Longitudinal study of intraneural perineurioma--a benign, focal hypertrophic neuropathy of youth

Magnetic resonance neurography: current perspectives and literature review

Magnetic resonance neurography (also called MRN or MR neurography) refers to MR imaging dedicated to the peripheral nerves. It is a technique that enhances selective multiplanar visualisation of the peripheral nerve and pathology by encompassing a combination of two-dimensional, three-dimensional and diffusion imaging pulse sequences. Referring physicians who seek imaging techniques that can depict and diagnose peripheral nerve pathologies superior to conventional MR imaging are driving the demand for MRN. This article reviews the pathophysiology of peripheral nerves in common practice scenarios, technical considerations of MRN, current indications of MRN, normal and abnormal neuromuscular appearances, and imaging pitfalls. Finally, the emerging utility of diffusion-weighted and diffusion tensor imaging is discussed and future directions are highlighted.

KEY POINTS

• Lesion relationship to neural architecture is more conspicuous on MRN than MRI. • 3D multiplanar imaging technique is essential for pre-surgical planning. • Nerve injuries can be classified on MRN using Sunderland's classification. • DTI provides quantitative information and insight into intraneural integrity and pathophysiology.

Targeted fascicular biopsy of the brachial plexus: rationale and operative technique

OBJECTIVE

Nerve biopsy is useful in the management of neuromuscular disorders and is commonly performed in distal, noncritical cutaneous nerves. In general, these procedures are diagnostic in only 20%–50%. In selected cases in which preoperative evaluation points toward a more localized process, targeted biopsy would likely improve diagnostic yield. The authors report their experience with targeted fascicular biopsy of the brachial plexus and provide a description of the operative technique.

METHODS

All cases of targeted biopsy of the brachial plexus biopsy performed between 2003 and 2015 were reviewed. Targeted nerve biopsy was performed using a supraclavicular, infraclavicular, or proximal medial arm approach. Demographic data and clinical presentation as well as the details of the procedure, adverse events (temporary or permanent), and final pathological findings were recorded.

RESULTS

Brachial plexus biopsy was performed in 74 patients (47 women and 27 men). The patients' mean age was 57.7 years. All patients had abnormal findings on physical examination, electrodiagnostic studies, and MRI. The overall diagnostic yield of biopsy was 74.3% (n = 55). The most common diagnoses included inflammatory demyelination (19), breast carcinoma (17), neurolymphomatosis (8), and perineurioma (7). There was a 19% complication rate; most of the complications were minor or transient, but 4 patients (5.4%) had increased numbness and 3 (4.0%) had additional weakness following biopsy.

CONCLUSIONS

Targeted fascicular biopsy of the brachial plexus is an effective diagnostic procedure, and in highly selected cases should be considered as the initial procedure over nontargeted, distal cutaneous nerve biopsy. Using MRI to guide the location of a fascicular biopsy, the authors found this technique to produce a higher diagnostic yield than historical norms as well as providing justification for definitive treatment.

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.

3D MR Neurography of the Lumbosacral Plexus: Obtaining Optimal Images for Selective Longitudinal Nerve Depiction

BACKGROUND AND PURPOSE

The number of centers currently performing 3D fat-suppressed isotropic imaging is limited. If the angular orientations of the major lumbosacral plexus nerves on 3D isotropic MR neurography could be determined, similar planes could be prescribed during acquisition of 2D or 3D nonisotropic techniques for optimal depiction of various nerves. Our aim was to determine oblique sagittal and coronal angular measurements for longitudinal depiction of lumbosacral plexus nerves. Interobserver and intraobserver performance and mean calibers of sciatic and femoral nerves were also determined.

MATERIALS AND METHODS

A consecutive series of lumbosacral plexus MR neurography examinations with 3D nerve-selective imaging performed during a 10-month period on a 3T scanner were evaluated. Two observers performed reconstructions and angular measurements. Sciatic and femoral nerve diameters were measured. Descriptive statistics and intraclass correlation coefficient correlations were used.

