis of intraneural perineurioma.

Peripheral nerve tumors

The chapter is focused on the neoplastic peripheral nerve lesions, which primarily involve "cranial and paraspinal nerves," as outlined in the CNS volume (WHO_Classification_of_Tumours_Editorial_Board, 2021). These include classic peripheral nerve sheath tumors such as schwannoma, neurofibroma, intraneural perineurioma, and malignant peripheral nerve sheath tumors, with their variants as well as new and more precisely defined entities, including hybrid nerve sheath tumors and malignant melanotic nerve sheath tumor (previously melanotic schwannoma).

What is new in intraneural perineurioma?

Since the initial description of intraneural (IN) perineurioma in 1964, advances in the understanding of the clinical presentation, diagnostic imaging, pathologic features, and genetic underpinnings have changed how this pathology is managed. IN perineuriomas are rare, benign peripheral nerve sheath tumors, most frequently coming to clinical attention when patients present with painless, progressive weakness or sensory loss in adolescence or young adulthood. The gold standard of diagnosis has traditionally been with targeted tissue biopsy demonstrating "pseudo-onion bulb" formation with positive epithelial membrane antigen (EMA) staining. However, modern magnetic resonance imaging is allowing some patients to forgo biopsy. Recent genetic studies of IN perineuriomas have demonstrated common TRAF7 point mutations and rare NF2 mutations, which may present targets for diagnosis or therapy in the future. Current advances have allowed for us to provide improved patient counseling with informed understanding for various clinical scenarios. With the workup and diagnosis now clearly defined, the next frontier is for improving the lives of patients with IN perineuriomas through the interaction between restoration of functional deficits and advances in our understanding of the genetics of this entity.

Beyond schwannomas and neurofibromas: a radiological and histopathological review of lesser-known benign lesions that arise in association with peripheral nerves

Peripheral nerve sheath tumors comprise a significant percentage of both benign and malignant soft tissue tumors. The vast majority of these lesions are schwannomas and neurofibromas, which most radiologists are familiar with including the well-described multimodality imaging features. However, numerous additional often under-recognized benign entities associated with nerves exist. These rarer entities are becoming increasingly encountered with the proliferation of cross-sectional imaging, particularly magnetic resonance imaging (MRI). It is important for the radiologist to have a basic understanding of these entities as many have near-pathognomonic MR imaging features as well as specific clinical presentations that when interpreted in concert, often allows for a limited differential or single best diagnosis. The ability to provide a prospective, pre-intervention diagnosis based solely on imaging and clinical presentation is crucial as several of these entities are "do not touch" lesions, for which even a biopsy may have deleterious consequences. To our knowledge, the majority of these benign entities associated with nerves have only been described in scattered case reports or small case series. Therefore, the aim of this article is to provide a radiopathologic comprehensive review of these benign entities that arise in association with nerves with a focus on characteristic MRI features, unique histopathologic findings, and entity specific clinical exam findings/presentation.

Diagnosis and Treatment of Peripheral and Cranial Nerve Tumors with Expert Recommendations: An EUropean Network for RAre CANcers (EURACAN) Initiative

The 2021 WHO classification of the CNS Tumors identifies as "Peripheral nerve sheath tumors" (PNST) some entities with specific clinical and anatomical characteristics, histological and molecular markers, imaging findings, and aggressiveness. The Task Force has reviewed the evidence of diagnostic and therapeutic interventions, which is particularly low due to the rarity, and drawn recommendations accordingly. Tumor diagnosis is primarily based on hematoxylin and eosin-stained sections and immunohistochemistry. Molecular analysis is not essential to establish the histological nature of these tumors, although genetic analyses on DNA extracted from PNST (neurofibromas/schwannomas) is required to diagnose mosaic forms of NF1 and SPS. MRI is the gold-standard to delineate the extension with respect to adjacent structures. Gross-total resection is the first choice, and can be curative in benign lesions; however, the extent of resection must be balanced with preservation of nerve functioning. Radiotherapy can be omitted in benign tumors after complete resection and in NF-related tumors, due to the theoretic risk of secondary malignancies in a tumor-suppressor syndrome. Systemic therapy should be considered in incomplete resected plexiform neurofibromas/MPNSTs. MEK inhibitor selumetinib can be used in NF1 children ≥2 years with inoperable/symptomatic plexiform neurofibromas, while anthracycline-based treatment is the first choice for unresectable/locally advanced/metastatic MPNST. Clinical trials on other MEK1-2 inhibitors alone or in combination with mTOR inhibitors are under investigation in plexiform neurofibromas and MPNST, respectively.

Plexal intraneural perineurioma: an analysis of the clinicoradiologic presentation of this rare variant

PURPOSE

Intraneural (IN) perineurioma is a rare benign peripheral nerve sheath tumor, typically presenting as a painless, progressive mononeuropathy in adolescents. A rare plexal variant has been described, although there are little data describing its clinicoradiologic features. Herein, we present the largest case series of plexal IN perineuriomas reported in the literature.

METHODS

Electronic medical records (EMR) from 1990 to 2022 from a single academic institution were reviewed for a diagnosis of IN perineurioma involving the brachial or lumbosacral plexus. This identified 18 patients, of which 17 had available MR imaging. We reviewed the EMR for demographics, clinical presentation, imaging characteristics, and surgical outcomes.

