Nerve and skin biopsy in neuropathies

Disease activity in chronic inflammatory demyelinating polyneuropathy: association between circulating B-cell subsets, cytokine levels, and clinical outcomes

Chronic inflammatory demyelinating polyneuropathy (CIDP), a common and treatable autoimmune neuropathy, is frequently misdiagnosed. The aim of this study is to evaluate the relationship between immunological markers and clinical outcome measures in a mixed cohort of patients with typical CIDP and CIDP variants at different disease stages. Twenty-three typical, 16 multifocal and five distal CIDP patients were included. Twenty-five sex and age-matched healthy controls and 12 patients with Charcot-Marie-Tooth type 1A (CMT1A) disease served as controls. Peripheral B-cell populations were analyzed by flow cytometry. IL6, IL10, TNFA mRNA and mir-21, mir-146a, and mir-155-5p expression levels were evaluated by real-time polymerase chain reaction in peripheral blood mononuclear cells (PBMC) and/or skin biopsy specimens. Results were then assessed for a possible association with clinical disability scores and intraepidermal nerve fiber densities (IENFD) in the distal leg. We detected a significant reduction in naive B cells (P ≤ 0.001), plasma cells (P ≤ 0.001) and regulatory B cells (P < 0.05), and an elevation in switched memory B cells (P ≤ 0.001) in CIDP compared to healthy controls. CMT1A and CIDP patients had comparable B-cell subset distribution. CIDP cases had significantly higher TNFA and IL10 gene expression levels in PBMC compared to healthy controls (P < 0.05 and P ≤ 0.01, respectively). IENFDs in the distal leg showed a moderate negative correlation with switched memory B-cell ratios (r = -0.51, P < 0.05) and a moderate positive correlation with plasma cell ratios (r = 0.46, P < 0.05). INCAT sum scores showed a moderate positive correlation with IL6 gene expression levels in PBMC (r = 0.54, P < 0.05). Altered B-cell homeostasis and IL10 and TNFA gene expression levels imply chronic antigen exposure and overactivity in the humoral immune system, and seem to be a common pathological pathway in both typical CIDP and CIDP variants.

Super-resolution imaging pinpoints the periodic ultrastructure at the human node of Ranvier and its disruption in patients with polyneuropathy

The node of Ranvier is the key element in saltatory conduction along myelinated axons, but its specific protein organization remains elusive in the human species. To shed light on nanoscale anatomy of the human node of Ranvier in health and disease, we assessed human nerve biopsies of patients with polyneuropathy by super-resolution fluorescence microscopy. We applied direct stochastic optical reconstruction microscopy (dSTORM) and supported our data by high-content confocal imaging combined with deep learning-based analysis. As a result, we revealed a ~ 190 nm periodic protein arrangement of cytoskeletal proteins and axoglial cell adhesion molecules in human peripheral nerves. In patients with polyneuropathy, periodic distances increased at the paranodal region of the node of Ranvier, both at the axonal cytoskeleton and at the axoglial junction. In-depth image analysis revealed a partial loss of proteins of the axoglial complex (Caspr-1, neurofascin-155) in combination with detachment from the cytoskeletal anchor protein ß2-spectrin. High content analysis showed that such paranodal disorganization occurred especially in acute and severe axonal neuropathy with ongoing Wallerian degeneration and related cytoskeletal damage. We provide nanoscale and protein-specific evidence for the prominent, but vulnerable role of the node of Ranvier for axonal integrity. Furthermore, we show that super-resolution imaging can identify, quantify and map elongated periodic protein distances and protein interaction in histopathological tissue samples. We thus introduce a promising tool for further translational applications of super resolution microscopy.

Leprosy rash precipitated by immunotherapy for suspected inflammatory neuropathy

Leprosy is a chronic granulomatous infection caused by Mycobacterium leprae complex, causing skin and nerve lesions with potential for permanent disability. Leprosy can be overlooked in Western settings, as it is more prevalent in low-income and middle-income countries. We describe a 38-year-old woman with a 4-year history of progressive numbness of the left hand incorrectly diagnosed as multifocal acquired demyelinating sensory and motor neuropathy on the basis of clinical and neurophysiological findings. Treatment with empirical weekly corticosteroid followed by intravenous immunoglobulin resulted in the sudden development of a widespread rash; we then diagnosed borderline lepromatous leprosy on skin biopsy. We postulate that the immune treatments induced a temporary state of immune tolerance followed by a rebound of a T cell-mediated immune response resulting in a type 1 immunological response.