RESULTS

There were 52 subjects, 11 men and 41 women. Mean sagittal thecal sac angles for coronal demonstration of lumbosacral plexus nerve roots from L1 to S1 for 2 independent observers measured 13.58° ± 2.87° and 13.61° ± 2.18°. Mean sagittal femoral nerve angles were 27.78° ± 4.81° and 28.94° ± 4.49°, and mean sagittal sciatic nerve angles were -10.7° ± 3.75° and -11.82° ± 2.87°. Coronal angular measurements of the femoral and sciatic nerves were similar. The intraclass correlation coefficient was moderate (0.582-0.671) for interobserver performance. For intraobserver performance among various angular measurements, the intraclass correlation coefficient was moderate to good (0.586-0.788). Femoral nerve caliber on MR imaging was almost half that of the sciatic nerve. Mean right femoral nerve thickness was 4.52 ± 1.11 mm and 4.85 ± 0.64 mm for the 2 observers, and mean left femoral nerve thickness was 4.48 ± 0.97 mm and 4.94 ± 0.57 mm. Mean right sciatic nerve thickness was 9.71 ± 1.76 mm and 9.94 ± 0.83 mm, and mean left sciatic nerve thickness was 10.03 ± 1.71 mm and 9.98 ± 0.99 mm.

CONCLUSIONS

Angular lumbosacral plexus measurements aid in the prescription of different planes on MR imaging for the optimal longitudinal demonstration of nerves.

Case report: Intraneural perineurioma of the sciatic nerve in an adolescent - strategies for revealing the diagnosis

Diagnosis of intraneural conditions can be revealed by a combination of clinical examination, electrophysiology, magnetic resonance imaging (MRI), and targeted fascicular biopsy with subsequent microscopic analyses.

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.

Peripheral nerve imaging

Disorders of peripheral nerve have been traditionally diagnosed and monitored using clinical and electrodiagnostic approaches. The last two decades have seen rapid development of both magnetic resonance imaging (MRI) and ultrasound imaging of peripheral nerve, such that these imaging modalities are increasingly invaluable to the diagnosis of patients with peripheral nerve disorders. Peripheral nerve imaging provides information which is supplementary to clinical and electrodiagnostic diagnosis. Both MRI and ultrasound have particular benefits in specific clinical circumstances and can be considered as complementary techniques. These technologic developments in peripheral nerve imaging will usher in an era of multimodality assessment of peripheral nerve disorders, with clinical evaluations supported by anatomic information from imaging, and functional information from electrodiagnostic studies. Such a multimodality approach will improve the accuracy and efficiency of patient care.

Pure neuritic leprosy presenting as ulnar nerve neuropathy: a case report of electrodiagnostic, radiographic, and histopathological findings

Hansen’s disease, or leprosy, is a chronic infectious disease with many manifestations. Though still a major health concern and leading cause of peripheral neuropathy in the developing world, it is rare in the United States, with only about 150 cases reported each year. Nevertheless, it is imperative that neurosurgeons consider it in the differential diagnosis of neuropathy.

The causative organism is Mycobacterium leprae, which infects and damages Schwann cells in the peripheral nervous system, leading first to sensory and then to motor deficits. A rare presentation of Hansen’s disease is pure neuritic leprosy. It is characterized by nerve involvement without the characteristic cutaneous stigmata. The authors of this report describe a case of pure neuritic leprosy presenting as ulnar nerve neuropathy with corresponding radiographic, electrodiagnostic, and histopathological data.

This 11-year-old, otherwise healthy male presented with progressive right-hand weakness and numbness with no cutaneous abnormalities. Physical examination and electrodiagnostic testing revealed findings consistent with a severe ulnar neuropathy at the elbow. Magnetic resonance imaging revealed diffuse thickening and enhancement of the ulnar nerve and narrowing at the cubital tunnel. The patient underwent ulnar nerve decompression with biopsy. Pathology revealed acid-fast organisms within the nerve, which was pathognomonic for Hansen’s disease. He was started on antibiotic therapy, and on follow-up he had improved strength and sensation in the ulnar nerve distribution.

Pure neuritic leprosy, though rare in the United States, should be considered in the differential diagnosis of those presenting with peripheral neuropathy and a history of travel to leprosy-endemic areas. The long incubation period of M. leprae, the ability of leprosy to mimic other conditions, and the low sensitivity of serological tests make clinical, electrodiagnostic, and radiographic evaluation necessary for diagnosis. Prompt diagnosis and treatment is imperative to prevent permanent neurological injury.