RESULTS

Eighteen patients were identified. Most patients were male (11/18, 61%) and first developed symptoms at the age of 9.6 years (range 7 months to 55 years). Diagnosis occurred on average at the age of 22 years (4-57 years), which is significantly earlier than distal IN perineurioma (p = 0.0096). All patients (100%, 17/17) presented with motor polyneuropathy and muscular atrophy in multiple nerve distributions, with associated sensory loss (12/17, 71%). Most plexal lesions occurred in the brachial plexus (66%, 12/18). Five (29%, 5/17) patients presented with a hand/foot discrepancy, and 5 patients (29%) had a limb length discrepancy. Five patients underwent tendon transfer, of which two had failure of tendon transfer at most recent follow-up (50%, 2/4) due to progression of neurologic loss affecting the donors. Of patients managed nonoperatively, 87% of patients (6/7) with follow-up information demonstrated disease progression with worsening motor function or sensory loss, and 2 patients demonstrated progression on imaging at most recent follow-up.

CONCLUSIONS

Plexal perineurioma represents an uncommon variant of IN perineurioma that presents as a progressive motor and sensory polyneuropathy in childhood or early adolescence. Surgical management remains controversial, and tendon transfer tends to result in poor long-term surgical outcomes.

Practical Approach to Histological Diagnosis of Peripheral Nerve Sheath Tumors: An Update

Peripheral nerve sheath tumors encompass a wide spectrum of lesions with different biological behavior, including both benign and malignant neoplasms as well as the recent diagnostic category, i.e., “atypical neurofibromatous neoplasm with uncertain biologic potential” to be used only for NF1 patients. Neurofibromas and schwannomas are benign Schwann-cell-derived peripheral nerve sheath tumors arising as isolated lesions or within the context of classical neurofibromatosis or schwannomatoses. Multiple tumors are a hallmark of neurofibromatosis type 1(NF1) and related forms, NF2-related-schwannomatosis (formerly NF2) or SMARCB1/LZTR1-related schwannomatoses. Perineuriomas are benign, mostly sporadic, peripheral nerve sheath tumors that show morphological, immunohistochemical, and ultrastructural features reminiscent of perineurial differentiation. Hybrid tumors exist, with the most common lesions represented by a variable mixture of neurofibromas, schwannomas, and perineuriomas. Conversely, malignant peripheral nerve sheath tumors are soft tissue sarcomas that may arise from a peripheral nerve or a pre-existing neurofibroma, and in about 50% of cases, these tumors are associated with NF1. The present review emphasizes the main clinicopathologic features of each pathological entity, focusing on the diagnostic clues and unusual morphological variants.

Spinal canal decompression for hypertrophic neuropathy of the cauda equina with chronic inflammatory demyelinating polyradiculoneuropathy: A case report

BACKGROUND

Hypertrophic neuropathy of the cauda equina (HNCE) is a rare disease, especially in children. It can be caused by different etiological agents such as inflammation, tumor or hereditary factors. Currently, there is no uniform standard for clinical treatment of HNCE. Furthermore, it is unclear whether spinal canal decompression is beneficial for patients with HNCE.

CASE SUMMARY

We report the case of a 13-year-old boy with enlargement of the cauda equina. The onset of the disease began at the age of 6 years and was initially marked by radiating pain in the buttocks and thighs after leaning over and weakness in the lower limbs when climbing a ladder. The child did not receive any medical treatment. As the disease slowly progressed, the child needed the help of others to walk, and he had a trendelenburg gait. He underwent spinal canal decompression and a nerve biopsy during his hospital stay. A diagnosis of chronic inflammatory demyelinating polyradiculoneuropathy was made based on electrophysiological findings and pathological examination results. Immunoglobulin or hormone therapy was recommended during hospitalization, but his mother refused. After discharge, the boy’s mother helped him carry out postoperative rehabilitation training at home. His lower-limb muscle strength gradually increased, and he could stand upright and take steps. Six mo after surgery, the child was readmitted and began immunoglobulin therapy. Long-term oral steroid treatment was initiated after discharge. The movement and sensation of the lower limbs were further improved, and the boy could walk normally 1 year after surgery.

CONCLUSION

Spinal canal decompression can improve the clinical symptoms of HNCE caused by inflammation, even in children. When combined with specific etiological interventions, spinal cord decompression can lead to optimal outcomes.

Rare case of Ulnar Nerve Intraneural Perineurioma in an elderly gentleman

Intraneural perineurioma (IPN) is a rare benign neoplasm of the peripheral nerve sheath, most commonly affecting the sciatic nerve of adolescents or young adults. We present a rare case of perineurioma in a 67-year-old man with an infiltrative clinical presentation affecting his ulnar nerve. Complete excision required en-bloc resection of the ulnar neurovascular bundle from mid-forearm to mid-palm with sural nerve and saphenous vein grafts used to reconstruct the ulnar nerve and artery, respectively. Despite recurrence from a previously localized excision, there has been no recurrence to date following en-bloc resection. The available literature on intraneural perineurioma is reviewed in light of this case report. IPN is an important entity because of its ability to mimic neural malignancies, and this case challenges the assertion that it is a tumour that occurs strictly in the young.

Nerve conduction assessment and magnetic resonance imaging for the diagnosis of localized hypertrophic neuropathy of the sciatic nerve and the lumbo-sacral plexus

Localized hypertrophic neuropathy (LHN) are slowly growing nerve lesions causing progressive nerve deficit and weakness. We present the case of a 32-year old woman with long history of motor and sensory deficit complains along the sciatic nerve territory. The muscles involved were featured by delay in F waves at nerve conduction assessment. Magnetic resonance imaging (MRI) showed specific patterns, low intense on T1 and abnormally hyper intense on short tau inversion recovery (STIR) and T2, with no obvious enhancement, features compatible with either LHN or intraneural perineurioma (IP) of the sciatic nerve and/or the lumbosacral plexus. Focal thickening and hypertrophy of the sciatic nerve with preserved fascicular configuration and progressive enlargement of the right lumbosacral plexus could be noted. A nerve conduction assessment followed by an MRI eventually allowed to diagnose LHN, without performing a nerve biopsy. Although similar, LHN and IP are two distinct lesions which should be diagnosed and differentiated as soon as possible, to avoid potential complications due to delayed diagnosis and/or misdiagnosis.

