Automated immunohistochemistry of intra-epidermal nerve fibres in skin biopsies: A proof-of-concept study.

AIMS: To develop a standardised, automated protocol for detecting protein gene product 9.5 (PGP9.5) positive intra-epidermal nerve fibres (IENFs) in skin biopsies, transitioning from the established manual technique to an automated platform. This automated method, although currently intended for research applications, may improve the accessibility of this diagnostic test for small fibre neuropathy in clinical settings. METHODS: Skin biopsies (n = 274) from 100 participants (fibromyalgia syndrome n = 62; idiopathic small fibre neuropathy: n = 16; healthy volunteers: n = 22) were processed using an automated immunohistochemistry platform. IENF quantification was performed by blinded examiners, with reliability assessed via a two-way mixed-effects model to evaluate inter- and intra-observer variability. RESULTS: The automated staining system reproduced intra-epidermal nerve fibre density (IENFD) counts consistent with free-floating sections (mean ± standard deviation: free-floating: 5.6 ± 3.4 fibres/mm; automated: 5.9 ± 3.2 fibres/mm). A median difference of 0.3 with a lower bound 95% Confidence Interval (CI) at -0.00005 established non-inferiority against a margin of -0.4 (p = .08). Specifically, the inter-class correlation coefficient (class denotes consistency in measured observations) was 99% (95% CI: 0.9-1), indicating excellent agreement between free-floating and automated methods. The inter- and intra-class coefficient between examiners were both 99% (95% CI: 0.9-0.1) for IENFD, demonstrating high reliability using sections stained using the automated method. INTERPRETATION: Automated immunohistochemistry provides high-throughput reliable and reproducible intra-epidermal nerve fibre quantification. This method, although currently proof-of-concept, for research use only, may be more widely deployed in histopathology laboratories to increase the adoption of IENFD assessment for the diagnosis of peripheral neuropathies.

Tear neuropeptide Y as a non-invasive marker of peripheral microvascular complications in type 1 diabetes.

AIMS: To investigate tear neuropeptide Y (NPY) and substance P concentrations in individuals with type 1 diabetes, comparing those with and without both diabetic retinopathy (DR) and peripheral neuropathy. METHODS: This cross-sectional study involved 41 participants with type 1 diabetes and none to moderate DR, and 22 healthy controls. Assessments included clinical ocular surface parameters, quantification of corneal nerve attributes (based on in vivo confocal microscopy imaging), DR grading, and evaluation for small and large fibre neuropathy. Concentrations of NPY and substance P in tear samples were measured using enzyme-linked immunosorbent assay. RESULTS: Mean (± standard deviation) tear NPY concentrations in participants with type 1 diabetes and length-dependent small fibre neuropathy (SFN) was lower than in controls (10.84 ± 4.10 ng/mL vs 14.72 ± 3.12 ng/mL; p=0.004), but not significantly different from type 1 diabetes participants without SFN (13.39 ± 4.66 ng/mL; p=0.11). Tear NPY levels were lower in individuals with type 1 diabetes and mild/moderate non-proliferative DR (10.44 ± 3.46 ng/mL) compared to none/minimal DR (13.79 ± 4.76 ng/mL; p=0.0005) and controls. In separate linear regression models, both the presence of SFN (ß = -0.75, p=0.02) and the presence of mild/moderate DR (ß = -0.84, p=0.009) were significantly associated with tear NPY levels relative to controls, after adjusting for participant age, sex, and dry eye disease. There were no inter-group differences for tear substance P concentrations. CONCLUSIONS: Tear NPY has potential utility as an indicator of peripheral microvascular complications associated with type 1 diabetes.

Myocarditis, Coagulopathy, and Small Fibre, Sensory, and Multiple Cranial Nerve Neuropathy Complicating BNT162b2 Vaccination: A Case Report.