Targeted fascicular biopsy of the sciatic nerve and its major branches: rationale and operative technique

OBJECT

Nerve biopsy is typically performed in distal, noncritical sensory nerves without using imaging to target the more involved regions. The yield of these procedures rarely achieves more than 50%. In selected cases where preoperative evaluation points toward a more localized (usually a more proximal) process, targeted biopsy would likely capture the disease. Synthesis of data obtained from clinical examination, electrophysiological testing, and MRI allows biopsy of a portion of the major mixed nerves safely and efficiently. Herein, experiences with the sciatic nerve are reported and a description of the operative technique is provided.

METHODS

All cases of sciatic nerve biopsy performed between 2000 and 2014 were reviewed. Only cases of fascicular nerve biopsy approached from the buttock or the posterior aspect of the thigh were included. Demographic data, clinical presentation, and the presence of percussion tenderness for each patient were recorded. Reviewed studies included electrodiagnostic tests and imaging. Previous nerve and muscle biopsies were noted. All details of the procedure, final pathology, and its treatment implications were recorded. The complication rate was carefully assessed for temporary as well as permanent complications.

RESULTS

One hundred twelve cases (63 men and 49 women) of sciatic nerve biopsy were performed. Mean patient age was 46.4 years. Seventy-seven (68.8%) patients presented with single lower-extremity symptoms, 16 (14.3%) with bilateral lower-extremity symptoms, and 19 (17%) with generalized symptoms. No patient had normal findings on physical examination. All patients underwent electrodiagnostic studies, the findings of which were abnormal in 110 (98.2%) patients. MRI was available for all patients and was read as pathological in 111 (99.1%). The overall diagnostic yield of biopsy was 84.8% (n = 95). The pathological diagnoses included inflammatory demyelination, perineurioma, nonspecific inflammatory changes, neurolymphomatosis, amyloidosis, prostate cancer, injury neuroma, neuromuscular choristoma, sarcoidosis, vasculitis, hemangiomatosis, arteriovenous malformation, fibrolipomatous hamartoma (lipomatosis of nerve), and cervical adenocarcinoma. The series included 11 (9.9%) temporary and 5 (4.5%) permanent complications: 3 patients (2.7%) reported permanent numbness in the peroneal division distribution, and 2 patients (1.8%) were diagnosed with neuromuscular choristoma that developed desmoid tumor at the biopsy site 3 and 8 years later.

CONCLUSIONS

Targeted fascicular biopsy of the sciatic nerve is a safe and efficient diagnostic procedure, and in highly selected cases can be offered as the initial procedure over distal cutaneous nerve biopsy. Diagnoses were very diverse and included entities considered very rare. Even for the more prevalent diagnoses, the biopsy technique allowed a more targeted approach with a higher diagnostic yield and justification for more aggressive treatment. In this series, new radiological patterns of some entities were identified, which could be biopsied less frequently.

MR Imaging of the Nerves of the Upper Extremity: Elbow to Wrist

The peripheral nervous system is susceptible to a diverse array of pathologic insults, broadly categorizable into those entities intrinsic to the nerves themselves, either primarily arising within the nerve(s) or direct involvement of the nerve(s) secondary to a systemic process, and those processes external to the nerve(s) proper but affecting them extrinsically via mass effect, such as entrapment neuropathies. The soft tissue contrast inherent to high-quality MR imaging allows for outstanding visualization of the peripheral nervous system and surrounding structures. This review focuses on the use of MR imaging in the diagnosis and management of peripheral nerve disorders of the upper extremity.

Lumbosacral plexopathy

PURPOSE OF REVIEW

This article provides an up-to-date review of the clinical features and pathogenesis of different types of lumbosacral plexopathy and a clinical approach to their evaluation and management. Often, the pathologic involvement is not limited to the plexus and also involves the root and nerve levels. These conditions are called lumbosacral radiculoplexus neuropathies.