Clinical Features, Natural History, and Outcomes of Intraneural Perineuriomas: A Systematic Review of the Literature

BACKGROUND

Intraneural perineurioma is a rare peripheral nerve sheath tumor characterized by localized proliferation of perineurial cells. The literature consists predominantly of case reports and institutional series, with inconsistent and confusing nomenclature. We present a pooled analysis of all reported cases of intraneural perineurioma in the literature.

METHODS

A systematic search of PubMed, MEDLINE, Embase, and Scopus was performed according to PRISMA guidelines to identify all reported cases of intraneural perineurioma in the literature. Individual cases were pooled and analyzed for demographics, clinical features, and outcomes.

RESULTS

A total of 172 cases were identified across 72 studies, of which 149 were found in major peripheral nerves and their branches. Median age of patients at diagnosis and onset of symptoms was 18 years (interquartile range [IQR], 12-34 years) years and 13.5 years (IQR, 8-26 years), respectively, with 54.4% (81/149) being female. The most common sites were the sciatic nerve or its branches (41.9%), median nerve (13.5%), radial nerve (12.2%), and brachial plexus (12.2%). Most patients were managed conservatively (52.9%; 72/136). Among those managed conservatively with available follow-up (n = 31), median follow-up was 11 months, and most (67.7%, n = 21) reported no change in neurologic status, although worsening was noted in 29.0% (9/31). Among surgically managed cases (n = 64), the most common intervention was resection with or without repair (62.5%; 40/64), neurolysis (25%; 16/64), or tendon transfers without resection (12.5%; 8/64). No lesion recurred after surgical resection.

CONCLUSIONS

Intraneural perineurioma represents a benign focal lesion presenting with weakness and atrophy affecting adolescents and young adults. Most cases are managed nonoperatively and surgical treatment strategies are varied.

Perineurioma: A Rare Entity of Peripheral Nerve Sheath Tumors

OBJECTIVE

 Intraneural perineurioma is a rare tumor entity. It is a benign, very slow growing peripheral nerve sheath tumor that typically occurs in children and young adults. Motor deficits and muscle atrophy are classic presenting symptoms, while sensory deficits are rare at the onset of the disease. Recommended treatment strategies are lacking. We have evaluated the clinical follow-up and our experience with treatment of this rare entity.

METHODS

 A total of 30 patients with intraneural perineuriomas were assessed retrospectively. Demographic data, clinical symptoms, diagnostic examinations, therapy strategies, and clinical outcome were analyzed. Descriptive statistical methods were used for evaluation.

RESULTS

 The mean age was 22 years. Eleven women and 19 men were affected. The lesion occurred in the area of the upper extremity in 16 patients and in the area of the lower extremity in 14 patients. The most frequently affected nerve was the sciatic nerve, followed by the radial nerve. All patients showed a motor deficit to some extent. Seventy percent (n = 21) revealed atrophy, 43.3% (n = 13) had sensitive deficits, and 17% (n = 5) suffered of pain. Fascicle biopsies were performed in 26 patients (87%). In four patients (13%), the tumor was completely resected and then reconstructed via nerve grafts. Seventy percent of the patients (n = 21) received a magnetic resonance imaging (MRI) within 5 years postoperatively, in which no progress was shown.

CONCLUSIONS

 To diagnose perineurioma, it is essential to take a biopsy of an enlarged, nonfunctional fascicle. Furthermore, a long-distance epineuriotomy to decompress the hypertrophic fascicle is reasonable. To preserve the nerves' residual function, a complete resection is not recommended. Results after grafting are poor. One reason for this might be residual tumor cells along the nerve that cannot be visualized. Malignant transformation is not yet reported and tumor growth is stable for years.

Recurrent Fusion of the GRB2 Associated Binding Protein 1 (GAB1) Gene With ABL Proto-oncogene 1 (ABL1) in Benign Pediatric Soft Tissue Tumors

BACKGROUND/AIM

Fusions of the ABL proto-oncogene 1 gene (ABL1 in 9q34) are common in leukemias but rare in solid tumors. The most notable is the t(9;22)(q34;q11)/BCR-ABL1 coding for a chimeric tyrosine kinase. We herein report an ABL1-fusion in a pediatric tumor.

MATERIALS AND METHODS

G-banding, fluorescence in situ hybridization, reverse transcription polymerase chain reaction and Sanger sequencing were performed on a soft tissue perineurioma found in the left musculus erector spinae of a child.

RESULTS

A der(4)t(4;9)(q31;q34) and a fusion of the GRB2 associated binding protein 1 (GAB1 in 4q31) gene with ABL1 were found. A literature search revealed 3 more cases with similar genetic and clinicopathological characteristics: a soft tissue perineurioma with t(2;9;4)(p23;q34;q31) and ABL1 rearrangement, a soft tissue angiofibroma with a GAB1-ABL1 chimeric gene, and a solitary fibrous tumor carrying a der(4)t(4;9)(q31.1;q34).

CONCLUSION

GAB1-ABL1 is a recurrent fusion gene in benign pediatric tumors.

Intraneural perineurioma of the median nerve at the elbow: A clinical case

A 31-year-old female patient presented with swelling on the anteromedial aspect of her right elbow with a sensory deficit in the median nerve territory. Biopsies led to the diagnosis of intraneural perineurioma (INP). Surgical excision was performed and followed by an intercalary graft. INP is a rare benign tumor of the peripheral nerves characterized by a multiplication of perineural cells invading the endoneurium. This lesion is often unknown, under-diagnosed, and its treatment is poorly defined. Few cases have been described in the literature; the majority involve the median nerve at the wrist and no references have been found about its localization to the median nerve at the elbow.

