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Objectives: Myasthenia gravis (MG) is an autoimmune disease associated with antibodies against the nicotinic muscle acetylcholine receptor (AChR) at the neuromuscular junction. Dysautonomia has been previously described in MG. Electrochemical skin conductance (ESC), assessed by Sudoscan ® , is a non-invasive method that allows evaluation of sudomotor function. Since sweat glands are innervated by sudomotor, postganglionic, cholinergic sympathetic C-fibers, we hypothesized that ESC could be a reliable method for assessing autonomic dysfunction in MG., Methods: ESC measurements were prospectively assessed in patients with generalized MG and in healthy controls. Patients with diabetes mellitus, anticholinergic medication or electrophysiological findings of peripheral neuropathy were excluded. Data regarding demographic and disease features were collected. Presence of autonomic symptoms in patients with MG was assessed by Compass-31. For statistical analysis we performed student t-test and Chi 2 test for comparison between both groups., Results: We included 24 patients (mean age of 46.4±10.6, 75% women, mean disease duration 12.5 years, 62.5% positive for AChR antibodies) and 37 controls. We found no difference in either foot (P=0.13) or hand (P=0.83) ESC measurements between patients and controls, even after correcting for age., Conclusion: We could not prove the presence of autonomic sympathetic dysfunction in our cohort of MG patients when assessed by Sudoscan ® . In addition, Compass-31 was not a useful questionnaire in this clinical context., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

Background and Purpose: Distal involvement of autonomic nerve fibers is critical in familial amyloid polyneuropathy (FAP) due to transthyretin (TTR) mutation. This study compares different methods for assessing autonomic foot innervation in TTR-FAP patients., Methods: Three groups of seven TTR-FAP patients were included, according to disease severity: clinically asymptomatic, moderate or advanced neuropathy. The autonomic investigation included the eutectic mixture of local anesthetics test and laser Doppler flowmetry for vasomotor aspects and the Sudoscan® (measuring electrochemical skin conductance) and Neuropad® test for sudomotor aspects. Somatic innervation was assessed by performing nerve conduction studies, quantitative sensory testing [including vibration, cold and warm detection threshold (WDT) measurements] and laser evoked potentials., Results: The results of all neurophysiological tests varied according to TTR-FAP severity (P ≤ 0.01, Kruskal-Wallis test), except for the eutectic mixture of local anesthetics test and laser Doppler flowmetry variables. In addition, the sudomotor tests (Sudoscan or Neuropad) or WDT measurement provided early markers of neuropathy in two of the seven asymptomatic carriers. Finally, all neurophysiological results correlated with the Neuropathy Impairment Score (r values between -0.88 and -0.66, P < 0.005, Spearman test), except the cold detection threshold., Conclusions: The Neuropad test could be used to detect TTR-FAP onset, but confirmation requires electrochemical skin conductance and WDT measurement. The Sudoscan technique, but not the Neuropad test (at least assessed at a fixed time point), could be valuable to follow the progression of the neuropathy. Follow-up investigation should also include large-fiber investigation (e.g. nerve conduction studies and vibration detection threshold). Conversely, reliable tests for assessing vasomotor disturbances in limb extremities of TTR-FAP patients are still awaited., (© 2018 EAN.)

Background: Autonomic dysfunctions including sudomotor abnormalities commonly occur in early Parkinson's disease (PD), but little is known about potential sudomotor abnormalities in idiopathic REM Sleep Behavior Disorder (iRBD), a strong prodromal marker of PD., Objective: Our aim was to assess sudomotor dysfunction by galvanic skin response using SudoScan, as well as other autonomic markers in 49 iRBD, 40 PD (21 with RBD, 19 without), 20 atypical parkinsonisms, and 41 age-matched controls., Methods: All subjects underwent SudoScan of their hands and feet, a 30-second electrocardiogram with assessment of beat-to-beat variability, assessment of orthostatic blood pressure changes and autonomic symptom questionnaires., Results: The galvanic skin response in the hands of PD patients with RBD was significantly smaller than controls (hand mean difference = -7.877, 95% CI (-13.283, -2.470), p-value = 0.004) and PD patients without RBD (hand mean difference = -9.578, 95% CI (-17.215, -1.941), p-value = 0.014). iRBD and atypical parkinsonism did not have different SudoScan profiles than controls., Conclusions: Galvanic skin responses, as measured by SudoScan did not demonstrate significant sudomotor dysfunction in iRBD, but decreases were seen in the PD subtype associated with RBD.

