Ultrahigh-frequency ultrasound of fascicles in the common fibular, superficial fibular, and sural nerves

INTRODUCTION/AIMS

While ultrasound assessment of cross-sectional area and echogenicity has gained popularity as a biomarker for various neuropathies, there is a scarcity of data regarding fascicle count and density in neuropathies or even healthy controls. The aim of this study was to determine whether fascicles within select lower limb nerves (common fibular, superficial fibular, and sural nerves) can be counted in healthy individuals using ultrahigh-frequency ultrasound (UHFUS).

METHODS

Twenty healthy volunteers underwent sonographic examination of the common fibular, superficial fibular, and sural nerves on each lower limb using UHFUS with a 48 MHz linear transducer. Fascicle counts and density in each examined nerve were determined by a single rater.

RESULTS

The mean fascicle number for each of the measured nerves included the following: common fibular nerve 9.85 (SD 2.29), superficial fibular nerve 5.35 (SD 1.59), and sural nerve 6.73 (SD 1.91). Multivariate linear regression analysis revealed a significant association between cross-sectional area and fascicle count for all three nerves. In addition, there was a significant association seen in the common fibular nerve between fascicle density and height, weight, and body mass index. Age and sex did not predict fascicle count or density (all p > .13).

DISCUSSION

UHFUS enabled the identification and counting of fascicles and fascicle density in the common fibular, superficial fibular, and sural nerves. Knowledge about normal values and normal peripheral nerve architecture is needed in order to further understand and identify pathological changes that may occur within each nerve in different disease states.

Mitochondrial DNA and Electron Transport Chain Protein Levels Are Altered in Peripheral Nerve Tissues from Donors with HIV Sensory Neuropathy: A Pilot Study

Distal sensory polyneuropathy (DSP) and distal neuropathic pain (DNP) remain significant challenges for older people with HIV (PWH), necessitating enhanced clinical attention. HIV and certain antiretroviral therapies (ARTs) can compromise mitochondrial function and impact mitochondrial DNA (mtDNA) replication, which is linked to DSP in ART-treated PWH. This study investigated mtDNA, mitochondrial fission and fusion proteins, and mitochondrial electron transport chain protein changes in the dorsal root ganglions (DRGs) and sural nerves (SuNs) of 11 autopsied PWH. In antemortem standardized assessments, six had no or one sign of DSP, while five exhibited two or more DSP signs. Digital droplet polymerase chain reaction was used to measure mtDNA quantity and the common deletions in isolated DNA. We found lower mtDNA copy numbers in DSP+ donors. SuNs exhibited a higher proportion of mtDNA common deletion than DRGs in both groups. Mitochondrial electron transport chain (ETC) proteins were altered in the DRGs of DSP+ compared to DSP- donors, particularly Complex I. These findings suggest that reduced mtDNA quantity and increased common deletion abundance may contribute to DSP in PWH, indicating diminished mitochondrial activity in the sensory neurons. Accumulated ETC proteins in the DRG imply impaired mitochondrial transport to the sensory neuron's distal portion. Identifying molecules to safeguard mitochondrial integrity could aid in treating or preventing HIV-associated peripheral neuropathy.

Granuloma, vasculitis, and demyelination in sarcoid neuropathy

BACKGROUND

Despite the suggestion that direct compression by granuloma and ischemia resulting from vasculitis can cause nerve fiber damage, the mechanisms underlying sarcoid neuropathy have not yet been fully clarified.

METHODS

We examined the clinicopathological features of sarcoid neuropathy by focusing on electrophysiological and histopathological findings of sural nerve biopsy specimens. We included 18 patients with sarcoid neuropathy who had non-caseating epithelioid cell granuloma in their sural nerve biopsy specimens.

RESULTS

Although electrophysiological findings suggestive of axonal neuropathy were observed, particularly in the lower limbs, all but three patients showed ≥1 abnormalities in nerve conduction velocity or distal motor latency. Additionally, a conduction block was observed in 11 of the 16 patients for whom waveforms were assessed; five of them fulfilled motor nerve conduction criteria strongly supportive of demyelination as defined in the European Academy of Neurology/Peripheral Nerve Society (EAN/PNS) guideline for chronic inflammatory demyelinating polyneuropathy (CIDP). In most patients, sural nerve biopsy specimens revealed a mild to moderate degree of myelinated fiber loss. Fibrinoid necrosis was observed in one patient, and electron microscopy analysis revealed demyelinated axons close to granulomas in six patients.

CONCLUSIONS

Patients with sarcoid neuropathy may meet the EAN/PNS electrophysiological criteria for CIDP due to the frequent presence of conduction blocks. Based on our results, in addition to the ischemic damage resulting from granulomatous inflammation, demyelination may play an important role in the mechanism underlying sarcoid neuropathy.

Clinical feature and sural biopsy study in nitrous oxide-induced peripheral neuropathy

Objective

The objective was to analyze the clinical characteristics and pathological characteristics of sural biopsy in nitrous oxide (N₂O) -induced peripheral neuropathy.

Methods

We recruited 18 patients with N₂O abuse-induced neurological disorders and reported their demographic data, clinical manifestations, laboratory examinations, and nerve conduction studies. Seven patients underwent sural nerve biopsy pathologic examination.

Results

All 18 patients had polyneuropathy, the nerve conduction results showed significant reductions in motor and sensory amplitudes, slowing of conduction velocities, and prolongation of latencies in most tested nerves compared to the controls. Toluidine blue staining of semi-thin sections of sural nerve biopsy showed decreased myelinated nerve fiber density, increased thin myelinated nerve fiber density, and axonal regeneration. Electron microscopy showed axonal degeneration and nerve regeneration.

Conclusion

The main manifestations of peripheral nerve damage caused by the abuse of N₂O are lower limb weakness and distal sensory disorder. The nerve conduction study results demonstrated that mixed axonal and demyelinating neuropathy was the most common type of neuropathy. Sural biopsy showed the main pathological change was chronic axonal degeneration.