Neuromuscular pathology

In this chapter, we discuss the indications for muscle, nerve, and skin biopsies, the techniques and normal processing of biopsy specimens, normal histological appearance, and the commonest histopathological abnormalities of different myopathies and neuropathies.

Corneal Nerve Parameter Reference Values for Chinese Adults Assessed by Corneal Confocal Microscopy

Background

Confocal corneal microscopy is an excellent new noninvasive tool for assessing diabetic peripheral neuropathy. We aimed to investigate the clinical variables associated with corneal nerve parameters and establish reference values for clinical use in healthy Chinese adults.

Methods

The study enlisted 257 healthy volunteers (137 females and 120 males) from two clinical academic centers in China. Two experts captured and selected images of the central corneal subbasal nerve plexus at each center using the same corneal confocal microscopy instrument according to a commonly adopted protocol. Corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), and corneal nerve fiber length (CNFL) were measured using fully automated software (ACCMetrics). The correlation between clinical indicators and confocal corneal microscopy measures was determined using partial correlation. Quantile regression was used to calculate reference values and estimate the effects of clinical factors on the normative values of confocal corneal microscopy measures.

Results

Females had significantly higher CNFD, CNBD, and CNFL than males. There was no correlation between age, glycated hemoglobin (HbA1c), height, weight, body mass index (BMI), and any corneal nerve fiber parameter in both sexes. In either sex, age, weight, height, BMI, and HbA1c did not affect the 0.05th quantile values of any corneal nerve parameter.

Conclusions

This study establishes sex-adjusted reference values for corneal confocal microscopy measures in Chinese adults and provides a reference for clinical practice and research with this technique.

Approach to Neuropathic Pain

Neuropathic pain is a common chief complaint encountered by neurologists and primary care providers. It is caused by disorders involving the somatosensory nervous system. The clinical evaluation of neuropathic pain is challenging and requires a multifaceted systematic approach with an emphasis on a thorough history and physical examination to identify characteristic signs and symptoms. Ancillary laboratory investigations, targeted imaging, and electrodiagnostic studies further help identify underlying etiologies to guide specific treatments. Management of neuropathic pain encompasses treating the underlying pathology as well as symptomatic control with nonpharmacological, pharmacological, and interventional therapies. Here, we present an approach to help evaluate patients with neuropathic pain.

A modality-specific somatosensory evoked potential test protocol for clinical evaluation: A feasibility study

OBJECTIVE

We aimed to establish an objective neurophysiological test protocol that can be used to assess the somatosensory nervous system.

METHODS

In order to assess most fiber subtypes of the somatosensory nervous system, repetitive stimuli of seven different modalities (touch, vibration, pinprick, cold, contact heat, laser, and warmth) were synchronized with the electroencephalogram (EEG) and applied on the cheek and dorsum of the hand and dorsum of the foot in 21 healthy subjects and three polyneuropathy (PNP) patients. Latencies and amplitudes of the modalities were assessed and compared. Patients received quantitative sensory testing (QST) as reference.

RESULTS

We found reproducible evoked potentials recordings for touch, vibration, pinprick, contact-heat, and laser stimuli. The recording of warm-evoked potentials was challenging in young healthy subjects and not applicable in patients. Latencies were shortest within Aβ-fiber-mediated signals and longest within C-fibers. The test protocol detected function loss within the Aβ-fiber and Aδ-fiber-range in PNP patients. This function loss corresponded with QST findings.

CONCLUSION

In this pilot study, we developed a neurophysiological test protocol that can specifically assess most of the somatosensory modalities. Despite technical challenges, initial patient data appear promising regarding a possible future clinical application.

SIGNIFICANCE

Established and custom-made stimulators were combined to assess different fiber subtypes of the somatosensory nervous system using modality-specific evoked potentials.

