Electrochemical Skin Conductance Correlates with Skin Nerve Fiber Density

Sudoscan as substitute for quantitative sudomotor axon reflex test in composite autonomic scoring scale and its correlation with composite autonomic symptom scale 31 in type 2 diabetes

OBJECTIVE

This study aims to evaluate the feasibility of substituting electrochemical skin conductance measurement using SUDOSCAN for sudomotor function testing in the Composite Autonomic Scoring Scale (CASS) and to correlate the results with the Composite Autonomic Symptom Scale 31 (COMPASS 31) among patients with type 2 diabetes mellitus (T2DM).

METHODS

Fifty patients with T2DM underwent cardiovascular autonomic function testing and the SUDOSCAN test and completed the COMPASS 31 questionnaire. We developed a SUDOSCAN-based sudomotor subscore as a substitute for the original sudomotor subscore (based on the quantitative sudomotor axon reflex test [QSART]). The modified CASS score (SUDOSCAN-based sudomotor subscore combined with the adrenergic and cardiovagal subscores) and the original CASS score without suomotor assessment (sum of the adrenergic and cardiovagal subscores) were obtained according to the results of the cardiovascular autonomic function and SUDOSCAN tests.

RESULTS

The total COMPASS 31 score was significantly correlated with the modified CASS score (p = 0.019 and 0.037 for the raw and weighted scores, respectively) but not with the CASS score without sudomotor assessment. After adding the SUDOSCAN-based sudomotor subscore, the number of patients identified as having diabetic autonomic neuropathy (DAN) increased from 24 (48 %, based on the CASS score without sudomotor assessment) to 35 (70 %, based on the modified CASS score). The modified CASS score enhances the accuracy of assessing autonomic function and improves the diagnosis of diabetic autonomic neuropathy (DAN) among patients with T2DM. In medical settings where QSART is not accessible, SUDOSCAN testing offers a practical and efficient alternative.

Dysfunction of peripheral somatic and autonomic nervous system in patients with severe forms of Crohn's disease on biological therapy with TNFα inhibitors-A single center study

OBJECTIVE

Crohn's disease (CD) can be associated with a wide range of extraintestinal manifestations (EIMs), including neurological ones. Published studies differ in their conclusions about the epidemiology and etiopathogenesis of neurological EIMs. The aims of this study were to demonstrate the presence and find risk factors of peripheral (somatic and autonomic) neuropathy patients with severe CD on anti-TNFα biological therapy.

MATERIAL AND METHODS

A clinical examination focusing on detection of peripheral sensor-motor nervous dysfunction (including Sudoscan) and examination of autonomic nervous system dysfunction (using Ewing´s battery tests and spectral analysis) together with laboratory tests and collection of demographic data followed by administration of questionnaires were performed on a total of 30 neurologically asymptomatic outpatients with severe CD on anti-TNFα biological therapy.

RESULTS

Peripheral sensor-motor nervous function via clinical neurological examination was pathological in 36.7% and Sudoscan in 33.3% of cases. Statistically significant associations between vibration perception test and age, CD and biological therapy duration, body mass index and Crohn's Disease Activity Index were proved while statistically significant associations between temperature perception test and age and BMI were proved as well. Additionally, a decrease of total protein in a patient´s serum below the physiological cut-off in the 6 months prior to measurement was associated with a pathological result of a Sudoscan. Cardiovascular autonomic neuropathy based on Ewing´s battery tests was present in 56.7% of patients, no statistically significant risk factors were found. Our peripheral neuropathy questionnaire correlated with the results of the Sudoscan test and some tests of the clinical examination of peripheral sensor-motor nervous function (discriminatory contact perception test, temperature perception test).

CONCLUSIONS

This study demonstrated a relatively high prevalence of peripheral (especially autonomic) neuropathy and verified some risk factors for the development of peripheral somatic neuropathy in asymptomatic patients with severe form of CD on anti-TNFα biological therapy.

Electrochemical skin conductances values and clinical factors affecting sudomotor dysfunction in patients with prediabetes, type 1 diabetes, and type 2 diabetes: A single center experience

BACKGROUND AND AIM

Sudomotor dysfunction is linked to small fibers damage. We investigated sudomotor dysfunction in a large group of participants with diabetes, prediabetes, and nondiabetic healthy subjects. This study aimed to complete knowledge on sudomotor dysfunction in this population, especially regarding the threshold values for the electrochemical skin conductance (ESC) and factors affecting it.

MATERIALS AND METHODS

A total of 690 volunteers in four groups were included in the study (type 1 [T1DG]: n = 80, 61.3% women; type 2 diabetes [T2DG]: n = 438, 63.5% women; prediabetes [Pre-DG]: n = 88, 80.7% women; healthy control [HC-G]: n = 84, 67.5% women). All subjects were investigated for clinical diabetic peripheral polyneuropathy and sudomotor dysfunction. The characteristics of participants obtained from outpatient records were evaluated. We used the Sudoscan device to measure ESC which was normalized for BMI, to improve the discriminative capability of the method.

RESULTS

Diabetic polyneuropathy was found in 17.5% of T1DG, 27.4% of T1DG, and 10.2% of Pre-DG. The mean ESC/BMI was lower in subgroups with diabetic polyneuropathy than those without. Mean ESC/BMI was lowest in T2DG and highest in HC-G but comparable in T1DG and Pre-DG. We accepted the "mean ESC/BMI-1 SD" in the HC-G as the threshold for sudomotor dysfunction. Accordingly, the prevalence of sudomotor dysfunction was 18.8%, 44.3%, 59.1%, and 15% in T1DG, T2DG, Pre-DG, and HC-G, respectively. In T2DG, sudomotor dysfunction was found in 66.7% of persons with retinopathy, of which 56.3% had clinical diabetic polyneuropathy. The prevalence of sudomotor dysfunction in subjects with peripheral artery disease, chronic kidney disease, cardiovascular disease, and hypertension was 46.7%, 47.4%, 43.4%, and 50%, respectively, and 42.9%, 38.9%, 45.5%, and 37.3% of whom in the same order detected with clinical diabetic polyneuropathy. Considering the entire group, a logistic regression model demonstrated that the variables associated with SMD were: retinopathy (OR: 2.969; 95% CI: 1.723, 5.114), female gender (OR: 1.952; 95% CI: 1.287, 2.962), and e-GFR (OR: 0.989; 95% CI: 0.981, 0.998). Since the rate of complications was very low in T1DG, excluding this group, a new model similarly revealed that retinopathy and female gender were associated with SMD, however, the association with e-GFR was disappeared.

CONCLUSION

The prevalence of sudomotor dysfunction is high when established peripheral polyneuropathy was present in diabetes. Even though, sudomotor dysfunction can also occur before clinical polyneuropathy in both types of diabetes (T1DG: 18.8%, T2DG 44.3%), prediabetes (59.1%), and nondiabetic healthy subjects (15%). The variables associated with sudomotor dysfunction were retinopathy and female sex. Normalization of ESC for BMI would be a beneficial approach. However, before this method is included in the routine screening programs for diabetic polyneuropathy, large-scale and prospective studies are required to reach a consensus on the pathological threshold values.