Nerve biopsy: Current indications and decision tools

After initial investigation of patients presenting with symptoms suggestive of neuropathy, a clinical decision is made for a minority of patients to undergo further assessment with nerve biopsy. Many nerve biopsies do not demonstrate a definitive pathological diagnosis and there is considerable cost and morbidity associated with the procedure. This highlights the need for appropriate selection of patients, nerves and neuropathology techniques. Additionally, concomitant muscle and skin biopsies may improve the diagnostic yield in some cases. Several advances have been made in diagnostics in recent years, particularly in genomics. The indications for nerve biopsy have consequently changed over time. This review explores the current indications for nerve biopsies and some of the issues surrounding its use. Also included are comments on alternative diagnostic modalities that may help to supplant or reduce the use of nerve biopsy as a diagnostic test. These primarily include extraneural biopsy and neuroimaging techniques such as magnetic resonance neurography and nerve ultrasound. Finally, we propose an algorithm to assist in deciding when to perform nerve biopsies.

Charcot-Marie-Tooth disease type 1A: Longitudinal change in nerve ultrasound parameters

BACKGROUND

This study aimed to elucidate the longitudinal changes in nerve ultrasound parameters of adult Charcot-Marie-Tooth disease type 1A (CMT1A) patients.

METHODS

Fifteen adult patients with CMT1A prospectively underwent nerve ultrasound and clinical assessment (CMT neuropathy score [CMTNS]) at baseline and 5 y later. Nerve cross-sectional area (CSA) and echogenicity were measured in the median and sural nerves. Changes in ultrasound parameters and CMTNS and correlation between changes of ultrasound parameters and CMTNS were analyzed.

RESULTS

Median and sural nerve CSAs did not change over 5 y, although CMTNS increased (P < .01). Nerve echogenicity in the sural nerve decreased over 5 y (P = .045). No correlations between changes in nerve ultrasound parameters and CMTNS were identified.

CONCLUSIONS

No longitudinal changes in nerve size was detected in adult CMT1A. Exploring the factors that determine nerve size in childhood CMT1A may lead to the development of treatments.

Perineuritis Successfully Treated with Early Aggressive Immunotherapy

Perineuritis is a rare type of peripheral neuropathy defined by swelling and cellular infiltration in the perineurium. We herein report a 52-year-old man who presented with subacute onset pain from the back to the lower limbs, muscle weakness and hypoesthesia. A sural nerve biopsy revealed perineuritis, consisting of inflammatory cell infiltration and swelling of the perineurium. Oral prednisolone, plasma exchange and intravenous immunoglobulin treatment were all effective, leading to significant improvement of the symptoms.

Pathological Observation of Blood Stasis Syndrome in Non-diabetic Peripheral Neuropathies: A Retrospective Analysis Based on Nerve Biopsy

OBJECTIVE

To investigate the pathological features of blood stasis syndrome (BSS) in non-diabetic peripheral neuropathy.

METHODS

Clinical data of 31 patients with non-diabetic peripheral neuropathy who had undergone nerve biopsy during December 2004 and December 2010 in Xuanwu Hospital Capital Medical University were retrospectively analyzed. According to Chinese medicine (CM) syndrome differentiation and signs, 26 patients were blood stasis type and 5 patients were non-blood stasis type. Clinical and pathological data were compared in detail.

RESULTS

Clinically, although both groups shared similar symptoms of limb numbness, weakness and sensory disturbances, the prevalence of neuralgia was much grievous in BSS group (73.1%, 26/31) compared with the non-BSS group (0%, 0/5). As for signs, dermal nutrients disturbance (84.6%, 22/26), dark or purple tongue (100.0%, 26/26), and sublingual varices (80.7%, 21/26) were more common in the BSS group than the non-BSS group (0%, 60%, 20%, respectively). The prevalence of qi deficiency cases (19/26) in the BSS group was significantly higher compared with the non-BSS group (1/5). The unique histological manifestations of BSS were axonal degeneration (16/26 vs 2/5 in non-BSS group), which was the hallmark of ischemia. Cases with BSS had prominent microangiopathy (61.5%, 16/26), manifested as epineurium vasculitis (inflammatory cell infiltrated to the vessel wall, obliteration and recanalization, vascular proliferation, extravascular hemosiderin deposition), angiotelectasis, proliferation and hyaline degeneration of endoneurium capillary. In the BSS group, impaired blood-nerve barrier was indicated by sub-perineurial edema (46.2%, 11/26) and endoneurial edema (15.4%, 4/26). The Renaut body (15.4%, 4/26) and amyloid deposition (3.8%, 1/26) found in the BSS group were absent in the non-BSS group.

CONCLUSIONS

BBS was common in non-diabetic peripheral neuropathies. The nerves exhibited ischemic alteration of primary axon degeneration and secondary demyelination. The interstitial tissue revealed microcirculation impairment, blood-nerve barrier disturbance, amyloid deposition and proliferation changes. The high prevalence of qi deficiency also highlights the therapy of promotion of blood circulation and removal of blood stasis.

Demyelinating Neuropathy in a Patient Treated With Revusiran for Transthyretin (Thr60Ala) Amyloidosis

Transthyretin amyloidosis patients develop length-dependent peripheral neuropathy, autonomic dysfunction, and restrictive cardiomyopathy associated with deposition of amyloid fibrils in these tissues. Despite advances in management over the past decade, this disorder causes profound debilitation and ultimately proves fatal. In this report, we describe a man with late-onset cardiac amyloidosis due to a transthyretin Thr60Ala mutation who was treated with an investigational RNAi therapeutic, revusiran, which targets hepatic transthyretin production. Sixteen months into treatment, he developed bilateral lower-extremity weakness and numbness, worsening balance, difficulty manipulating objects with his hands, and finger numbness. Nerve conduction studies were consistent with multifocal demyelinating neuropathy. Intravenous immunoglobulin therapy improved sensation in his hands and feet, and improved hand dexterity. A sural nerve biopsy demonstrated demyelination with substantial axonal loss in the absence of histologically detectable endoneurial amyloid deposition. This case expands the clinicopathologic spectrum of transthyretin amyloidosis and may represent complex disease and treatment effects.

