A quantitative method for the assessment of intraepidermal nerve fibers in small–fiber neuropathy

Detection of sensory deficits in fine nerve fibres in leprosy diagnosis

OBJECTIVES

The purpose of this study was to determine reference points for thermal perception in cutaneous lesions of leprosy, a disease caused by Mycobacterium leprae characterised by hypoesthesia in skin lesions due to nerve and Schwann cell infection. Early diagnosis is essential to control transmission and effectively treat the disease.

METHODS

Quantitative thermal testing (QTT) has been proposed as a valuable tool for early detection of the disease, initiation of treatment, and monitoring of nerve damage. A thermal analyser was used to determine warm and cold perception thresholds (WPT and CPT, respectively) in skin lesions of 42 leprosy patients and 22 healthy controls.

RESULTS

The thresholds were determined using a 0.25 cm2 thermal stimulator, the method of limits, and the receiver operating characteristic (ROC) curve. Thermal thresholds were higher in patients' skin lesions compared to unaffected areas and controls. The reference points calculated for the WPT and CPT were 36.55 and 26.35°C, respectively, with high sensitivity and specificity.

CONCLUSION

The nerve fibres affected by leprosy caused altered thermal sensitivity in the patients' lesions, especially in warm sensation. A smaller thermal stimulator and the method of limits were effective in detecting early sensory deficits in nerve fibres, demonstrating the potential for early detection of the disease.

New phenotyping questionnaire for diagnosing sarcoidosis-associated small fiber neuropathy

Small fiber neuropathy is a common complication in patients with sarcoidosis and its prevalence is estimated at 40-86%. The underlying mechanism influences the presentation of small fiber neuropathy. For example, patients with metabolic diseases are often associated with a classic length-dependent small fiber neuropathy pattern, while patients with inflammatory diseases are more often present with a non-length-dependent small fiber neuropathy. Detailed phenotyping may be useful to improve diagnostic efficiency, as a clue to underlying mechanisms and as a precondition for personalized medicine. This study examined four phenotypes distinguishing between length-dependent and non-length-dependent presentation with a new subdivision for continuous and intermittent presentation. Forty-eight sarcoid patients with symptoms and at least two clinical signs of small fiber neuropathy and normal nerve conduction studies were classified as having probable small fiber neuropathy. A new small fiber neuropathy phenotyping questionnaire has been developed that allows patients to mark the anatomical locations of pain at three different levels: the skin, muscles, and joints. The location of symptoms was used to define length dependence, and two colors were used to distinguish continuous (red) from intermittent (blue) symptoms. In addition, skin biopsy, corneal confocal microscopy, Sudoscan and water immersion skin wrinkling were used to investigate a correlation between the four phenotypes, sensory function, nerve fiber density, and autonomic nerve function. Overall, 35% of patients with probable small fiber neuropathy showed length-dependent symptoms and 44% showed non-length-dependent symptoms while 21% suffered from non-neuropathic musculoskeletal pain. The distinction between intermittent and continuous symptoms showed significantly less continuous than intermittent non-length-dependent symptoms (odds ratio = 0.3, P = 0.01). Moreover, continuous length-dependent symptoms were the only phenotype that correlated with thermal threshold testing (R = 0.3; P = 0.02) and the small fiber neuropathy screening list (R = 0.3; P = 0.03). In addition, thermal threshold testing (TTT) also correlated with the small fiber neuropathy (SFN) screening list (R = 0.3; P = 0.03). Other diagnostic methods showed no correlation with any of the four defined phenotypes. A novel finding is that TTT is only associated with continuous length-dependent pain, suggesting that TTT could result in more false negatives in patients with other pain phenotypes. Determining the pathophysiologic mechanisms could help develop new diagnostic methods. If patients suspected of SFN show symptoms without a length-dependent continuous presentation, the diagnosis should focus less on the diagnostic methods used.

Reliable Method for Estimating Nerve Fiber Density in Epidermis Using Routine Histopathologic Tissue Preparation: A Promising Diagnostic Tool for Small Fiber Neuropathy

Practical yet reliable diagnostic tools for small-fiber neuropathy are needed. We aimed to establish a histopathologic protocol for estimating intraepidermal nerve fiber density (eIENFD) on formalin-fixed, paraffin-embedded tissue (FFPE), evaluate its reliability through intraobserver and interobserver analyses, and provide normative reference values for clinical use. Sixty-eight healthy participants underwent nerve conduction studies and quantitative sensory testing. Skin biopsies from the distal and proximal leg were taken and processed using routine immunohistochemistry (anti-PGP9.5 antibodies) on thin 5 µm sections. eIENFD was assessed with a modified counting protocol. Interobserver and intraobserver reliabilities were excellent (ICC=0.9). eIENFD was higher in females than males (fibers/mm, 14.3±4.4 vs. 11.6±5.8, P <0.05), decreased with age ( r s =-0.47, P <0.001), and was higher proximally than distally (15.0±5.5 vs. 13.0±5.3, P =0.002). Quantile regression equations for the fifth percentile of distal and proximal eIENFD were presented: 13.125-0.161×age (y)-0.932×sex (male=1; female=0) and 17.204-0.192×age (y)-3.313×sex (male=1; female=0), respectively. This study introduces a reliable and reproducible method for estimating epidermal nerve fiber density through immunostaining on 5-µm thin FFPE tissue samples. Normative data on eIENFD is provided. Regression equations help identify abnormal decreases in small nerve fiber density.

The Relevance of Skin Biopsies in General Internal Medicine: Facts and Myths

INTRODUCTION

Non-dermatology medical specialties may refer patients for skin biopsies, searching for a particular diagnosis. However, the diagnostic impact of the skin biopsy is not clearly established. This article aims to assess the indications for, and evaluate the clinical relevance of, skin biopsies in non-dermatology medical specialties.

METHODS

A questionnaire was sent to 23 non-dermatology specialty departments in a university medical center, requesting a list of indications for skin biopsies, as well as to 10 staff dermatologists to collect the indications of skin biopsies requested by non-dermatology specialties. Once the indications were collected, a literature search was performed to evaluate their clinical value and relevance.

