Sural Nerve Biopsy Research Articles

Activated Schwann cells and increased inflammatory cytokines IL-1β, IL-6, and TNF-α in patients' sural nerve are lack of tight relationship with specific sensory disturbances in Parkinson's disease.

AimsNeuroinflammation is one of the most important processes in the pathogenesis of Parkinson's disease (PD). Sensory disturbances are common in patients with PD, but the underlying pathophysiological mechanisms remain unknown. This study aimed to characterize the activation of Schwann cells (SCs) and the increase of expression of inflammatory cytokines IL‐1β, IL‐6, and TNF‐α in the sural nerve of PD, and further explore whether peripheral nerve inflammation is the cause of PD sensory disturbances.MethodsA total of 14 patients with PD (including 5 with sensory disturbances and 9 without sensory disturbances) and 6 controls were included. The excitation and conduction function of sural nerve was detected by sural nerve electrophysiological examination. With sural nerve biopsy samples, ultrastructural changes of sural nerve were observed by electron microscopy; Schwann cell biomarker glial fibrillary acid protein (GFAP) and inflammatory cytokines including interleukin‐1beta (IL‐1β), interleukin 6 (IL‐6), and tumor necrosis factor‐alpha (TNF‐α) were detected by immunohistochemistry, and the outcome of immunostaining slice was semiquantitatively counted; double immunofluorescence was used to identify the locus immunoreactive for inflammatory cytokines.ResultsCompared with healthy controls, nerve conduction velocity (NCV) slowed down and sensory nerve action potential (SNAP) amplitude decreased in PD patients, accompanied by axonal degeneration and demyelinating lesions, and expression of GFAP and inflammatory cytokines was increased. Inflammatory cytokines were significantly colocalized with GFAP and slightly colocalized with NF. These indicators did not differ significantly between PD patients with and without sensory disturbances.ConclusionOur study results suggest that peripheral sensory nerve injury exists in PD patients, accompanied by Schwann cell activation and inflammation, thus demonstrate peripheral nerve inflammation participates in the pathophysiological process of PD but it is not necessarily related to the patient's sensory disturbance.

Diagnostic Value of Sural Nerve Biopsy: Retrospective Analysis of Clinical Cases From 1981 to 2017.

Nerve biopsy represents the conclusive step in the diagnostic work-up of peripheral neuropathies, and its diagnostic yield is still debated. The aim of this study is to consider the impact of nerve biopsy on reaching a useful diagnosis in different peripheral neuropathies and its changing over time. We retrospectively analyzed 1,179 sural nerve biopsies performed in the period 1981–2017 at Neurological Clinic of Policlinico San Martino (Genoa). We relied on medical records and collected both clinical and pathological data in a database. Biopsy provided univocal diagnoses in 53% of cases (with an increase over time), multiple diagnostic options in 14%, while diagnosis was undetermined in 33% (undetermined reports decreased during the years). In 57% of patients, the pre-biopsy suspicion was confirmed, while in 43% sural biopsy modified the clinical diagnosis. The highest yield was in axonal neuropathies (29% undetermined reports vs. 40% in demyelinating and 48% in mixed neuropathies). In 68% of patients with vasculitic neuropathy, this etiology was already suspected, whereas in 32% nerve biopsy modified the clinical diagnosis. During the years, the number of annually performed biopsies decreased significantly (p = 0.007), with an increase in the mean age of patients (p < 0.0001). The percentage of hereditary neuropathies had a significant decrease (p = 0.016), while the rate of vasculitic and chronic inflammatory neuropathies increased (p < 0.0001). This is the largest Italian study addressing the yield of sural nerve biopsy. During the years, we observed a progressive refinement of the indication of this procedure, which confirms its utility for interstitial neuropathies, particularly if non-systemic vasculitic neuropathy is suspected.

Sural nerve biopsy in peripheral neuropathies: 30-year experience from a single center.