SARS-CoV-2 vaccinations can lead to complications, including post-acute COVID-19 vaccination syndrome (PACVS). There has been no report of a patient with PACVS presenting with Guillain-Barre syndrome (GBS), myocarditis/pericarditis, immunodeficiency, or coagulopathy after the second BNT162b2 dose. The patient is a 51-year-old woman with chronic myopericarditis, coagulopathy due to factor-VIII increase and protein-S deficiency, GBS, and a number of other ocular, dermatological, immunological, and central nervous system abnormalities related to the second dose of the BNT172b2 vaccine. GBS manifested with mild, multiple cranial nerve lesions, small fibre neuropathy (SFN) affecting the autonomic system with postural tachycardia syndrome (POTS) and orthostatic hypotension, and sensory disturbances in the upper and lower limbs. PACVS was diagnosed months after onset, but despite the delayed diagnosis, the patient benefited from glucocorticoids, repeated HELP apheresis, and multiple symptomatic treatments. The case shows that SARS-CoV-2 vaccination can be complicated by PACVS manifesting as chronic myopericarditis, coagulopathy, GBS with predominant dysautonomia, and impaired immune competence, and that diagnosis of PACVS can be delayed for months. Delayed diagnosis of PACVS may result in a delay in appropriate treatment and the prolongation of disabling symptoms. Patients and physicians should be made aware of PACVS to improve diagnostic and therapeutic management in terms of patient and healthcare system costs.

Tryptophan metabolism and small fibre neuropathy: a correlation study.

Small nerve fibres located in the epidermis sense pain. Dysfunction of these fibres decreases the pain threshold known as small fibre neuropathy. Diabetes mellitus is accompanied by metabolic changes other than glucose, synergistically eliciting small fibre neuropathy. These findings suggest that various metabolic changes may be involved in small fibre neuropathy. Herein, we explored the correlation between pain sensation and changes in plasma metabolites in healthy Japanese subjects. The pain threshold evaluated from the intraepidermal electrical stimulation was used to quantify pain sensation in a total of 1021 individuals in the 2017 Iwaki Health Promotion Project. Participants with a pain threshold evaluated from the intraepidermal electrical stimulation index <0.20 mA were categorized into the pain threshold evaluated from the intraepidermal electrical stimulation index-low group (n = 751); otherwise, they were categorized into the pain threshold evaluated from the intraepidermal electrical stimulation index-high group (n = 270). Metabolome analysis of plasma was conducted using capillary electrophoresis time-of-flight mass spectrometry. The metabolite set enrichment analysis revealed that the metabolism of tryptophan was significantly correlated with the pain threshold evaluated from the intraepidermal electrical stimulation index in all participants (P < 0.05). The normalized level of tryptophan was significantly decreased in participants with a high pain threshold evaluated from the intraepidermal electrical stimulation index. In addition to univariate linear regression analyses, the correlation between tryptophan concentration and the pain threshold evaluated from the intraepidermal electrical stimulation index remained significant after adjustment for multiple factors (ß = -0.07615, P < 0.05). These findings indicate that specific metabolic changes are involved in the deterioration of pain thresholds. Here, we show that abnormal tryptophan metabolism is significantly correlated with an elevated pain threshold evaluated from the intraepidermal electrical stimulation index in the Japanese population. This correlation provides insight into the pathology and clinical application of small fibre neuropathy.

Development, validation and feasibility of a Patient Satisfaction Questionnaire for evaluating the quality performance of a diagnostic small fibre neuropathy service: A qualitative study.

INTRODUCTION AND AIM: Small fibre neuropathy (SFN) is a peripheral neuropathy, leading to neuropathic pain and autonomic dysfunction. An evidence-based standardized patient diagnostic SFN service has been implemented in the Netherlands for improving patient-centred SFN care. However, the quality of care of this diagnostic SFN service has never been assessed from a patient perspective. The aim of this study was to develop and validate an SFN-Patient Satisfaction Questionnaire (SFN-PSQ) to measure the quality performance of a standardized diagnostic SFN service. METHODS: A descriptive qualitative study to create the SFN-PSQ was performed using the (COREQ (Consolidated Criteria for Reporting Qualitative Research) checklist. For item generation and content development, domains and/or items from validated PSQs were selected. The content development and content validity were performed using a Delphi method with SFN expert caregivers with different backgrounds. By using the three-step-test method in individual cognitive interviews, the content validity by patients was finalized. RESULTS: In one online Delphi panel round, the content of the first concept of the SFN-PSQ was validated, which resulted in the second concept of the SFN-PSQ. From July 2019 till March 2020, nine patients consented to participate in the individual cognitive interviews. The most significant changes of the new questionnaire were adding domains and items concerning the waiting list, the diagnostic services and consultation by the hospital psychiatrist. Also, a differentiation was made for both an inpatient and outpatient diagnostic SFN service. Furthermore, the clarity and intelligibility of the domains/items were improved, resulting in an increased comprehension of the SFN-PSQ. Ultimately, the new developed SFN-PSQ consisted of 10 domains and 51 items, suitable for measuring patient satisfaction of the neurological analysis in patients with SFN. CONCLUSION: Through item generation, expert opinions and interviews with patients, the SFN-PSQ was developed and validated, and feasibility was confirmed. The structure of the questionnaire, based on the logistic and diagnostic SFN pathway, could be used as a model in other hospitals to improve the quality, continuity and access of SFN care and other chronic diseases taking into account potential cross-cultural differences. PATIENT OR PUBLIC CONTRIBUTION: Caregivers were involved in the item generation and content development of the questionnaire. Patients were directly involved in testing the content validity and feasibility of the SFN-PSQ. CLINICAL TRIAL REGISTRATION: Not applicable.