Ultrasonography of the Sural Nerve: Normal and Pathologic Appearances

Ultrasonography (US) of peripheral nerves has gained wide popularity because of the increased definition of modern high-frequency electronic transducers, as well as the well-known advantages of US, which include easy availability, low cost, and the possibility of realizing a dynamic examination. Traditionally, US has been deployed to assess the major nerves of the limbs. More recently, US has also been used to assess the normal appearance and pathologic changes of smaller subcutaneous nerves. The sural nerve is a small sensory nerve in the subcutaneous tissues of the calf that can be affected by a variety of disorders. This pictorial essay illustrates the normal anatomy of the sural nerve, the technique for its examination by US, as well as the US appearance of its main pathologic changes.

CD40-mediated HIF-1α expression underlying microangiopathy in diabetic nerve pathology

To understand the pathology and molecular signatures of microangiopathy in diabetic neuropathy, we systemically and quantitatively examined the morphometry of microvascular and nerve pathologies of sural nerves. In the endoneurium of diabetic nerves, prominent microangiopathy was observed, as evidenced by reduced capillary luminal area, increased capillary basement membrane thickness and increased proportion of fibrin(+) blood vessels. Furthermore, capillary basement membrane thickness and the proportion of fibrin(+) blood vessels were correlated with small myelinated fiber density in diabetic nerves. In diabetic nerves, there was also significant macrophage and T cell infiltration, and cluster of differentiation 40 (CD40) expression was increased. The molecular alterations observed were upregulation of hypoxia-inducible factor-1α (HIF-1α), mitogen-activated protein kinase-activated protein kinase 2 (MK2; MAPKAPK2) and phosphatase and tensin homolog (PTEN). In addition, HIF-1α was correlated with small myelinated fiber density and capillary luminal area, while both MK2 and PTEN were correlated with capillary basement membrane thickness. The molecular cascades were further demonstrated and replicated in a cell model of microangiopathy on human umbilical vein endothelial cells (HUVECs) exposed to high-glucose medium by silencing of CD40, PTEN and HIF-1α in HUVECs using shRNA. These data clarified the hierarchy of the molecular cascades, i.e. upregulation of CD40 leading to HIF-1α expression in endothelium and nerve fibers. In conclusion, this study revealed the association of microangiopathy, thrombosis and inflammatory infiltrates with nerve degeneration in diabetic nerves, demonstrating that CD40 is a key molecule for the upregulation of HIF-1α and PTEN underlying the severity of microangiopathy.

Deletion of P2 promoter of GJB1 gene a cause of Charcot-Marie-Tooth disease

X-linked Charcot-Marie-Tooth disease (CMT) is the second most common cause of CMT, and is usually caused by mutations in the gap junction protein beta 1 (GJB1) gene. This gene has nerve specific P2 promoter that work synergistically with SOX10 and EGR2 genes to initiate transcription. Mutation in this region is known to cause Schwann cell dysfunction. A single large family of X linked peripheral neuropathy was identified in our practice. Next generation sequencing for targeted panel assay identified an upstream exon-splicing deletion identified extending from nucleotide c.-5413 to approximately - c.-49. This matches the sequence of 32 nucleotides at positions c.*218-*249 in the 3'UTR downstream of the GJB1 gene. The deleted fragment included the entire P2 promoter region. The deletion segregated with the disease. To our knowledge a deletion of the P2 promoter alone as a cause of CMT has not been reported previously.

Intrastriatal Cografts of Autologous Adrenal Medulla and Sural Nerve in MPTP-Induced Parkinsonian Macaques: Behavioral and Anatomical Assessment

To examine the effects of autologous sural nerve and adrenal medullary tissue intrastriatal cografts upon voluntary motor performance in parkinsonism, a non-human primate 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model was employed to quantitatively assess skilled hand movements. Motor performance was studied in normal, MPTP-induced parkinsonian, and then cografted states. Reaction and movement times were prolonged and variability increased in experimental and control animals in the parkinsonian state. Animals undergoing autologous cografts demonstrated improved motor performance whereas the control animal continued in a chronic, stable parkinsonian state. Intrastriatal cografts of autologous adrenal medullary tissue and sural nerve resulted in good to excellent chromaffin cell survival. The mechanism of the restoration of function in the cografted monkeys remains to be determined.

Sonographic features of peripheral nerves at multiple sites in patients with diabetic polyneuropathy

OBJECTIVE

Diabetic polyneuropathy (DPN) is one of the major complications of diabetes mellitus. Ultrasound has been frequently used for evaluation of peripheral nerves. However, there are few studies that have evaluated multiple peripheral nerves in DPN. In this study, ultrasonographic features of multiple peripheral nerves in upper and lower extremities of DPN patients were investigated and compared with those of healthy controls.

METHODS

This study was a case-control study that enrolled 20 patients with confirmed diagnosis of DPN and 20 healthy controls. The ultrasonography was performed on the sural, tibial, fibular, sciatic, median, ulnar, radial, and musculocutaneous nerves. Nerve cross-sectional area (CSA) was measured at multiple points for each peripheral nerve. The CSAs were compared between DPN and control groups, and analyzed in relation to the clinical characteristics and electrophysiologic findings.

RESULTS

The CSAs were significantly larger in the DPN group for sural nerve, fibular nerve at the fibular head level, median nerve at the carpal tunnel and mid-humerus level, ulnar nerve at the cubital tunnel outlet and mid-humerus level, and radial nerve at the spiral groove. The CSAs of sural nerve, tibial nerve and median nerve were significantly correlated with electrophysiologic findings. The sural nerve CSA revealed significant correlation with HbA1c.

CONCLUSIONS

These results suggest that the ultrasonography can provide useful information in diagnosis and evaluation of DPN.