Nerve biopsy has been widely used to investigate patients with peripheral neuropathy, and in many centers, it is still a useful diagnostic tool in this setting. In this study, we reviewed the histopathological spectrum of the nerve biopsies performed in our center in a 30-year period and we analyzed their relevance in the clinical setting. Retrospective analysis of the retrieved data was done for cases of nerve biopsies performed in our institute between 1988 and 2018. Surgical technique and histopathological analysis were done accordingly to standard protocol. Complete clinical and pathological data were available only for 717 cases. The procedure was generally safe, with only 0.3% superimposed infection. Main pathological results were "unspecific" axonal polyneuropathy (49.8%), vasculitis neuropathy (9.3%), acquired demyelinating neuropathy (8.9%), and Charcot-Marie-Tooth (8.2%). Considering clinical-neurophysiological suspicionof vasculitis, nerve biopsy confirmed the diagnosis in 60.9% of cases. In conclusion, for inherited neuropathies, we do not recommend this invasive procedure, but we strongly suggest a genetic test. Conversely, in vasculitic neuropathies or in dysimmune neuropathies not clearly confirmed by neurophysiological examination, nerve biopsy continues to represent a useful and irreplaceable tool.

2309 Vasculitic Mononeuritis Multiplex Mimicking Bilateral Carpal Tunnel Syndrome: A Diagnostic Challenge

INTRODUCTION: Cryoglobulinemic vasculitis(CV) can have variety of presentations including palpable purpura, arthralgias, glomerulonephritis, peripheral neuropathy, lymphadenopathy, hepatosplenomegaly, and hypocomplementemia. We present a patient with bilateral hand mononeuritis multiplex secondary to hepatitis C related CV. CASE DESCRIPTION/METHODS: A 52-year-old man with untreated hepatitis C (Viral load 520388, Genotype 1b), diabetes mellitus type II, hypertension and chronic kidney disease, presented with two months of bilateral hand pain. He also complained of numbness and tingling over the palmar aspects of the medial three digits of his hands, in addition to his medial left foot. He had no rash, arthritis, fevers, or weight loss. Physical exam was significant for positive Tinel's sign bilaterally, with weakness on finger extension, flexion and decreased power of interossei. Fundoscopy demonstrated non proliferative diabetic retinopathy (NPDR).Laboratory work-up revealed negative ANA, C-ANCA, MPO/PR3, HIV and RPR. Vitamin B12 and TSH levels were normal. However, serum cryoglobulins were positive with low C3, C4 and nephrotic range proteinuria Electromyography showed non-length-dependent neuropathy, which was more suggestive of mononeuritis multiplex rather than carpal tunnel syndrome (CTS). Sural nerve biopsy was performed and revealed vasculopathic changes consistent with vasculitis. He was diagnosed with mononeuritis multiplex secondary to hepatitis C related cryoglobulinemia. Immunosuppresive treatment was withheld because the patient tested positive for latent Tuberculosis (TB). He is currently undergoing treatment for the latent TB. DISCUSSION: CV is a small-to-medium-vessel vasculitis that occurs in 10 to 15 percent of patients chronically infected with hepatitis C virus (HCV). The two competing diagnosis for our patient’s neurological symptoms were diabetic neuropathy and CV secondary to untreated Hepatitis C. NPDR favored the microvascular complications of diabetes but the rapid onset of symptoms, positive cryoglobulins in the setting of HCV infection and sural nerve biopsy helped to establish the diagnosis of CV. This case is especially unique because it’s a very rare extrahepatic manifestation of HCV infection .Management of HCV cryoglobulinemic vasculitis involves administration of immunosuppressive therapy such as rituximab and antivirals but all patients should be tested and treated for latent TB prior to treatment initiation.