Corneal confocal microscopy demonstrates varying degrees of neurodegeneration in atypical parkinsonian disorders.

OBJECTIVE: We have used corneal confocal microscopy (CCM) to identify corneal nerve loss as a potential marker of neurodegeneration in participants with Parkinson's disease (PD), multiple system atrophy (MSA) and progressive supranuclear palsy (PSP). METHODS: Patients with PD (n = 19), PSP (n = 11), MSA (n = 8) and healthy controls (n = 18) underwent neurological assessment and CCM. RESULTS: Corneal nerve fibre density was significantly lower in participants with PD (p = 0.005), PSP (p = 0.005) and MSA (p = 0.0003) compared to controls. Corneal nerve branch density was significantly lower in participants with PD (p = 0.01) and MSA (p = 0.019), but not in participants with PSP (p = 0.662), compared to controls. Corneal nerve fibre length was significantly lower in participants with PD (p = 0.002) and MSA (p = 0.001) but not in participants with PSP (p = 0.191) compared to controls. CONCLUSION: CCM detects corneal nerve loss in participants with PD and MSA and to a lesser extent in PSP compared to healthy controls.

Frontiers in diagnostic and therapeutic approaches in diabetic sensorimotor neuropathy (DSPN).

Diabetes sensory polyneuropathy (DSPN) is a significant complication of diabetes affecting up to 50% of patients in their lifetime and approximately 20% of patients suffer from painful diabetes neuropathic pain. DSPN - both painless and painful - leads to considerable morbidity including reduction of quality of life, increased lower limb amputations and is associated with worsening mortality. Significant progress has been made in the understanding of pathogenesis of DSPN and the last decade has seen newer techniques aimed at its earlier diagnosis. The management of painful DSPN remains a challenge despite advances made in the unravelling the pathogenesis of pain and its transmission. This article discusses the heterogenous clinical presentation of DSPN and the need to exclude key differential diagnoses. Furthermore, it reviews in detail the current diagnostic techniques involving both large and small neural fibres, their limitations and advantages and current place in the diagnosis of DSPN. Finally, the management of DSPN including newer pharmacotherapies are also discussed.

Corneal confocal microscopy reveals small nerve fibre loss correlating with motor function in adult spinal muscular atrophy.

BACKGROUND: 5q Spinal muscular atrophy (SMA) is a progressive, inherited, and severely disabling - yet treatable - motor neuron disease. Although treatment options have evolved in recent years, biomarkers for treatment monitoring and prognosis prediction remain elusive. Here, we investigated the utility of corneal confocal microscopy (CCM), a non-invasive imaging technique to quantify small corneal nerve fibres in vivo, as a diagnostic tool in adult SMA. METHODS: In this cross-sectional study, 19 patients with SMA type 3 and 19 healthy controls underwent CCM to measure corneal nerve fibre density (CNFD), corneal nerve fibre length (CNFL), and corneal nerve branch density (CNBD), as well as corneal immune cell infiltration. Hammersmith Functional Motor Scale Expanded (HFMSE) and Revised Upper Limb Module (RULM) scores and a 6-Minute Walk Test (6MWT) were conducted to explore any correlation between CCM findings and motor function. RESULTS: Corneal nerve fibre parameters were decreased in SMA patients versus healthy controls (CNFD: p = 0.030; CNFL: p = 0.013; CNBD: p = 0.020) in the absence of relevant immune cell infiltration. CNFD and CNFL correlated with HFMSE scores (CNFD: r = 0.492, p = 0.038; CNFL: r = 0.484, p = 0.042) and distance covered in the 6MWT (CNFD: r = 0.502, p = 0.042; CNFL: r = 0.553, p = 0.023). CONCLUSIONS: Corneal confocal microscopy CCM reveals sensory neurodegeneration in SMA, thereby supporting a multisystem view of the disorder. Subclinical small nerve fibre damage correlated with motor function. Thus, CCM may be ideally suited for treatment monitoring and prognosis.