RESULTS

Eleven non-dermatology specialties provided a list of skin biopsy indications, to which staff dermatologists added seven more indications. A literature search revealed evidence-based medicine data for six diseases, that is, amyloidosis, peripheral autonomic neuropathy, Sneddon's syndrome, intravascular lymphoma, sarcoidosis, and chronic graft-versus-host disease. Results were questionable concerning infectious endocarditis, acute graft-versus-host-disease, and the lupus band test. Skin biopsy were not evidenced as useful for the diagnosis of calciphylaxis, systemic scleroderma, Behçet's disease, or hypermobile Ehlers-Danlos syndrome. For the diagnosis of Alport's syndrome, pseudoxanthoma elasticum, and vascular Ehlers-Danlos syndrome, skin biopsy is currently outperformed by genetic analyses. For diagnoses such as Henoch-Schönlein purpura and Sjögren's syndrome, skin biopsy represents an additional item among other diagnostic criteria.

CONCLUSION

The usefulness of skin biopsy as requested by non-dermatology specialties is only evidenced for amyloidosis, peripheral autonomic neuropathy, Sneddon's syndrome, intravascular lymphoma, sarcoidosis, chronic graft-versus-host-disease, Henoch-Schönlein purpura, and Sjögren's syndrome.

Advantages of an Automated Method Compared With Manual Methods for the Quantification of Intraepidermal Nerve Fiber in Skin Biopsy

Intraepidermal nerve fiber density (IENFD) measurements in skin biopsy are performed manually by 1–3 operators. To improve diagnostic accuracy and applicability in clinical practice, we developed an automated method for fast IENFD determination with low operator-dependency. Sixty skin biopsy specimens were stained with the axonal marker PGP9.5 and imaged using a widefield fluorescence microscope. IENFD was first determined manually by 3 independent observers. Subsequently, images were processed in their Z-max projection and the intradermal line was delineated automatically. IENFD was calculated automatically (fluorescent images automated counting [FIAC]) and compared with manual counting on the same fluorescence images (fluorescent images manual counting [FIMC]), and with classical manual counting (CMC) data. A FIMC showed lower variability among observers compared with CMC (interclass correlation [ICC] = 0.996 vs 0.950). FIMC and FIAC showed high reliability (ICC = 0.999). A moderate-to-high (ICC = 0.705) was observed between CMC and FIAC counting. The algorithm process took on average 15 seconds to perform FIAC counting, compared with 10 minutes for FIMC counting. This automated method rapidly and reliably detects small nerve fibers in skin biopsies with clear advantages over the classical manual technique.

Early Detection of Diabetic Peripheral Neuropathy: A Focus on Small Nerve Fibres

Diabetic peripheral neuropathy (DPN) is the most common complication of both type 1 and 2 diabetes. As a result, neuropathic pain, diabetic foot ulcers and lower-limb amputations impact drastically on quality of life, contributing to the individual, societal, financial and healthcare burden of diabetes. DPN is diagnosed at a late, often pre-ulcerative stage due to a lack of early systematic screening and the endorsement of monofilament testing which identifies advanced neuropathy only. Compared to the success of the diabetic eye and kidney screening programmes there is clearly an unmet need for an objective reliable biomarker for the detection of early DPN. This article critically appraises research and clinical methods for the diagnosis or screening of early DPN. In brief, functional measures are subjective and are difficult to implement due to technical complexity. Moreover, skin biopsy is invasive, expensive and lacks diagnostic laboratory capacity. Indeed, point-of-care nerve conduction tests are convenient and easy to implement however questions are raised regarding their suitability for use in screening due to the lack of small nerve fibre evaluation. Corneal confocal microscopy (CCM) is a rapid, non-invasive, and reproducible technique to quantify small nerve fibre damage and repair which can be conducted alongside retinopathy screening. CCM identifies early sub-clinical DPN, predicts the development and allows staging of DPN severity. Automated quantification of CCM with AI has enabled enhanced unbiased quantification of small nerve fibres and potentially early diagnosis of DPN. Improved screening tools will prevent and reduce the burden of foot ulceration and amputations with the primary aim of reducing the prevalence of this common microvascular complication.

Current View of Diagnosing Small Fiber Neuropathy

Small fiber neuropathy (SFN) is a disorder of the small myelinated Aδ-fibers and unmyelinated C-fibers [5, 6]. SFN might affect small sensory fibers, autonomic fibers or both, resulting in sensory changes, autonomic dysfunction or combined symptoms [7]. As a consequence, the symptoms are potentially numerous and have a large impact on quality of life [8]. Since diagnostic methods for SFN are numerous and its pathophysiology complex, this extensive review focusses on categorizing all aspects of SFN as disease and its diagnosis. In this review, sensitivity in combination with specificity of different diagnostic methods are described using the areas under the curve. In the end, a diagnostic work-flow is suggested based on different phenotypes of SFN.

Diabetic Peripheral Neuropathy: Diagnosis and Treatment

BACKGROUND

Diabetic peripheral neuropathy (DPN) is traditionally divided into large and small fibre neuropathy (SFN). Damage to the large fibres can be detected using nerve conduction studies (NCS) and often results in a significant reduction in sensitivity and loss of protective sensation, while damage to the small fibres is hard to reliably detect and can be either asymptomatic, associated with insensitivity to noxious stimuli, or often manifests itself as intractable neuropathic pain.

OBJECTIVE

To describe the recent advances in both detection, grading, and treatment of DPN as well as the accompanying neuropathic pain.

METHODS

A review of relevant, peer-reviewed, English literature from MEDLINE, EMBASE and Cochrane Library between January 1st 1967 and January 1st 2020 was used.

RESULTS

We identified more than three hundred studies on methods for detecting and grading DPN, and more than eighty randomised-controlled trials for treating painful diabetic neuropathy.

CONCLUSION

NCS remains the method of choice for detecting LFN in people with diabetes, while a gold standard for the detection of SFN is yet to be internationally accepted. In the recent years, several methods with huge potential for detecting and grading this condition have become available including skin biopsies and corneal confocal microscopy, which in the future could represent reliable endpoints for clinical studies. While several newer methods for detecting SFN have been developed, no new drugs have been accepted for treating neuropathic pain in people with diabetes. Tricyclic antidepressants, serotonin-norepinephrine reuptake inhibitors and anticonvulsants remain first line treatment, while newer agents targeting the proposed pathophysiology of DPN are being developed.