The value of electrochemical skin conductance measurement by Sudoscan® for assessing autonomic dysfunction in peripheral neuropathies beyond diabetes

The diagnosis and follow-up of peripheral neuropathies involving small-diameter nerve fibers require specific examinations beyond conventional nerve conduction studies which only concern large-diameter nerve fibers. Among these tests, some are dedicated to the investigation of cutaneous innervation by the autonomic nervous system, mainly by unmyelinated sympathetic C fibers. To this end, various laboratory tests have been proposed, but the measurement of electrochemical skin conductance (ESC) by Sudoscan® is increasingly becoming the most widely used technique, because it allows a quick and simple assessment of the sudomotor function of the limb extremities. This technique is based on the principles of reverse iontophoresis and chronoamperometry and since its introduction in 2010, has been the source of nearly 200 publications. In the clinical field, most of these publications concern the evaluation of diabetic polyneuropathy, for which the value of Sudoscan® no longer needs to be demonstrated. However, there is also evidence for a role for Sudoscan® in the testing of the autonomic nervous system in various peripheral neuropathies of other origins or diseases primarily affecting the central nervous system. In this article, a comprehensive review of the literature on the clinical value of Sudoscan® outside of diabetes is presented, detailing ESC changes in neuropathies associated with various clinical conditions, such as hereditary amyloidosis or other genetic pathologies, chemotherapy neurotoxicity, dysimmune or infectious disorders, fibromyalgia, parkinsonism or other neurodegenerative diseases.

Assessment of autonomic nervous system dysfunction associated with peripheral neuropathies in the context of clinical neurophysiology practice

Peripheral neuropathies may involve the small diameter nerve fibers of the autonomic nervous system. In the presence of clinical signs compatible with dysautonomia, it is very difficult to affirm that these signs are really linked to an alteration in postganglionic autonomic innervation, and not to a lesion of the central nervous system or to a direct damage to the tissues and innervated organs. Also, in the context of the investigation of peripheral neuropathies, there is an interest in performing objective and quantitative assessment of distal autonomic innervation. The corresponding autonomic tests are mainly based on the exploration of sudomotor or vasomotor disorders of the limb extremities. In this article, we provide an overview of the various tests available for the study of the autonomic nervous system in clinical practice, including vasomotor reactivity tests, in particular based on laser Doppler techniques, and sudomotor tests, based on axon-reflexes produced by iontophoresis of cholinergic drugs or on the simpler measurement of electrochemical skin conductance by the Sudoscan® device.

Expanding the genetic causes of small-fiber neuropathy: SCN genes and beyond

Small-fiber neuropathy (SFN) is a disorder that exclusively affects the small nerve fibers, sparing the large nerve fibers. Thinly myelinated Aδ-fibers and unmyelinated C-fibers are damaged, leading to development of neuropathic pain, thermal dysfunction, sensory symptoms, and autonomic disturbances. Although many SFNs are secondary and due to immunological causes or metabolic disturbances, the etiology is unknown in up to half of the patients. Over the years, this proportion of "idiopathic SFN" has decreased, as familial and genetic causes have been discovered, thus shifting a proportion of once "idiopathic" cases to the genetic category. After the discovery of SCN9A-gene variants in 2012, SCN10A and SCN11A variants have been found to be pathogenic in SFN. With improved accessibility of SFN diagnostic tools and genetic tests, many non-SCN variants and genetically inherited systemic diseases involving the small nerve fibers have also been described, but only scattered throughout the literature. There are 80 SCN variants described as causing SFN, 8 genes causing hereditary sensory autonomic neuropathies (HSAN) described with pure SFN, and at least 7 genes involved in genetically inherited systemic diseases associated with SFN. This systematic review aims to consolidate and provide an updated overview on the genetic variants of SFN to date---SCN genes and beyond. Awareness of these genetic causes of SFN is imperative for providing treatment directions, prognostication, and management of expectations for patients and their health-care providers.

Assessing the Feasibility of Using Electrochemical Skin Conductance as a Substitute for the Quantitative Sudomotor Axon Reflex Test in the Composite Autonomic Scoring Scale and Its Correlation with Composite Autonomic Symptom Scale 31 in Parkinson's Disease

The Composite Autonomic Scoring Scale (CASS) is a quantitative scoring system that integrates the sudomotor, the cardiovagal, and the adrenergic subscores, and the Composite Autonomic Symptom Scale 31 (COMPASS 31) is based on a well-established comprehensive questionnaire designed to assess the autonomic symptoms across multiple domains. We tested the hypothesis that electrochemical skin conductance (Sudoscan) can be a substitute for the quantitative sudomotor axon reflex test (QSART) in the sudomotor domain and assessed its correlation with COMPASS 31 in patients with Parkinson's disease (PD). Fifty-five patients with PD underwent clinical assessment and cardiovascular autonomic function tests and completed the COMPASS 31 questionnaire. We compared the modified CASS (integrating the Sudoscan-based sudomotor, adrenergic, and cardiovagal subscores) and CASS subscores (the sum of the adrenergic and cardiovagal subscores). The total weighted score of COMPASS 31 was significantly correlated with both the modified CASS and the CASS subscore (p = 0.007 and p = 0.019). The correlation of the total weighted score of COMPASS 31 increased from 0.316 (CASS subscores) to 0.361 (modified CASS). When we added the Sudoscan-based sudomotor subscore, the case numbers for autonomic neuropathy (AN) increased from 22 (40%, CASS subscores) to 40 (72.7%, modified CASS). The modified CASS not only better reflects the exact autonomic function, but also improves the characterization and quantification of AN in patients with PD. In areas in which a QSART facility is not easily available, Sudoscan could be a time-saving substitution.

Sympathetic and electrochemical skin responses in the assessment of sudomotor function: a comparative study

OBJECTIVES

The sympathetic skin response (SSR) is a well-established test, whereas the electrochemical skin conductance (ESC) is still under evaluation. Our aim was therefore to assess the diagnostic accuracy of ESC to detect abnormal sudomotor function, using SSR as a reference test.

METHODS

A cross sectional observational study was performed of 61 neurological patients assessed for possible sudomotor dysfunction and 50 age-matched healthy controls (HC). Patients with diagnoses of vasovagal syncope (VVS, n=25), Parkinson's disease (PD, n=15), multiple system atrophy (MSA, n=11) and peripheral neuropathies (PN, n=10) were included. Sudomotor function was assessed with SSR and ESC tests in all participants. The absence of SSR in the palms or soles indicates abnormal sudomotor function. Receiver operating characteristic (ROC) analysis was used to assess the diagnostic value of the ESC. Cardiovascular autonomic (CV-Aut) function was evaluated through the Ewing score, based on the following tests: Heart rate change with deep breathing, Valsalva ratio, 30:15 ratio, blood pressure changes on standing and during isometric exercise. A Ewing score ≥ 2 indicates the presence of CV-Aut dysfunction.

RESULTS

Mean SSR amplitudes and ESC values showed differences between HC and patients with MSA or PN (p < 0.05), but not in patients with VVS or PD. Absence of SSR was associated with abnormal ESC (p < 0.05). Patients with abnormal CV-Aut dysfunction had lower ESC (p< 0.05). Palm ESC (P-ESC) and sole ESC (S-ESC) assessment had a sensitivity of 0.91 and 0.95 to predict sudomotor dysfunction, with a specificity of 0.78 and 0.85, respectively. The area under ROC curve was 0.905 and 0.98, respectively.

CONCLUSIONS

ESC in palms and soles has a high diagnostic accuracy for sudomotor dysfunction as detected by absent SSR in patients with MSA and PN.

Central Sensitization and Small-fiber Neuropathy Are Associated in Patients With Fibromyalgia

OBJECTIVE

To study the prevalence of small-fiber neuropathy (SFN) in a large cohort of patients with fibromyalgia (FM) and to better characterize the subset of patients with both FM and SFN.

METHODS

This 1-year, retrospective, observational cohort study included 265 patients with FM. They all performed electrochemical skin conductance (ESC) using the Sudoscan device, 1 of the simplest and most reliable technique to assess the distal autonomic nerve fibers. They completed 4 self-assessment questionnaires: (1) the Central Sensitization Inventory (CSI), (2) the Neuropathic Pain Symptom Inventory (NPSI), and (3) the Hospital Anxiety and Depression Scale (HADS), the Fibromyalgia Impact Questionnaire (FIQ).