Sporadic Malignant Perineurioma: A Rare Diagnosis Among Malignant Peripheral Nerve Sheath Tumors

BACKGROUND

Malignant perineurioma is a rare subset of malignant peripheral nerve sheath tumors (MPNSTs) with ultrastructural and immunohistochemical features of perineurial differentiation, distinguishing it from other MPNSTs, which typically demonstrate Schwannian features. The clinical course and prognosis of this rare tumor is not well defined.

METHODS

The electronic medical records were searched for patients with a diagnosis of MPNST. Patients with a pathologic diagnosis of malignant perineurioma or MPNST with perineurial features were identified and further evaluated.

RESULTS

Five patients with malignant perineurioma, or MPNST with perineurial features, were identified. Four patients (2 male and 2 female) were included with tumors associated with a common digital nerve, small muscular branch to the deltoid, sciatic nerve, and accessory nerve. One patient with the pathology diagnosis meeting inclusion criteria was excluded, as no clinical information was available for this patient.

CONCLUSIONS

Patients in our series presented at varied stages of disease. Clinical courses after diagnosis of malignant perineurioma, where follow-up was available, were largely uncomplicated with regard to recurrence and metastatic disease. Careful follow-up is indicated, and further work is needed to characterize the clinical course of these rare tumors.

What Every Neuropathologist Needs to Know: Peripheral Nerve Biopsy

Peripheral neuropathy is a common disorder with many possible etiologies including metabolic diseases, inflammatory conditions, infections, malignancy, inherited diseases, drugs, and toxins. In most instances, diagnosis and treatment plan can be established based on clinical presentation, family history, laboratory results, genetic testing, and electrophysiological studies. But in some situations, a peripheral nerve biopsy remains a valuable tool. This is especially true in patients with rapidly progressive disease, with atypical presentation or for whom other approaches fail to yield a definitive diagnosis. The pathologic examination starts with basic decisions about specimen triage. A few basic questions help to provide an initial framework for the assessment of a nerve biopsy-is the specimen adequate; are there inflammatory changes; are there vascular changes; is there amyloid; are there changes to axonal density and the Schwann cell-myelin-axon unit. In the appropriate context and with such an approach peripheral nerve biopsies can still represent a clinically helpful test.

Primary intra-osseous Hybrid Schwannoma-Perineurioma in the mandible

Benign nerve sheath tumours include perineuriomas, schwannomas and neurofibromas. Hybrid schwannoma-perineurioma represents a cutaneous, subcutaneous or occasionally intra-osseous tumour with schwannian cytomorphology and perineurioma-like architecture consisting of a mixture of both types of cells. These tumours can develop at any age and there is no gender-predilection. Tongue is the most frequently affected site, followed by palate, mouth floor, jugal mucosa, lips and, more rarely, mandible. We present a case of hybrid tumour with schwannoma-perineurioma morphology located on the right mandibular body (intra-osseous) of a 54-year-old female patient. The tumour was symptomatic and evolving for six months. Microscopically, it was encapsulated and highly cellularised, presenting fascicular aspect and exhibiting scant mitotic activity. The tumour consisted of distinct cellular populations involving fusiform cells, cells with wavy and hyperchromatic nucleus or even epithelioid cells. Positive immunostaining for S-100 and epithelial membrane antigen (EMA) was observed. The lesion was completely removed under general anaesthesia, with the patient showing no clinical or radiographic sign of relapse after two-year follow-up. Despite the limited knowledge on the pathogenesis of Hybrid Schwannoma-Perineurioma, these tumours seem to present a non-aggressive biological behaviour. Conservative surgery provides adequate solution without recurrence, even after a long-term follow-up. Key words:Nerve sheath tumours, Schwannoma, Perineurioma, Immunohistochemistry.

Clinical and Radiological Follow-up of Intraneural Perineuriomas

BACKGROUND

Management of intraneural perineuriomas remains controversial, largely due to the lack of knowledge regarding the natural history of these lesions.

OBJECTIVE

To describe the typical radiological growth pattern of intraneural perineuriomas and to determine how the pattern of growth relates to clinical progression.

METHODS

We performed a retrospective review of the magnetic resonance imaging (MRI) studies and serial clinical examinations of a cohort of patients with biopsy-proven intraneural perineuriomas who had 2 MRI studies at least 2 yr apart. The outcome of interest was radiological growth in length or width of the intraneural perineurioma. Radiological growth was tested for association with clinical progression.

RESULTS

Twenty patients were included in the study. By width, the lesions were on average larger on repeat imaging (P = .009). By absolute length, the lesions were on average longer on repeat imaging (P = .02). By lesion:landmark ratio, there was no difference in length of the lesions between sequential images (P = .09), with 10 (50%) lesions being shorter and 7 (35%) showing no change. No lesions grew to involve a new nerve or division of a nerve on sequential imaging. None of the variables tested were associated with clinical progression.

CONCLUSION

We found that intraneural perineuriomas only rarely grow in length, do not grow to involve new nerves or nerve divisions, and growth does not correlate with clinical progression. These findings have significant ramifications for management of these tumors.

Modern treatment of perineuriomas: a case-series and systematic review

Background

Perineuriomas are rare benign peripheral nerve sheath tumours of perineurial cell origin and can be classified into intraneural and extraneural perineuriomas. They most commonly present a mononeuropathy of gradual onset and slow progression, resulting in progressive neurological deficits like hypoesthesia or motor weakness. Therapy is still variable. Aim of the study was to compare our surgical treatment and our follow-up regime including high-resolution nerve sonography with the current literature to evaluate best treatment of perineuriomas.