Ayurvedic management of idiopathic small fibre neuropathy- A case report.

Small fibre neuropathy (SFN) is a subgroup of peripheral neuropathy which is characterized by a disorder of the thin myelinated A-δ and unmyelinated C-fibres. With a prevalence of 52.95 per 100,000 population per year, the reported etiology of SFN has remained unclear in 23-93% of investigated patients and hence termed idiopathic small fibre neuropathy (iSFN). Pain is the most common symptom which is often described as burning. Conventional pain management is the only treatment option for iSFN, which is only modestly effective and associated with adverse events which lead to reduced drug compliance. It also affects the overall quality of life. This case report discusses the effect of Ayurvedic interventions in the management of iSFN. The patient was a 37-year-old male, who presented with severe pain, burning, and tingling sensation of B/L lower limbs and hands with decreased sleep for 5 years (visual analogue scale (VAS) was 10 and neuropathic pain scale (NPS) score was 39). Considering the signs and symptoms, the disease was diagnosed under the Vata Vyadhi (disease/syndrome caused by Vata Dosha) spectrum. The treatment included an initial OPD-based Shamana (treatment that pacifies the aggravated doshas) treatment with Drakshadi Kwatha, Sundibaladwaya Ksheera Kwatha, Kalyanaka Gritha, and Ashwagandhadi Churna. As the symptoms persisted, Shodhana (treatment in which aggravated doshas are expelled from the body) treatment was adopted which included Mridu (mild) Shodhana, Nasya (medicine administered through nasal route) and Basti (administration of medicine through the procto-colonic route). The intervention resulted in significant clinical improvement as evidenced by the reduction in VAS and NPS scores to zero and five respectively. The patient's quality of life also showed significant improvement. This case report signifies the pivotal role of Ayurvedic intervention in the management of iSFN and encourages further research in this area. Integrative therapeutic approaches can be developed which may offer a promising strategy for managing iSFN and improving patient outcomes.

Corneal confocal microscopy identifies corneal nerve loss and increased Langerhans cells in presymptomatic carriers and patients with hereditary transthyretin amyloidosis.

BACKGROUND: Hereditary transthyretin amyloidosis (ATTRv amyloidosis) is a rare, but life-threatening protein misfolding disorder due to TTR gene mutations. Cardiomyopathy (ATTRv-CM) and polyneuropathy (ATTRv-PN) with early small nerve fibre involvement are the most common manifestations. Timely diagnosis and treatment initiation are key to limiting progression of disease. Corneal confocal microscopy (CCM) is a non-invasive method to quantify corneal small nerve fibres and immune cell infiltrates in vivo. METHODS: This cross-sectional study investigated the utility of CCM in 20 patients with ATTRv amyloidosis (ATTRv-CM, n = 6; ATTRv-PN, n = 14) and presymptomatic carriers (n = 5) compared to 20 age- and sex-matched healthy controls. Corneal nerve fibre density, corneal nerve fibre length, corneal nerve branch density, and cell infiltrates were assessed. RESULTS: Corneal nerve fibre density and nerve fibre length were significantly lower in patients with ATTRv amyloidosis compared to healthy controls regardless of the clinical phenotype (ATTRv-CM, ATTRv-PN) and corneal nerve fibre density was significantly lower in presymptomatic carriers. Immune cell infiltrates were only evident in patients with ATTRv amyloidosis, which correlated with reduced corneal nerve fibre density. CONCLUSIONS: CCM identifies small nerve fibre damage in presymptomatic carriers and symptomatic patients with ATTRv amyloidosis and may serve as a predictive surrogate marker to identify individuals at risk of developing symptomatic amyloidosis. Furthermore, increased corneal cell infiltration suggests an immune-mediated mechanism in the pathogenesis of amyloid neuropathy.

Prevalence of polyneuropathies among systemic sclerosis patients and impact on health-related quality of life.