RECENT FINDINGS

The pathophysiology of diabetic and nondiabetic lumbosacral radiculoplexus neuropathy has been elucidated; it is ischemic injury due to a perivascular inflammatory process and microvasculitis. The clinical and neurophysiologic features of these two entities have been found to be similar, consisting of acute or subacute onset of pain and paresthesia followed by profound motor weakness asymmetrically involving the lower limbs and associated with weight loss. A lower limb and motor predominant neuropathy without pain also occurs in diabetes mellitus and has been shown to be a form of diabetic lumbosacral radiculoplexus neuropathy and not diabetic chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). The pathophysiology of some cases of postsurgical lumbosacral plexopathies has recently been shown also to be inflammatory from microvasculitis, and treatment with immunotherapy in a timely fashion may be desirable.

SUMMARY

Many pathophysiologic processes, such as neoplastic, traumatic, infectious, radiation, and inflammatory/microvasculitic processes, can affect the lumbosacral plexus causing lumbosacral plexopathy. The clinical symptoms and signs depend on the part of the plexus involved and the temporal course. Management depends on the cause of the lumbosacral plexopathy. Many cases of lumbosacral plexopathy previously thought to be idiopathic have been shown to be caused by ischemic injury from microvasculitis; despite lack of evidence for efficacy in improving neurologic deficits, the authors of this article include immunotherapy in their management of patients with this condition.

Intraneural perineurioma affecting multiple nerves: a case report and literature review

Intraneural perineurioma is a neoplasm of perineurial cells, corresponding to WHO grade I. We present a case of intraneural perineurioma affecting multiple nerves, which usually involved one or two of major nerve trunks in one patient. We describe the clinical presentation, magnetic resonance (MR) neurography characteristics, and pathological characteristics. The differential diagnosis with other diseases, such as neurofibroma, Schwannomatosis and HNPP, will also be discussed. We also review the literature in efforts to highlight recent studies on intraneural perineurioma and heighten and awareness for the possible presentations of this disorder.

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.

Hemi-body port-wine stains and progressive paresis due to territorial perineuriomas

We present a case of a biopsy-proven intraneural perineurioma involving the left lumbosacral and brachial plexus with prominent hemi-body port wine stains in the associated dermatomes. The relationship between the two entities is not clear, but this case may provide a clue to understanding the etiological pathogenesis of intraneural perineurioma in the future.

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.

On pseudo-onion bulb intraneural proliferations of the non-major nerves of the oral mucosa

Perineurial cells (PCs) participate in reactive and neoplastic processes, of the latter pure perineurial being intraneural (IP) and soft tissue perineuriomas with oral examples being reported in both. In our review of over 500 peripheral nerve sheath tumors including granular cell tumor, we identified a single ostensible case of IP occurring on the tongue of a 45-year-old African-American male that was characterized by classic perineurial pseudo-onion bulbs (PsOb), proliferating PCs among these PsOb, sclerosis apparently due to long term duration and a plexiform pattern. We have also encountered 37 examples of apparently reactive, hyperplastic or traumatic, PsOb intraneural pseudoperineuriomatous proliferation (IPP) simulating microscopically some of the properties of IP. The majority of the lesions occurred in women and close to 80 % affected the tongue. Three microscopic patterns were appreciated. Type I lesions were those where IPP was seen only focally, type II where it was seen in roughly half of the lesion, and type III where the majority of the lesional tissue or the lesion itself was characterized by IPP. Immunohistochemically, IPP featured PsOb with generally a single layer of PCs decorated by epithelial membrane antigen, glut-1 or claudin-1, and decreased numbers of S-100 positive Schwann cells. The number of axons was not apparently altered. A prominent collagenous intraneural component was occasionally evident among PsOb and the affected nerve featured discontinuous or absent perineurial envelop. While type I and II IPP can be distinguished from IP, the distinction from type III lesions can be problematic. However, the discontinuity of the perineurium of the affected nerve, the spacing and collagenization among PsOb, the limited perineurial cell layer defining the pseudo-onion bulbs, the absence of proliferating PCs between PsObs and the decreasing number of Schwann cells may be of help in the distinction from IP.