Which Method for Diagnosing Small Fiber Neuropathy?

Introduction: Small fiber neuropathies (SFN) induce pain and/or autonomic symptoms. The diagnosis of SFN poses a challenge because the role of skin biopsy as a reference method and of each neurophysiological test remain to be discussed. This study compares six methods evaluating small sensory and autonomic nerve fibers: skin biopsy, Quantitative Sensory Testing (QST), quantitative sweat measurement system (Q-Sweat), Laser Evoked Potentials (LEP), Electrochemical Skin Conductance (ESC) measurement and Autonomic CardioVascular Tests (ACVT). Methods: This is a single center, retrospective study including patients tested for symptoms compatible with SFN between 2013 and 2016 using the afore-mentioned tests. Patients were ultimately classified according to the results and clinical features as "definite SFN," "possible SFN" or "no SFN." The sensitivity (Se) and specificity (Sp) of each test were calculated based on the final diagnosis and the best diagnostic strategy was then evaluated. Results: Two hundred and forty-five patients were enrolled (164 females (66.9%), age: 50.4 ± 15 years). The results are as follows: skin biopsy: Se = 58%, Sp = 91%; QST: Se = 72%, Sp = 39%; Q-Sweat: Se = 53%, Sp = 69%; LEP: Se = 66%, Sp = 89%; ESC: Se = 60%, Sp = 89%; Cardiovascular tests: Se = 15%, Sp = 99%. The combination of skin biopsy, LEP, QST and ESC has a Se of 90% and a Sp of 87%. Conclusion: Our study outlines the benefits of combining skin biopsy, ESC, LEP and QST in the diagnosis of SFN.

Evaluation of small nerve fiber dysfunction in type 2 diabetes

OBJECTIVES

To assess potential correlations between intraepidermal nerve fiber densities (IENFD), graded with light microscopy, and clinical measures of peripheral neuropathy in elderly male subjects with normal glucose tolerance (NGT), impaired glucose tolerance (IGT), and type 2 diabetes (T2DM), respectively.

MATERIALS AND METHODS

IENFD was assessed in thin sections of skin biopsies from distal leg in 86 men (71-77 years); 24 NGT, 15 IGT, and 47 T2DM. Biopsies were immunohistochemically stained for protein gene product (PGP) 9.5, and intraepidermal nerve fibers (IENF) were quantified manually by light microscopy. IENFD was compared between groups with different glucose tolerance and related to neurophysiological tests, including nerve conduction study (NCS; sural and peroneal nerve), quantitative sensory testing (QST), and clinical examination (Total Neuropathy Score; Neuropathy Symptom Score and Neuropathy Disability Score).

RESULTS

Absent IENF was seen in subjects with T2DM (n = 10; 21%) and IGT (n = 1; 7%) but not in NGT. IENFD correlated weakly negatively with HbA1c (r = -.268, P = .013) and Total Neuropathy Score (r = -.219, P = .042). Positive correlations were found between IENFD and sural nerve amplitude (r = .371, P = .001) as well as conduction velocity of both the sural (r = .241, P = .029) and peroneal nerve (r = .258, P = .018). Proportions of abnormal sural nerve amplitude became significantly higher with decreasing IENFD. No correlation was found with QST. Inter-rater reliability of IENFD assessment was good (ICC = 0.887).

CONCLUSIONS

Signs of neuropathy are becoming more prevalent with decreasing IENFD. IENFD can be meaningfully evaluated in thin histopathological sections using the presented technique to detect neuropathy.

Sarm1 Gene Deficiency Attenuates Diabetic Peripheral Neuropathy in Mice

Diabetic peripheral neuropathy (DPN) is the most common complication in both type 1 and type 2 diabetes, but any treatment toward the development of DPN is not yet available. Axon degeneration is an early feature of many peripheral neuropathies, including DPN. Delay of axon degeneration has beneficial effects on various neurodegenerative diseases, but its effect on DPN is yet to be elucidated. Deficiency of Sarm1 significantly attenuates axon degeneration in several models, but the effect of Sarm1 deficiency on DPN is still unclear. In this study, we show that Sarm1 knockout mice exhibit normal glucose metabolism and pain sensitivity, and deletion of the Sarm1 gene alleviates hypoalgesia in streptozotocin-induced diabetic mice. Moreover, Sarm1 gene deficiency attenuates intraepidermal nerve fiber loss in footpad skin; alleviates axon degeneration, the change of g-ratio in sciatic nerves, and NAD⁺ decrease; and relieves axonal outgrowth retardation of dorsal root ganglia from diabetic mice. In addition, Sarm1 gene deficiency markedly diminishes the changes of gene expression profile induced by streptozotocin in the sciatic nerve, especially some abundant genes involved in neurodegenerative diseases. These findings demonstrate that Sarm1 gene deficiency attenuates DPN in mice and suggest that slowing down axon degeneration is a potential promising strategy to combat DPN.

Nonlinear Inverted-U Shaped Relationship Between Aging and Epidermal Innervation in the Rat Plantar Hind Paw: A Laser Scanning Confocal Microscopy Study

The under-reporting of pain and atypical manifestations of painful syndromes within the elderly population have been well documented, however, the specific relationship between pain and aging remains ambiguous. Previous studies have reported degenerative changes in primary afferents with aging. In this study, we questioned whether there is any change in the density of primary afferent endings within the epidermis of aged animals. Rats were categorically assessed in 4 age groups, each representing a key developmental stage across their life span: juvenile (2 months), adult (7 months); aged (18 months), and senescent (24-26 months). The plantar hind paw skin was removed, post-fixed, cut, and immunostained for protein gene product 9.5 and type IV collagen. Rats in the adult aged groups had significantly increased epidermal nerve densities and total lengths of immunoreactive nerve fibers, compared with juvenile as well as senescent rats. However, the paw withdrawal thresholds to punctate mechanical stimulation progressively increased with age, and did not exhibit a clear relationship with epidermal innervation. We conclude a nonlinear, inverted-U shaped relationship between rat plantar epidermal nerve density with aging, which does not correlate with mechanically-induced paw withdrawal behaviors.