INTRODUCTION: Systemic sclerosis (SSc) is a chronic rheumatic disease that affects multiple organ systems, including the peripheral nervous system. However, studies into the involvement of polyneuropathies (PNP) have shown inconsistent results. The aim of this study was to determine the prevalence of small (SFN) and large (LFN) fibre neuropathy among SSc patients and the impact on health-related quality of life (HRQoL). MATERIAL AND METHODS: The study enrolled 67 patients with diagnosed SSc. The severity of neuropathic symptoms was evaluated using shortened and revised total neuropathy scoring criteria. Nerve conduction studies were used for LFN, and quantitative sensory testing was used to evaluate SFN. Neuropathic pain was evaluated using a Douleur Neuropathique en 4 questionnaire, and the severity of anxiety symptoms was assessed using a Generalised Anxiety Disorder-7 scale. The Health Assessment Questionnaire-Disability Index was used to assess HRQoL. Previous data on antinuclear autoantibodies (ANA) test results was obtained. Statistical analysis was performed using SPSS software. RESULTS: LFN was diagnosed in 47.8% (n = 32/67) and SFN in 40.3% (n = 27/67) of the subjects. ANA positivity was not associated with the presence of LFN/SFN. The severity of neuropathic pain had a significant correlation with anxiety symptoms (r = 0.61, p < 0.001), the severity of neuropathy symptoms (r = 0.51, p < 0.001) and HRQoL (r = 0.45, p < 0.001). The severity of neuropathy symptoms correlated with HRQoL (r = 0.39, p = 0.001). CONCLUSIONS: We demonstrated that PNP are found in almost all SSc patients. Also, SFN is as common as LFN. Additionally, we found that the severity of neuropathy symptoms and neuropathic pain are both associated with a worse HRQoL.

The co-existence of sensory and autonomic neuropathy in type 1 diabetes with and without pain.

AIMS: To investigate the co-existence of diabetic peripheral neuropathy (DPN), painful diabetic peripheral neuropathy (PDPN), and cardiac autonomic neuropathy (CAN) and to establish a model to predict CAN based on peripheral measurements. METHODS: Eighty participants (20 type 1 diabetes (T1DM) + PDPN, 20 T1DM + DPN, 20 T1DM-DPN (without DPN), and 20 healthy controls (HC)) underwent quantitative sensory testing, cardiac autonomic reflex tests (CARTs), and conventional nerve conduction. CAN was defined as ≥ 2 abnormal CARTs. After the initial analysis, the participants with diabetes were re-grouped based on the presence or absence of small (SFN) and large fibre neuropathy (LFN), respectively. A prediction model for CAN was made using logistic regression with backward elimination. RESULTS: CAN was most prevalent in T1DM + PDPN (50%), followed by T1DM + DPN (25%) and T1DM-DPN and HC (0%). The differences in prevalence of CAN between T1DM + PDPN and T1DM-DPN/HC were significant (p < 0.001). When re-grouping, 58% had CAN in the SFN group and 55% in the LFN group, while no participants without either SFN or LFN had CAN. The prediction model had a sensitivity of 64%, a specificity of 67%, a positive predictive value of 30%, and a negative predictive value of 90%. CONCLUSION: This study suggests that CAN predominantly co-exists with concomitant DPN.

Integrative miRNA-mRNA profiling of human epidermis: unique signature of SCN9A painful neuropathy.

Personalized management of neuropathic pain is an unmet clinical need due to heterogeneity of the underlying aetiologies, incompletely understood pathophysiological mechanisms and limited efficacy of existing treatments. Recent studies on microRNA in pain preclinical models have begun to yield insights into pain-related mechanisms, identifying nociception-related species differences and pinpointing potential drug candidates. With the aim of bridging the translational gap towards the clinic, we generated a human pain-related integrative miRNA and mRNA molecular profile of the epidermis, the tissue hosting small nerve fibres, in a deeply phenotyped cohort of patients with sodium channel-related painful neuropathy not responding to currently available therapies. We identified four miRNAs strongly discriminating patients from healthy individuals, confirming their effect on differentially expressed gene targets driving peripheral sensory transduction, transmission, modulation and post-transcriptional modifications, with strong effects on gene targets including NEDD4. We identified a complex epidermal miRNA-mRNA network based on tissue-specific experimental data suggesting a cross-talk between epidermal cells and axons in neuropathy pain. Using immunofluorescence assay and confocal microscopy, we observed that Nav1.7 signal intensity in keratinocytes strongly inversely correlated with NEDD4 expression that was downregulated by miR-30 family, suggesting post-transcriptional fine tuning of pain-related protein expression. Our targeted molecular profiling advances the understanding of specific neuropathic pain fine signatures and may accelerate process towards personalized medicine in patients with neuropathic pain.