RESULTS

Fifty-three patients (20%) had reduced ESC values. These patients had higher CSI and HADS scores, and a larger intake of analgesic drugs compared with patients with no ESC abnormalities. Central sensitization, which was extreme in 69% of the patients (CSI score ≥60), was 1 of the main determinants of ESC abnormalities and was associated with a higher NPSI score, even though these 2 factors were not correlated.

CONCLUSION

Over the past 10 years, studies have shown that a significant proportion of patients with FM have signs of small nerve fiber impairment. The possible involvement of SFN, in the occurrence and presentation of clinical symptoms in FM patients, remains however unclear. This is the first study that showed an association between central sensitization and both small nerve fiber impairment and neuropathic pain features in FM patients, rather than a direct association between SFN and neuropathic pain.

Sweat gland morphology and physiology in diabetes, neuropathy, and nephropathy: a review

Context: Sweat glands (SGs) play a vital role in thermal regulation. The function and structure are altered during the different pathological conditions.Objective: These alterations are studied through three techniques: biopsy, sweat analytes and electrical activity of SG.Methods: The morphological study of SG through biopsy and various techniques involved in quantifying sweat analytes is focussed on here. Electrical activities of SG in diabetes, neuropathy and nephropathy cases are also discussed, highlighting their limitations and future scope.Results and Conclusion: The result of this review identified three areas of the knowledge gap. The first is wearable sensors to correlate pathological conditions. Secondly, there is no device to look for its structure and quantify its associated function. Finally, therapeutic applications of SG are explored, especially for renal failure. With these aspects, this paper provides information collection and correlates SG with pathologies related to diabetes. Hence this could help researchers develop suitable technologies for the gaps identified.

Cardiac and Sudomotor Autonomic Function in Subjects with Psoriasis With and Without Metabolic Syndrome

Purpose: Studies have shown that subjects with psoriasis (PsO) are associated with an increased risk of developing metabolic syndrome (MetS), diabetes, and cardiovascular disease. In addition, MetS and diabetes are associated with autonomic dysfunction (AD). The aim of this study was to investigate cardiac and sudomotor autonomic function in subjects with PsO and without diabetes. Methods: A cross-sectional study was performed in 20 subjects with PsO, compared with age- and sex-matched 21 healthy controls, and 20 subjects with MetS. Subjects underwent skin evaluation by dermatologist, glycated hemoglobin (HbA1c), insulin, glucose, and lipid levels, sudomotor function testing with Sudoscan^™ device (Impeto Medical, Paris, France), and cardiac autonomic function testing with ANSAR device (ANX 3.0; ANSAR Group, Inc., Philadelphia, PA). Quality of Life (QOL) and peripheral neurologic function were also assessed. Results: Participants with PsO were significantly more obese, had higher levels of fasting insulin and triglycerides, and were more insulin resistant when compared to controls. Subjects with PsO showed significantly worse cardiac autonomic function when compared to control and MetS groups. Sudomotor function and QOL scores were similar between the groups. Subgroup analysis of PsO subjects without MetS criteria (n = 15) showed persistent significantly deteriorated cardiac autonomic function when compared to the other two groups. Conclusion: This study suggests an association between PsO and cardiac AD, independent of the presence of overt dysglycemia and MetS. Additional larger studies are needed to clarify the significance of these findings and the relationship between PsO, AD, and metabolic disease.

Diabetes Distal Peripheral Neuropathy: Subtypes and Diagnostic and Screening Technologies

Diabetes distal symmetrical peripheral neuropathy (DSPN) is the most prevalent form of neuropathy in industrialized countries, substantially increasing risk for morbidity and pre-mature mortality. DSPN may manifest with small-fiber disease, large-fiber disease, or a combination of both. This review summarizes: (1) DSPN subtypes (small- and large-fiber disease) with attention to clinical signs and patient symptoms; and (2) technological diagnosis and screening for large- and small-fiber disease with inclusion of a comprehensive literature review of published studies from 2015-present (N = 66). Review findings, informed by the most up-to-date research, advance critical understanding of DSPN large- and small-fiber screening technologies, including those designed for point-of-care use in primary care and endocrinology practices.

Assessment of diabetic small-fiber neuropathy by using short-wave infrared hyperspectral imaging

Among patients with type 2 diabetes mellitus (T2DM), the association between hyperspectral imaging (HSI) examination and diabetic neuropathy (DN) is ascertained using HSI of the feet using four types of spectral difference measurements. DN was evaluated by traditional Michigan Neuropathy Screening Instrument (MNSI), evaluation of painful neuropathy (ID-Pain, DN4) and sudomotor function by measuring electrochemical skin conductance (ESC). Of the 120 T2DM patients and 20 healthy adults enrolled, T2DM patients are categorized into normal sudomotor (ESC >60 μS) and sudomotor dysfunction (ESC ≤ 60 μS) groups. Spectral difference analyses reveal significant intergroup differences, whereas traditional examinations cannot distinguish between the two groups. HSI waveform reflectance gradually increases with disease severity, at 1400 to 1600 nm. The area under the curve (AUC) of receiver operating characteristic (ROC) analysis for abnormal ESC is ≥0.8 for all four HSI methods. HSI could be an objective, sensitive, rapid, noninvasive and remote approach to identify early small-fiber DN.

Consistency Analysis Between SUDOSCAN Examinations and Electromyography Results in Patients with Diabetes

OBJECTIVE

To evaluate the consistency between SUDOSCAN examinations and electromyography (EMG) results in patients with diabetes.

METHODS

A total of 326 patients with diabetes (201 males and 125 females) who were hospitalized in the endocrinology ward of the Affiliated Hospital of Nanjing University of Chinese Medicine (Jiangsu Province Hospital of Chinese Medicine) from June 2020 to February 2021 were selected as participants. All the patients were tested using a SUDOSCAN conductance analyzer for electrical skin conductivities and EMG for nerve conduction. The differences and consistencies between the results of the two examinations were analyzed. McNemar's test was used to analyze the differences between the results, and Cohen's kappa test was utilized to test the consistencies.

RESULTS

A total of 174 patients had abnormal SUDOSCAN results, and 152 patients had normal SUDOSCAN results. The EMG results of 299 patients were abnormal, and the EMG results of 27 patients were normal. The McNemar test result was P = 0.000, and the differences between the results of the SUDOSCAN and EMG examinations were statistically significant (P < 0.01). No significant consistency was found between the SUDOSCAN and EMG results, meaning that the consistency between the two examination results was not statistically significant (P = 0.868, P > 0.05). The difference between the results was statistically significant (P < 0.05), and the consistency was poor (kappa = 0.005).

CONCLUSION

Differences existed between the SUDOSCAN examination and EMG results, and the results of the two examination methods were inconsistent, indicating that SUDOSCAN examinations cannot replace EMG examinations for DSPN.

Association of electrochemical skin conductance with neuropathy in chemotherapy-treated patients

PURPOSE

Chemotherapy-induced peripheral neuropathy (CIPN) is an adverse event of cancer treatment that can affect sensory, motor, or autonomic nerves. Assessment of autonomic neuropathy is challenging, with limited available tools. Accordingly, it is not routinely assessed in chemotherapy-treated patients. In this study, we aimed to examine whether electrochemical skin conductance (ESC) via Sudoscan, a potential measure of autonomic function, associates with subjective and objective measures of CIPN severity and autonomic neuropathy.