Objective: Transthyretin familial amyloid polyneuropathy (TTR-FAP) is an axonal sensory-motor and autonomic neuropathy. Reliable quantification of sudomotor function could prove essential in the diagnosis and early treatment management. We aim to assess the diagnostic value of a new sudomotor test (Sudoscan) in TTR-FAP., Methods: One hundred and thirty-three TTR-FAP Val30Met carriers, divided in asymptomatic and symptomatic stage 1, were compared with 37 healthy controls. We analyzed the right sural sensory nerve action potential (SNAP), the plantar sympathetic skin response (SSR) and the electrochemical skin conductance (ESC) measured by Sudoscan in both hands and feet., Results: All neurophysiological measures were significantly worse in the symptomatic group. However, feet ESC was the only test distinguishing symptomatic patients with autonomic dysfunction from those without autonomic dysfunction, and both groups from asymptomatic subjects and healthy controls. Feet ESC was a significant independent predictor for the presence of symptoms and autonomic failure, after adjusting for demographic characteristics, sural SNAP and SSR amplitudes (p<0.05). Feet ESC showed 76% sensitivity and 85% specificity for detection of dysautonomia., Conclusion: Feet ESC is a sensitive test to assess early autonomic dysfunction in TTR-FAP subjects. This investigation should be considered for routine assessment in this population., Significance: Abnormal feet responses on Sudoscan support early diagnosis in TTR-FAP., (Copyright © 2016 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.)

The human body has two main types of sweat glands: apocrine and eccrine. Eccrine glands are widely distributed across the skin, including areas with hair. While the eccrine glands on palms and soles help improve grip, those on the rest of the body primarily aid in thermoregulation. Sudomotor function, which controls sweating, is regulated by the sympathetic division of the autonomic nervous system through cholinergic and adrenergic pathways. The activation of eccrine glands involves intricate processes, including neurotransmitter binding, ion channel modulation, and voltage generation. Sudoscan technology utilizes electrochemical skin conductance (ESC) to non-invasively measure sudomotor function. This method, which has been standardized for accuracy, has established normative benchmarks and has proven reliable across diverse populations. Sudoscan's diagnostic performance is comparable to invasive methods such as intraepidermal nerve fiber density testing, making it a valuable tool for diagnosing small fiber neuropathy. Moreover, it has been shown to correlate with corneal nerve fiber length, providing insights into various neuropathic conditions. Compared to traditional sudomotor function tests, Sudoscan proves superior in terms of its accessibility, simplicity, and reliability, with the potential to replace or complement existing diagnostic methods. It is important to differentiate ESC, as measured by Sudoscan, from other skin conductance measures, such as galvanic skin response (GSR) or electrodermal activity (EDA). Although these methods share a common physiological principle, ESC is specifically designed for diagnosing sudomotor function, unlike GSR/EDA, which is typically used for continuous monitoring. Sudoscan's success has led to its integration into consumer health devices, such as the BodyScan from Withings, showcasing its versatility beyond clinical settings. Future research may explore ESC applications in diverse medical fields, leveraging real-world data from integrated consumer devices. Collaborative efforts between researchers and engineers promise to offer new insights into sudomotor function and its implications for broader health monitoring. This study provides a comprehensive overview of ESC, including topics such as eccrine gland physiology, sudomotor function, Sudoscan technology, normative benchmarks, diagnostic comparisons, and potential future applications. [ABSTRACT FROM AUTHOR]

• Electrochemical skin conductance is a new method to quantify sudomotor function. • ALS patients had a decreased palmar and plantar sudomotor function. • Abnormal sudomotor function is part of the ALS disease spectrum. Amyotrophic lateral sclerosis (ALS) is now recognized as a multisystem neurodegenerative disorder, comprising autonomic dysfunction. We aimed to assess sudomotor function in ALS by measuring the electrochemical skin conductance (ESC). Thirty-one ALS patients [median age of 62 years (1st-3rd interquartile range – IQR, 56–72), male 71%] were prospectively compared with 29 healthy controls, matched for age and sex. We analysed ESC results from hands and feet, bilaterally. A total of 120 ESC recordings were obtained. Hands and feet ESC measurements were significantly lower in patients compared with controls [64 μS (1st-3rd IQR, 57–58) versus 78 μS (1st-3rd IQR, 70.5–84), p < 0.001 and 76 μS (1st-3rd IQR, 68–83) versus 81 μS (1st-3rd IQR, 78–86), p = 0.008, respectively]. In ALS group, no differences were observed between spinal and bulbar-onset forms for hands and feet results (p > 0.05). Hands and feet ESC measurements did not correlate also with disease duration, total ALSFRS-R scale, or ALSFRS-R progression rate (all p > 0.05). ESC is a non-invasive, fast and quantitative method suitable for assessing sudomotor function. ALS patients revealed a decreased function in upper and lower extremities. Sudomotor dysfunction is part of the ALS manifestations. [ABSTRACT FROM AUTHOR]