PULMONARY FIBROSIS AND FOOT DROP: A CASE OF MICROSCOPIC POLYANGIITIS FOLLOWING IDIOPATHIC PULMONARY FIBROSIS (IPF) DIAGNOSIS

SESSION TITLE: Tuesday Fellows Case Report Posters SESSION TYPE: Fellow Case Report Posters PRESENTED ON: 10/22/2019 01:00 PM - 02:00 PM INTRODUCTION: Pulmonary fibrosis (PF) associated with antineutrophil cytoplasmic antibody (ANCA) is a rare but described diagnosis, with some patients meeting criteria for microscopic polyangiits (MPA). Conversion to ANCA-MPO positivity and MPA with vasculitic findings can lag behind the initial diagnosis of PF. CASE PRESENTATION: We present a case of a 75 year old man with a history of a bladder tumor and PF who presented to clinic with 6 months of worsening cough, fatigue, weight loss and neuropathy. His PF was initially diagnosed 1 year prior and considered idiopathic. At that time he had an abnormal CT chest, significantly decreased DLCO, positive ANA, and normal inflammatory markers. Approximately one year later he complained of progressive cough, fatigue and weight loss, and was hospitalized for anemia and leukocytosis with an unrevealing workup. He was prescribed antibiotics for Aeromonas pneumonia. He then presented to clinic where his physical exam was notable for mild tachypnea, left foot drop and right hand numbness. PFTs revealed a significant decline in vital capacity and DLCO. He was admitted and workup revealed CT chest with new infiltrates, an elevated ANA, elevated ESR/CRP and elevated ferritin. ANCA- MPO was positive. He underwent sural nerve and skeletal muscle biopsy which showed necrotizing vasculitis with fibrinoid necrosis, and he was started on high dose steroids. He improved and was discharged to home to start rituximab infusion as outpatient. DISCUSSION: Pulmonary fibrosis associated with ANCA vasculitis is rare and typically associated with MPA. Case studies have placed prevalence of ANCA positive PF from 2-14% of PF patients initially considered idiopathic. Of those patients, about half had seroconversion/develop MPA after initial PF diagnosis. CT imaging for ANCA-MPO patients may be indistinguishable IPF on imaging with a UIP pattern of fibrosis. The pathogenesis of ANCA-MPO associated fibrosis is unclear, but possibly related to recurrent alveolar hemorrhage, direct damage from neutrophils or ANCA induced by a pulmonary inflammatory process. ANCA positive PF patients are more likely to be treated with steroids and immunosuppression including cyclophosphamide or ritxumab. These treatments may be useful in early disease, but likely have limited efficacy in late stage/fibrotic disease. Patients with MPA and PF have a clinical progression similar to patients with IPF, with worse survival compared to MPA patients without PF. Not all PF patients with ANCA-MPO positivity develop systemic vasculitis, however, clinicians should be on alert for signs and symptoms of systemic disease as early intervention could prevent progression. CONCLUSIONS: It is important to consider ANCA vasculitis both at the time of diagnosis of pulmonary fibrosis and later in a patient’s clinical course. Reference #1: Casares MF, Gonzales MF, Caputo F, Bottinelli Y, Zamboni M. Microscopic polyangiitis associated with pulmonary fibrosis. Clin Rheumatol 2015 34:1273-1277. Reference #2: Kagiyama N, Takayanagi N, Kanauchi T, et al. Antineutrophil cytoplasmic antibody-positive conversion and microscopic polyangiitis development in patients with idiopathic pulmonary fibrosis.BMJ Open Respiratory Research 2015;2:e000058. Reference #3: Tzelepis GE, Kokosi M, Tzioufas A, et al. Prevalence and outcome of pulmonary fibrosis in microscopic polyangiitis. Eur Resp J 2010; 36:116-121 DISCLOSURES: No relevant relationships by Samantha Parker, source=Web Response

P.19Novel aspects in immune-mediated necrotizing myopathy with pipestem capillaries