METHODS

A cross-sectional assessment of patients who completed neurotoxic chemotherapy 3-24 months prior was undertaken using CIPN patient-reported outcomes (EORTC-QLQ-CIPN20), clinically graded scale (NCI-CTCAE), neurological examination score (TNSc), autonomic outcome measure (SAS), and Sudoscan. Differences in CIPN severity between participants with or without ESC dysfunction were investigated. Linear regression analyses were used to identify whether ESC values could predict CIPN severity.

RESULTS

A total of 130 participants were assessed, with 93 participants classified with CIPN according to the clinically graded scale (NCI-CTCAE/grade ≥ 1), while 49% demonstrated hands or feet ESC dysfunction (n = 46). Participants with ESC dysfunction did not significantly differ from those with no dysfunction on multiple CIPN severity measures (clinical-grade, patient-report, neurological examination), and no differences on the autonomic outcome measure (SAS) (all p > 0.0063). Linear regression analyses showed that CIPN could not be predicted by ESC values.

CONCLUSIONS

The inability of ESC values via Sudoscan to predict clinically-graded and patient-reported CIPN or autonomic dysfunction questions its clinical utility for chemotherapy-treated patients. The understanding of autonomic neuropathy with chemotherapy treatment remains limited and must be addressed to improve quality of life in cancer survivors.

Mast cell disorders are associated with decreased cerebral blood flow and small fiber neuropathy

BACKGROUND

Mast cell disorders including hereditary alpha tryptasemia (HαT) and idiopathic mast cell activation syndrome (MCAS) can be associated with neurologic symptoms such as orthostatic intolerance, pain, and cognitive impairment. The origin of these symptoms is not well understood.

OBJECTIVE

To characterize neurologic findings in patients with HαT and MCAS through objective measurements.

METHODS

Patients with a confirmed diagnosis of HαT or MCAS with neurologic symptoms were referred for standardized autonomic testing encompassing Valsalva maneuver, deep breathing, sudomotor and tilt tests with cerebral blood flow velocity (CBFv) determination, and skin biopsies for small fiber neuropathy (SFN).

RESULTS

There were 15 patients with HαT (age 44.4 ± 15.9 years), 16 with MCAS (34.4 ± 15.5), and 14 matched controls who were evaluated. Baseline serum tryptase level was increased in patients with HαT when compared with patients with MCAS (14.3 ± 2.5 ng/mL vs 3.8 ± 1.8; P <.001) and neurologic symptoms were similar between the 2 groups. When compared with controls, orthostatic CBFv was reduced in HαT (-24.2 ± 14.3%; P <.001) and MCAS (-20.8 ± 5.5%; P <.001). Reduced nerve fibers consistent with SFN were found in 80% of patients with HαT and 81% of those with MCAS. Mild-to-moderate dysautonomia was detected in all patients with HαT and MCAS when results of sympathetic, parasympathetic, and sudomotor tests were combined.

CONCLUSION

We provide evidence of reduced orthostatic CBFv and SFN associated with mild-to-moderate autonomic dysfunction in patients with HαT and MCAS. Our findings suggest that comprehensive autonomic testing may be helpful to explain neurologic symptoms and guide treatment in patients with HαT and MCAS.

Feasibility of combining heart rate variability and electrochemical skin conductance as screening and severity evaluation of cardiovascular autonomic neuropathy in type 2 diabetes

AIMS/INTRODUCTION

Clinical studies show that either heart rate variability (HRV) or electrochemical skin conductance (ESC) alone can serve as a simple and objective method for screening cardiovascular autonomic neuropathy (CAN). We tested the hypothesis that combining these two quantitative approaches can not only reinforce accuracy in CAN screening but also provide a better estimate of CAN severity in patients with type 2 diabetes (T2DM) who had already had CAN in outpatient clinics.

MATERIALS AND METHODS

Each patient received a complete battery of cardiovascular autonomic reflex tests (CARTs), with ESC measured by SUDOSCAN, time domain of HRV measured by standard deviation of all normal RR intervals (SDNN) and frequency domain of HRV (low frequency [LF], high frequency [HF], and LF/HF ratio), and peripheral blood studies for vascular risk factors. Severity of CAN was measured by CAN score.

RESULTS

The 90 T2DM patients included 50 males and 40 females. Those with more severe CAN had lower values in feet ESC (P = 0.023) and SDNN (P < 0.0001). Multiple linear regression analysis also showed that feet ESC and SDNN value (P = 0.003 and P < 0.0001) were significantly associated with CAN score. Combining SDNN and feet ESC also can increase the diagnostic accuracy of CAN with respective to sensitivity and specificity by using receiver operating characteristic analysis.

CONCLUSIONS

Combining the results of SDNN and feet ESC can not only assess, but also quantitatively reflect the progress or improvement of autonomic nerve function (including sympathetic and parasympathetic activity) in patients with T2DM.

Advances in Screening, Early Diagnosis and Accurate Staging of Diabetic Neuropathy

The incidence of both type 1 and type 2 diabetes is increasing worldwide. Diabetic peripheral neuropathy (DPN) is among the most distressing and costly of all the chronic complications of diabetes and is a cause of significant disability and poor quality of life. This incurs a significant burden on health care costs and society, especially as these young people enter their peak working and earning capacity at the time when diabetes-related complications most often first occur. DPN is often asymptomatic during the early stages; however, once symptoms and overt deficits have developed, it cannot be reversed. Therefore, early diagnosis and timely intervention are essential to prevent the development and progression of diabetic neuropathy. The diagnosis of DPN, the determination of the global prevalence, and incidence rates of DPN remain challenging. The opinions vary about the effectiveness of the expansion of screenings to enable early diagnosis and treatment initiation before disease onset and progression. Although research has evolved over the years, DPN still represents an enormous burden for clinicians and health systems worldwide due to its difficult diagnosis, high costs related to treatment, and the multidisciplinary approach required for effective management. Therefore, there is an unmet need for reliable surrogate biomarkers to monitor the onset and progression of early neuropathic changes in DPN and facilitate drug discovery. In this review paper, the aim was to assess the currently available tests for DPN's sensitivity and performance.

Prevalence and prognostic value of autonomic neuropathy assessed by Sudoscan® in transthyretin wild-type cardiac amyloidosis

Aims

The prevalence of autonomic neuropathy (AN) is high in patients with hereditary transthyretin amyloidosis but remains unknown in transthyretin wild‐type cardiac amyloidosis (ATTRwt‐CA). This study aimed to determine the prevalence of AN in patients with ATTRwt‐CA using Sudoscan®, a non‐invasive method used to provide evidence of AN in clinical practice and based on measurement of electrochemical skin conductance at the hands and feet (fESC).

Methods and results

A series of 62 non‐diabetic patients with ATTRwt‐CA was prospectively included over 2 years and compared with healthy elderly subjects, matched by age, gender, and body mass index. The presence of AN was defined as electrochemical skin conductance at the hands <60 μS and/or fESC <70 μS, and conductances were analysed according to clinical, biological, and echocardiographic data. Mean fESC was significantly lower in patients with ATTRwt‐CA compared with elderly controls: 68.3 (64.1–72.5) vs. 76.9 (75.6–78.1) μS (P < 0.0001), respectively. Prevalence of fESC <70 μS was higher in ATTRwt‐CA patients than in controls: 48.4% vs. 19.9%, P < 0.05. Univariate analysis showed that fESC, N‐terminal pro‐B‐type natriuretic peptide, creatinine plasma levels, and echocardiographic global longitudinal strain were associated with decompensated cardiac failure and death. Multivariate analysis revealed that fESC was an independent prognostic factor, and Kaplan–Meier estimator evidenced a greater occurrence of cardiac decompensation and death in patients with fESC <70 μS, P = 0.046.

Conclusions

Reduced fESC was observed in almost 50% of patients with ATTRwt‐CA and was associated with a worse prognosis. Sudoscan® could easily be used to screen ATTRwt‐CA patients for the presence of AN and identify patients at higher risk for a poor outcome.