PERSPECTIVE

This article presents age-related decreased epidermal innervation in rat hind paw skin, which partly explains mechanisms underlying decreased pain sensitivity in aged subjects. The report may help clinicians to understand that any compromise of pain-sensing pathway can lead to under-reporting of pain, inadequate analgesia, and slower recovery from a painful condition.

Automated PGP9.5 immunofluorescence staining: a valuable tool in the assessment of small fiber neuropathy?

BACKGROUND

In this study we explored the possibility of automating the PGP9.5 immunofluorescence staining assay for the diagnosis of small fiber neuropathy using skin punch biopsies. The laboratory developed test (LDT) was subjected to a validation strategy as required by good laboratory practice guidelines and compared to the well-established gold standard method approved by the European Federation of Neurological Societies (EFNS). To facilitate automation, the use of thinner sections. (16 µm) was evaluated. Biopsies from previously published studies were used. The aim was to evaluate the diagnostic performance of the LDT compared to the gold standard. We focused on technical aspects to reach high-quality standardization of the PGP9.5 assay and finally evaluate its potential for use in large scale batch testing.

RESULTS

We first studied linear nerve fiber densities in skin of healthy volunteers to establish reference ranges, and compared our LDT using the modifications to the EFNS counting rule to the gold standard in visualizing and quantifying the epidermal nerve fiber network. As the LDT requires the use of 16 µm tissue sections, a higher incidence of intra-epidermal nerve fiber fragments and a lower incidence of secondary branches were detected. Nevertheless, the LDT showed excellent concordance with the gold standard method. Next, the diagnostic performance and yield of the LDT were explored and challenged to the gold standard using skin punch biopsies of capsaicin treated subjects, and patients with diabetic polyneuropathy. The LDT reached good agreement with the gold standard in identifying small fiber neuropathy. The reduction of section thickness from 50 to 16 µm resulted in a significantly lower visualization of the three-dimensional epidermal nerve fiber network, as expected. However, the diagnostic performance of the LDT was adequate as characterized by a sensitivity and specificity of 80 and 64 %, respectively.

CONCLUSIONS

This study, designed as a proof of principle, indicated that the LDT is an accurate, robust and automated assay, which adequately and reliably identifies patients presenting with small fiber neuropathy, and therefore has potential for use in large scale clinical studies.

Peripheral nervous system involvement in primary burning mouth syndrome--results of a pilot study

OBJECTIVE

The pathophysiology of primary burning mouth syndrome (BMS) has remained enigmatic, but recent studies suggest pathology within the nervous system at multiple levels. This study aimed to investigate in detail the contribution of either focal or generalized alterations within the peripheral nervous system (PNS) in the etiopathogenesis of BMS.

SUBJECTS AND METHODS

Intraepithelial nerve fiber density (IENFD) of tongue mucosa was assessed in 10 carefully characterized BMS, and the results were compared to 19 age- and gender-matched cadaver controls, 6 with lifetime diabetes. Extensive neurophysiologic and psychophysical examinations of the trigeminal system and distal extremities were performed to profile PNS function in BMS.

RESULTS

Patients with BMS had significantly fewer intraepithelial nerve fibers (0,27, s.e. 0,18 mm(-1); P = 0.0253) than non-diabetic controls (0,92, s.e. 0,15 mm(-1)). In the subepithelial space, the amount of nerve fibers did not differ between the groups. The majority (9/10) of patients with BMS showed neurophysiologic or psychophysical signs of a more generalized PNS dysfunction.

CONCLUSIONS

Our results in neurophysiologically optimally characterized BMS patients confirm that pure focal small fiber neuropathy of the oral mucosa has a role in the pathophysiology of primary BMS. Furthermore, BMS may be related to a more generalized, yet subclinical peripheral neuropathy.

The usefulness of quantifying intraepidermal nerve fibers density in the diagnostic of diabetic peripheral neuropathy: a cross-sectional study

BACKGROUND

Distal symmetric polyneuropathy (DSPN) is the most common complication of type 2 diabetes mellitus (T2DM) and the most common form of peripheral neuropathy. DSPN increases the risk of foot ulceration up to seven-fold, and is a significant risk factor in more than 60 % of the amputations of the lower limbs in patients with T2DM. The aims of our study were to evaluate the difference in the density of intraepidermal nerve fibers (IENF) in patients with respectively without DSPN, to evaluate the strength of the relationship between the symptomatology of the DSPN and IENF density and to define a cutoff value of the IENF density for the diagnosis of DSPN.

METHODS

We enrolled, according to a consecutive, population-based method, 36 patients with T2DM admitted in our Clinic. For all patients, we measured HbA1c, lipid profile, body mass index and we assessed the presence and severity of DSPN using the evaluation of clinical symptoms, nerve conduction velocity and IENF density quantification.

RESULTS

The presence of neuropathy was significantly associated with a decreased density of IENF for both the proximal (11.6 vs. 14.9 fibers/mm; p = 0.014) and the distal biopsies (7.2 vs. 8.6 fibers/mm; p = 0.020). The optimal threshold value of IENF density (the point with the maximum sum of specificity and sensitivity), according to our model, was 10.1 fibers/mm.

CONCLUSIONS

Skin biopsy followed by IENF density quantification is a valid, reliable tool for the diagnosis of DSPN.

The Variant p.(Arg183Trp) in SPTLC2 Causes Late-Onset Hereditary Sensory Neuropathy

Hereditary sensory and autonomic neuropathy 1 (HSAN1) is an autosomal dominant disorder that can be caused by variants in SPTLC1 or SPTLC2, encoding subunits of serine palmitoyl-CoA transferase. Disease variants alter the enzyme's substrate specificity and lead to accumulation of neurotoxic 1-deoxysphingolipids. We describe two families with autosomal dominant HSAN1C caused by a new variant in SPTLC2, c.547C>T, p.(Arg183Trp). The variant changed a conserved amino acid and was not found in public variant databases. All patients had a relatively mild progressive distal sensory impairment, with onset after age 50. Small fibers were affected early, leading to abnormalities on quantitative sensory testing. Sural biopsy revealed a severe chronic axonal neuropathy with subtotal loss of myelinated axons, relatively preserved number of non-myelinated fibers and no signs for regeneration. Skin biopsy with PGP9.5 labeling showed lack of intraepidermal nerve endings early in the disease. Motor manifestations developed later in the disease course, but there was no evidence of autonomic involvement. Patients had elevated serum 1-deoxysphingolipids, and the variant protein produced elevated amounts of 1-deoxysphingolipids in vitro, which proved the pathogenicity of the variant. Our results expand the genetic spectrum of HSAN1C and provide further detail about the clinical characteristics. Sequencing of SPTLC2 should be considered in all patients presenting with mild late-onset sensory-predominant small or large fiber neuropathy.