Methods

Retrospective analysis of our dataset “peripheral nerve lesion” to identify patients suffering from perineuriomas between 01.01.2012 until 31.12.2018. Surgical treatment and the follow-up examination of three patients were described. Additionally, a systematic review including PubMed, the Cochrane Collaboration Library, Scopus and Google Scholar was performed for literature published between January 1, 1990 and October 31, 2019 independently by 2 authors.

Results

In the first case, the left ulnar nerve was affected. In the second case, the left peroneal nerve and in the third case the right median nerve was affected. High-resolution nerve sonography was performed in each case. All patients underwent interfascicular neurolysis combined with a targeted fascicular biopsy under electrophysiological monitoring. Neurological deficits improved subsidized by rehabilitation. Surgical therapy and the neurological outcome were compared with literature. Systematic review revealed 22 articles, which met the inclusion criteria. Therefore, demographics, surgical treatment and neurological outcome of 77 patients were analysed.

Conclusions

Perineuriomas are rare benign nerve sheath tumours with a slow progression, sometimes difficult to diagnose. Decompression and neurolysis may improve neurological deficits. High resolution nerve sonography might serve as a helpful additional diagnostic tool in this process.

Sodium Fluorescein as Intraoperative Visualization Tool During Peripheral Nerve Biopsies

OBJECTIVE

Owing to technical development of specific fluorophore filters, the neurosurgical application of sodium fluorescein (SF) has regained value in brain tumor surgery. The aim of this study was to determine the usefulness of SF during nerve biopsies.

METHODS

This single-center study included 5 cases of nerve biopsies performed under microscope-based fluorescence with SF performed between March 2016 and February 2017. SF was applied intravenously (1 mg/kg body weight). After microsurgical dissection of the involved nerve segment, fluorescence-guided fascicular biopsy was performed. Selection of target fascicles was at the surgeon's discretion and took into account nerve stimulation for preservation of motor function and fluorescence intensity. Correlation to histopathologic examination was examined. Video analysis of intraoperative images comparing target fascicles with intense fluorescent response to adjacent fascicles of the same nerve segment was performed using ImageJ.

RESULTS

All patients had motor or sensory deficits. Magnetic resonance imaging findings were similar, depicting long segments of gadolinium enhancement (minimum 11.7 cm). Each biopsy sample was positive resulting in diverse histopathologic results. Digital image analysis revealed a statistically significant difference of the complementary color green (P = 0.0473).

CONCLUSIONS

Magnetic resonance imaging is the gold standard in diagnostic work-up of peripheral nerve disorders. Longitudinal nerve thickening with positive contrast enhancement is an unspecific magnetic resonance imaging finding. Various pathologies, such as tumors and inflammatory lesions, may cause this morphologic phenomenon. Nerve biopsies may be needed for diagnostic work-up. Intraoperative SF may help to depict the most affected fascicles and identify target fascicles for biopsy and increase diagnostic certainty of nerve biopsies.

Intraneural perineurioma: a retrospective study of 19 patients

Intraneural perineurioma is a benign neoplasm of peripheral nerve sheath with perineurial cell origin that typically affects teenagers and young adults and tends to result in a motor-predominant neuropathy. The aim of our study is to present the epidemiology, clinical presentation, way of diagnosis and management plan in a consecutive patient series. Ninteen patients diagnosed as having intraneural perineurioma were retrospectively chart reviewed. Diagnosis was done by MRI and/or biopsy with morphological, immunohistochemical staining study confirmation. Patients assessments included gender, age, symptoms, tumor localization, radiological aspect, management and pathological confirmation.Sex ratio was 10 males to 9 females with mean age of 31.2 (15-64). All the patients presented with motor deficit, ten with sensory deficit. Upper limb was involved in 11 cases (among them 4 lesions of brachial plexus), the lower limb in 8 cases. On magnetic resonance imaging, 16 patients showed a nerve enlargement whereas 5 presented with atypical fusiform tumor. Eighteen patients were operated for excision biopsy and/or palliative treatment for their motor deficit. Anatomopathological analysis confirmed the diagnosis in seventeen cases with a morphological pseudo-onion bulb shape and/or specific immunohistochemical assay. One patient had only palliative treatment without excision biopsy. Our data confirmed the equal penetration of intraneural perineurioma to both sex and affected limb. Because of the benignity of the tumor, the surgical treatment focused on optimizing the functional outcome. A prospective study with long term follow-up is required for this under-diagnosed tumor.

Clinicoradiological features of intraneural perineuriomas obviate the need for tissue diagnosis

OBJECTIVE

This study aimed to define a set of clinicoradiological parameters with a high specificity for the diagnosis of intraneural perineurioma, obviating the need for operative tissue diagnosis.

METHODS

The authors retrospectively reviewed MR images obtained in a large cohort of patients who underwent targeted fascicular biopsy and included only those patients for whom the biopsy yielded a diagnosis. Clinical and radiological findings were then tested for their ability to predict a tissue diagnosis of intraneural perineurioma. The authors propose a new set of diagnostic criteria, referred to as the Perineurioma Diagnostic Criteria. The sensitivity, specificity, positive predictive value, and negative predictive value of several clinicoradiological methods of diagnosis were compared.

RESULTS

A total of 195 patients who underwent targeted fascicular biopsy were included in the cohort, of whom 51 had a tissue diagnosis of intraneural perineurioma. When the clinicoradiological methods used in this study were compared, the highest sensitivity (0.86), negative predictive value (0.95), and F1 score (0.88) were observed for the decision trees generated in C5.0 and rPart, whereas the highest specificity (1.0) and positive predictive value (1.0) were observed for the Perineurioma Diagnostic Criteria.