Immune-mediated necrotizing myopathy with pipestem capillaries are very rare inflammatory myopathies that are characterized by combination of necrotizing myopathy and presence of enlarged capillary walls, strongly staining for complement (C5b-9) and homogeneously thickened basement membranes on electron microscopy. In the past, there have been anecdotal reports on single cases or series of very few patients. Here we report on a series of 15 patients collected during a 10-years period of time. 3/15 of patients suffered from cancer or developed cancer during follow-up. 8/15 of patients had severe systemic inflammatory disease – mostly rheumatologic diseases and 10/15 of them also had nerve involvement including presence of pipestem capillaries and inflammatory changes in sural nerve biopsies. Morphologically, all skeletal muscle biopsies showed sarcolemmal MHC class I stains and many of them showed sarcolemmal MHC class II positivity. Complement (C5b-9) strongly stained capillary walls in 10/15 in the entire biopsy and in 5/15 cases in parts of the biopsy. Strong and complete stain correlated with severe atrophy of the myofibres. We show that atrophic fibers are not regenerating fibers (MHC neo negative) and highlight relevance of molecular markers involved in atrophy. Another interesting feature is presence of numerous cytoplasmic bodies (6/15) and non-rimmed vacuoles (7/15) mostly in severely affected biopsies. This is the largest series of IMNM with pipestem capillaries reported so far. Clinically the association with cancer and with severe inflammatory diseases is of prognostic relevance. Morphologically, we present novel features highlighting atrophy as well as cytoplasmic bodies as relevant features in these biopsies.

Reduced gene expression of netrin family members in skin and sural nerve specimens of patients with painful peripheral neuropathies.

To investigate the expression of axon guidance cues in skin and sural nerve biopsies of patients with polyneuropathies (PNP) as potential markers of nerve de- and regeneration and inflammation. We prospectively recruited 88 patients with PNP and compared data between patient subgroups and healthy controls. All patients underwent skin punch and/or sural nerve biopsy at the lower leg and proximal thigh. We characterized gene expression profiles of netrin family members as target genes involved in neuronal de- and regeneration [netrin 1, deleted in colorectal cancer (DCC), uncoordinated5H2, neogenin 1 (NEO1), netrin G1, netrin G2] using quantitative real-time PCR. Gene expression of netrin 1 (p < 0.05 in proximal skin), DCC (p < 0.001 in distal skin), NEO1 (p < 0.05 in distal skin), netrin G1 (p < 0.05 in proximal and p < 0.01 in distal skin), and netrin G2 (p < 0.001 in distal skin) was lower in skin biopsies of patients with neuropathy compared to healthy controls. Gene expression of NEO1 (p < 0.05 in distal skin), netrin G2 (p < 0.05 in distal skin), and DCC (p < 0.05 in sural nerve) was lower in samples of patients with painful compared to painless PNP and also correlated positively with intraepidermal nerve fiber density. Skin and sural nerve gene expression of the investigated target genes did not differ between neuropathies of different etiologies. We show reduced cutaneous and neural axon guide expression, which may contribute to a dysregulation of nerve fiber de- and regeneration.

Arsenic Neurotoxicity in Humans.

Arsenic (As) contamination affects hundreds of millions of people globally. Although the number of patients with chronic As exposure is large, the symptoms and long-term clinical courses of the patients remain unclear. In addition to reviewing the literature on As contamination and toxicity, we provide useful clinical information on medical care for As-exposed patients. Further, As metabolite pathways, toxicity, speculated toxicity mechanisms, and clinical neurological symptoms are documented. Several mechanisms that seem to play key roles in As-induced neurotoxicity, including oxidative stress, apoptosis, thiamine deficiency, and decreased acetyl cholinesterase activity, are described. The observed neurotoxicity predominantly affects peripheral nerves in sensory fibers, with a lesser effect on motor fibers. A sural nerve biopsy showed the axonal degeneration of peripheral nerves mainly in small myelinated and unmyelinated fibers. Exposure to high concentrations of As causes severe central nervous system impairment in infants, but no or minimal impairment in adults. The exposure dose–response relationship was observed in various organs including neurological systems. The symptoms caused by heavy metal pollution (including As) are often nonspecific. Therefore, in order to recognize patients experiencing health problems caused by As, a multifaceted approach is needed, including not only clinicians, but also specialists from multiple fields.