A Mutation in PMP2 Causes Dominant Demyelinating Charcot-Marie-Tooth Neuropathy

Charcot-Marie-Tooth disease (CMT) is a heterogeneous group of peripheral neuropathies with diverse genetic causes. In this study, we identified p.I43N mutation in PMP2 from a family exhibiting autosomal dominant demyelinating CMT neuropathy by whole exome sequencing and characterized the clinical features. The age at onset was the first to second decades and muscle atrophy started in the distal portion of the leg. Predominant fatty replacement in the anterior and lateral compartment was similar to that in CMT1A caused by PMP22 duplication. Sural nerve biopsy showed onion bulbs and degenerating fibers with various myelin abnormalities. The relevance of PMP2 mutation as a genetic cause of dominant CMT1 was assessed using transgenic mouse models. Transgenic mice expressing wild type or mutant (p.I43N) PMP2 exhibited abnormal motor function. Electrophysiological data revealed that both mice had reduced motor nerve conduction velocities (MNCV). Electron microscopy revealed that demyelinating fibers and internodal lengths were shortened in both transgenic mice. These data imply that overexpression of wild type as well as mutant PMP2 also causes the CMT1 phenotype, which has been documented in the PMP22. This report might expand the genetic and clinical features of CMT and a further mechanism study will enhance our understanding of PMP2-associated peripheral neuropathy.

Isolation of causative mutation is still challenging in genetic diseases with a variety of genetic causes. We discovered a mutation in a novel gene from a family exhibiting a peripheral neuropathy by virtue of next-generation sequencing. Although the family shows characteristic clinical features of hereditary motor and sensory neuropathy, we could not find a mutation from well-known genes. To demonstrate the clinical relevance of the novel gene, we generated transgenic mice, which carry the patients’ mutation within their chromosome. The transgenic mice exhibited the same phenotype as the patients including peripheral neuropathic symptoms and reduced locomotor function. We also observed the affected peripheral nervous system through electron microscopy. It seems that the expression of the mutant protein impairs the myelin of peripheral nervous system. These data might expand the genetic, clinical, and pathophysiological features of the peripheral neuropathy and a further investigation will enhance our understanding of disease in the peripheral nervous system.

Glomus tumor closely related to a branch of the left sural nerve: a case of a rare lesion occurring at unusual location

Glomus tumors are rare benign neoplasms arising from the glomus bodies of the skin; they account for 1.6 % of all soft tissue tumors. Since the great majority of these lesions are found on fingers and toes (especially under the nail, on the fingertip, or in the foot), a correct clinical diagnosis may prove difficult if one or more glomus tumors occur on an extra digital location. We report a case of a glomus tumor with prominent vascular component found in the left leg closely related to a branch of the sural nerve and originally believed to be a schwannoma.

Progressive polyradiculoneuropathy due to intraneural oxalate deposition in type 1 primary hyperoxaluria

INTRODUCTION

A 24-year-old man with primary hyperoxaluria type 1 (PH1) presented with a rapidly progressive axonal and demyelinating sensorimotor polyradiculoneuropathy shortly after the onset of end-stage renal disease. His plasma oxalate level was markedly elevated at 107 µmol/L (normal<1.8 µmol/L).

METHODS

A sural nerve biopsy was performed. Teased fiber and paraffin and epoxy sections were done and morphometric procedures were performed on this sample and on an archived sample from a 22-year-old man as an age- and gender-matched control. Embedded teased fiber electron microscopy was also performed.

RESULTS

The biopsy revealed secondary demyelination and axonal degeneration. Under polarized light, multiple bright hexagonal, rectangular, and starburst inclusions, typical of calcium oxalate monohydrate crystals, were seen.

CONCLUSIONS

The proposed mechanisms of nerve damage include disruption of axonal transport due to crystal deposition, toxic effect of oxalate, or nerve ischemia related to vessel occlusion from oxalate crystal deposition.

Amelioration of cisplatin-induced experimental peripheral neuropathy by a small molecule targeting p75 NTR

Cisplatin is an effective and widely used first-line chemotherapeutic drug for treating cancers. However, many patients sustain cisplatin-induced peripheral neuropathy (CIPN), often leading to a reduction in drug dosages or complete cessation of treatment altogether. Therefore, it is important to understand cisplatin mechanisms in peripheral nerve tissue mediating its toxicity and identify signaling pathways for potential intervention. Rho GTPase activation is increased following trauma in several models of neuronal injury. Thus, we investigated whether components of the Rho signaling pathway represent important neuroprotective targets with the potential to ameliorate CIPN and thereby optimize current chemotherapy treatment regimens. We have developed a novel CIPN model in the mouse. Using this model and primary neuronal culture, we determined whether LM11A-31, a small-molecule, orally bioavailable ligand of the p75 neurotrophin receptor (p75(NTR)), can modulate Rho GTPase signaling and reduce CIPN. Von Frey filament analysis of sural nerve function showed that LM11A-31 treatment prevented decreases in peripheral nerve sensation seen with cisplatin treatment. Morphometric analysis of harvested sural nerves revealed that cisplatin-induced abnormal nerve fiber morphology and the decreases in fiber area were alleviated with concurrent LM11A-31 treatment. Cisplatin treatment increased RhoA activity accompanied by the reduced tyrosine phosphorylation of SHP2, which was reversed by LM11A-31. LM11A-31 also countered the effects of calpeptin, which activated RhoA by inhibiting SHP2 tyrosine phosphatase. Therefore, suppression of RhoA signaling by LM11A-31 that modulates p75(NTR) or activates SHP2 tyrosine phosphatase downstream of the NGF receptor enhances neuroprotection in experimental CIPN in mouse model.

The modifying effect a PMP22 deletion in a family with Charcot-Marie-Tooth type 1 neuropathy due to an EGR2 mutation

BACKGROUND

Mutations of both the PMP22 and EGR2 genes cause Charcot-Marie-Tooth (CMT) disease type 1. Deletion of the PMP22 gene, results in hereditary neuropathy with liability to pressure palsies. More publications exist about the interaction of PMP22 duplication and other CMT-causing gene mutations. In these cases the intrafamiliar discordant phenotypes draw the attention to the possible role of modifying genes. The gene-gene interactions between the PMP22 and EGR2 genes are not well understood.

CASE REPORT

We report two brothers with late onset CMT1 due to a c. 1142 G>A (Arg381His) heterozygous substitution in the EGR2 gene. Additionally, the older brother with the less severe symptoms harbored the PMP22 gene deletion also.