Anatomic MR imaging and functional diffusion tensor imaging of peripheral nerve tumors and tumorlike conditions

BACKGROUND AND PURPOSE

A number of benign and malignant peripheral nerve tumor and tumorlike conditions produce similar imaging features on conventional anatomic MR imaging. Functional MR imaging using DTI can increment the diagnostic performance in differentiation of these lesions. Our aim was to evaluate the role of 3T anatomic MR imaging and DTI in the characterization of peripheral nerve tumor and tumorlike conditions.

MATERIALS AND METHODS

Twenty-nine patients (13 men, 16 women; mean age, 41±18 years; range, 11-83 years) with a nerve tumor or tumorlike condition (25 benign, 5 malignant) underwent 3T MR imaging by using anatomic (n=29), functional diffusion, DWI (n=21), and DTI (n=24) techniques. Images were evaluated for image quality (3-point scale), ADC of the lesion, tractography, and fractional anisotropy of nerves with interobserver reliability in ADC and FA measurements.

RESULTS

No significant differences were observed in age (benign, 40±18 versus malignant, 45±19 years) and sex (benign, male/female=12:12 versus malignant, male/female=3:2) (P>.05). All anatomic (29/29, 100%) MR imaging studies received "good" quality; 20/21 (95%) DWI and 21/24 (79%) DTI studies received "good" quality. ADC of benign lesions (1.848±0.40×10(-3) mm2/s) differed from that of malignant lesions (0.900±0.25×10(-3) mm2/s, P<.001) with excellent interobserver reliability (ICC=0.988 [95% CI, 0.976-0.994]). There were no FA or ADC differences between men and women (P>.05). FA of involved nerves was lower than that in contralateral healthy nerves (P<.001) with excellent interobserver reliability (ICC=0.970 [95% CI, 0.946-0.991]). ADC on DTI and DWI was not statistically different (P>.05), with excellent intermethod reliability (ICC=0.943 [95% CI, 0.836-0.980]). Tractography differences were observed in benign and malignant lesions.

CONCLUSIONS

3T MR imaging and DTI are valuable methods for anatomic and functional evaluation of peripheral nerve lesions with excellent interobserver reliability. While tractography and low FA provide insight into neural integrity, low diffusivity values indicate malignancy in neural masses.

Compression and entrapment neuropathies

Peripheral nerve entrapments are frequent. They usually appear in anatomical tunnels such as the carpal tunnel. Nerve compressions may be due to external pressure such as the fibular nerve at the fibular head. Malignant or benign tumors may also damage the nerve. For each nerve from the upper and lower limbs, detailed clinical, electrophysiological, imaging, and therapeutic aspects are described. In the upper limbs, carpal tunnel syndrome and ulnar neuropathy at the elbow are the most frequent manifestations; the radial nerve is less frequently involved. Other nerves may occasionally be damaged and these are described also. In the lower limbs, the fibular nerve is most frequently involved, usually at the fibular head by external compression. Other nerves may also be involved and are therefore described. The clinical and electrophysiological examination are very important for the diagnosis, but imaging is also of great use. Treatments available for each nerve disease are discussed.

[Bilateral peroneal neuropathy following bariatric surgery]

We report the case of bilateral peroneal neuropathy following massive weight loss after bariatric surgery. A few months after a gastric by-pass, the patient developed sequentially within 6 months a L2-L3 herniated disc that required surgery, a severe right peroneal nerve palsy that led to decompressive surgery and finally contralateral peroneal nerve palsy also operated. The electrophysiological analysis confirmed the clinical suspicion of peroneal nerve compression at the fibular head. Postoperative course was favorable. Literature reports peroneal nerve palsy after slimming, mostly when weight loss is fast and marked although the issue is rarely bilateral.

Electrodiagnostic testing in lumbosacral plexopathies

Patients presumed to have lower limb symptoms localizing to the lumbar or lumbosacral plexus require rigorous electrophysiological evaluation. Entities that cause lumbosacral plexopathies may be patchy, asymmetrical and more diffuse than initially suspected. As a result, bilateral nerve conduction studies and needle examination outside those routinely tested and clinically affected may be needed to document the extent of involvement including needle examination of the thoracic paraspinals and consideration of upper limb studies. This article outlines the lumbar and lumbosacral plexus anatomy, and discusses a differential diagnosis and electrophysiological approach in assessing patients with presumed lumbosacral plexopathies.