Continuous glucose monitoring defined time-in-range is associated with sudomotor dysfunction in type 2 diabetes

BACKGROUND

Time in range (TIR), as a novel metric for glycemic control, has robust relevance with diabetic complications. Diabetic peripheral neuropathy (DPN) is characterized by sudomotor dysfunction.

AIM

To explore the relationship between TIR obtained from continuous glucose monitoring (CGM) and sudomotor function detected by SUDOSCAN in subjects with type 2 diabetes.

METHODS

The research enrolled 466 inpatients with type 2 diabetes. All subjects underwent 3-d CGM and SUDOSCAN. SUDOSCAN was assessed with electrochemical skin conductance in hands (HESC) and feet (FESC). Average feet ESC < 60 µS was defined as sudomotor dysfunction (+), otherwise it was sudomotor dysfunction (-). TIR refers to the percentage of time when blood glucose is between 3.9-10 mmol/L during 1 d period.

RESULTS

Among the enrolled subjects, 135 (28.97%) presented with sudomotor dysfunction. Patients with sudomotor dysfunction (+) showed a decreased level of TIR (P < 0.001). Compared to the lowest tertile of TIR, the middle and the highest tertiles of TIR was associated with an obviously lower prevalence of sudomotor dysfunction (20.51% and 21.94% vs 44.52%) (P < 0.001). In addition, with the increase of TIR, HESC and FESC increased (P < 0.001). Regression analysis demonstrated that TIR was inversely and independently linked with the prevalence of sudomotor dysfunction after adjusting for confounding values (odds ratio = 0.979, 95%CI: 0.971-0.987, P < 0.001).

CONCLUSION

The tight glycemic control assessed by TIR is of vitally protective value for sudomotor dysfunction in type 2 diabetes mellitus.

The Role of Electrochemical Skin Conductance as a Screening Test of Cardiovascular Autonomic Neuropathy in Patients with Parkinson's Disease

Autonomic disorders have been recognized as an important non-motor feature in Parkinson's disease (PD). However, there is a paucity of information on the presence and severity of cardiovascular autonomic neuropathy (CAN) among different motor phenotypes. The aims of this study were to examine the feasibility of electrochemical skin conductance (ESC) measured by Sudoscan as a screening service for CAN in patients with PD and investigate the severity of CAN among different motor phenotypes. Design: This was a cross-sectional observational study that enrolled 63 patients with PD. Patients were divided into three phenotypes, postural instability/gait difficulty (PIGD), tremor-dominant (TD), and akinetic-rigid (AR), according to their motor symptoms. Cardiovascular autonomic function was measured, and the presence and severity of CAN was determined according to the composite autonomic scoring scale (CASS). Functional scores were measured by the Hoehn and Yahr (HY) stage and the Unified Parkinson's Disease Rating Scale (UPDRS). The median HY stage was 2.0 [1.5, 3.0]. Median UPDRS total score was 23.0 (17.5, 30.5), 10.0 (6.0, 11.0) and 14.0 (6.3, 23.8) in groups of PIGD, TD and AR, respectively (p = 0.001). Mean CASS was 1.7 ± 1.3, 0.6 ± 0.4, and 1.8 ± 1.5 in groups of PIGD, TD and AR, respectively (p = 0.204). Although the ESC was not strongly associated with the cardiovascular autonomic parameters, the CAN risk score provided by Sudoscan significantly correlated with parameters of cardiovascular autonomic function, including heart rate response to deep breathing (HR_DB), Valsalva ratio (VR), and baroreflex sensitivity (BRS). By receiver-operating characteristic (ROC) analysis, if a patient's CAN risk score is higher than 33.5 (%), it is recommended to be aware of the presence of CAN even in PD patients who are asymptomatic. The area under ROC curve was 0.704. Based on our results, CAN risk score may be used for screening of CAN in patients with PD before resorting to the more sophisticated and specific, but ultimately more time-consuming, complete autonomic function testing.

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.

Is sudoscan a reliable tool in detecting small fiber neuropathy in Parkinson's disease patients?

Aim: Previous studies have revealed uncertainties concerning the utility of sudoscan in identifying small fiber neuropathy in Parkinson's disease (PD). Patients & methods: We searched for a significant reduction of electrochemical skin conductance (ESC) in 67 PD patients versus 66 controls with similar characteristics. We conducted analysis of the subgroups of PD patients without diabetes using sudoscan technology. Results: There is no discrimination between patients and controls relative to feet ESC, the modified Hoehn and Yahr Scale and/or Unified Parkinson's Disease Rating Scale. ESC in patients did not differ significantly according to the Unified Parkinson's Disease Rating Scale score. The oldest PD patients with cardiovascular risk factors have more marked small fibers dysfunction. Conclusion: The sudoscan procedure did not show advantage in the diagnosis of small fiber neuropathy. Its diagnostic value increases in some subgroups of patients with cardiovascular co-morbidity.

Diagnostic Accuracy of Electrochemical Skin Conductance in the Detection of Sudomotor Fiber Loss

Background: Small fiber neuropathy (SFN) is a common health problem. SFN is associated with loss of small fibers, either sensory, autonomic or both. Reduced autonomic sudomotor sweat gland nerve fiber density (SGNFD) and sensory epidermal nerve fiber density (ENFD) can be seen in SFN. Electrochemical skin conductance (ESC) is a non-invasive test for measurement of sudomotor function. This study evaluated the diagnostic accuracy of ESC to detect abnormal SGNFD and ENFD.

Methods: This was a retrospective blinded study of participants referred for evaluation of SFN. The primary outcome measure was the specificity and sensitivity of ESC to diagnose loss of small fibers using SGNFD and ENFD as reference tests. The secondary outcome measures were the correlation between ESC and neuropathy severity, pain, and autonomic clinical scales.

Results: Two hundred ten patients were enrolled in the study, age (mean ± sd) 45.5 ± 16.1 years, men/women = 52/158. ESC adjusted for weight (ESC/kg) was reduced in subjects with abnormally low SGNFD (normal/abnormal, ESC/kg = 1.19 ± 0.31/0.94 ± 0.37 μS/kg, p < 0.0001) and abnormally low ENFD (normal/abnormal ESC/kg 1.20 ± 0.37/1.04 ± 0.33 μS/kg, p < 0.0011). ESC/kg correlated with SGNFD (ρ = 0.39, p < 0.0001) and ENFD (ρ = 0.47, p < 0.0001). ESC/kg did not correlate with symptom scales. ESC/kg had 64% sensitivity and 77% specificity (ROC 0.73, p = 0.0001) to predict abnormal SGNFD and 69% sensitivity and 55% specificity (ROC 0.63, p = 0.0017) to predict abnormal ENFD. In comparison, SGNFD had 50.1% sensitivity and 85.1% specificity to predict abnormal ENFD (ROC 0.69, p = 0.0001).

Conclusion: ESC/kg has modest accuracy to detect SGNFD loss. ESC may be a useful test in characterization of small fiber neuropathy.

Monozygotic Twins Discordant for Kennedy Disease: A Case Report

Spinal and bulbar muscular atrophy or Kennedy disease (KD) is an X-linked recessive disorder caused by a pathogenic CAG expansion in the first exon of the androgen receptor. Proximal muscle atrophy, weakness, contraction fasciculations, bulbar involvement, and sensory disturbances are part of the clinical picture of KD. We report the unusual genetic and phenotypic expression in 2 monozygotic twins. Genetic analysis has shown abnormal expansion of CAG repeat in the first exon of the androgen receptor gene on chromosome X different between the twin brothers (44, respectively, 46) but with large phenotypical differences including onset age, evolution, and clinical features. Disease began at age 31 for the first brother, respectively, and at 56 years for the second one and consisted of muscle wasting and progressive impairment of walking. In addition, the second brother did not manifest bulbar involvement 3 years after clinical onset and has more sensory features. Besides classical EMG testing, we evaluate sensory participation in spinal and bulbar muscular atrophy with sudoscan device and confirmed the sensory deficit. We discussed epigenetic factors potentially involved in KD that could play a role in the phenotypical differences. To the best of our knowledge, this is the first case describing CAG trinucleotide repeats in monozygotic twins and also the first sudoscan diagnostic of sensory disturbances in Kennedy syndrome.