CONCLUSIONS

This study identified clinical and radiological features that are associated with a diagnosis of perineurioma. The Perineurioma Diagnostic Criteria were determined to be the following: 1) no cancer history, 2) unifocal disease, 3) moderate to severe hyperintensity on T2-weighted MR images, 4) moderate to severe contrast enhancement, 5) homogeneous contrast enhancement, 6) fusiform shape, 7) enlargement of the involved nerves, and 8) age ≤ 40 years. Use of the Perineurioma Diagnostic Criteria obviates the need for tissue diagnosis when all of the criteria are satisfied.

Intraosseous intraneural perineurioma derived from the inferior alveolar nerve with an abnormality of chromosome 22 and expression of the BCR-ABL fusion gene: report of a case and review of recent literature

BACKGROUND

Perineurioma (PN) is a peripheral nerve disease that primarily develops in the limbs and trunk and very rarely occurs in the oral cavity. PN is classified into two types: intraneural perineurioma (INPN) and soft tissue perineurioma (extraneural perineurioma, ENPN). In this article, we report a patient with mandibular body INPN derived from the perineurium of the inferior alveolar nerve.

CASE PRESENTATION

The patient was a 43-year-old male. He consulted our department for a detailed examination of the right mandibular body. A biopsy was performed at another hospital and he was diagnosed with a schwannoma. At his first visit, hypesthesia extending from the right lower lip to the mental region was recognized and enlargement of the right mandibular canal was confirmed with X-ray CT and MRI. Considering the possibility of future tumor growth, we extirpated the tumor under general anesthesia. Cystic tumor was seen continuously in the inferior alveolar nerve. Immunohistologically, the tumor cells were positive for Glut-1, weakly positive for EMA, and weakly positive for Claudin-1, and the histopathological diagnosis was INPN. In addition, absence of the BCR region of chromosome 22 and expression of the BCR-ABL fusion gene were observed by fluorescent in situ hybridization (FISH), and a chromosome 22 abnormality was confirmed. These findings indicated that the disease was a neoplastic lesion.

CONCLUSION

Expression of the BCR-ABL fusion gene in INPN that develops in the oral cavity is thought to be very rare, and to the best of our knowledge, ours is the first case to be reported in the literature. About three postoperative years have passed, but findings suggestive of recurrence have not been observed.

Intraneural perineuriomas: diagnostic value of magnetic resonance neurography

Intraneural perineurioma (IP) is an under-recognized hypertrophic peripheral nerve tumor. It affects young patients involving frequently the sciatic nerve and its branches and presents with a progressive, painless and predominantly motor deficit. Magnetic resonance neurography (MRN) is a useful tool to localize the lesion, evaluate its extension, and discriminate between different etiologies. We reviewed the clinical records of 11 patients with pathologically confirm IP. Eight patients were males with mean age 19 years. Initial complains were unilateral steppage (seven patients), bilateral steppage (one patient), unilateral gastrocnemius wasting (one patient), unilateral thigh atrophy (one patient), and unilateral hand weakness (one patient). Nine patients had mild painless sensory loss. Examinations revealed involvement of sciatic nerve extending into the peroneal nerve (eight patients), posterior tibial nerve (one patient), radial nerve (one patient), and femoral nerve (one patient). MRN revealed enlargement of the affected nerve isointense on T1-weighted, hyperintense on T2 fat-saturated images, and with avid enhancement on post-contrast imaging. In all patients, a nerve biopsy confirmed the diagnosis. MRN allows early and non-invasive identification of this tumor and is a key tool providing localization and differential diagnosis in patients with slowly progressive focal neuropathies.

Malignant renal schwannoma in a cat

A nine-year-old male European shorthair cat with rapidly enlarging mass at the left kidney doubted to be malignant was presented. The purpose of this study is to present the clinical, radiological and pathological findings of a primary renal tumor in the cat. Grossly, the mass mostly encapsulated the kidney. Histologically, excisional biopsy showed worrying histological features. A sarcoma-like tumor composed mainly of neoplastic spindle-shaped cells. Neoplastic nodules of aggregations of fusiform cells arranged in multidirectional bundles. Immunohistochemically, several immunohistochemical satins (melan-A, S-100, vimentin, actin, desmin, cytokeratin, neurofilament, melan-A, NSE, synaptophysin, chromogranin, Glial Fibrillary Acidic Protein GFAP, Collagen IV and CD99) were used to differentially diagnose the mass. The stained neoplastic sections positively tested to S-100, but negative to the other aforementioned immunohistochemical stains. Immunohistochemistry with S-100 antibody staining showed an unusually strong positive reaction throughout the tumor cells. Based on our comparative diagnosis relative to other tumors, in addition to the progressive clinical signs, histopathological and immunohistochemical results, this case was presumptively diagnosis as a malignant schwannoma. According to our investigation of the relevant literature, this study of malignant renal Schwannoma (malignant peripheral nerve sheath tumor) is a highly rare case not previously characterized in a cat.

Genomic analysis reveals frequent TRAF7 mutations in intraneural perineuriomas

Intraneural perineuriomas are benign peripheral nerve sheath tumors that cause progressive debilitating focal extremity weakness. The etiology of perineuriomas is largely unknown. We utilized whole exome sequencing, copy number algorithm evaluation, and high-resolution whole genome microarray to investigate for a genetic causal link to intraneural perineuriomas. Ten of 16 (60%) tumor cases had mutations in the WD40 domain of TRAF7, the same location for causal mutations of meningiomas. Two additional perineurioma cases had large chromosomal abnormalities in multiple chromosomes, including chromosome 22q. This study identifies a common cause for intraneural perineuriomas and an unexpected shared pathogenesis with intracranial meningiomas. Ann Neurol 2017;81:316-321.

Can Intraneural Perineuriomas Occur Intradurally? An Anatomic Perspective

BACKGROUND: Intraneural perineuriomas are rare, benign lesions produced by the neoplastic proliferation of perineurial cells. They typically present in adolescents and affect nerves of the limbs. In our experience, we have not encountered a single case of classic intraneural perineurioma at an intradural location.