MRI in hypertrophic mono- and polyneuropathies

Different conditions that may lead to enlarged nerves or nerve roots include hereditary motor and sensory neuropathy (HMSN), neurofibromatosis (NF) type 1, chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), and intraneural perineurioma. Differential diagnosis of hypertrophic mono- and polyradiculopathies remains challenging but is important because of different treatments and prognosis. Magnetic resonance imaging (MRI) can identify the hypertrophic nerve segments and guide a fascicular biopsy. A fascicular biopsy will often be necessary for precise diagnosis.

Localized hypertrophic neuropathy of the sciatic nerve in children: MRI findings

BACKGROUND

Localized hypertrophic neuropathy (LHN) of the sciatic nerve in children is a rare condition characterized by a painless neurological deficit in the sciatic nerve territory.

OBJECTIVE

To demonstrate the role of MRI using a specific protocol and describe the primary findings in LHN.

MATERIALS AND METHODS

Imaging in four children (age 2 years to 12 years) is presented. All children presented with lower limb asymmetry. Three had a steppage gait. LHN was confirmed by electrophysiological studies and by MRI of the whole sciatic nerve with a dedicated protocol covering the lumbar spine and the lower limb.

RESULTS

There were four direct MRI findings: (1) linear and focal hypertrophy with progressive enlargement of a peripheral nerve or plexus diameter, (2) abnormal hyperintensity of the nerve on T2-weighted images, (3) preserved fascicular configuration, and (4) variable enhancement after intravenous gadolinium administration. In addition there were atrophy and fatty infiltration of innervated muscles. MRI was helpful for determining the extent of lesions and in excluding peripheral nerve compression or tumour.

CONCLUSION

MRI of the whole sciatic nerve is the method of choice for diagnosing LHN of the sciatic nerve.

Sciatic nerve tumor and tumor-like lesions - uncommon pathologies

Sciatic nerve mass-like enlargement caused by peripheral nerve sheath tumors or neurocutaneous syndromes such as neurofibromatosis or schwannomatosis has been widely reported. Other causes of enlargement, such as from perineuroma, fibromatosis, neurolymphoma, amyloidosis, endometriosis, intraneural ganglion cyst, Charcot-Marie-Tooth disease, and chronic inflammatory demyelinating polyneuropathy are relatively rare. High-resolution magnetic resonance imaging (MRI) is an excellent non-invasive tool for the evaluation of such lesions. In this article, the authors discuss normal anatomy of the sciatic nerve and MRI findings of the above-mentioned lesions.

Neurogenic tumors of soft tissue

Neurogenic tumors are an uncommon yet important category of soft tissue tumors in children and adolescents because of their frequent association with various genetic syndromes. The heterogeneous cellular composition of the peripheral nerve and the wide metaplastic capacity of the neural crest and its derivatives generate a variety of neoplasms with neurogenic differentiation. This article reviews the clinicopathologic features and differential diagnosis of neurogenic tumors in the first two decades of life, and highlights use of selected ancillary methods for diagnosis.

Pathology of peripheral nerve sheath tumors: diagnostic overview and update on selected diagnostic problems

Peripheral nerve sheath tumors are common neoplasms, with classic identifiable features, but on occasion, they are diagnostically challenging. Although well-defined subtypes of peripheral nerve sheath tumors were described early in the history of surgical pathology, controversies regarding the classification and grading of these tumors persist. 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. In this review, we discuss current concepts and problematic areas in the pathology of peripheral nerve sheath tumors. Diagnostic criteria and differential diagnosis for the major categories of nerve sheath tumors are proposed, including neurofibroma, schwannoma, and perineurioma. Diagnostically challenging variants, including plexiform, cellular and melanotic schwannomas are highlighted. A subset of these affects the childhood population, and has historically been interpreted as malignant, although current evidence and outcome data suggest they represent benign entities. The growing current literature and the author's experience with difficult to classify borderline or "hybrid tumors" are discussed and illustrated. Some of these classification gray zones occur with frequency in the gastrointestinal tract, an anatomical compartment that must always be entertained when examining these neoplasms. Other growing recent areas of interest include the heterogeneous group of pseudoneoplastic lesions involving peripheral nerve composed of mature adipose tissue and/or skeletal muscle, such as the enigmatic neuromuscular choristoma. Malignant peripheral nerve sheath tumors (MPNST) represent a diagnostically controversial group; difficulties in grading and guidelines to separate "atypical neurofibroma" from MPNST are provided. There is an increasing literature of MPNST mimics which neuropathologists must be aware of, including synovial sarcoma and ossifying fibromyxoid tumor. Finally, we discuss entities that are lacking from the section on cranial and paraspinal nerves in the current WHO classification, and that may warrant inclusion in future classifications. In summary, although the diagnosis and classification of most conventional peripheral nerve sheath tumors are relatively straightforward for the experienced observer, yet borderline and difficult-to-classify neoplasms continue to be problematic. In the current review, we attempt to provide some useful guidelines for the surgical neuropathologist to help navigate these persistent, challenging problems.