Functional and morphometric assessment of small-fibre damage in late-onset hereditary transthyretin amyloidosis with polyneuropathy: the controversial relation between small-fibre-related symptoms and diagnostic test findings.

INTRODUCTION: We aimed at investigating whether functional and morphometric tests assessing small-fibre damage, ie quantitative sensory testing, Sudoscan and skin biopsy, reliably reflect neuropathic pain and autonomic symptoms in patients with late-onset hereditary transthyretin amyloidosis with polyneuropathy (ATTRv-PN). METHODS: In 30 patients with late-onset ATTRv-PN, we collected quantitative sensory testing, Sudoscan and skin biopsy with assessment of intraepidermal, piloerector muscle and sweat gland nerve fibre density. We then correlated these functional and morphometric parameters with neuropathic pain and autonomic symptoms as assessed with the Neuropathic Pain Symptom Inventory (NPSI) and Composite Autonomic Symptom Score-31 (COMPASS-31). RESULTS: 50% of patients showed small-fibre damage in the form of a pure small-fibre neuropathy, 47% in the context of a mixed fibre neuropathy with small and large fibre involvement. All patients complained of at least one autonomic symptom and 60% had neuropathic pain. Whereas quantitative sensory testing and Sudoscan parameters correlated with neuropathic pain and autonomic symptoms as assessed by NPSI and COMPASS-31, intraepidermal, piloerector muscle and sweat gland nerve fibre density quantification did not. CONCLUSIONS: Our findings indicate that functional test parameters reliably reflect neuropathic pain and autonomic symptoms related to small-fibre damage. These findings might help to identify clinically useful biomarkers to assess patient follow-up.

Skin biopsy reveals generalized small fibre neuropathy in hypermobile Ehlers-Danlos syndromes.

BACKGROUND AND PURPOSE: Ehlers-Danlos syndromes are hereditary disorders of connective tissue that are characterized by joint hypermobility, skin hyperextensibility and tissue fragility. The most common subtype is the hypermobile type. In addition to symptoms of small fibre neuropathy (SFN) due to damage to the small peripheral nerve fibres, with degeneration of the distal nerve endings, autonomic disorders such as postural tachycardia syndrome (PoTS) are frequently reported features in patients with hypermobile Ehlers-Danlos syndrome (hEDS). To date, the underlying pathophysiological mechanisms are still not completely understood. STUDY PURPOSE: To better understand pathophysiological mechanisms of small fiber neuropathy and autonomic neuropathy in hypermobile Ehlers-Danlos Syndromes. METHODS: We prospectively investigated 31 patients with hEDS compared to 31 healthy controls by using skin biopsy, quantitative sensory testing, tilt-table testing, the painDetect, Small Fibre Neuropathy Screening List and the COMPASS-31 (Composite Autonomic Symptom Score 31) questionnaire. RESULTS: Nineteen (61%) patients with hEDS were diagnosed with SFN, and 10 (32%) fulfilled the criteria for PoTS. Patients with hEDS had significantly higher heart rates than controls. According to quantitative sensory testing, these patients had generalized thermal and tactile hypesthesia. Skin biopsy revealed significantly reduced intraepithelial nerve fibre density proximally (thigh) and distally (lower leg) in patients compared to controls. This was consistent with various complaints of pain and sensory disturbances in both the proximal and distal body regions. CONCLUSION: These results confirm histologically proven SFN as a common feature in patients with hEDS, revealing a generalized distribution of nerve fibre loss. Regarding the frequently reported autonomic and neuropathic dysfunctions, the findings support SFN as an important, but not the only, underlying pathomechanism.

Small-fibre neuropathy in leprosy the role of in vivo confocal microscopy: A cross-sectional study.