Quantitative and morphological study of intraepidermal nerve fibre in healthy individuals

The study was aimed to observe the morphology of intraepidermal nerve fibre (IENF) and to explore the relationships between intraepidermal nerve fibre density (IENFD) and anatomic sites, age, genders and races. Intraepidermal nerve fibre was observed using immunohistochemistry. The relationships between IENFD and anatomic sites, ages, genders and races were analysed by quantitative analysis of IENFD. Five patterns of the IENFs were observed according to the morphological classification. A significant difference was observed in IENFD between different anatomic sites (P < 0.05). A linear negative correlation was observed between IENFD and age (r = - 0.2931, P < 0.01). No significant difference was found between IENFD and genders. Intraepidermal nerve fibre density at distal leg of Chinese (395.54 ± 166.92) was higher than that of Finnish (114.62 ± 32.32, P < 0.01). Skin biopsy may be an effective tool in quantitation of IENFD in healthy individuals. Intraepidermal nerve fibre density is independent of genders, and closely associated with anatomic sites, races and ages.

A reversible functional sensory neuropathy model

Small-fiber neuropathy was induced in young adult mice by intraperitoneal injection of resiniferatoxin (RTX), a TRPV1 agonist. At day 7, RTX induced significant thermal and mechanical hypoalgesia. At day 28, mechanical and thermal nociception were restored. No nerve degeneration in skin was observed and unmyelinated nerve fiber morphology and density in sciatic nerve were unchanged. At day 7, substance P (SP) was largely depleted in dorsal root ganglia (DRG) neurons, although calcitonin gene-related peptide (CGRP) was only moderately depleted. Three weeks after, SP and CGRP expression was restored in DRG neurons. At the same time, CGRP expression remained low in intraepidermal nerve fibers (IENFs) whereas SP expression had improved. In summary, RTX induced in our model a transient neuropeptide depletion in sensory neurons without nerve degeneration. We think this model is valuable as it brings the opportunity to study functional nerve changes in the very early phase of small fiber neuropathy. Moreover, it may represent a useful tool to study the mechanisms of action of therapeutic strategies to prevent sensory neuropathy of various origins.

Mechanisms of diabetic neuropathy: Schwann cells

As ensheathing and secretory cells, Schwann cells are a ubiquitous and vital component of the endoneurial microenvironment of peripheral nerves. The interdependence of axons and their ensheathing Schwann cells predisposes each to the impact of injury in the other. Further, the dependence of the blood-nerve interface on trophic support from Schwann cells during development, adulthood, and after injury suggests these glial cells promote the structural and functional integrity of nerve trunks. Here, the developmental origin, injury-induced changes, and mature myelinating and nonmyelinating phenotypes of Schwann cells are reviewed prior to a description of nerve fiber pathology and consideration of pathogenic mechanisms in human and experimental diabetic neuropathy. A fundamental role for aldose-reductase-containing Schwann cells in the pathogenesis of diabetic neuropathy, as well as the interrelationship of pathogenic mechanisms, is indicated by the sensitivity of hyperglycemia-induced biochemical alterations, such as polyol pathway flux, formation of reactive oxygen species, generation of advanced glycosylation end products (AGEs) and deficient neurotrophic support, to blocking polyol pathway flux.

Gliadin antibodies in older population and neurological and psychiatric disorders

OBJECTIVES

A variety of neurological and psychiatric disorders have recently been linked to coeliac disease and gluten sensitivity. We here explored whether persistently positive gliadin antibodies (AGA) and coeliac-type HLA increase the risk of gluten sensitivity-related neurological and psychiatric manifestations. The study was carried out in an older population who had consumed gluten for decades but who had no previous coeliac disease diagnosis.

MATERIALS AND METHODS

The original study population comprised 4272 randomly selected older individuals, of whom 2089 had AGA and transglutaminase 2 antibodies (antiTG2) measured twice within a 3-year interval. Forty-nine persistently AGA-positive but antiTG2-negative subjects with coeliac-type HLA and 52 randomly selected persistently AGA- and antiTG2-negative age- and sex-matched controls were clinically examined for neurological disorders. The Psychological General Well-Being (PGWB) questionnaire, the SF-36 health survey questionnaire and the Depression Scale (DEPS) were employed to evaluate psychological well-being. The medical files of all the study subjects were analysed for previous illnesses.

RESULTS

Persistently AGA-positive but antiTG2-negative older subjects carrying coeliac disease-type HLA did not evince significantly more neurological symptoms or diseases than AGA-negative control subjects (P = 0.682, P = 0.233). There were no statistically significant differences between AGA-positive and AGA-negative groups in psychological well-being and quality of life when measured by PGWB (P = 0.426), SF-36 questionnaires (P = 0.120) and DEPS (P = 0.683).

CONCLUSIONS

At population level, persistent AGA positivity did not indicate gluten sensitivity-related neurological and psychiatric disorders.

Degree of skin denervation and its correlation to objective thermal sensory test in leprosy patients

Background

Leprosy is an infectious disease affecting skin and peripheral nerves resulting in increased morbidity and physical deformities. Early diagnosis provides opportune treatment and reduces its complications, relying fundamentally on the demonstration of impaired sensation in suggestive cutaneous lesions. The loss of tactile sensitivity in the lesions is preceded by the loss of thermal sensitivity, stressing the importance of the thermal test in the suspicious lesions approach. The gold-standard method for the assessment of thermal sensitivity is the quantitative sensory test (QST). Morphological study may be an alternative approach to access the thin nerve fibers responsible for thermal sensitivity transduction. The few studies reported in leprosy patients pointed out a rarefaction of thin dermo-epidermal fibers in lesions, but used semi-quantitative evaluation methods.