An unusual location of ulnar nerve pathology: a perineurioma of the ulnar nerve in the upper arm

A young man presented with progressive motor weakness and atrophy of the ulnar muscles of his left hand over a period of more than 2 years. Electrodiagnostic studies indicated an ulnar nerve lesion, but it was not localized. High-resolution sonography of the ulnar nerve revealed an enlarged and hypoechogenic ulnar nerve at an unusual location, namely 12.5 cm proximal to the medial epicondyle. Histology showed that this was an intraneural perineurioma. High-resolution sonography of the ulnar nerve is very useful in the discovery of this unusual location of nerve pathology and may assist in its early detection.

Peripheral tumor and tumor-like neurogenic lesions

Neoplasms of neurogenic origin account for about 12% of all benign and 8% of all malignant soft tissue neoplasms. Traumatic neuroma, Morton neuroma, lipomatosis of a nerve, nerve sheath ganglion, perineurioma, benign and malignant peripheral nerve sheath tumors (PNST) are included in this group of pathologies. Clinical and radiologic evaluation of patients with neurogenic tumors and pseudotumors often reveals distinctive features. In this context, advanced imaging techniques, especially ultrasound (US) and magnetic resonance (MR) play an important role in the characterization of these lesions. Imaging findings such as location of a soft tissue mass in the region of a major nerve, nerve entering or exiting the mass, fusiform shape, abnormalities of the muscle supplied by the nerve, split-fat sign, target sign and fascicular appearance should always evoke a peripheric nerve sheath neoplasm. Although no single imaging finding or combination of findings allows definitive differentiation between benign from malign peripheric neurogenic tumors, both US and MR imaging may show useful features that can lead us to a correct diagnosis and improve patient treatment. Traumatic neuromas and Morton neuromas are commonly associated to an amputation stump or are located in the intermetatarsal space. Lipomatosis of a nerve usually appears as a nerve enlargement, with thickened nerve fascicles, embedded in evenly distributed fat. Nerve sheath ganglion has a cystic appearance and commonly occurs at the level of the knee. Intraneural perineuroma usually affects young people and manifests as a focal and fusiform nerve enlargement. In this article, we review clinical characteristics and radiologic appearances of these neurogenic lesions, observing pathologic correlation, when possible.

Nerve biopsy: requirements for diagnosis and clinical value

In many instances, nerve biopsy is not necessary in the diagnostic work-up of a peripheral neuropathy. However, histological examination of a tissue sample is still mandatory to show specific lesions in various conditions involving peripheral nerves. As there are fewer laboratories that examine human nerve samples, practitioners including neurologists and general pathologists may not be completely aware of the technical issues and data that are provided by nerve biopsy. Nerve biopsy is considered an invasive diagnostic method, although, its complications are by far less disabling than most of the disorders that lead to its indications. Nevertheless, the decision to perform a nerve biopsy has to be made on a case-by-case basis, and its results must be discussed between the pathologist and the clinician who is in charge of the patient's care. In this paper, we review the minimal technical requirements for proper peripheral nerve tissue analysis. Moreover, we provide data on the usefulness of nerve biopsy in various situations including abnormal deposits, cell infiltrates, link between peripheral neuropathy and monoclonal gammopathy, and numerous hereditary disorders.