Clinical Manifestations, Pathogenesis, Diagnosis and Treatment of Peripheral Neuropathies in Connective Tissue Diseases: More Diverse and Frequent in Different Subtypes than Expected

Purpose of review: To discuss and summarize recent findings in peripheral neuropathy (PN) related to connective tissue diseases (CTD) including its prevalence, clinical manifestations, pathogenesis, diagnosis and treatment. Recent findings: Although PN is a common complication in CTD and has been well studied, recent research has shown that PN is more diverse and frequent in different subtypes of CTD than was expected. The incidence of PN in Sjögren’s syndrome and rheumatoid arthritis (RA) varies according to different disease subtypes, and the pathogenesis of neuropathic pain in different subtypes of eosinophilic granulomatosis with polyangiitis (EGPA) may also differ. Neurogenic inflammation, autoantibody-mediated changes, ischemia of the vascular wall and metabolic mechanisms have been shown to contribute to the pathogenesis of PN in CTD. Moreover, allergic inflammation has been recently identified as a possible new mechanism producing peripheral neuropathic pain associated with MPO-ANCA negative EGPA patients. Glucocorticoids are routinely used to relieve pain caused by PN. However, these steroids may cause hyperalgesia, exacerbate neuropathic pain, and activate the early phase of pain induction and produce hyperalgesia. Recently, neuroactive steroids, such as progesterone, tetrahydroprogesterone and testosterone, have been shown to exert protective effects for several PN symptoms, and in particular neuropathic pain. Neuroactive steroids will be an interesting topic for future research into PN in CTD. Summary: It is essential for the diagnosis and treatment of PN in CTD to be updated. Timely diagnosis, appropriate treatments, and multidisciplinary care are essential to minimize morbidity and decrease the risk of permanent neurologic deficits. Further studies are needed to guide diagnosis and treatment.

Mechanisms and Treatments in Demyelinating CMT

Demyelinating forms of Charcot-Marie-Tooth disease (CMT) are genetically and phenotypically heterogeneous and result from highly diverse biological mechanisms including gain of function (including dominant negative effects) and loss of function. While no definitive treatment is currently available, rapid advances in defining the pathomechanisms of demyelinating CMT have led to promising pre-clinical studies, as well as emerging clinical trials. Especially promising are the recently completed pre-clinical genetic therapy studies in PMP-22, GJB1, and SH3TC2-associated neuropathies, particularly given the success of similar approaches in humans with spinal muscular atrophy and transthyretin familial polyneuropathy. This article focuses on neuropathies related to mutations in PMP-22, MPZ, and GJB1, which together comprise the most common forms of demyelinating CMT, as well as on select rarer forms for which promising treatment targets have been identified. Clinical characteristics and pathomechanisms are reviewed in detail, with emphasis on therapeutically targetable biological pathways. Also discussed are the challenges facing the CMT research community in its efforts to advance the rapidly evolving biological insights to effective clinical trials. These considerations include the limitations of currently available animal models, the need for personalized medicine approaches/allele-specific interventions for select forms of demyelinating CMT, and the increasing demand for optimal clinical outcome assessments and objective biomarkers.

Stellenwert klinischer, funktioneller und bildgebender Diagnostik zur Früherkennung, Differenzialdiagnose und Verlaufskontrolle diabetischer Neuropathien