Background Leprosy (or Hansen's disease) continues to present considerable challenges regarding containment and early diagnosis. Leprosy is considered to be primarily a neural disease that first affects the sensory function of small fibres. Although the condition is well described in terms of clinical manifestations and histology, few studies have been undertaken to detect damage done to small-fibre sensory nerves. In vivo confocal microscopy is a useful tool for conducting a detailed evaluation of these structures, although its use in individuals affected by leprosy has still not been explored. Objective To evaluate in vivo confocal microscopy findings in Hansen's disease patients and their association with clinical variables relating to this disease. Method A cross-sectional case-series type study was carried out between October 2019 and May 2021, in Recife, Pernambuco, Brazil. Socio-demographic and clinical data were gathered from 21 patients with leprosy. The douleur neuropathique 4 neuropathic pain questionnaire was used to evaluate pain. In vivo confocal microscopy of the cornea was employed to evaluate the small-calibre fibres. Findings were compared with those for a control group of 23 healthy individuals. Results In relation to clinical parameters, 90.5% of the patients were classified as "multibacillary" according to the World Health Organization criteria, and 70% as dimorphic or borderline, in accordance with the Madrid classification. Around 52.4% had received a diagnosis after one year or less of living with the disease, while 95.2% presented alterations in small-fibre sensory function and 35% presented such alterations in the large fibre. Neuropathic pain was present in 81% of the patients. In vivo confocal microscopy found no statistically significant difference in mean age and distribution according to sex between the Hansen disease patients and the control group of healthy individuals. The median-of-means for dendritic cells and volume of sub-basal nerve fibres in the control group were used to test for normality. Both eyes of all leprosy patients examined contained higher number of dendritic cells than the median value and a volume of sub-basal nerve fibres lower than the mean. These differences were statistically significant (P < 0.001 and P < 0.001, respectively). Multibacillary individuals had a median number of dendritic cells two times that of paucibacillary individuals (P = 0.035). Limitations No association was found between the variables examined using in vivo confocal microscopy and clinical variables relating to small-fibre damage, the neuropathic pain questionnaire or alterations detected by the neurological examination. We believe, however, that Cochet-Bonnet esthesiometry of the cornea may have revealed such an association. Conclusion In vivo confocal microscopy is a useful diagnostic tool for detecting small fibre loss in individuals affected by leprosy and may constitute a useful addition to the range of tools available to help curb the effects of neuropathy in these patients.

Pain associated with COVID-19 vaccination is unrelated to skin biopsy abnormalities.

Introduction: Previous clinical observations raised the possibility that COVID-19 vaccination might trigger a small-fibre neuropathy. Objectives: In this uncontrolled observational study, we aimed to identify small fibre damage in patients complaining of generalized sensory symptoms and pain after COVID-19 vaccination. Methods: We collected clinical data, including a questionnaire for assessing autonomic symptoms (Composite Autonomic Symptom Score-31), and investigated quantitative sensory testing (QST) and skin biopsy in 15 prospectively enrolled patients with generalized sensory symptoms and pain after COVID-19 vaccination. Nine patients complaining of orthostatic intolerance also underwent cardiovascular autonomic tests. Results: We found that all patients experienced widespread pain, and most of them (11 of 15) had a fibromyalgia syndrome. All patients had normal skin biopsy findings, and in the 9 patients with orthostatic intolerance, cardiovascular autonomic tests showed normal findings. Nevertheless, 5 patients had cold and warm detection abnormalities at the QST investigation. Conclusions: In our study, most patients complaining of generalized sensory symptoms and pain after COVID-19 vaccination had clinical and diagnostic test findings compatible with a fibromyalgia syndrome. Although the abnormal QST findings we found in 5 patients might be compatible with a small-fibre neuropathy, they should be cautiously interpreted given the psychophysical characteristics of this diagnostic test. Further larger controlled studies are needed to define precisely the association between small fibre damage and COVID-19 vaccination.

Nonregional small fibre neuropathy in cases of autoimmune autonomic neuropathy.