Background Intradialytic hypotension (IDH), a common complication in haemodialysis (HD) patients, is associated with multiple risk factors including cardiac dysfunction and alterations of the peripheral autonomic nervous system. To what extent dysautonomia may contribute to the occurrence of IDH remains elusive. We sought to investigate the clinical utility of Sudocan®, a device that quantifies dysautonomia, in the prediction of IDH. Methods We conducted a prospective monocentric study in adult HD patients from July 2019 to February 2020. Dysautonomia was assessed by the measurements of hand and foot electrochemical skin conductance (ESC) using Sudocan®, before HD. The primary endpoint was the incidence of IDH (The National Kidney Foundation/Kidney-Dialysis Outcome Quality Initiative definition), according to the presence of a pathological hand and/or foot ESC value, during the 3-month study period. Results A total of 176 HD patients (64 ± 14 years old) were enrolled. Mean pre-dialysis HD hand and foot ESC was 45 ± 20 and 54 ± 22 µS, respectively. About 35% and 40% of patients had a pathological ESC at the hand and foot, respectively. IDH occurred in 46 patients. Logistic regression showed that pathologic pre-dialysis HD hand ESC was associated with an increased risk of IDH [odds ratio = 2.56, 95% CI (1.04–6.67), P = 0.04]. The cumulative risk incidence of IHD during the study was 5.65 [95% CI (2.04–15.71), P = 0.001] and 3.71 [95% CI (1.41–9.76), P = 0.008], with a pathological hand and foot ESC, respectively. Conclusions A pathological hand ESC, as assessed by a non-invasive Sudoscan® test, is associated with an increased risk of IDH. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Keywords: Autonomic; Sleep; Narcolepsy; Sudoscan; Electrochemical skin conductance EN Autonomic Sleep Narcolepsy Sudoscan Electrochemical skin conductance 501 502 2 12/02/20 20201201 NES 201201 Narcolepsy, although a rare disease, is one of the most common causes of chronic sleepiness. Patients with narcolepsy type 1 (NT1) typically show cataplexy and a dramatic reduction in the cerebrospinal fluid concentration of the neuropeptide orexin A (hypocretin 1), which results from extensive loss of the orexin-producing neurons in the hypothalamus [[1]]. Moreover, the patients with NT1 and the controls in the study by Rocchi and colleagues were not matched for body mass index (BMI) [[7]]. [Extracted from the article]

Impairment of autonomic nervous system seems underestimated in SCA. To assess the prevalence of sudomotor dysfunction in SCA patients, and to identify relevant associated clinical/biological phenotypes. A total of 90 adult homozygous SCA patients–exclusively sub-Saharan-African-native–referred to our centre for a routine-follow-up were included. Clinical and biological data were collected as well as electrochemical skin conduction (ESC) measurements using Sudoscan®. A total of 34 healthy subjects with the same ethnic origin and matched for age, gender and BMI, were enrolled for ESC comparison. Among SCA patients, median age was 29.3 years, 51% were males. Neither overweight nor hypertension was reported. Mean Haemoglobin, reticulocyte-count, bilirubin and lactate-dehydrogenase was respectively of 8.9 ± 1.5 g/dL, 242 ± 122,109/L, 49.5 ± 34.7 μmol/L and 467 ± 169 IU/L. Percentage of glomerular hyperfiltration, micro and macroalbuminuria was respectively of 31.4%, 31% and 26.2%. ESC values for both hands (HESC) and feet (FESC) were significantly reduced in SCA patients compared to controls (P < 0.0001), with ESC measures below normal values in 61% of patients (HESC < 60 μSiemens and/or FESC < 70 μSiemens). Among SCA population, FESC values were negatively associated with age (P < 0.0001) and albumin-creatinine-ratio (P = 0.02), and positively with Haemoglobin (P = 0.03) and estimated-glomerular-filtration-rate (P < 0.0001). However, after adjustment with multivariate regression, FESC remained associated with only age and Haemoglobin (b = −1.14, P = 0.0001 and b = 3.6, P = 0.03 respectively). Sudomotor dysfunction is an underdiagnosed frequent event in SCA patients. Its quantification could be of potential interest to assess the magnitude of peripheral autonomic impairment and/or microvascular lesions. [ABSTRACT FROM AUTHOR]