Tests Of Sudomotor Function Research Articles

Evaluation of the autonomic nervous system in patients with essential tremor

BackgroundEssential tremor (ET) is a prevalent movement disorder that may be linked to neurodegenerative changes. It is marked by a mix of motor and non-motor symptoms, which include disturbances in the autonomic nervous system. Aim of the study: We aimed to assess autonomic dysfunction in individuals with essential tremor. Thirty patients with essential tremor (Group 1) and 30 age and sex-matched healthy subjects as the control group (Group 2) were recruited. Comprehensive medical and neurological examinations were conducted on all participants, followed by electrophysiological assessments of autonomic function, including heart rate variability (HRV) tests (E/I ratio, Valsalva ratio, 30:15 ratio), adrenergic tests (blood pressure responses to active standing and sustained hand grip), and sympathetic skin response (SSR) tests. Finally, the results of these tests were classified according to the Ewing classification of autonomic failure. Results: The study revealed significant differences between ET patients and the control group. Heart rate variability tests showed a marked difference between the groups. Adrenergic tests, measuring sympathetic innervation, also displayed a significant difference. The sudomotor function test exhibited noteworthy differences in onset latencies and amplitudes in the palm and sole, with ET patients showing prolonged onset latencies and decreased amplitudes. Moreover, the study found a significant correlation between disease severity and autonomic function test results and the Ewing score. Conclusion: The study highlights the presence of autonomic dysfunction in essential tremor patients, with disease severity being associated with the level of autonomic affection, as evidenced by various autonomic function tests and the Ewing score.

Correlation between a commercial electrophysiological test of sudomotor function and intraepidermal nerve fiber density in hereditary transthyretin amyloidosis.

In the early stage, hereditary transthyretin (ATTRv) amyloidosis predominantly affects small nerve fibers, resulting in autonomic dysfunction and impaired sensation of pain and temperature. Evaluation of small fiber neuropathy (SFN) is therefore important for early diagnosis and treatment of ATTRv amyloidosis. Herein, we aimed to investigate the accuracy of a quick and non-invasive commercial sudomotor function test (SFT) for the assessment of SFN in ATTRv amyloidosis. We performed the SFT in 39 Japanese adults with ATTRv amyloidosis, and we analyzed the correlations between electrochemical skin conductance (ESC) values obtained via the SFT and the parameters of other neuropathy assessment methods. ESC in the feet demonstrated significant, moderate correlations with intraepidermal nerve fiber density (IENFD) results (Spearman's rank correlation coefficient [rs ], 0.58; p < .002) and other neuropathy assessment methods including the sensory nerve action potential amplitude in the nerve conduction studies (rs , 0.52; p < .001), the Neuropathy Impairment Score (rs , -0.45; p < .01), the heat-pain detection threshold (rs , -0.62; p < .0001), and the autonomic section of the Kumamoto ATTRv clinical score (rs , -0.53; p < .0001). In this study, we found that ESC values in the feet via the SFT demonstrated significant, moderate correlations with IENFD and other SFN assessment methods in patients with ATTRv amyloidosis, suggesting that the SFT appears to be an appropriate method for assessment of SFN in this disease.

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

ObjectiveThis 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). MethodsFifty 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. ResultsThe 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.

Normal values of sudomotor function assessed by electrochemical skin conductance in African population

BackgroundDysfunction of small nerve fibers remains a major public health concern. Subjects suspected of having small nerve fiber damage need to undergo reliable tests to confirm the diagnosis. Sudomotor function test is a reliable noninvasive exploration for detecting peripheral neuropathies. Nevertheless, the normal reference values derived from the sudomotor function test are not known in the African population. The objective of this study was therefore to describe the normal values of Electrochemical Skin Conductance (ESC) measured by the sudomotor function test in healthy African subjects. Materials and methodsBetween December 1st, 2021 and May 31st, 2022, ESC was measured in 475 healthy subjects (median age: 42 [31–53] years, 46% men) using a sudomotor function test, in the hands and feet. Investigators proposed the examination and received participants’ consent; demographic, anthropometric, biological, and clinical data were obtained before the test. Data on 475 healthy study participants who underwent sudomotor function testing was collected and analyzed. The sociodemographic (age, sex), anthropometric (weight, height, waist circumference, body mass index), diastolic blood pressure, systolic blood pressure, heart rate, and electrochemical skin conductances of the hands and feet were assessed. ResultsESC values were statistically higher in men compared to women (right hand ESC: 70 [60–78] versus 63 [53–72], left hand ESC: 72 [61–80] versus 68 [57–75], right foot ESC: 77 [82–99] versus 72 [64–79], ESC left foot: 76 [68–82] versus 72 [62–78] respectively). ESC values were significantly inversely correlated with age (right hand ESC: r=−0.12, P=0.006; left hand ESC: r=−0.11, P=0.01; right foot ESC: r=−0.37, P<0.0001; ESC left foot: r=−0.38, P<0.0001). ESC values measured in feet were significantly inversely correlated with body mass index (right foot r=−0.22, P<0.0001; left foot r=−0.21, P<0.0001). ConclusionThis study reports normal reference values for ESCs according to age and gender in the healthy African population. Progressive decrease in ESC with aging is confirmed by our data. The value of ESC seems lower in the African population than in other reported ethnicities. This finding needs to be further explored in additional studies.

TH-255. Assessment of small nerve fiber in healthy controls: Comparing sudomotor function testing and laser evoked potentials

TH-255. Assessment of small nerve fiber in healthy controls: Comparing sudomotor function testing and laser evoked potentials

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.