112 Axonal polyneuropathy with onset in young adulthood due to TUBB3 mutation

IntroductionThe TUBB3 gene encodes the protein Beta-tubulin isotype III, a component of the microtubule cytoskeleton. Mutations in this gene have been associated with axonal polyneuropathy, however usually associated with congenital fibrosis of the extraocular muscles (CFOEM) and other abnormalities of cerebral development.1 2 We report a case of isolated neuropathy associated with a TUBB3 mutation.MethodsCase report - clinical information and next generation sequencing results were obtained.ResultsA 64 year old man presented with a severe, progressive, length dependent sensorimotor polyneuropathy which commenced in his late twenties. There was no clinical involvement of the extraocular muscles and cognition was normal. Family history was limited, but there were no other members affected.The patient had previously been extensively investigated including sural nerve biopsy, which confirmed axonal neuropathy without a specific diagnosis. Intravenous immunoglobulins and steroids had been trialled without benefit.A neuromuscular gene panel utilising next generation sequencing was performed and demonstrated heterozygosity for a variant of the TUBB3 gene (D417N substitution).Case series describing TUBB3 mutations show a large heterogeneity in phenotypic expression depending on the amino acid substitution.2–4 There is also heterogeneity in patients with D417N mutations, although a small number have been reported to develop a polyneuropathy without CFOEM1.ConclusionsThis case strengthens previous reports that TUBB3 mutation can be associated with a pure, axonal, sensorimotor polyneuropathy and highlights the use of next generation sequencing in streamlining the diagnostic process.ReferenceTischfield M, et al. Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance. Cell 2010;140(1):pp.74–87.Ncbi.nlm.nih.gov. (2019). Congenital fibrosis of the extraocular muscles - Conditions - GTR - NCBI. [online] Available at: https://www.ncbi.nlm.nih.gov/gtr/conditions/CN043677/ [Accessed 14 Feb. 2019].Omim.org. (2019). OMIM Entry - * 602661 - TUBULIN, BETA-3; TUBB3. [online] Available at: https://www.omim.org/entry/602661 [Accessed 14 Feb. 2019].Krupa, K. and Bekiesinska-Figatowska, M. (2013). Congenital and Acquired Abnormalities of the Corpus Callosum: A Pictorial Essay. BioMed Research International, 2013, pp.1–14.

Clinicopathological characteristics of subtypes of chronic inflammatory demyelinating polyradiculoneuropathy

ObjectiveTo evaluate the clinical and pathological correlations characterising each clinical subtype of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP).MethodsWe assessed 106 consecutive patients who had CIDP fulfilling the European Federation of Neurological...

Intraepidermal Nerve Fiber Analysis in Human Patients and Animal Models of Peripheral Neuropathy: A Comparative Review.

Analysis of intraepidermal nerve fibers (IENFs) in skin biopsy samples has become a standard clinical tool for diagnosing peripheral neuropathies in human patients. Compared to sural nerve biopsy, skin biopsy is safer, less invasive, and can be performed repeatedly to facilitate longitudinal assessment. Intraepidermal nerve fiber analysis is also more sensitive than conventional nerve histology or electrophysiological tests for detecting damage to small-diameter sensory nerve fibers. The techniques used for IENF analysis in humans have been adapted for large and small animal models and successfully used in studies of diabetic neuropathy, chemotherapy-induced peripheral neuropathy, HIV-associated sensory neuropathy, among others. Although IENF analysis has yet to become a routine end point in nonclinical safety testing, it has the potential to serve as a highly relevant indicator of sensory nerve fiber status in neurotoxicity studies, as well as development of neuroprotective and neuroregenerative therapies. Recently, there is also interest in the evaluation of IENF via skin biopsy as a biomarker of small fiber neuropathy in the regulatory setting. This article provides an overview of the anatomic and pathophysiologic principles behind IENF analysis, its use as a diagnostic tool in humans, and applications in animal models with focus on comparative methodology and considerations for study design.