OBJECTIVE: To determine whether intraneural perineuriomas could occur intradurally, given the prevalence of intradural nerve sheath tumors, and explain our findings with an anatomic perspective.

METHODS: We retrospectively reviewed the high-resolution magnetic resonance images of 56 patients from an institutional registry of patients with intraneural perineurioma. All cases were analyzed for signs of proximal extension toward spinal nerves, roots, and spinal cord. A literature review was performed. The clinical, radiological, and histopathological features of potential intradural lesions were critically appraised against strict criteria for a diagnosis of classic intraneural perineurioma.

RESULTS: Fifteen of 56 (27%) patients with intraneural perineurioma had a proximal localization in the lumbosacral or brachial plexus. Not a single case occurred proximal to the dorsal root ganglia (DRG). One case of trigeminal intraneural perineurioma occurred distal to the gasserian ganglion. A literature review did not reveal any convincing cases of classic intraneural perineuriomas occurring in an intraspinal intradural location and revealed only 1 possible case in an intracranial intradural location.

CONCLUSION: Based on our study, the occurrence of classic intraneural perineuriomas intradurally is exceedingly rare, if at all present. This may be related to the paucity of perineurial cells at the nerve root level and reciprocal interactions between neuroglial cells at the central-to-peripheral transition zones.

Diagnosis and outcome of childhood perineurioma

INTRODUCTION

Intraneural perineurioma is a rare peripheral nerve tumor of childhood and early adulthood. Patients demonstrate progressive muscle weakness and atrophy largely without sensory complaints.

CASE

We report two children with perineurioma affecting the radial and femoral nerves. Electromyography (EMG), ultrasound, and 3-T MR imaging were important tools for localizing perineurioma and permitting its differentiation from other nerve lesions. The first patient underwent surgical excision of the perineurioma and a traditional nerve graft. At 10 months post-operative follow-up, she demonstrated no meaningful recovery of muscle strength compared to her pre-operative assessment. EMG did confirm axonal continuity indicating that reinnervation had occurred via the nerve graft. The second patient underwent a two-staged surgical procedure that included an end-to-side nerve transfer. At 18 months post-operative follow-up, she demonstrated mild improvement in muscle strength and EMG evidence of ongoing reinnervation.

CONCLUSION

The surgical management of perineurioma remains controversial, and reports of clinical recovery after nerve grafts and nerve transfers vary. Nerve transfers have been reported to provide superior results to traditional nerve grafting in adults with post-traumatic plexus injuries. The modest gain in strength of our patient who underwent a nerve transfer raises the question if this may also apply to patients with perineurioma. Additional studies will be required, which must also take into consideration that features of long-standing neuropathy (i.e., limb length discrepancy) have the potential to reduce the likelihood of reinnervation and clinical recovery.

Intraoperative high-resolution ultrasound and contrast-enhanced ultrasound of peripheral nerve tumors and tumorlike lesions

The diagnostic workup and surgical therapy for peripheral nerve tumors and tumorlike lesions are challenging. Magnetic resonance imaging is the standard diagnostic tool in the preoperative workup. However, even with advanced pulse sequences such as diffusion tensor imaging for MR neurography, the ability to differentiate tumor entities based on histological features remains limited. In particular, rare tumor entities different from schwannomas and neurofibromas are difficult to anticipate before surgical exploration and histological confirmation. High-resolution ultrasound (HRU) has become another important tool in the preoperative evaluation of peripheral nerves. Ongoing software and technical developments with transducers of up to 17-18 MHz enable high spatial resolution with tissue-differentiating properties. Unfortunately, high-frequency ultrasound provides low tissue penetration. The authors developed a setting in which intraoperative HRU was used and in which the direct sterile contact between the ultrasound transducer and the surgically exposed nerve pathology was enabled to increase structural resolution and contrast. In a case-guided fashion, the authors report the sonographic characteristics of rare tumor entities shown by intraoperative HRU and contrast-enhanced ultrasound.

The almost-invisible perineurioma

Intraneural perineurioma is a rare, benign slow-growing lesion arising from the perineurial cells that surrounds the peripheral nerve fibers. Typically it presents during childhood and young adulthood as a motor mononeuropathy. MRI plays an essential role in the diagnosis and localization of the lesion, which appears as a fusiform enlargement of the nerve fascicles that enhances intensely with gadolinium. Despite the typical clinical and radiological features, intraneural perineurioma remains largely underdiagnosed because of the lack of familiarity with this entity, but also as a result of technical limitations with conventional MRI that is typically performed as a screening test over a large field of view and without contrast sequences. The purpose of this article is to present the pitfalls and pearls learned from years of experience in the diagnosis and management of this relatively rare condition. Clinical suspicion and detailed neurological examination followed by high-quality electrophysiological studies (EPS) must lead to an adequate preimaging localization of the lesion and narrowing of the imaging area. The use of high-resolution (3-T) MRI combined with gadolinium administration will allow adequate visualization of the internal anatomy of the nerve and help in differentiating other causes of neuropathy. In cases where the lesion is not recognized but clinical suspicion is high, possible errors must be assessed, including the EPS localization, area of imaging, MRI resolution, and slice thickness.

Intraoral Pseudo-Onion Bulb Intraneural Proliferations in a Patient with Hemimandibular Hyperplasia: A Case Report and Review of the Literature

This report and review of the literature describes a case of benign intraoral lesions of perineurial origin in a patient with symptomatic hemimandibular hyperplasia causing partial denture soreness. Perineuriomas are a benign peripheral nerve sheath tumor composed of perineurial cells. Intraoral perineuriomas are an extremely rare entity. Two main types of perineuriomas have been described: intraneural and extraneural perineuriomas. A third, similar entity, called an intraneural pseudoperineuriomatous proliferation, has recently been proposed in the literature as a separate and distinctive diagnosis. This report describes the histologic and clinical presentation of intraneural pseudoperineuriomatous proliferations in a patient with hemimandibular hyperplasia.