Functional and histological improvements of small nerve neuropathy after high-concentration capsaicin patch application: A case study

Introduction

Small fiber neuropathy has been found to occur in a large variety of pathological onditions, and the gold standard for diagnosis of small fiber neuropathy is skin biopsy. Sudorimetry is now considered an accurate technique to evaluate small fiber function with a good sensitivity and specificity for the diagnosis of small fiber neuropathy. Capsaicin high-concentration patch is approved for the treatment of peripheral neuropathic pain in adults either alone or in combination with other medicinal products for pain.

Methods

We describe the case of a 50-year-old woman diagnosed with small fiber neuropathy. After 2 previous treatment failures, she was proposed a treatment with high-dose capsaicin patches on the sole of her foot. The patient experienced an important diminution of her neuropathic pain. There was a 50% decrease in the pain numeric scale. Electrochemical skin conductance and skin biopsy were repeated 3 months after patch application.

Results

At 3 months, the patient then experienced an important diminution of her neuropathic pain, electrochemical skin conductance had normalized both in the hands and feet and intraepidermal nerve fiber density at distal leg increased almost reaching normal range.

Conclusion

This case report shows the correlation between clinical improvement, electrochemical skin conductance normalization, and intraepidermal nerve fiber density improvement after a high-dose capsaicin patch in a patient with small fiber neuropathy.

Small fiber neuropathy and phosphorylated alpha-synuclein in the skin of E46K-SNCA mutation carriers

BACKGROUND AND OBJECTIVE

In 2004 we described the E46K mutation in alpha-synuclein gene (E46K-SNCA), a rare point mutation causing an aggressive Lewy body disease with early prominent non-motor features and small fiber denervation of myocardium. Considering the potential interest of the skin as a target for the development of biomarkers in Parkinson's Disease (PD), in this work we aimed to evaluate structural and functional integrity of small autonomic nerve fibers and phosphorylated alpha-synuclein (p-synuclein) deposition in the skin of E46K-SNCA carriers as compared to those observed in parkin gene mutation (PARK2) carriers and healthy controls.

PATIENTS AND METHODS

We studied 7 E46K-SNCA carriers (3 dementia with Lewy bodies, 2 pure autonomic failure, 1 PD and 1 asymptomatic), 2 PARK2 carriers and 2 healthy controls to quantify intraepidermal nerve fiber density and p-synuclein deposition with cervical skin punch biopsies (immunohistochemistry against anti PGP9.5/UCHL-1, TH and p-synuclein) and sudomotor function with electrochemical skin conductance (ESC) (SudoScan).

RESULTS

All E46K-SNCA carriers had moderate to severe p-synuclein deposits and small fiber neurodegeneration in different epidermal and dermal structures including nerve fascicles and glands, especially in carriers with Pure Autonomic Failure, while p-synuclein aggregates where absent in healthy controls and in one of two PARK2 carriers. The severity of the latter skin abnormalities in E46K-SNCA were correlated with sudomotor dysfunction (lower ESC) in hands (p = 0.035).

INTERPRETATION

These results together with our previous findings support the relevance of E46K-SNCA mutation as a suitable model to study small fiber neuropathy in Lewy body diseases.

Autonomic Disorders

Autonomic complaints are frequently encountered in clinical practice. They can be due to primary autonomic disorders or secondary to other medical conditions. Primary autonomic disorders can be categorized as orthostatic intolerance syndromes and small fiber neuropathies; the latter are associated with autonomic failure, pain, or their combinations. The review outlines orthostatic intolerance syndromes (neurally mediated syncope, orthostatic hypotension, postural tachycardia syndrome, inappropriate sinus tachycardia, orthostatic cerebral hypoperfusion syndrome, and hypocapnic cerebral hypoperfusion) and small fiber neuropathies (sensory/autonomic/mixed, acute/subacute/chronic, idiopathic/secondary, inflammatory and noninflammatory). Several specific autonomic syndromes (diabetic neuropathy, primary hyperhidrosis, paroxysmal sympathetic hyperactivity, autonomic dysreflexia), neurogenic bladder, and gastrointestinal motility disorders are discussed as well.

Association of small fiber neuropathy and post treatment Lyme disease syndrome

OBJECTIVES

To examine whether post-treatment Lyme disease syndrome (PTLDS) defined by fatigue, cognitive complaints and widespread pain following the treatment of Lyme disease is associated with small fiber neuropathy (SFN) manifesting as autonomic and sensory dysfunction.

METHODS

This single center, retrospective study evaluated subjects with PTLDS. Skin biopsies for assessment of epidermal nerve fiber density (ENFD), sweat gland nerve fiber density (SGNFD) and functional autonomic testing (deep breathing, Valsalva maneuver and tilt test) were performed to assess SFN, severity of dysautonomia and cerebral blood flow abnormalities. Heart rate, end tidal CO2, blood pressure, and cerebral blood flow velocity (CBFv) from middle cerebral artery using transcranial Doppler were monitored.

RESULTS

10 participants, 5/5 women/men, age 51.3 ± 14.7 years, BMI 27.6 ± 7.3 were analyzed. All participants were positive for Lyme infection by CDC criteria. At least one skin biopsy was abnormal in all ten participants. Abnormal ENFD was found in 9 participants, abnormal SGNFD in 5 participants, and both abnormal ENFD and SGNFD were detected in 4 participants. Parasympathetic failure was found in 7 participants and mild or moderate sympathetic adrenergic failure in all participants. Abnormal total CBFv score was found in all ten participants. Low orthostatic CBFv was found in 7 participants, three additional participants had abnormally reduced supine CBFv.

CONCLUSIONS

SFN appears to be associated with PTLDS and may be responsible for certain sensory symptoms. In addition, dysautonomia related to SFN and abnormal CBFv also seem to be linked to PTLDS. Reduced orthostatic CBFv can be associated with cerebral hypoperfusion and may lead to cognitive dysfunction. Autonomic failure detected in PTLDS is mild to moderate. SFN evaluation may be useful in PTLDS.

Thermoregulation in neuropathies

Peripheral neuropathy affecting autonomic and small sensory fibers can cause abnormalities of both autonomic and behavioral thermoregulation. Quantitative autonomic and sensory neurophysiologic tests and quantification of the linear density of intraepidermal nerve fibers potentially can stratify those at risk of impaired thermoregulation during cold and heat challenges. New data relating to thermoregulatory sweating impairment in neuropathy are presented in this chapter. Of 516 neuropathy patients analyzed, 345 were found to have thermoregulatory sweat test (TST) abnormalities with a mean percentage of anterior body surface anhidrosis (TST%) of 12% and a significant reduction in total body sweat rate, although the rate of core temperature rise with heating (slope) was not significantly different from that of patients with a normal TST. However a subset of abnormal TST patients having 25% or greater TST% showed a significantly more rapid rise in core temperature (lower slope) than age- and sex-matched neuropathy patients with a normal TST. Etiologies of neuropathy in this more severe group included diabetes, erythromelalgia, immune-mediated autonomic neuropathy, primary systemic amyloidosis, and neuropathy associated with postganglionic-autonomic degenerative disorders.