Genome-wide DNA methylation profiling of human diabetic peripheral neuropathy in subjects with type 2 diabetes mellitus

ABSTRACTDNA methylation is an epigenetic mechanism important for the regulation of gene expression, which plays a vital role in the interaction between genetic and environmental factors. Aberrant epigenetic changes are implicated in the pathogenesis of diabetes and diabetic complications, but the role of DNA methylation in diabetic peripheral neuropathy (DPN) is not well understood. Therefore, our aim in this study was to explore the role of DNA methylation in the progression of DPN in type 2 diabetes. We compared genome-wide DNA methylation profiles of human sural nerve biopsies from subjects with stable or improving nerve fibre counts to biopsies from subjects with progressive loss of nerve fibres. Nerve fibre counts were determined by comparing myelinated nerve fibre densities between an initial and repeat biopsy separated by 52 weeks. Subjects with significant nerve regeneration (regenerators) and subjects with significant nerve degeneration (degenerators) represent the two extreme DPN phenotypes. Using reduced representation bisulfite sequencing, we identified 3,460 differentially methylated CpG dinucleotides between the two groups. The genes associated with differentially methylated CpGs were highly enriched in biological processes that have previously been implicated in DPN such as nervous system development, neuron development, and axon guidance, as well as glycerophospholipid metabolism and mitogen-activated protein kinase (MAPK) signalling. These findings are the first to provide a comprehensive analysis of DNA methylation profiling in human sural nerves of subjects with DPN and suggest that epigenetic regulation has an important role in the progression of this prevalent diabetic complication.

Homozygous NMNAT2 mutation in sisters with polyneuropathy and erythromelalgia

We identified a homozygous missense mutation in the gene encoding NAD synthesizing enzyme NMNAT2 in two siblings with childhood onset polyneuropathy with erythromelalgia. No additional homozygotes for this rare allele, which leads to amino acid substitution T94M, were present among the unaffected relatives tested or in the 60,000 exomes of the ExAC database. For axons to survive, axonal NMNAT2 activity has to be maintained above a threshold level but the T94M mutation confers a partial loss of function both in the ability of NMNAT2 to support axon survival and in its enzymatic properties. Electrophysiological tests and histological analysis of sural nerve biopsies in the patients were consistent with loss of distal sensory and motor axons. Thus, it is likely that NMNAT2 mutation causes this pain and axon loss phenotype making this the first disorder associated with mutation of a key regulator of Wallerian-like axon degeneration in humans. This supports indications from numerous animal studies that the Wallerian degeneration pathway is important in human disease and raises important questions about which other human phenotypes could be linked to this gene.

MiR-101 relates to chronic peripheral neuropathic pain through targeting KPNB1 and regulating NF-κB signaling.

Accumulating evidences indicates that chronic neuropathic pain is a kind of neuro-immune disorder with enhanced activation of the immune system. Although the prevalence is very high, neuropathic pain remains extremely difficult to cure. miRNAs are a group of short nonprotein coding RNAs, regulating target genes expression via targeting 3'-untranslated region. More and more research indicates that altered miRNAs expression profile relates to the pathogenesis of neuropathic pain. In this study, we firstly detected the expression of six candidate miRNAs in the plasma samples from 23 patients with neuropathic pain and 10 healthy controls. Subsequently, the level of miR-132 and miR-101 was detected in the sural nerve biopsies. We found miR-101 level was significantly repressed in both the plasma samples and sural nerve biopsies from neuropathic pain patients. Predicted by bioinformatics tools and confirmed by dual luciferase assay and immunoblotting, we identified that KPNB1 is a direct target of miR-101. The negative correlation between miR-101 and KPNB1 was also confirmed in the sural nerve biopsies, and miR-101 reduction relates to the activation of NF-κB signaling in vivo and in vitro which contributes to the pathogenesis of neuropathic pain.

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.

Clinicopathological correlations of sural nerve biopsies in TTR Val30Met familial amyloid polyneuropathy.