Peripheral Nerve Sheath Tumors

This article presents an overview of the diagnostic categories of benign and malignant nerve sheath tumors, including neuroma, neurofibroma, nerve sheath myxoma, perineurioma, schwannoma, and malignant peripheral nerve sheath tumor. The discussion emphasizes histologic patterns; ancillary studies, such as immunohistochemistry; and differential diagnoses. The information is of value to practicing pathologists in both community and academic settings.

MRI of intraneural perineurioma of the brachial plexus

Intraneural perineurioma is an uncommon benign tumor of the perineurium of peripheral nerve sheaths occurring primarily in adolescents or young adults. MRI is a valuable tool in suggesting this diagnosis and in surgical planning. We report an 18-year old female with progressive right-hand weakness, numbness, and severe atrophic changes of the hand secondary to an intraneural perineurioma involving the right brachial plexus, in whom the initial diagnosis was suggested by MRI.

Case report of bilateral relapsing-remitting sciatic nerve palsy during two pregnancies

BACKGROUND

Unlike puerperal peripheral nerve lesions, mononeuropathy during pregnancy is rarely encountered. We report a case of bilateral relapsing-remitting sciatic nerve palsy during two pregnancies. An extensive literature search in PubMed brought no similar cases.

CASE PRESENTATION

A healthy young woman presented with initially unilateral sciatic nerve palsy, which manifested and worsened during the early phases of two successive pregnancies. Electrophysiology revealed axonal lesion of the sciatic nerve with predominant affection of the peroneal part. Extensive laboratory examination including cerebrospinal fluid examination was unremarkable. MR imaging was compatible with bilateral intraneural perineurioma. Recurrent occurrence during two pregnancies and an anamnestic relationship between intermediate worsening of the paresis and the menstrual cycle suggested hormone-dependency of the tumor. However, response to repeated intravenous immunoglobuline (IVIG) therapy during pregnancy and shortly after childbirth resulted in partial reversion of foot drop. This was also indicative of an immunoneuropathy. Nerve biopsy was not performed because of clinical improvement. The precise underlying neuropathological mechanism remained unclear.

CONCLUSION

To increase knowledge and awareness of this rare entity, potential etiologies of mononeuropathies during pregnancy are discussed in the context of this case report. In the rare occasion of peripheral nerve mononeuropathy during pregnancy, in which therapeutic opportunities are limited, IVIG therapy may be an option when the etiology cannot clearly be determined after thorough medical investigation.

Rapid Recurrence of a Benign Meningial Perineurioma

BACKGROUND

We describe a rare case of a rapidly recurring benign meningial-based perineurioma. Clinical, radiologic, and pathologic features of a rapidly recurring falxial perineurioma are described; the perineurioma was discovered incidentally in an 86-year-old woman.

CASE DESCRIPTION

Due to progressive gait disturbances and radiologically proven progression after a 3-year symptom-free interval, subtotal resection of a large falxial-based meningeal tumor was performed.

CONCLUSIONS

The pathologic examination confirmed the diagnosis of a perineurioma (World Health Organization grade I). Follow-up magnetic resonance tomography 5 months later due to neurologic deterioration revealed an abnormally rapidly growing and extensive local tumor recurrence. Due to the mass effect, reoperation was performed and adjuvant radiation of 20 Gy to the tumor bed was implemented thereafter. Meningeal-based perineuriomas of the central nervous system are extremely rare, and literature on proper management is scarce. Although histologic classification reveals a benign lesion, follow-up may be considered for this type of tumor.

[Nerve sheath tumours]

Peripheral nerve sheath tumors are common neoplasms in daily practice. Diagnosis and classification of most conventional peripheral nerve sheath tumors are relatively straightforward for the experienced observer; but on occasion, they are diagnostically challenging (especially with locally aggressive and malignant tumors). This article aims to provide an update of the data (clinical, histological, immunohistochemistry and genomic) of benign, intermediate and malignant peripheral nerve sheath tumors, thanks to the latest WHO "Classification of Tumors of Soft Tissue and Bone", published in 2013, which includes a new chapter on "Nerve Sheath Tumors". Advances in molecular biology have provided new insights into the nature of the various peripheral nerve sheath tumors, and have begun to suggest novel targeted therapeutic approaches.

Intraneural perineurioma of the sciatic nerve: an under-recognized nerve neoplasm with characteristic MRI findings

Intraneural perineurioma is a benign peripheral nerve neoplasm that typically affects teenagers and young adults and tends to result in a motor-predominant neuropathy. The lesion is rare, but has likely been underdiagnosed due to a lack of familiarity among both clinicians and radiologists. There have been few reports in the radiology literature despite the lesion having a fairly characteristic imaging appearance. We report a case of a 26-year-old woman with an intraneural perineurioma of the left sciatic nerve confirmed with excisional biopsy and pathologic analysis.

Intraneural perineurioma of unilateral radial and median nerves manifesting with long-standing focal amyotrophy in a 14-year-old-boy

Intraneural perineuriomas are rare tumors of the peripheral nerves with unique immunohistochemical findings. In this report, we highlight the clinical and imaging findings of an adolescent male with histologically proven intraneural perineurioma involving multiple nerves. The salient features included a clinically progressive course, imaging evidence of involvement of long segments of multiple nerves, enlargement of individual fascicles within the affected nerves, and intense contrast enhancement of the enlarged fascicles. The identification of enlarged fascicles with intense contrast enhancement within the affected and distended nerve segments may aid in distinguishing intraneural perineurioma from other tumors affecting the peripheral nerves.