Pediatric sciatic neuropathy associated with neoplasms

Seven children with sciatic neuropathy associated with an underlying neoplasm are reported. Clinical presentation, electrophysiological data, imaging, pathology, and/or autopsy results are described. Pain and weakness, primarily foot drop, were the most common presenting symptoms. The mechanism of sciatic neuropathy was varied and included: nerve infiltration by the adjacent neoplasm (neuroblastoma, rhabdomyosarcoma, and leukemic or lymphomatous infiltration); an expanding, intrinsic neurogenic tumor (perineurioma); or intraoperative stretch injury (osteosarcoma resection). The prognosis for sciatic nerve recovery was good among children who survived their associated cancer. Three children died from the cancer or complications of treatment. One child with perineurioma remained clinically stable, and two children improved after treatment of their neoplasm.

Inflammatory pseudotumor of nerve: clinicopathological characteristics and a potential therapy

We sought to determine the clinical, electrophysiological, neuroimaging, and pathological features of inflammatory pseudotumor of nerve. Five patients were identified. All cases presented with a gradually progressive mononeuropathy with symptoms of weakness, sensory loss, and prominent neuropathic pain. The median duration of symptoms was 7 months (range 3-36 months). Electrophysiological results were in keeping with chronic axonal mononeuropathies with variable findings of active denervation and reinnervation. MRI demonstrated irregular, large masses involving and surrounding nerve with heterogenous signal characteristics on T1- and T2-weighted and post-contrast sequences. Histopathological features of the nerve slightly varied but shared commonalities including chronic inflammatory infiltrates, increased collagen, and increased numbers of microvessels. Axonal degeneration and decreased density of myelinated fibers were also noted. Three patients were treated with weekly courses of intravenous steroids for 3 months. All reported improvement in pain and weakness. Inflammatory pseudotumor of nerve is not a neoplasm and has reactive features of inflammation, increased vascularity, and marked fibrosis. It presents as a progressive axonal mononeuropathy with weakness, sensory loss, and pain that may be episodic. The primary pathophysiology is unknown but the inflammation and response to treatment suggests that there may be an immune component.

Perineurioma of the sciatic nerve: a possible cause of idiopathic foot drop in children: report of 4 cases

The authors report on a loss of foot dorsiflexion in pediatric-age individuals and suggest that the possible cause could be a perineurioma of the sciatic nerve. The authors describe 4 cases in which foot drop in the absence of sensory discomfort was the heralding sign of perineurioma of the sciatic nerve. Magnetic resonance imaging showed a focal enlargement of the sciatic nerve, but the tumor was confined only to its lateral compartment. Treatment in 2 cases involved excision of the affected segment and subsequent graft repair. The two other patients shared the same clinical, radiological, and surgical findings, but no nerve biopsy sample was obtained; the patients underwent only a tibialis posterior muscle transfer. Long-term recovery of nerve function never occurred. Because tumor resection and nerve graft yield no functional results, a tendon transfer to restore walking may be the sole useful surgical procedure in these cases. Removal of the tumor may not be necessary because long-term follow-up confirms that perineuriomas are self-limiting and the final prognosis is favorable.

A case of intraneural perineurioma presenting with monomelic atrophy in a child

We report the case of an 11-year-old girl who developed slowly progressive atrophy of the left lower extremity. She suffered from mild dilated cardiomyopathy of unknown cause since 4years of age. When she was 7years old, her family noticed that her left extremity was thinner compared to the right one. Computed tomography showed atrophy and areas of low density in the left gluteus maximus, thigh, and calf muscles. The left sciatic nerve showed gadolinium enhancement on magnetic resonance imaging. A biopsy of the left sural nerve revealed pseudo-onion bulbs. Immunohistochemical staining was positive for epithelial membrane antigen and negative for S100 protein. Electron microscopy demonstrated myelinated or unmyelinated nerve fibers surrounded by concentric layers of perineurial cells. These results indicated intraneural perineurioma. The tumor was estimated at least from the nerve root to the ankle joint. The length of nerve involvement in this patient was the highest recorded in the literatures. Intraneural perineurioma is a very rare disorder, but is tend to be found in youth. This disorder should be considered when we see children with monomelic weakness and/or atrophy.