Familial amyloid polyneuropathy with the substitution of methionine for valine at position 30 in the TTR gene is the most common type of hereditary transthyretin amyloidosis. Although several authors have previously reported a size-dependent fibre loss, predominantly involving unmyelinated and small-diameter myelinated fibres, the mechanisms of nerve fibre loss have not been fully understood. In this study, we establish the morphometric pattern of peripheral neuropathy in patients with familial amyloid polyneuropathy and asymptomatic mutation carriers in the biopsies from our archive and correlated the pathological findings with clinical features. A total of 98 patients with familial amyloid polyneuropathy and 37 asymptomatic mutation carriers (TTR Val30Met mutation), aged between 17 and 84 years, who underwent sural nerve biopsy between 1981 and 2017 at Centro Hospitalar Universitário do Porto were studied. Thirty-one controls were included for comparison. The median age at nerve biopsy was 26.0 [interquartile range = 23.5–39.5] years for asymptomatic mutation carriers, 45.0 [35.0–60.0] years for patients with familial amyloid polyneuropathy and 44.0 [30.0–63.0] years for controls. The median duration between nerve biopsy and symptoms’ onset was 7.0 [3.3–11.8] years (range: 1–27 years) in the asymptomatic carriers. Most patients were in an earlier disease stage (93% with a polyneuropathy disability scale ≤2). Patients had loss of small and myelinated fibres compared with both asymptomatic carriers and controls (P < 0.001), whereas asymptomatic carriers showed loss of small myelinated fibres when compared with controls (P < 0.05). The loss of myelinated fibres increased with disease progression (P < 0.001), and patients in more advanced clinical stage showed more frequent amyloid deposition in the nerve (P = 0.001). There was a positive correlation between large myelinated fibre density and time to symptoms’ onset in the asymptomatic carriers that developed early-onset form of the disease (r = 0.52, P < 0.01). In addition, asymptomatic carriers with amyloid deposition already present in sural nerve biopsies developed symptoms earlier than those with no amyloid (P < 0.01). In conclusion, this study confirms that the loss of small fibre size is an initial event in familial amyloid polyneuropathy, already present in asymptomatic gene carriers, starting several years before the onset of symptoms. We show for the first time that large myelinated fibres’ loss and amyloid deposition are pathological features that correlate independently with short period to the onset of symptoms for asymptomatic carriers that developed early-onset form of the disease. These findings are therapeutically relevant, as it would allow for a better interpretation of the role of disease-modifying agents in transthyretin familial amyloid polyneuropathy.

A – C.A.N.V.A.S (CEREBELLAR ATAXIA, NEURONOPATHY AND VESTIBULAR AREFLEXIA WITH AUTONOMIC DYSFUNCTION): A FASCINATING CLINICAL PORTRAIT

57-year-old male patient with a 30-year history chronic cough, balance difficulties (most noticeable in the dark), ataxia and sensory neuropathy. There was also evidence of orthostatic hypotension and hypohydrosis. Examination revealed downbeat nystagmus, an abnormal visually-enhanced vestibulo-ocular reflex, length-dependent sensory neuropathy, high-stepping tandem ataxia and bilateral dysmetria. MRI brain shows marked vermian cerebellar atrophy (more noticeable in lobes VI and VIIa/b) and nerve conduction studies reveal absent sensory conductions (ganglionopathy). Genetic testing for Friedrich’s ataxia, spinocerebellar ataxia and hereditary motor sensory neuropathy (Charcot-Marie-Tooth disease) were all negative. Sural nerve biopsy showed pattern of severe loss of myelinated fibres. This patient was diagnosed with cerebellar ataxia, neuronopathy (ganglionopathy) and vestibular areflexia with autonomic dysfunction. Keywords: ataxia, neuronopathy, vestibular areflexia, autonomic dysfunction.

Ultrastructural mechanisms of macrophage-induced demyelination in CIDP.