Gender Differences in Skin Biopsy Findings in Small Fiber Neuropathy: A Retrospective Chart Review

OBJECTIVES

To determine whether there are gender differences in the clinical presentation or skin biopsy measures of nerve fiber density in patients with small fiber neuropathy (SFN).

METHODS

Retrospective chart review of subjects with suspected SFN.

RESULTS

Of 218 cases (137 women and 81 men) with suspected SFN, 96 (44%), including 63% of the men and 33% of the women (P < 0.05), had low epidermal nerve fiber density (ENFD) or sweat gland nerve fiber density (SGNFD). There were no differences in the clinical presentation between men and women. In those with abnormal findings, low ENFD alone was more frequent in women than men (51.1% vs. 7.8%, P < 0.05), whereas abnormal SGNFD alone was more frequent in men than women (68.6% vs. 11.1%, P < 0.05). Both SGNFD and ENFD were low in 23.5% of men and 33.3% of women. Skin biopsy findings were independent of clinical presentation or etiology.

CONCLUSIONS

The clinical presentation of SFN is similar in men and women. In skin biopsy studies, low ENFD is more common in women and low SGNFD in men.

Electrochemical Skin Conductance as a Marker of Painful Oxaliplatin-Induced Peripheral Neuropathy

Purpose

Oxaliplatin is a platinum compound widely used in gastrointestinal cancer treatment but produces dose-limiting peripheral neuropathy. New insights into oxaliplatin-induced peripheral neuropathy (OIPN) assessment are needed to detect more effectively this condition. In this context, we conducted Canaloxa study, a prospective preliminary clinical trial that aimed to investigate how Electrochemical Skin Conductance (ESC), a parameter used in small fiber neuropathy assessment, could be helpful in OIPN diagnosis.

Methods

Cancer patients treated for at least three months with oxaliplatin and suffering from clinically OIPN were included. Electrochemical Skin Conductance, thermal thresholds, and neuropathic pain were assessed in all included patients.

Results

During one year, 36 patients were included. The main result was the correlation between ESC and Neuropathic Pain Symptom Inventory score for hands (rho value = -0.69, p < 0.0001) and feet (rho value = -0.79, p < 0.0001). ESC values were lower in neuropathic patients with painful symptoms than in ones without painful symptoms (p = 0.0003 and p < 0.0001 for hands and feet, respectively). No correlation was observed between ESC and thermal thresholds.

Conclusion

These preliminary data suggest that ESC could be a useful objective marker of painful oxaliplatin-induced neuropathy and could complement the use of subjective clinical scales. This study was prospectively registered on clinicaltrials.gov (NCT02827916) before patient recruitment has begun.

Sudomotor Testing of Diabetes Polyneuropathy

Objective: The performance of the Sudoscan technology for diagnosing diabetic polyneuropathy (DPN) was evaluated against the quantitative sudomotor axon reflex test (QSART). Furthermore, the association of Sudoscan with two clinical neuropathy scoring systems was evaluated. Methods: Forty-seven patients with type 2 diabetes (20 without DPN, 27 with DPN) and 16 matched controls were examined for neuropathic symptoms and for the extent of sensory deficits. Sweat latency and volume by QSART and the skin electrochemical conductance (ESC) by Sudoscan were measured. Results: The feet and hand ESC was significantly lower in patients with DPN as compared to controls. Patients with DPN had also lower hand ESC than patients without DPN. Sensitivity and specificity of feet and hand ESC for detecting DPN were 70/85% and 53/50% respectively. QSART could not differentiate between the three groups. ESC was inversely related to neuropathic symptoms and sensory impairment. ESC was significantly correlated with sensory impairment and pain. Conclusions: Sudoscan shows a good performance in detecting subjects with DPN and it correlates well with clinical signs and symptoms of neuropathy. Significance: This study provides evidence that Sudoscan has high potential to be used as screening tool for DPN and possibly also for small fiber neuropathy in diabetic patients. HIGHLIGHTS - The sudomotor function test Sudoscan shows a good performance to detect diabetes peripheral neuropathy.- Sudoscan measures significantly correlate with clinical signs and symptoms of neuropathy.- The Sudoscan technology may help to secure clinical diagnosis of small fiber neuropathy.

The relationship between sudomotor function and skin microvascular reactivity in individuals with type 1 diabetes of long duration

AIM

The aim of this study was to assess the relationship between sudomotor function and microvascular perfusion in patients with type 1 diabetes (DM1).

METHODS

We evaluated 415 patients (206 women), with DM1, median age of 41 (IQR: 33-53) years, disease duration of 25 (IQR: 20-32) years. We assessed metabolic control of diabetes and the presence of peripheral and cardiac autonomic neuropathy. Sudomotor function was assessed using Sudoscan device by electrochemical skin conductance (ESC). Microvascular function was measured by laser-Doppler flowmetry with basal perfusion, the peak flow after occlusion (PORHpeak) and THmax which is the percentage change between basal perfusion and the peak flow during thermal hyperemia (TH). The accumulation of advanced glycation end products in the skin was assessed by skin autofluorescence (AF) measurement using AGE Reader. We subdivided patients based on the presence of diabetic peripheral neuropathy (DPN), cardiac autonomic neuropathy (CAN) and according to normal value of ESC.

RESULTS

Patients with abnormal ESC had higher skin AF [2.5 (2.1-2.9) vs 2.1 (1.9-2.5) AU, p < 0.001], lower eGFR [83 (72-96) vs 98 (86-108) ml/min/1.73 m2, p < 0.001], higher basal perfusion [25 (12-81) vs 14 (7-43) PU, p < 0.001], lower THmax [664 (137-1461) vs 1115 (346-1933) %, p = 0.002], higher PORHpeak [104 (59-167) vs 70 (48-135) PU, p < 0.001] as compared to subjects with normal ESC results. We found negative correlation between THmax and TG level (Rs = -0.14, p < 0.005), AF (Rs = -0.19, p = 0.001), vibration perception threshold - VPT (Rs = -0.24, p < 0.001) and positive correlation with HDL level (Rs = 0.14, p = 0.005), Feet ESC (Rs = 0.21, p < 0.001) and Hands ESC (Rs = 0.14, p = 0.004). We found positive correlation between PORHpeak and TG level (Rs = 0.14, p = 0.003), skin AF (Rs = 0.29, p < 0.001), VPT (0.27, p < 0.001) and negative correlation with eGFR (Rs = -0.2, p < 0.001), HDL (Rs = -0.12, p = 0.01), Feet ESC (Rs = -0.27, p < 0.001) and Hand ESC (Rs = -0.16, p = 0.002).

CONCLUSION

Impaired microvascular reactivity is associated with sudomotor dysfunction in patients with type 1 diabetes.

Sudomotor function testing by electrochemical skin conductance: does it really measure sudomotor function?

OBJECTIVE

Electrochemical skin conductance (ESC) is a non-invasive test of sweat function developed as a potential marker of small fiber neuropathy. Here we systematically review the evolution of this device and the data obtained from studies of ESC across different diseases.

METHODS

Electronic databases, including MEDLINE, and Google Scholar were searched through to February 2018. The search strategy included the following terms: "electrochemical skin conductance," "EZSCAN," and "Sudoscan." The data values provided by each paper were extracted, where available, and input into tabular and figure data for direct comparison.

RESULTS

Thirty-seven studies were included this systematic review. ESC did not change by age or gender, and there was significant variability in ESC values between diseases, some of which exceeded control values. Longitudinal studies of disease demonstrated changes in ESC that were not biologically plausible. Of the 37 studies assessed, 25 received support from the device manufacturer. The extracted data did not agree with other published normative values. Prior studies do not support claims that ESC is a measure of small fiber sensory function or autonomic function.