CONCLUSION

The coexistence of the two genetic alterations did not aggravate the clinical symptoms. Moreover, the PMP22 deletion appeared to have a beneficial modifying effect, thus implying potential gene-gene interaction of PMP22 and EGR2. PMP22 deletion may increase Schwann cells proliferation and compensate the dominant-negative effect of the Arg381 His substitution in the EGR2 gene.

Truncating and missense mutations in IGHMBP2 cause Charcot-Marie Tooth disease type 2

Using a combination of exome sequencing and linkage analysis, we investigated an English family with two affected siblings in their 40s with recessive Charcot-Marie Tooth disease type 2 (CMT2). Compound heterozygous mutations in the immunoglobulin-helicase-μ-binding protein 2 (IGHMBP2) gene were identified. Further sequencing revealed a total of 11 CMT2 families with recessively inherited IGHMBP2 gene mutations. IGHMBP2 mutations usually lead to spinal muscular atrophy with respiratory distress type 1 (SMARD1), where most infants die before 1 year of age. The individuals with CMT2 described here, have slowly progressive weakness, wasting and sensory loss, with an axonal neuropathy typical of CMT2, but no significant respiratory compromise. Segregating IGHMBP2 mutations in CMT2 were mainly loss-of-function nonsense in the 5' region of the gene in combination with a truncating frameshift, missense, or homozygous frameshift mutations in the last exon. Mutations in CMT2 were predicted to be less aggressive as compared to those in SMARD1, and fibroblast and lymphoblast studies indicate that the IGHMBP2 protein levels are significantly higher in CMT2 than SMARD1, but lower than controls, suggesting that the clinical phenotype differences are related to the IGHMBP2 protein levels.

Neuropathy in eosinophilic granulomatosis with polyangiitis: a comparison study of 24 cases with or without prior leukotriene antagonist exposure

Eosinophilic granulomatosis with polyangiitis (EGPA), also known as Churg-Strauss syndrome (CSS), is a systemic vasculitis affecting almost exclusively patients with asthma. Neuropathy is the presenting feature in 55-75 % of cases. An increased incidence of the syndrome has been reported in asthmatics treated with leukotriene antagonists (LTAs). The causal relation is still debated. We retrospectively examined clinical, biochemical, histological features, and outcome of patients referred between 1990 and 2006 for sural nerve biopsy affected by neuropathy related to EGPA. We identified 24 patients, 6 treated with LTA montelukast (T-group) and 18 not treated (NT-Group). All had chronic asthma; in T-group neuropathy developed from 1 to 150 days after starting montelukast. Demographic features as well as asthma duration and pre-onset treatment were remarkably similar, with the only exception of a statistically nonsignificant larger involvement of the nasal mucosa in T group. Nerve biopsy revealed in both group an axonal neuropathy. At follow-up, all within the T-group and most within the NT-group improved clinically; neurophysiological parameters remained stable, improved or worsened in the same proportion within the two groups. Only 2 NT and no T-patient had stopped steroid treatment before the appearance of the peripheral neuropathy, making withdrawal overall unlikely as a causative factor of the onset of neuropathy. In summary, the temporal relationship between montelukast administration and the onset of neuropathy, would make the latter more likely as an "adverse drug reaction". Despite this, no significant clinical neither neurophysiological differences were noted between the two groups.

[The clinical electrophysiology and pathological characteristics of 15 cases of vasculitic neuropathy]

OBJECTIVE

To summarize the clinical features, electrophysiology and neuropathological characteristics of peripheral nerves in patients with vasculitic neuropathy.

METHODS

We retrospectively analyzed the clinical, electrophysiology and neuropathological characteristics of 15 patients with vasculitic neuropathy who underwent electrophysiology and sural nerve biopsy in our department from January 2009 to June 2013.

RESULTS

There were 8 males and 7 females, aged from 38 to 82 years old, with a peripheral neuropathy course ranged from 0.5 month to 60 months. In the total of 15 patients, 3 patients were diagnosed as nonsystemic vasculitic neuropathy, while the other 12 patients were diagnosed as systemic vasculitis neuropathy (SVN) including 5 cases of primary systemic vasculitis and 7 cases of secondary systemic vasculitis. In patients diagnosed as primary systemic vasculitis, there were 2 cases of Churg-Strass syndrome (CSS) and 3 cases of ANCA associated vasculitis. In patients diagnosed as secondary systemic vasculitis, there were 1 case of systemic lupus erythematosus (SLE), 2 cases of sicca syndrome (SS), 3 cases of rheumatoid arthritis (RA), 1 case of Behcet' s disease associated with thyroid papillary carcinoma, 1 case of hepatitis B and 1 case of RA-associated SS. For the pathological features of vasculitic neuropathy, type 1 lesion was found in 4 patients, type 2 lesion in 2 patients, and type 3 lesion in 9 patients. Axon degeneration was observed in 8 patients, while 7 patients manifested as axon degeneration associated with demyelination and local thickening of the perineurium was found in 2 patients.

CONCLUSION

Multiple mononeuropathy and asymmetric polyneuropathy are the common clinical presentations of vasculitic neuropathy. Electrodiagnostic testing almost always reveals the evidence of a predominantly axonal and sensorimotor process with associated demyelination presented in some cases. Sural nerve biopsy shows changes indicative of an axonopathy.

Fibrolipomatous hamartoma of sural nerve: a new site of an unusual lesion

Neural fibrolipomatous hamartoma is a rare benign tumour commonly involving the median nerve. Other less frequently involved nerves include the ulnar, radial, brachial plexus, superficial peroneal nerve, inferior calcaneal nerve and median plantar nerve. Involvement of sural nerve has not been reported in the available literature so far. A three-year-old female child presented with a painless swelling over the posterolateral aspect of left leg with no associated motor or sensory deficits. Radiological investigations revealed a fat density lesion with interspersed neural element in the subcutaneous plane of the left leg. Histopathological examination of the excised specimen showed features of a fibrolipomatous hamartoma of the nerve. This report describes the occurrence of fibrolipomatous hamartoma in the sural nerve for the first time in the literature. This rare tumour should be considered in the differential diagnosis of such lesions.