Von weltweit mehr als 400 Mio. Menschen mit Diabetes mellitus entwickeln bis zu 50% im Laufe ihrer Erkrankung eine Neuropathie. Trotz oder gerade wegen dieser Häufigkeit darf jedoch nicht jede Neuropathie, die in Koinzidenz mit einem Diabetes mellitus auftritt, unkritisch als diabetische Neuropathie diagnostiziert werden. Eine präzise Ausschluss- und Ausmaßdiagnostik ist entscheidend, um andere behandelbare Erkrankungen wie z. B. die Chronisch Inflammatorische Demyelinisierende Polyradikuloneuropathie oder die hereditäre Transthyretin-Amyloidose nicht zu übersehen. Einfache, nicht-invasive, preiswerte und allzeit verfügbare Screeningmethoden stellen Anamnese und klinische Untersuchung dar. Ergänzend ist in frühen Erkrankungsstadien die Quantitativ Sensorische Testung hilfreich zur Eingrenzung einer Small Fiber-Dysfunktion. Sind, typischerweise im Verlauf, große Nervenfasern geschädigt, so ist das charakteristische elektrophysiologische Bild das einer längenabhängigen, axonalen, sensibel betonten oder sensomotorischen Neuropathie. Die Nervensonografie kann zur Unterscheidung von autoimmun-demyelinisierenden Neuropathien hilfreich sein. Moderne Untersuchungsverfahren wie die MR-Neurografie können auch proximale Nervenabschnitte bis auf Faszikelebene darstellen, sind allerdings nur an wenigen Zentren verfügbar. Haut- und Nervenbiopsien sind v. a. bei untypischen Verläufen zur Abgrenzung von Differenzialdiagnosen hilfreich. Diabetische Neuropathien können zu einer erheblichen Reduktion von Lebensqualität und Lebensdauer führen. Zur frühest- und bestmöglichen ursächlichen und symptomatischen Therapieeinleitung ist eine präzise Diagnostik essentiell.

Chronic axonal idiopathic polyneuropathy: is it really benign

PURPOSE OF REVIEW

Chronic idiopathic axonal polyneuropathy (CIAP), a common neurological condition, is considered to be a benign neurological condition with a small risk of disability. However, many studies have shown a reduced quality of life and a nonnegligible affection of daily activities in patients with CIAP. Here we summarize recent data about CIAP.

RECENT FINDINGS

We discuss some of the latest articles regarding risk factors, comorbidities, and possible pathogenic factors regarding CIAP. Patients with chronic polyneuropathy have impaired walking capacity, disturbed balance, and an increased risk of falls. Idiopathic polyneuropathy has a negative impact on activities of daily living. Patients with CIAP may develop plantar ulcers and neuropathic arthropathy. Small fiber involvement may occur, and two recent studies indicate that neuropathic pain is present in about two thirds of the CIAP group. Furthermore, patients with CIAP with neuropathic pain have increased fatigue and poorer emotional well being.

SUMMARY

Despite the relatively mild motor impairment seen in most patients with CIAP, the condition causes limitations in life with decreased mobility, pain, and affection of basal daily activities. Because the pathogenesis of CIAP in unclear, there is no disease modifying treatment. Further studies regarding pathogenesis, and randomized controlled clinical trials regarding possible treatment options are needed.

Ultra-high-frequency ultrasound imaging of sural nerve: A comparative study with nerve biopsy in progressive neuropathies

INTRODUCTION

Nerve ultrasound has been used increasingly in clinical practice as a complementary test for diagnostic assessment of neuropathies, but nerve biopsy remains invaluable in certain cases. The aim of this study was to compare ultra-high-frequency ultrasound (UHF-US) to histologic findings in progressive polyneuropathies.

METHODS

Ten patients with severe, progressive neuropathies underwent ultrasound evaluation of the sural nerve before nerve biopsy. Ultrasound data were compared with histologic results in a retrospective manner.

RESULTS

Sural nerves were easily identified on UHF-US. Nerve hyperechogenicity correlated with inflammatory infiltrates on biopsy. Nerve fascicles could be identified and measured on ultrasound in the majority of patients.

DISCUSSION

Hyperechogenicity on UHF-US may be a marker of nerve inflammation in neuropathies. Furthermore, the UHF-US probe allows for evaluation of sensory nerves in spite of their small size, providing valuable information on their size and on their internal structure.

Diagnostic utility of corneal confocal microscopy in type 2 diabetic peripheral neuropathy

Aims/Introduction

The early pathological changes of diabetic peripheral neuropathy (DPN) are mainly small nerve fiber injuries. Corneal confocal microscopy (CCM) is an easy, rapid, non‐invasive and repeatable technique to detect the damage of small nerve fibers. The purpose of this study was to explore the application of CCM in DPN and other chronic complications of type 2 diabetes mellitus.