Methodology/Principal Findings

This work aimed to study the correlation between the degree of thermal sensitivity impairment measured by QST and the degree of denervation in leprosy skin lesions, evaluated by immunohistochemistry anti-PGP 9.5 and morphometry. Twenty-two patients were included. There were significant differences in skin thermal thresholds among lesions and contralateral skin (cold, warm, cold induced pain and heat induced pain). The mean reduction in the density of intraepidermal and subepidermal fibers in lesions was 79.5% (SD = 19.6) and 80.8% (SD = 24.9), respectively.

Conclusions/Significance

We observed a good correlation between intraepidermal and subepidermal fibers deficit, but no correlation between these variables and those accounting for the degree of impairment in thermal thresholds, since the thin fibers rarefaction was homogeneously intense in all patients, regardless of the degree of sensory deficit. We believe that the homogeneously intense denervation in leprosy lesions should be objective of further investigations focused on its diagnostic applicability, particularly in selected cases with only discrete sensory impairment, patients unable to perform the sensory test and especially those with nonspecific histopathological finds.

Our study has addressed objectively the rarefaction of cutaneous thin nerve fibers density and its correlation with quantitative thermal sensory test in leprosy patients. Thermal sensitivity evaluation is crucial to the early diagnosis of leprosy, since it is the first type of cutaneous sensitivity lost in the lesions. However, some patients are unable to perform thermal tests, like children and patients with cognitive impairment. The pathological study of those lesions is also fundamental and it is the gold standard method to diagnose and classify leprosy patients. However, it may also be unspecific, especially in the indeterminate form of leprosy. Our findings show that even in lesions with slight thermal sensitivity impairment, there is a homogeneously intense denervation, specifically in the superficial skin layers. We believe that our findings pave the way to future studies focused on the diagnostic applicability of the cutaneous thin nerve fibers density quantification in leprosy suspected lesions.

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.

Assessment of symptomatic diabetic patients with normal nerve conduction studies: utility of cutaneous silent periods and autonomic tests

Established electrophysiological methods have limited clinical utility in the diagnosis of small-fiber neuropathy (SFN). In this study, diabetic patients with clinically diagnosed SFN were evaluated with autonomic tests and cutaneous silent periods (CSPs). Thirty-one diabetic patients with clinically suspected SFN and normal nerve conduction studies were compared with 30 controls. In the upper extremities (UE), the CSP parameters did not differ statistically between the patient and control groups, whereas, in the lower extremities (LE), patients had prolonged CSP latencies (P = 0.018) and shortened CSP durations (P < 0.001). The sensitivity of the CSP duration was 32.6%, and the specificity was 96.7%. The expiration-to-inspiration ratios and amplitudes of the sympathetic skin responses in the lower extremities were also reduced. Our findings indicate that the diagnostic utility of CSPs was higher than that of the autonomic tests to support the clinically suspected diagnosis of SFN.

European Federation of Neurological Societies/Peripheral Nerve Society Guideline on the use of skin biopsy in the diagnosis of small fiber neuropathy. Report of a joint task force of the European Federation of Neurological Societies and the Peripheral Nerve Society

BACKGROUND

Revision of the guidelines on the use of skin biopsy in the diagnosis of peripheral neuropathy, published in 2005, has become appropriate owing to publication of more relevant articles. Most of the new studies focused on small fiber neuropathy (SFN), a subtype of neuropathy for which the diagnosis was first developed through skin biopsy examination. This revision focuses on the use of this technique to diagnose SFN.

METHODS

Task force members searched the Medline database from 2005, the year of the publication of the first EFNS guideline, to June 30th, 2009. All pertinent articles were rated according to the EFNS and PNS guidance. After a consensus meeting, the task force members created a manuscript that was subsequently revised by two experts (JML and JVS) in the field of peripheral neuropathy and clinical neurophysiology, who were not previously involved in the use of skin biopsy.

RESULTS AND CONCLUSIONS

Distal leg skin biopsy with quantification of the linear density of intraepidermal nerve fibers (IENF), using generally agreed upon counting rules, is a reliable and efficient technique to assess the diagnosis of SFN (Recommendation Level A). Normative reference values are available for bright-field immunohistochemistry (Recommendation Level A) but not yet for confocal immunofluorescence or the blister technique. The morphometric analysis of IENF density, either performed with bright-field or immunofluorescence microscopy, should always refer to normative values matched for age (Recommendation Level A). Newly established laboratories should undergo adequate training in a well-established skin biopsy laboratory and provide their own stratified for age and gender normative values, intra- and interobserver reliability, and interlaboratory agreement. Quality control of the procedure at all levels is mandatory (Good Practice Point). Procedures to quantify subepidermal nerve fibers and autonomic innervated structures, including erector pili muscles, and skin vessels, are under development but need to be confirmed by further studies. Sweat gland innervation can be examined using an unbiased stereologic technique recently proposed (Recommendation Level B). A reduced IENF density is associated with the risk of developing neuropathic pain (Recommendation Level B), but it does not correlate with its intensity. Serial skin biopsies might be useful for detecting early changes of IENF density, which predict the progression of neuropathy, and to assess degeneration and regeneration of IENF (Recommendation Level C). However, further studies are warranted to confirm its potential usefulness as an outcome measure in clinical practice and research. Skin biopsy has not so far been useful for identifying the etiology of SFN. Finally, we emphasize that 3-mm skin biopsy at the ankle is a safe procedure based on the experience of 10 laboratories reporting absence of serious side effects in approximately 35,000 biopsies and a mere 0.19% incidence of non-serious side effects in about 15 years of practice (Good Practice Point).

Intraepidermal nerve fibre density at wrist level in diabetic and non-diabetic patients

AIMS

Myelinated nerve fibre pathology has been demonstrated at wrist level in diabetic patients. We examined if quantification of intra-epidermal nerve fibre density (IENFD) in hairy and glabrous skin at wrist level could detect signs of subclinical small nerve fibre neuropathy.

METHODS

In 35 diabetic patients who were age and gender matched with 31 non-diabetic patients, punch biopsies were obtained in conjunction with surgical carpal tunnel release. Biopsies were immunostained with anti-protein gene product (PGP) 9.5. The IENFD was quantified using manual counting by light microscopy.