Treatable childhood neuronopathy caused by mutations in riboflavin transporter RFVT2

Childhood onset motor neuron diseases or neuronopathies are a clinically heterogeneous group of disorders. A particularly severe subgroup first described in 1894, and subsequently called Brown-Vialetto-Van Laere syndrome, is characterized by progressive pontobulbar palsy, sensorineural hearing loss and respiratory insufficiency. There has been no treatment for this progressive neurodegenerative disorder, which leads to respiratory failure and usually death during childhood. We recently reported the identification of SLC52A2, encoding riboflavin transporter RFVT2, as a new causative gene for Brown-Vialetto-Van Laere syndrome. We used both exome and Sanger sequencing to identify SLC52A2 mutations in patients presenting with cranial neuropathies and sensorimotor neuropathy with or without respiratory insufficiency. We undertook clinical, neurophysiological and biochemical characterization of patients with mutations in SLC52A2, functionally analysed the most prevalent mutations and initiated a regimen of high-dose oral riboflavin. We identified 18 patients from 13 families with compound heterozygous or homozygous mutations in SLC52A2. Affected individuals share a core phenotype of rapidly progressive axonal sensorimotor neuropathy (manifesting with sensory ataxia, severe weakness of the upper limbs and axial muscles with distinctly preserved strength of the lower limbs), hearing loss, optic atrophy and respiratory insufficiency. We demonstrate that SLC52A2 mutations cause reduced riboflavin uptake and reduced riboflavin transporter protein expression, and we report the response to high-dose oral riboflavin therapy in patients with SLC52A2 mutations, including significant and sustained clinical and biochemical improvements in two patients and preliminary clinical response data in 13 patients with associated biochemical improvements in 10 patients. The clinical and biochemical responses of this SLC52A2-specific cohort suggest that riboflavin supplementation can ameliorate the progression of this neurodegenerative condition, particularly when initiated soon after the onset of symptoms.

Hepatitis C virus-associated neuropathy accompanied by eosinophilic vasculitis and granuloma formation

We herein report the case of a patient with hepatitis C virus (HCV)-associated neuropathy with atypical pathological findings of a biopsied sural nerve. A 48-year-old man was admitted for a gait disturbance. Purpura and edema on the legs and hyperalgesia on the distal extremities were noted. The plasma HCV viral load was high, and cryoglobulin was positive. In the biopsied sural nerve, perivascular eosinophilic infiltration was associated with extravascular granuloma formation in the epineurium. The patient's symptoms disappeared following treatment with interferon-α and ribavirin. The present case suggests that HCV infection can lead to peripheral neuropathy associated with eosinophilic infiltration and granuloma formation.

Uncommon pathological findings in sural nerve biopsy from a patient with Churg-Strauss related multiple mononeuropathy

We describe a patient with severe multiple mononeuropathy associated with hypereosinophilia, asthma and pulmonary non cavitating micronodules. Sural nerve biopsy revealed marked perineural thickening and microfasciculation with inflammatory infiltrates in the perinerium and in the epinerium. The patient markedly improved with steroid therapy. Our final diagnosis was Churg-Strauss related multiple mononeuropathy. Thus, we report a case of Churg-Strauss related multiple mononeuropathy with uncommon pathological findings on sural nerve and we underline the importance of clinical evaluation for this diagnosis.

Deficiency of the E3 ubiquitin ligase TRIM2 in early-onset axonal neuropathy

Inherited peripheral neuropathies are a heterogeneous group of disorders that can affect patients of all ages. Children with inherited neuropathy often develop severe disability, but the genetic causes of recessive early-onset axonal neuropathies are not fully known. We have taken a whole-exome sequencing approach to identify causative disease mutations in single patients with early-onset axonal neuropathy. Here, we report compound heterozygous mutations in the tripartite motif containing 2 (TRIM2) gene in a patient with childhood-onset axonal neuropathy, low weight and small muscle mass. We show that the patient fibroblasts are practically devoid of TRIM2, through mRNA and protein instability caused by the mutations. TRIM2 is an E3 ubiquitin ligase that ubiquitinates neurofilament light chain, a component of the intermediate filament in axons. Resembling the findings in our patient's sural nerve biopsy, Trim2-gene trap mice showed axonopathy with accumulations of neurofilaments inside axons. Our results suggest that loss-of-function mutations in TRIM2 are a cause of axonal neuropathy, which we propose to develop as a consequence of axonal accumulation of neurofilaments, secondary to lack of its ubiquitination by TRIM2.

A clinically relevant rodent model of the HIV antiretroviral drug stavudine induced painful peripheral neuropathy

HIV-associated sensory neuropathy is the most frequent manifestation of HIV disease, afflicting 40-50% of patients whose HIV disease is otherwise controlled by antiretroviral therapy. It often presents with significant neuropathic pain and is consistently associated with previous exposure to nucleoside reverse transcriptase inhibitors including stavudine (d4T), which is widely used in resource-limited settings. Here we investigated complex pain-related behaviours associated with d4T treatment using ethologically relevant thigmotaxis and burrowing behaviours in adult rats. Detailed neuropathological response was also examined using neurochemistry, electron microscopy, and proteomics. After 2 intravenous injections of d4T (50 mg/kg, 4 days apart), rats developed hind paw mechanical hypersensitivity, which plateaued at 21 days after initial d4T injection, a time that these animals also had significant changes in thigmotaxis and burrowing behaviours when compared to the controls; reductions in hind paw intraepidermal nerve fibre density and CGRP/IB4 immunoreactivity in L5 spinal dorsal horn, suggesting injury to both the peripheral and central terminals of L5 dorsal root ganglion neurons; and increases in myelinated and unmyelinated axon diameters in the sural nerve, suggesting axonal swelling. However, no significant glial and inflammatory cell response to d4T treatment was observed. Sural nerve proteomics at 7 days after initial d4T injection revealed down-regulated proteins associated with mitochondrial function, highlighting distal axons vulnerability to d4T neurotoxicity. In summary, we have reported complex behavioural changes and a distinctive neuropathology in a clinically relevant rat model of d4T-induced sensory neuropathy that is suitable for further pathophysiological investigation and preclinical evaluation of novel analgesics.