Materials and Methods

A total of 220 individuals (48 normal healthy control participants and 172 patients with type 2 diabetes mellitus) were included in the study. All participants were assessed and scored for neurological symptoms and neurological deficits, quantitative sensory test, neuroelectrophysiological test, and CCM.

Results

Corneal nerve fiber density, corneal nerve fiber length and corneal nerve branch density were significantly reduced in patients with type 2 diabetes mellitus compared with normal healthy control subjects (P < 0.001, P < 0.001 and P < 0.001, respectively). In the DPN group, corneal nerve fiber density, corneal nerve branch density and corneal nerve fiber length were significantly lower than for patients without DPN (P < 0.001, P < 0.001 and P < 0.001, respectively). Receiver operating characteristic analysis showed that the optimal cut‐off values were 24.68, 39 and 15.315, respectively, in which corneal nerve fiber density and corneal nerve fiber length had moderate sensitivity and specificity.

Conclusion

This study provides more support for the clinical use of CCM to diagnose type 2 diabetes mellitus‐related complications, especially DPN.

Sural Nerve Size in Fibromyalgia Syndrome: Study on Variables Associated With Cross-Sectional Area

Increased cross-sectional area (CSA) of sural nerve, documented by ultrasound (US), has been revealed in small fibers neuropathy, condition present in about half of patients with fibromyalgia (FM). The aims of this study were to evaluate sural nerve CSA and to establish the variables associated with increased CSA in FM patients. A cross-sectional assessment was conducted in consecutive FM patients. Demographic data, clinimetric parameters [Fibromyalgia Impact Questionnaire (FIQR)], the neuropathic pain features [PainDetect Questionnaire (PDQ)], and the sural nerve CSA were recorded. CSA was determined by US, examining the sural nerve at the lateral region of the calf. CSA was compared with demographic and clinical variables. A multiple regression analysis was conducted applying CSA as dependent variable. One hundred and ten FM patients were enrolled. Sural nerve CSA showed a significant association with body mass index (BMI) (r = 0.422; p < 0.0001) and with PDQ (r = 0.361; p = 0.0001). The multiple regression analysis confirmed that BMI (p = 0.0001) and PDQ (p = 0.0028) were the two independent variables associated with CSA. The severity of the disease, measured with FIQR, showed no association. An increase in sural nerve CSA is closely related to BMI and to distinctive neuropathic symptoms. Overweight and obesity appear to be associated with a FM phenotype with documented peripheral nervous system involvement. Ultrasound examination of the sural nerve at calf level may reveal useful information in patients with FM, identifying a cluster of patients with peripheral nervous system alterations. This cluster of patients is generally overweight or obese, and complains of painful symptoms with neuropathic features.

Intraepidermal nerve fibre density as biomarker in Charcot-Marie-Tooth disease type 1A

Charcot-Marie-Tooth disease type 1A, caused by a duplication of the gene peripheral myelin protein 22 kDa, is the most frequent subtype of hereditary peripheral neuropathy with an estimated prevalence of 1:5000. Patients suffer from sensory deficits, muscle weakness and foot deformities. There is no treatment approved for this disease. Outcome measures in clinical trials were based mainly on clinical features but did not evaluate the actual nerve damage. In our case-control study, we aimed to provide objective and reproducible outcome measures for future clinical trials. We collected skin samples from 48 patients with Charcot-Marie-Tooth type 1A, 7 patients with chronic inflammatory demyelinating polyneuropathy, 16 patients with small fibre neuropathy and 45 healthy controls. To analyse skin innervation, 40-µm cryosections of glabrous skin taken from the lateral index finger were double-labelled by immunofluorescence. The disease severity of patients with Charcot-Marie-Tooth type 1A was assessed by the Charcot-Marie-Tooth neuropathy version 2 score, which ranged from 3 (mild) to 27 (severe) and correlated with age (P < 0.01, R = 0.4). Intraepidermal nerve fibre density was reduced in patients with Charcot-Marie-Tooth type 1A compared with the healthy control group (P < 0.01) and negatively correlated with disease severity (P < 0.05, R = -0.293). Meissner corpuscle (MC) density correlated negatively with age in patients with Charcot-Marie-Tooth type 1A (P < 0.01, R = -0.45) but not in healthy controls (P = 0.07, R = 0.28). The density of Merkel cells was reduced in patients with Charcot-Marie-Tooth type 1A compared with healthy controls (P < 0.05). Furthermore, in patients with Charcot-Marie-Tooth type 1A, the fraction of denervated Merkel cells was highly increased and correlated with age (P < 0.05, R = 0.37). Analysis of nodes of Ranvier revealed shortened paranodes and a reduced fraction of long nodes in patients compared with healthy controls (both P < 0.001). Langerhans cell density was increased in chronic inflammatory demyelinating polyneuropathy, but not different in Charcot-Marie-Tooth type 1A compared with healthy controls. Our data suggest that intraepidermal nerve fibre density might be used as an outcome measure in Charcot-Marie-Tooth type 1A disease, as it correlates with disease severity. The densities of Meissner corpuscles and Merkel cells might be an additional tool for the evaluation of the disease progression. Analysis of follow-up biopsies will clarify the effects of Charcot-Marie-Tooth type 1A disease progression on cutaneous innervation.