CONCLUSIONS

Although many papers report significant differences in ESC values between disease and control subjects, the compiled data assessed in this review raises questions about the technique. Many of the published results violate biologic plausibility. A single funding source with a vested interest in the study outcomes has supported most of the studies. Normative values are inconsistent across publications, and large combined data sets do not support a high sensitivity and specificity. Finally, there is insufficient evidence supporting the claim that Sudoscan tests sudomotor or sensory nerve fiber function.

Clinical correlates of sudomotor dysfunction in patients with type 2 diabetes and peripheral neuropathy

AIMS

To investigate the factors associated with abnormal electrochemical skin conductance (ESC) in patients with type 2 diabetes mellitus (T2D) and early diabetic peripheral neuropathy (DPN).

METHODS

We recruited 523 consecutive patients with T2D (median age: 50 [interquartile range: 16] years; median T2D duration: 4 [5] years). Sudomotor dysfunction was defined as an ESC <60 µS, and DPN as a neuropathy disability score (NDS) ≥6. Logistic regression was performed to determine the predictors of sudomotor dysfunction in patients with DPN.

RESULTS

The prevalence of sudomotor dysfunction was 29% for all patients and 84.5% for patients with DPN. A significant negative correlation was observed between the NDS and ESC measurements (r = -0.52, p < 0.0001). In the univariate analysis, abnormal ESC measures were associated with age, diabetes duration, glycated hemoglobin, diabetic retinopathy, insulin therapy, and foot abnormalities. In the multivariate analysis, ESC abnormalities were associated with age, diabetes duration, glycated hemoglobin levels, insulin therapy, and foot deformities. There was a robust association between foot deformities and abnormal ESC (p = 0.049; odds ratio = 16.02) in patients with DPN.

CONCLUSION

Sudomotor dysfunction is highly prevalent in patients with T2D, especially in those with DPN. Various diabetes-related factors were linked to lower ESC values, indicating an association between chronic hyperglycemia and sudomotor function. We also observed a strong relationship between foot deformities and ESC abnormalities. We conclude that the factors associated with DPN are also relevant to sudomotor dysfunction.

AMERICAN ASSOCIATION OF CLINICAL ENDOCRINOLOGISTS AND AMERICAN COLLEGE OF ENDOCRINOLOGY POSITION STATEMENT ON TESTING FOR AUTONOMIC AND SOMATIC NERVE DYSFUNCTION

This document represents the official position of the American Association of Clinical Endocrinologists and the American College of Endocrinology. Where there were no randomized controlled trials or specific U.S. FDA labeling for issues in clinical practice, the participating clinical experts utilized their judgment and experience. Every effort was made to achieve consensus among the committee members. Position statements are meant to provide guidance, but they are not to be considered prescriptive for any individual patient and cannot replace the judgment of a clinician.

Normative Values for Electrochemical Skin Conductance Measurements for Quantitative Assessment of Sudomotor Function in Healthy Indian Adults

CONTEXT

Electrochemical skin conductance (ESC) test is a widely accepted objective technique for quantitatively assessing sudomotor dysfunction, which is one of the earliest-detected neurophysiologic abnormalities in diabetic patients with distal symmetric polyneuropathy.

AIMS

This study aimed to provide normative data for ESC values among healthy Indian participants and assess the potential influence of age, sex, and body mass index (BMI) on ESC measurements.

SETTINGS AND DESIGN

A sample of 217 healthy participants aged 18-75 years were recruited and assessed for parameters including age, gender, BMI, and ESC measurements of the hands and feet.

STATISTICAL ANALYSIS USED

The Shapiro-Wilk test was used to assess the normality of the data. Pearson's correlation was used to evaluate the association between age, gender, and BMI, and ESC measurements.

RESULTS

The mean age of the participants was 43.3 ± 13.2 years, and mean BMI was 26.0 ± 4.3 kg/m2. Mean ESC for the hands and feet was 68.9 ± 13.1 and 71 ± 12.9 micro-Siemens, respectively, and there was a significant correlation between values from the right and left hands and feet (r = 0.9, P < 0.0001). A significant correlation was also observed between ESC measurements of the hands and feet (r = 0.94, P < 0.0001). ESC values of both hands and feet declined with age. A weak but significant inverse correlation between ESC and age was observed for the hands (r = 0.02, P = 0.01) and for the feet (r = 0.12, P < 0.0001). There was no significant difference in hand or feet ESC measurement between male and female participants. No significant correlation was observed between BMI and ESC of hands or feet. Only age was identified as a significant determinant of ESC on multivariate logistic regression analysis.

CONCLUSIONS

Normative values for Indians are lower than that reported for Caucasians.

Electrochemical skin conductance: a systematic review

PURPOSE

Currently available techniques for the evaluation of small fiber neuropathy and related sudomotor function remain suboptimal. Electrochemical skin conductance (ESC) has recently been introduced as a simple noninvasive and fast method for the detection of sudomotor dysfunction. The purpose of this review is to synthesize and appraise research using ESC measurements for sudomotor evaluation in adults.

METHODS

Electronic databases including MEDLINE and Google Scholar were searched (up to March 13, 2017). The search strategy included the following terms: "electrochemical skin conductance," "Sudoscan," and "EZSCAN." Evidence was graded according to defined quality indicators including (1) level of evidence; (2) use of established tests as reference tests (e.g., quantitative sudomotor axon test [QSART], sympathetic skin responses [SSR], thermoregulatory sweat test [TST], and skin biopsies to assess sudomotor and epidermal small fibers); (3) use of consecutive/non-consecutive subjects; and (4) study design (prospective/retrospective).

RESULTS

A total of 24 studies met the inclusion criteria. These were classified into preclinical, normative, comparative/diagnostic, or interventional. ESC measurement properties, diagnostic accuracy, and similarities to and differences from established tests were examined.

CONCLUSIONS

ESC measurements expand the arsenal of available tests for the evaluation of sudomotor dysfunction. The advantages and disadvantages of ESC versus established tests for evaluating sudomotor/small fiber function reviewed herein should be used as evidence to inform future guidelines on the assessment of sudomotor function.

Comparison of Somatic and Sudomotor Nerve Fibers in Type 2 Diabetes Mellitus

Background and Purpose

The objective of this study was to find a sensitive method for the early detection of diabetic polyneuropathy (DPN) and determine the relationship between the functions of somatic and autonomic small nerve fibers in DPN.

Methods

Patients with type 2 diabetes mellitus and DPN based on clinical symptoms, signs, intraepidermal nerve fiber density (IENFD), and findings in the quantitative sudomotor axon reflex test (QSART) were enrolled retrospectively. Neurological examinations and nerve conduction studies were performed on all patients. Heart-rate variability during deep breathing (DB ratio) and the Valsalva maneuver (Valsalva ratio) were used to quantify the cardiovagal function. Patients were divided into two groups: 1) normal nerve conduction, defined as small-fiber neuropathy (SFN) and 2) abnormal nerve conduction, defined as mixed-fiber neuropathy.

Results

In total, 82 patients were enrolled (age: 60.7±10.7 years, mean±SD). A decreased IENFD was the most frequent abnormality across all of the patients, followed by abnormalities of the QSART and cardiovagal function. A decreased IENFD was more sensitive than the QSART, DB ratio, and Valsalva ratio for detecting diabetic SFN. The DB ratio was significantly correlated with the duration of diabetes mellitus and clinical symptoms and signs. There was no correlation between the IENFD and the findings of the QSART for the distal leg.

Conclusions

Measuring the IENFD was a more sensitive method than the QSART for the early detection of DPN. The degree of involvement of the somatic small nerve fibers and sudomotor nerve fibers was independent in DPN.