[Autoimmune autonomic ganglionopathy and acute autonomic and sensory neuropathy]

Autonomic neuropathies may occur primarily or secondarily to various underlying diseases. Primary autonomic neuropathies are divided into pure autonomic neuropathy, autonomic neuropathy with sensory impairment, and autonomic neuropathy with sensory and motor impairment based on the concomitance or absence of sensory or motor dysfunctions. Autoimmune autonomic ganglionopathy refers to a pure autonomic neuropathy, which typically affects both cholinergic and adrenergic functions. About a half of the patients with autoimmune autonomic ganglionopathy are positive for anti-ganglionic acetylcholine receptor antibodies. The mode of progression widely ranges from acute to chronic, including that mimicking pure autonomic failure. The number of unmyelinated fibers in the sural nerve biopsy specimens tends to decrease with the duration of disease become longer. Immunomodulatory treatments are suggested to be effective for autoimmune autonomic ganglionopathy. Acute autonomic and sensory neuropathy is characterized by autonomic and sensory impairment without motor dysfunction that reaches its nadir within a short period of time mimicking the progression of Guillain-Barré syndrome. The monophasic clinical course and frequent presence of a history of antecedent infections suggests a participation of immune mechanisms. The initial symptoms are those related to autonomic disturbance or superficial sensory impairment, while deep sensory impairment accompanied by sensory ataxia subsequently appears in some patients. Sural nerve biopsy specimens reveal small-fiber predominant axonal loss, and autopsy cases show neuronal loss in the thoracic sympathetic and dorsal root ganglia. Hence, small neurons in the autonomic and sensory ganglia may be affected in the initial phase and, subsequently, large neurons in the sensory ganglia are damaged in acute autonomic and sensory neuropathy.

Rapid reversal of uremic neuropathy following renal transplantation in an adolescent

Clinical and pathologic studies on adults with uremic neuropathy are numerous, but less is known about this disorder in children and adolescents. We report the clinical, electrophysiologic, and pathologic findings in an adolescent female with uremic neuropathy. Electrophysiologic findings were consistent with a primarily axonal sensorimotor polyneuropathy. Sural nerve biopsy revealed areas of focal depletion in myelin sheaths and loss of axons. Axonal degeneration with secondary myelin changes appears to be the characteristic pathology in this case, one of the youngest to our knowledge for which nerve biopsy data are available. Our patient experienced dramatic recovery after renal transplantation, similar to the reports of older patients.

[Polyneuropathy associated with monoclonal gammopathy of undetermined significance]

The prevalence of polyneuropathy in patients with monoclonal gammopathy of undetermined significance (MGUS) has been reported to be 10-50%. The majority of patients have a chronic, slowly progressive, distal, symmetric and predominantly sensory polyneuropathy. A caused relationship between polyneuropathy and immunoglobulin (Ig)M MGUS is better established than the relationship between polyneuropathy and IgG/IgA MGUS because of the observed binding of IgM to myelin sheaths and widening of myelin lamellae. In randomized controlled trials plasma exchange, immunosuppressive, rituximab and intravenous Ig have been found to have a clinical meaningful effect.

[Occupational toxic neuropathies: morphology in peripheral nerve biopsies]

Many peripheral neuropathies are caused by the (acute or chronic) toxic action of metals, solvents, pesticides, and other occupational and environmental contaminants. These agents often reproduce the anatomoclinical pictures of hereditary (e.g., Charcot-Marie-Tooth disease), autoimmune (Guillain-Barrè syndrome), or dysmetabolic (thiamine deficiency, diabetic neuropathy) forms. Toxic peripheral neuropathies can be classified on the basis of etiology, clinical features (sensitive, motor, sensitive-motor), or histopathology: neuronopathies (uncommon, mostly secondary to retrograde axonal degeneration; e.g., arsenic, thallium), axonopathies (acrylamide, esacarbons, CS2, organophosphate-induced delayed neuropathy), myelinopathies (trichloroethylene), mixed forms (axonal and demyelinating: lead). For many substances, experimental research has led to the identification of the molecular and cellular targets of neurotoxicity. Several compounds are active by biotransformation (e.g., the esacarbons n-hexane and MnBK are neurotoxic since they are metabolized to 2,5-hexanedione), Genetic, physiological and environmental factors determine the individual metabolic set-up, and they may give origin to differences in the workers' sensitivity. Cessation of exposure is often followed by (microscopically observable) regenerative phenomena and clinical improvement. The morphology of neuropathies can be studied through peripheral nerve biopsy. Samples of sural nerve (or other nervous trunks of the limbs), adequately fixed, sectioned, and stained, allow the observation of alterations in axonal fibres (e.g., giant-axonal neuropathy, dying back neuropathy), myelin (demyelination), Schwann cells, interstitium, and blood vessels; possible inflammatory infiltrates; fibre density; regenerative phenomena (growth cone, remyelination). In occupational medicine, biopsy is indicated when the anamnestic-clinical picture, laboratory tests, and instrumental exams leave doubts about the nature, type, and entity of the neurological damage. In such cases, current optical and electron microscopy techniques can be very useful for injury evaluation, prognosis, and follow-up.

Small fiber neuropathy: is skin biopsy the holy grail?

Small fiber neuropathy (SFN) is characterized by negative sensory symptoms (thermal and pinprick hypoesthesia) reflecting peripheral deafferentation and positive sensory symptoms and signs (burning pain, allodynia, hyperalgesia), which often dominate the clinical picture. In patients with pure SFN, clinical and neurophysiologic investigation do not show involvement of large myelinated nerve fiber making the diagnosis of SFN challenging in clinical practice. Over the last 15 years, skin biopsy has emerged as a novel tool that readily permits morphometric and qualitative evaluation of somatic and autonomic small nerve fibers. This technique has overcome the limitations of routine neurophysiologic tests to detect the damage of small nerve fibers. The recent availability of normative reference values allowed clinicians to reliably define the diagnosis of SFN in individual patients. This paper reviews usefulness and limitations of skin biopsy and the relationship between degeneration and regeneration of small nerve fibers in patients with diabetes and metabolic syndrome.