Association of small-fiber polyneuropathy with three previously unassociated rare missense SCN9A variants

BACKGROUND

Small fiber polyneuropathy (SFN) involves ectopic firing and degeneration of small-diameter, somatic/autonomic peripheral axons. Causes include diabetes, inflammation and rare pathogenic mutations, including in SCN9-11 genes that encode small fiber sodium channels.

AIMS

The aim of this study is to associate a new phenotype-immunotherapy-responsive SFN-with rare amino acid-substituting SCN9A variants and present potential explanations.

METHODS

A retrospective chart review of two Caucasians with skin biopsy confirmed SFN and rare SCN9A single nucleotide polymorphisms not previously reported in neuropathy.

RESULTS

A 47-year-old with 4 years of disabling widespread neuropathic pain and exertional intolerance had nerve- and skin biopsy-confirmed SFN, with blood tests revealing only high-titer antinuclear antibodies and low complement C4 consistent with B cell dysimmunity. Six years of intravenous immunoglobulin (IVIg) therapy markedly improved sensory and autonomic symptoms and normalized his neurite density. After whole exome sequencing revealed a potentially pathogenic SCN9A-A3734G variant, sodium channel blockers were tried. Herpes zoster left a 32-year-old with disabling exertional intolerance ("chronic fatigue syndrome"), postural syncope and tachycardia, arm and leg paresthesias, reduced sweating, and distal hairloss. Screening revealed antinuclear and potassium channel autoantibodies, so prednisone and then IVIg were prescribed with great benefit. During 4 years of immunotherapy, his symptoms and function improved, and all abnormal biomarkers (autonomic testing and skin biopsies) normalized. Whole exome sequencing then revealed two nearby compound heterozygous SCN9A variants that were computer-predicted to be deleterious.

CONCLUSIONS

These cases newly associate three novel amino acid-substituting SCN9A variants with immunotherapy-responsive neuropathy. Only larger studies can determine whether these are contributory or coincidental, but they associate new variants with moderate or high likelihood of pathogenicity with a new highly related phenotype.