Chronic inflammatory demyelinating polyneuropathy (CIDP) is a form of chronic neuropathy that is presumably caused by heterogeneous immune-mediated processes. Recent advances in the search for autoantibodies against components expressed at nodal regions, such as the nodes of Ranvier and paranodes, have substantially contributed to clarifying the pathogenesis of CIDP in a subpopulation of patients. In particular, immunoglobulin G4 (IgG4) antibodies to paranodal junction proteins, including neurofascin-155 and contactin-1, have attracted the attention of researchers. Paranodal dissection resulting from the attachment of IgG4 at paranodal junctions and the absence of macrophage-induced demyelination are characteristic pathologic features in patients who have these antibodies. By contrast, the mechanisms of neuropathy in cases with classical macrophage-induced demyelination remain unclear despite the long-standing recognition of this process in CIDP. In addition to complement-dependent damage provoked by autoantibodies, recent studies have shed light on antibody-dependent phagocytosis by macrophages without participation of complements. However, a direct association between specific autoantibodies and macrophage-induced demyelination has not been reported. Electron microscopic examination of longitudinal sections of sural nerve biopsy specimens suggested that macrophages recognize specific sites of myelinated fibers as the initial target of demyelination. The site that macrophages select to initiate myelin breakdown is located around the nodal regions in some patients and internode in others. Hence, it seems that the components that distinguish between the nodal regions and internode play a pivotal role in the behavior of macrophages that initiate phagocytosis of myelin. Further studies are needed to elucidate the mechanisms underlying macrophage-induced demyelination from this perspective.

Phosphorylated α-synuclein deposits in sural nerve deriving from Schwann cells: A biomarker for Parkinson's disease

IntroductionParesthesia is common in Parkinson's disease (PD) patients. We assumed that peripheral nerve might be implicated. This study aimed to investigate whether phosphorylated α-synuclein (pSNCA) pathology occurred in sural nerve fibers and to explore the underlying pathogenesis of paresthesia of lower limbs associated with PD. MethodsClinical assessments and sural nerve biopsy were performed to evaluate clinical characteristics and the deposition of total α-synuclein (tSNCA) and pSNCA in biopsy pieces using immunochemistry methods on 16 PD patients and 15 controls. In addition, immunofluorescence staining was performed using certain antibodies to characterize the component of sural nerve and to localize the expression of pSNCA. ResultsDeposition of pSNCA was found in 16/16 PD patients with a high positive percentage of 100% but in 0/15 controls, however, all biopsy pieces showed positive response to tSNCA immunohistological staining in nerve fibers. pSNCA was expressed mainly in Schwann cells but scarcely in axons, demonstrating a novel pattern of pSNCA expression in peripheral nervous system. ConclusionOur findings suggest that peripheral somatic sensory nerve is also involved in SNCA pathology in PD. The search for pSNCA in sural nerve might serve as a novel biomarker for early diagnosis of PD and pSNCA in sural nerve may derive from Schwann cells rather than propagate retrograde along the primary sensory neurons from the central nervous system.

Nerve and skin biopsy in neuropathies.

To give an overview of recent data on the use of nerve and skin biopsy as a diagnostic tool in neuropathies. Axonal damage in a biopsy from a patient with chronic inflammatory demyelinating polyradiculoneuropathy may point to the presence of autoantibodies to paranodal proteins. In nonsystemic vasculitis of the peripheral nervous system, nerve biopsy is still the only means to make a definite diagnosis. Increased autophagy has been found in idiopathic neuropathy and may also be a common final pathway in various types of neuropathy. Nerve biopsy has unexpectedly revealed familial amyloid neuropathy in a number of cases that were taken for idiopathic, for Charcot-Marie-Tooth disease, or for chronic inflammatory demyelinating polyradiculoneuropathy. Skin biopsy can differentiate between length-dependent and non-length-dependent small fiber neuropathy, which aids in the etiological differential diagnosis. It can also be used to identify small fiber involvement in mixed neuropathies and for follow-up studies. Nerve biopsy is still the gold standard for the diagnosis of peripheral nerve vasculitis. In other indications, sural or superficial peroneal nerve biopsies are less frequently done, because less invasive methods have become available. Modern imaging methods allow localization of nerve damage, such that targeted fascicular biopsies can be done. Immunofluorescence staining of teased nerve fibers has contributed to the understanding of the pathophysiology of inflammatory neuropathies. Skin biopsy has become a routine method to diagnose small fiber neuropathy.