Sub-acute demyelinating polyradiculoneuropathy as an initial symptom of peripheral T cell lymphoma, not otherwise specified (PTCL-NOS)

Here we report the first case of peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS), who initially presented with peripheral neuropathy. Nerve conduction, cerebral spinal fluid studies and his clinical course were compatible with sub-acute demyelinating polyradiculoneuropathy. In addition, left cervical lymph node swelling was observed on admission. Diagnosis of PTCL-NOS was made by the histological, immunohistochemical, and Southern blot analyses on the biopsy specimen from the enlarged lymph node. Combination chemotherapy composed of cyclophosphamide, vincristine, doxorubicin and prednisolone (CHOP) was effective for polyneuropathy as well as for lymphoma. Several antibodies relating to paraneoplastic syndrome such as Ma1, Ma2, Amphiphysin, CV2, Ri, Yo and Hu were all negative. Because sural nerve biopsy performed prior to CHOP therapy revealed no infiltration of lymphoma cells, immune dysfunction mediated by some cytokine or unidentified autoantibody related to PTCL-NOS was thought to be involved in the polyradiculoneuropathy.

Colony-stimulating factor-1 mediates macrophage-related neural damage in a model for Charcot-Marie-Tooth disease type 1X

Previous studies in our laboratory have shown that in models for three distinct forms of the inherited and incurable nerve disorder, Charcot-Marie-Tooth neuropathy, low-grade inflammation implicating phagocytosing macrophages mediates demyelination and perturbation of axons. In the present study, we focus on colony-stimulating factor-1, a cytokine implicated in macrophage differentiation, activation and proliferation and fostering neural damage in a model for Charcot-Marie-Tooth neuropathy 1B. By crossbreeding a model for the X-linked form of Charcot-Marie-Tooth neuropathy with osteopetrotic mice, a spontaneous null mutant for colony-stimulating factor-1, we demonstrate a robust and persistent amelioration of demyelination and axon perturbation. Furthermore, functionally important domains of the peripheral nervous system, such as juxtaparanodes and presynaptic terminals, were preserved in the absence of colony-stimulating factor-1-dependent macrophage activation. As opposed to other Schwann cell-derived cytokines, colony-stimulating factor-1 is expressed by endoneurial fibroblasts, as revealed by in situ hybridization, immunocytochemistry and detection of β-galactosidase expression driven by the colony-stimulating factor-1 promoter. By both light and electron microscopic studies, we detected extended cell-cell contacts between the colony-stimulating factor-1-expressing fibroblasts and endoneurial macrophages as a putative prerequisite for the effective and constant activation of macrophages by fibroblasts in the chronically diseased nerve. Interestingly, in human biopsies from patients with Charcot-Marie-Tooth type 1, we also found frequent cell-cell contacts between macrophages and endoneurial fibroblasts and identified the latter as main source for colony-stimulating factor-1. Therefore, our study provides strong evidence for a similarly pathogenic role of colony-stimulating factor-1 in genetically mediated demyelination in mice and Charcot-Marie-Tooth type 1 disease in humans. Thus, colony-stimulating factor-1 or its cognate receptor are promising target molecules for treating the detrimental, low-grade inflammation of several inherited neuropathies in humans.

Sural nerve pathology in ALS patients: a single-centre experience

Amyotrophic lateral sclerosis (ALS) is a progressive degenerative disease of upper and lower motor neurons. Sensory involvement is thought not to be a feature of ALS. We reviewed 17 cases of sural nerve biopsies performed in a large cohort of ALS patients referred to our centre over a 23-year period. More than two-third of biopsies revealed a variable degree of axonal loss. In one case, pathological findings suggested the concomitant presence of an inherited neuropathy, subsequently confirmed by genetic evaluation. In another case, pathological and neurographic data were similar to those of an inflammatory demyelinating neuropathy, but the clinical course corroborated the diagnosis of ALS. Our data confirm that sensory nerve involvement may be found in ALS patients. This finding should prompt physicians to carefully investigate a possible alternative diagnosis, but does not exclude the possibility that the patient may have ALS.

Characterizing the phenotypic manifestations of MFN2 R104W mutation in Charcot-Marie-Tooth type 2

Mutations of the mitofusin 2 (MFN2) gene have been reported to be the most common cause of the axonal form of Charcot-Marie-Tooth disease (CMT). The aim of this study was to describe a de novo MFN2 p.R104W mutation and characterize the associated phenotype. We screened the entire coding region of MFN2 gene and characterized its clinical phenotype, nerve conduction studies and sural nerve biopsy. Neuropsychological tests and brain MRI were also performed. A de novo mutation was found in exon 4 (c.310C>T; p.R104W). In addition to a severe and early onset axonal neuropathy, the patient presented learning problems, obesity, glucose intolerance, leukoencephalopathy, brain atrophy and evidence of myelin involvement and mitochondrial structural changes on sural nerve biopsy. These results suggest that MFN2 p.R104W mutation is as a hot-spot for MFN2 gene associated to a large and complex range of phenotypes.

Acute autonomic sensory and motor neuropathy associated with parvovirus B19 infection

We report a 9-year-old girl with acute autonomic sensory and motor neuropathy (AASM) associated with human parvovirus B19 (HPV-B19) infection. The patient presented with fever, erythema of the entire body, and abdominal pain with vomiting. The titer of HPV-B19 IgM antibody was significantly elevated. Symptoms such as muscle weakness, severe hyperesthesia, dyshidrosis, and neurogenic bladder associated with autonomic disturbance developed over several days. Intravenous immunoglobulin therapy gave no obvious improvement of her symptoms. Motor and sensory impairment improved slowly without medical treatment, but dysautonomia persisted for a long time. Sural nerve biopsy revealed axonal degeneration of small fibers, involving both myelinated and unmyelinated fibers, which is compatible with the autonomic sensory and motor neuropathy. AASM is very rare in pediatric populations, and there is no report of AASM associated with HPV-B19 infection.