Diagnostic criteria for small fibre neuropathy in clinical practice and research

The diagnostic criteria for small fibre neuropathy are not established, influencing the approach to patients in clinical practice, their access to disease-modifying and symptomatic treatments, the use of healthcare resources, and the design of clinical trials. To address these issues, we performed a reappraisal study of 150 patients with sensory neuropathy and a prospective and follow-up validation study of 352 new subjects with suspected sensory neuropathy. Small fibre neuropathy diagnostic criteria were based on deep clinical phenotyping, quantitative sensory testing (QST) and intraepidermal nerve fibre density (IENFD). Small fibre neuropathy was ruled out in 5 of 150 patients (3.3%) of the reappraisal study. Small fibre neuropathy was diagnosed at baseline of the validation study in 149 of 352 patients (42.4%) based on the combination between two clinical signs and abnormal QST and IENFD (69.1%), abnormal QST alone (5.4%), or abnormal IENFD alone (20.1%). Eight patients (5.4%) had abnormal QST and IENFD but no clinical signs. Further, 38 patients complained of sensory symptoms but showed no clinical signs. Of those, 34 (89.4%) had normal QST and IENFD, 4 (10.5%) had abnormal QST and normal IENFD, and none had abnormal IENFD alone. At 18-month follow-up, 19 of them (56%) reported the complete recovery of symptoms and showed normal clinical, QST and IENFD findings. None of those with one single abnormal test (QST or IENFD) developed clinical signs or showed abnormal findings on the other test. Conversely, all eight patients with abnormal QST and IENFD at baseline developed clinical signs at follow-up. The combination of clinical signs and abnormal QST and/or IENFD findings can more reliably lead to the diagnosis of small fibre neuropathy than the combination of abnormal QST and IENFD findings in the absence of clinical signs. Sensory symptoms alone should not be considered a reliable screening feature. Our findings demonstrate that the combined clinical, functional and structural approach to the diagnosis of small fibre neuropathy is reliable and relevant both for clinical practice and clinical trial design.

Sodium Fluorescein as Intraoperative Visualization Tool During Peripheral Nerve Biopsies

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Dissociable Contributions of Precuneus and Cerebellum to Subjective and Objective Neuropathy in HIV

Neuropathy, typically diagnosed by the presence of either symptoms or signs of peripheral nerve dysfunction, remains a frequently reported complication in the antiretroviral (ART)-treated HIV population. This study was conducted in 109 healthy controls and 57 HIV-infected individuals to investigate CNS regions associated with neuropathy. An index of objective neuropathy was computed based on 4 measures: deep tendon ankle reflex, vibration sense (great toes), position sense (great toes), and 2-point discrimination (feet). Subjective neuropathy (self-report of pain, aching, or burning; pins and needles; or numbness in legs or feet) was also evaluated. Structural MRI data were available for 126/166 cases. The HIV relative to the healthy control group was impaired on all 4 signs of neuropathy. Within the HIV group, an objective neuropathy index of 1 (bilateral impairment on 1 measure) or 2 (bilateral impairment on at least 2/4 measures) was associated with older age and a smaller volume of the cerebellar vermis. Moderate to severe symptoms of neuropathy were associated with more depressive symptoms, reduced quality of life, and a smaller volume of the parietal precuneus. This study is consistent with the recent contention that ART-treated HIV-related neuropathy has a CNS component. Distinguishing subjective symptoms from objective signs of neuropathy allowed for a dissociation between the precuneus, a brain region involved in conscious information processing and the vermis, involved in fine tuning of limb movements. Graphical Abstract In HIV patients, objective signs of neuropathy correlated with smaller cerebellar vermis (red) volumes whereas subjective symptoms of neuropathy were associated with smaller precuneus (blue) volumes.

Hereditary transthyretin amyloidosis: a model of medical progress for a fatal disease

Hereditary amyloidogenic transthyretin (ATTRv) amyloidosis with polyneuropathy (also known as familial amyloid polyneuropathy) is a condition with adult onset caused by mutation of transthyretin (TTR) and characterized by extracellular deposition of amyloid and destruction of the somatic and autonomic PNS, leading to loss of autonomy and death. This disease represents a model of the scientific and medical progress of the past 30 years. ATTRv amyloidosis is a worldwide disease with broad genetic and phenotypic heterogeneity that presents a diagnostic challenge for neurologists. The pathophysiology of the neuropathy is increasingly understood and includes instability and proteolysis of mutant TTR leading to deposition of amyloid with variable lengths of fibrils, microangiopathy and involvement of Schwann cells. Wild-type TTR is amyloidogenic in older individuals. The main symptoms are neuropathic, but the disease is systemic; neurologists should be aware of cardiac, eye and kidney involvement that justify a multidisciplinary approach to management. Infiltrative cardiomyopathy is usually latent but present in half of patients. Disease-modifying therapeutics that have been developed include liver transplantation and TTR stabilizers, both of which can slow progression of the disease and increase survival in the early stages. Most recently, gene-silencing drugs have been used to control disease in the more advanced stages and produce some degree of improvement.