OBJECTIVE: Autonomic small fibre neuropathy is described in patients with autoimmune autonomic neuropathy (AAN). Few data are available on somatosensory function and skin biopsies in AAN. METHODS: Retrospective analysis of 17 patients (51.2 ± 6.8 years, n = 7 males) with AAN, including autoantibodies, quantitative sensory testing (QST, n = 13) and intraepithelial nerve fibre density (IENFD) in skin biopsy (n = 16). QST was performed according to the DFNS protocol over hands and feet dorsum. QST data were compared to healthy controls. Comparison of antibody-positive and antibody-negative cases. RESULTS: 70.6% of patients were antibody positive. 82.4% described at least one episode with sensory symptoms. Skin biopsies revealed reduced IENFD in 58.8% of patients, whereas neuropathic pain was only present in 41.2%. QST showed a nonregional increase for nonpainful thermal and mechanical detection rather than for mechanical pain thresholds. Compared to healthy controls, sensory loss for cold and warm detection thresholds and for the thermal sensory limen-the temperature difference between alternating warm and cold stimuli-was found on hands and feet (all p < 0.05). For nonpainful mechanical stimuli, the vibration detection threshold on the hand was increased (p < 0.05). Of all pain thresholds, only the mechanical pain threshold was elevated for pinprick stimuli to the feet (p < 0.05). INTERPRETATION: Findings are consistent with a sensory small fibre more than large fibre neuropathy in AAN. Sensory loss was comparably distributed across hands and feet, indicating that nerve fibre dysfunction was rather generalized. Serostatus was not a significant predictor of the small fibre deficit present in AAN.

A combined functional dorsal nerve model of the foot.

The nerves in the skin surface of the foot are comprised of unmyelinated smaller somatic nerves and larger myelinated sensory nerves. Current diagnostic methods are unable to evaluate combined nerve conduction velocity (NCV) from both unmyelinated smaller somatic nerve (USSN) and myelinated larger nerves (MLN) respectively. Computational models may provide an alternative tool to determine the NCV of the combined nerve. Therefore, a combined functional dorsal nerve model (CFDNM) of the various dorsal nerves along with its associated nerve ending of the human foot is proposed and constructed. The combined dorsal nerve model consists of synthetic USSN (SUSSN) and dorsal MLN of the foot. The unmyelinated as well as myelinated electrophysiological nerve models were used to simulate selected SUSSN and MLN of the foot by injecting an external stimulus at the most distal part of SUSSN of the foot through the use of bidomain model. Results from our work demonstrated that the action potential propagated from the most distal part to proximal part of distinct dorsal nerves of the foot, e.g., the simulated NCV of the combined intermediate dorsal cutaneous nerve (IDCN) of the foot was 28.4 m s-1. The CFDNM will provide a vital tool for diagnosis initially small fibre neuropathy (SFN) by computing NCV in the prospective studies.

The diversity and abundance of gut microbiota are associated with the pain sensation threshold in the Japanese population.

Small fibre neuropathy (SFN) is an initial pathology of diabetic polyneuropathy (DPN). Serum lipopolysaccharide binding protein levels are positively correlated with the pain threshold in the foot, suggesting that the abundance of gut Gram-negative bacilli, which are a source of lipopolysaccharides, may be involved in the development of DPN. Furthermore, the abundance of the gut and oral microbiota is assumed to be involved in the pathogenesis of diabetes. Nevertheless, the association between SFN and the microbiota has not been clarified. A total of 1056 individuals were recruited in the 2018 Iwaki Health Promotion Project. Pain sensation was evaluated based on the pain threshold from intraepidermal electrical stimulation (PINT). Patients with PINT scores <0.15 mA were categorized into the low-PINT group (n = 718); otherwise, they were categorized into the high-PINT group (n = 283). Furthermore, each group was divided into the subjects with or without glucose tolerance based on HbA1c levels, fasting blood glucose levels and diabetic history. Principal coordinate analysis and α- and ß-diversity of the microbiota were evaluated. The correlation between clinical and microbiota data was examined. Oral microbiota diversity showed no structural differences according to PINT scores, whereas principal coordinate analysis and α- and ß-diversity revealed significant structural differences in gut microbiota (p < 0.01, p < 0.05 and p < 0.05, respectively), even after the participants with glucose intolerance were excluded (p < 0.01, p < 0.05 and p < 0.05, respectively). The relative abundance of the genus Bacteroides was significantly lower in high-PINT participants compared with low-PINT participants (10 ± 6.7% vs. 11.3 ± 7.0%, p < 0.01), even after the exclusion of subjects with diabetes and impaired fasting glucose (10.0 ± 6.5% vs. 11.2 ± 6.9%, p < 0.05). In univariate linear regression analyses, PINT was significantly correlated with metabolic syndrome parameters, eGFR, uric acid level and the abundance of Bacteroides. The correlation between Bacteroides and PINT scores remained significant after adjustment for multiple factors (ß = -0.07181, p < 0.05). Changes of bacterial diversity and a low abundance of gut Bacteroides were correlated with elevated PINT scores in the Japanese population. This correlation may represent a new therapeutic option for SFN.