RESULTS

We could not demonstrate significant differences in IENFD between diabetic or non-diabetic patients. Additionally, no differences were found between patients with Type 1 and Type 2 diabetes or in diabetic patients with and without neurophysiologic signs of mild peripheral neuropathy. However, the IENFD was significantly higher in hairy skin compared with glabrous skin. Furthermore, the IENFD was significantly higher in females than in males and correlated with age, but not with duration of diabetes or glycated haemoglobin (HbA(1c)).

CONCLUSIONS

In mild neuropathy no difference in IENFD at the wrist level could be detected between diabetic and non-diabetic patients. Independent of diabetes, we found IENFD to be higher in hairy skin compared with glabrous skin and higher in females than in males. These results must be taken into consideration when assessing small nerve fibre pathology in the upper extremity.

Acetyl-l-carnitine increases nerve regeneration and target organ reinnervation - a morphological study

Peripheral nerve injury frequently results in functional morbidity since standard management fails to adequately address many of the neurobiological hurdles to optimal regeneration. Neuronal survival and regeneration are neurotrophin dependent and require increased aerobic capacity. Acetyl-l-carnitine (ALCAR) facilitates this need and prevents neuronal loss. ALCAR is clinically safe and is shown here to significantly improve nerve regeneration and target organ reinnervation. Two groups of five rats underwent sciatic nerve division followed by immediate repair. One group received parenteral ALCAR (50mg/kg/day) from time of operation until termination at 12 weeks. A 'sham treatment' group received normal saline. A third group was left unoperated and did not receive any treatment. A segment of nerve was harvested between 5mm proximal and 10mm distal to the repair in operated groups, and at the corresponding level in the unoperated group. Mean axonal count in normal, non-axotomised nerve was 14,720 (SD 2378). That of the saline group (17,217 SD 1808) was not significantly different from normal nerve (P=0.0985). Mean number of myelinated axons in the ALCAR group (24,460 SD 3750) was significantly greater than both sham group (P<0.01) and normal nerve (P=0.0012). Mean myelin thickness in the saline treated group (0.408 microm SD 0.067 microm) was less than normal nerve (0.770 microm SD 0.143 microm) (P<0.001). Mean myelin thickness in the ALCAR group (0.627 microm SD 0.052 microm) was greater than the sham (saline) group (P<0.01) and not statistically different from normal nerve (P=0.07). ALCAR increased dermal PGP9.5 staining by 210% compared to sham treatment (P<0.0001) and significantly reduced the mean percentage weight loss in gastrocnemius muscle (ALCAR group 0.203% vs. 0.312% in sham group P=0.015). ALCAR not only increases the number of regenerating nerve fibres but also morphologically improves the quality of regeneration and target organ reinnervation. Adjuvant ALCAR treatment may improve both sensory and motor outcomes and merits further investigation.

Significant difference between three observers in the assessment of intraepidermal nerve fiber density in skin biopsy

BACKGROUND

The determination of Intraepidermal Nerve Fiber Density (IENFD) in skin biopsy is a useful method for the evaluation of different types of peripheral neuropathies. To allow a reliable use of the method it is necessary to determine interobserver reliability. Previous studies dealing with this topic used limited suitable statistical methods.

METHODS

In the present study three observers determined the IENFD and estimated the staining quality of the basement membrane for an adequate quantity of 120 skin biopsies (stained with indirect immunofluorescence technique) from 68 patients. More adequate statistical methods like intraclass correlation coefficient and Bland Altman Plot were chosen to estimate interobserver reliability.

RESULTS

We found an unexpected significant difference in IENFD between the observers (p < 0.05) and so the results of this study are not in line with the high interobserver reliability reported before (intraclass correlation coefficient: 0.73). The Bland Altmann Plot showed a variance growing with rising mean. The difference in IENFD between the observers and the resulting low interobserver reliability is likely caused by different interpretations of the standard counting rules. There was no significant difference in IENFD between observers for biopsies with a well-defined basement membrane. Thus skin biopsies with an inexactly defined basement membrane should not be used diagnostically for the determination of IENFD.

CONCLUSION

These results emphasise that standardisation of the method is extremely important and at least two observers should analyse skin biopsies with critical IENFD near the cut-off values.

Evaluation of distal symmetric polyneuropathy: the role of autonomic testing, nerve biopsy, and skin biopsy (an evidence-based review)

Distal symmetric polyneuropathy (DSP) is the most common variety of neuropathy. Since the evaluation of this disorder is not standardized, the available literature was reviewed to provide evidence-based guidelines regarding the role of autonomic testing, nerve biopsy, and skin biopsy for the assessment of polyneuropathy. A literature review using MEDLINE, EMBASE, Science Citation Index, and Current Contents was performed to identify the best evidence regarding the evaluation of polyneuropathy published between 1980 and March 2007. Articles were classified according to a four-tiered level of evidence scheme and recommendations were based on the level of evidence. (1) Autonomic testing may be considered in the evaluation of patients with polyneuropathy to document autonomic nervous system dysfunction (Level B). Such testing should be considered especially for the evaluation of suspected autonomic neuropathy (Level B) and distal small fiber sensory polyneuropathy (SFSN) (Level C). A battery of validated tests is recommended to achieve the highest diagnostic accuracy (Level B). (2) Nerve biopsy is generally accepted as useful in the evaluation of certain neuropathies as in patients with suspected amyloid neuropathy, mononeuropathy multiplex due to vasculitis, or with atypical forms of chronic inflammatory demyelinating polyneuropathy (CIDP). However, the literature is insufficient to provide a recommendation regarding when a nerve biopsy may be useful in the evaluation of DSP (Level U). (3) Skin biopsy is a validated technique for determining intraepidermal nerve fiber (IENF) density and may be considered for the diagnosis of DSP, particularly SFSN (Level C). There is a need for additional prospective studies to define more exact guidelines for the evaluation of polyneuropathy.

Epidermal nerve fiber quantification in the assessment of diabetic neuropathy

Assessment of cutaneous innervation in skin biopsies is emerging as a valuable means of both diagnosing and staging diabetic neuropathy. Immunolabeling, using antibodies to neuronal proteins such as protein gene product 9.5, allows for the visualization and quantification of intraepidermal nerve fibers. Multiple studies have shown reductions in intraepidermal nerve fiber density in skin biopsies from patients with both type 1 and type 2 diabetes. More recent studies have focused on correlating these changes with other measures of diabetic neuropathy. A loss of epidermal innervation similar to that observed in diabetic patients has been observed in rodent models of both type 1 and type 2 diabetes and several therapeutics have been reported to prevent reductions in intraepidermal nerve fiber density in these models. This review discusses the current literature describing diabetes-induced changes in cutaneous innervation in both human and animal models of diabetic neuropathy.

Skin biopsy as a diagnostic tool in peripheral neuropathy

Skin biopsy is a safe, minimally invasive, painless and cheap tool for providing diagnostic information on small nerve fibers, which are invisible to routine neurophysiological tests. Biopsy can be performed in hairy skin to investigate unmyelinated and thinly myelinated fibers and in glabrous skin to examine large myelinated fibers. Morphometric analysis of skin nerves is readily accomplished through the use of immunohistochemical techniques, and has proved to be reliable, reproducible and unaffected by the severity of neuropathy. One further advantage of skin biopsy over conventional nerve biopsy is that it allows somatic nerve fibers to be distinguished from autonomic nerve fibers. Morphological changes, axonal degeneration and abnormal regeneration occur in cutaneous nerves very early in the course of peripheral neuropathies, making skin biopsy a promising tool for investigating the progression of neuropathy and the effect of neuroprotective treatments in clinical practice and trials. This article reviews the techniques that are used to investigate the innervation of human skin, the possible uses of skin biopsy in diagnosing and monitoring peripheral neuropathies, and correlations between skin biopsy findings and those of other diagnostic methods.

Use of the novel Contact Heat Evoked Potential Stimulator (CHEPS) for the assessment of small fibre neuropathy: correlations with skin flare responses and intra-epidermal nerve fibre counts

Background

The Contact Heat Evoked Potential Stimulator (CHEPS) rapidly stimulates cutaneous small nerve fibres, and resulting evoked potentials can be recorded from the scalp. We have studied patients with symptoms of sensory neuropathy and controls using CHEPS, and validated the findings using other objective measures of small nerve fibres i.e. the histamine-induced skin flare response and intra-epidermal fibres (IEF), and also quantitative sensory testing (QST), a subjective measure.

Methods

In patients with symptoms of sensory neuropathy (n = 41) and healthy controls (n = 9) we performed clinical examination, QST (monofilament, vibration and thermal perception thresholds), nerve conduction studies, histamine-induced skin flares and CHEPS. Skin punch biopsies were immunostained using standard ABC immunoperoxidase for the nerve marker PGP 9.5 or the heat and capsaicin receptor TRPV1. Immunoreactive IEF were counted per length of tissue section and epidermal thickness recorded.

Results

Amplitudes of Aδ evoked potentials (μV) following face, arm or leg stimulation were reduced in patients (e.g. for the leg: mean ± SEM – controls 11.7 ± 1.95, patients 3.63 ± 0.85, p = 0.0032). Patients showed reduced leg skin flare responses, which correlated with Aδ amplitudes (r_s = 0.40, p = 0.010). In patient leg skin biopsies, PGP 9.5- and TRPV1-immunoreactive IEF were reduced and correlated with Aδ amplitudes (PGP 9.5, r_s = 0.51, p = 0.0006; TRPV1, r_s = 0.48, p = 0.0012).

Conclusion

CHEPS appears a sensitive measure, with abnormalities observed in some symptomatic patients who did not have significant IEF loss and/or QST abnormalities. Some of the latter patients may have early small fibre dysfunction or ion channelopathy. CHEPS provides a clinically practical, non-invasive and objective measure, and can be a useful additional tool for the assessment of sensory small fibre neuropathy. Although further evaluation is required, the technique shows potential clinical utility to differentiate neuropathy from other chronic pain states, and provide a biomarker for analgesic development.

Skin biopsy in the management of peripheral neuropathy

Skin biopsy has been widely used in recent years for the investigation of small-calibre sensory nerves, including somatic unmyelinated intraepidermal nerve fibres, dermal myelinated nerve fibres, and autonomic nerve fibres in peripheral neuropathies, with different techniques for tissue processing and nerve fibre assessment. Here, we review the techniques for skin biopsy, the processing and assessment of the biopsy sample, their possible uses in different types of peripheral neuropathy, and their use in the follow-up of patients and in clinical trials. We also review the association between morphological measures of skin innervation and function and the limits of this method in the aetiological classification of peripheral neuropathies.

Comparison of a simple method for quantitation of intraepidermal nerve fibres with a standard image analysis method using hypothenar skin

OBJECTIVES

To compare a simpler method for counting intraepidermal nerve fibres with a standard computer based image analysis method in normal subjects with skin taken from the hypothenar region.

METHODS

In 40 healthy controls (mean age 41.1 years, range 21-71, 24 Chinese, 11 Indian, 5 Malay, 30 females) intraepidermal nerve fibres per length of epidermis were determined using immunoperoxidase staining with the panaxonal antibody PGP 9.5. Under brightfield microscopy, two methods of determining the length of the epidermis were compared. A simpler method employing a microscope intraocular lens ruler was compared with the more complex gold standard using image software analysis .

RESULTS

Intraepidermal nerve fibres per length of epidermis using the intraocular ruler method were 3.07 nerve fibres/mm (2SD 1.56). The image software analysis obtained values of 3.05 nerve fibres/mm (2SD 1.54). Correlation between the two tests was excellent (r=0.999 p= or <0.00001). Epidermal nerve fibre counts from hypothenar skin are lower than in more proximal sites.

CONCLUSION

A simple method for counting intraepidermal nerve fibres produces results similar to those using standard software image analysis. This should help the implementation of this technique for wider use.

Recent developments in the assessment of efficacy in clinical trials of diabetic neuropathy

A large number of measures may be employed in clinical practice and for epidemiologic studies to quantify and risk stratify diabetic patients with neuropathy. However, not all measures are suitable for assessing the benefits of therapeutic intervention. Therefore, for the purpose of this review we focus on measures that may be employed to define the efficacy of interventions in clinical trials of human diabetic neuropathy. Two major types of end points are used: 1) those that assess symptoms for defining efficacy in painful diabetic neuropathy, and 2) those that assess neurologic deficits that assess the effects of treatments that may prevent further degeneration or promote repair.