27993 Cardiac autonomic dysfunction in psoriasis patients with and without metabolic syndrome

Studies have shown an association between psoriasis (PsO) and metabolic syndrome (MS). In addition, MS is associated with autonomic dysfunction (AD). The aim of this study was to look for an association between PsO and AD. This was a cross-sectional study of 20 PsO subjects, 20 MS subjects (age, sex and BMI matched) and 21 healthy controls (HC). Subjects underwent skin evaluation by a dermatologist, blood work for HbA1c, insulin, fasting glucose, and lipids, sudomotor function testing with Sudoscan device and cardiac autonomic function (CAF) testing with ANSAR device.

2152-PUB: Cardiac Autonomic Dysfunction in Patients with Psoriasis and without Metabolic Syndrome

Background: Studies have shown a connection between psoriasis (PsO) and metabolic syndrome (MS), diabetes mellitus and cardiovascular disease. In addition, MS is associated with autonomic dysfunction (AD). AD has also been associated with chronic arthritis including psoriatic arthritis, but there is lack of similar evidence in patients with PsO. The aim of this study was to look for an association between PsO and AD, independent of the presence of MS. Methods: Cross-sectional study of subjects with PsO without MS; age, sex and BMI matched healthy controls (HC); and age and sex matched subjects with MS. Subjects underwent skin evaluation by dermatologist, blood work for HbA1c, insulin, glucose, and lipids, sudomotor function testing with SudoscanTM device (Impeto Medical-Paris, France) and cardiac autonomic function testing with ANSAR device (ANX 3.0; ANSAR Group, Inc. Philadelphia). Results: We included 47 subjects (13 PsO, 16 HC and 18 MS). PsO subjects had worse cardiac autonomic function compared to the other groups, although glucose and insulin parameters were similar to the HC group (Table 1). No differences were seen in sudomotor function between the groups. Conclusions: PsO seems to have an association with cardiac autonomic dysfunction, independent of its relationship with insulin resistance and MS. Further studies are needed to clarify the significance of these findings and how they relate to MS and diabetes. Disclosure C.M. Casellini: None. H. Parson: None. M.D. Bailey: None. A. Barney: None. A.S. Van Voorhees: Consultant; Self; Celgene. Other Relationship; Self; AbbVie Inc., Lilly Diabetes. A.I. Vinik: None. E.S. Siraj: Consultant; Self; Boehringer Ingelheim Pharmaceuticals, Inc. Research Support; Self; Novo Nordisk Inc. Speaker’s Bureau; Self; Boehringer Ingelheim Pharmaceuticals, Inc., Novo Nordisk Inc.

T13. CORNEAL CONFOCAL MICROSCOPY DETECTS NEURAL CHANGES IN SCHIZOPHRENIA

BackgroundA combination of neurodevelopmental and degenerative neural changes are likely to underpin positive and negative symptoms in schizophrenia. However, there are currently no validated biomarkers to accurately quantify the extent of neural changes in schizophrenia.Corneal confocal microscopy (CCM) is a non-invasive ophthalmic imaging technique that has been used to demonstrate in vivo corneal nerve fiber abnormalities in a range of peripheral neuropathies and central neurodegenerative disorders including Parkinson’s disease, multiple sclerosis and dementia.We wished to test the hypothesis that corneal nerve abnormalities occur in patients with schizophrenia, particularly those with negative symptoms and cognitive impairment.MethodsPatients with DSM-V schizophrenia without other causes of peripheral neuropathy other than metabolic syndrome underwent assessment of clinical ratings (Positive and Negative Symptoms Scale (PANSS), cognitive function (Montreal Cognitive Assessment (MOCA) and Corneal confocal microscopy (CCM), vibration perception threshold (VPT) and sudomotor function testing.Healthy controls underwent the same assessments apart from PANSS.Results55 subjects without (n=38) and with schizophrenia (n=17) with comparable mean age (35.7±8.5 vs 35.6±12.2, P=0.96) were studied.Patients with schizophrenia had significantly higher body weight (93.9±25.5 vs 77.1±10.1, P=0.02) and lower Low Density Lipoproteins (2.6±1.0 vs 3.4±0.7, P=0.02) compared with healthy controls.The proportion of gender, systolic and diastolic blood pressure, HbA1c, cholesterol, triglyceride and High Density Lipoproteins were comparable between the two groups.Patients with schizophrenia had significantly lower corneal nerve fibre density (CNFD, fibers/mm2) (35.6±6.5 vs 23.5±7.8, p<0.0001), branch density (CNBD, branches/mm2) (98.1±30.6 vs 34.4±26.9, p<0.0001), and fibre length (CNFL, mm/mm2) (24.2±3.9 vs 14.3±4.7, p<0.0001) compared with healthy controls but no difference in peripheral neuropathy assessed by VPT and sudomotor function testing.The area under the Receiver Operating Characteristic Curve (95% CI) of CNFD, CNBD, CNFL to distinguish patients with schizophrenia from healthy controls were 87.0% (76.8–98.2%), 93.2% (84.2–102.3%), 93.2% (84.4–102.1%), respectively.DiscussionThese preliminary results:support the hypothesis that corneal nerve abnormalities occur in schizophrenia;corneal confocal microscopy has high diagnostic capability to distinguish subjects with schizophrenia from healthy controls;provide evidence to support the potential application of corneal confocal microscopy as a non-invasive technique to detect neural change in schizophrenia.

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.

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

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. 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. 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. 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.

Assessment of sudomotor function.

To review the currently available literature on clinical autonomic tests of sudomotor function. We searched PubMED/MEDLINE for articles on technical principles and clinical applications of sudomotor tests with a focus on their drawbacks and perspectives in order to provide a narrative review. The quantitative sudomotor axon reflex sweat test (QSART) is the most widely used test of sudomotor function. The technique captures pathology with low intra- and inter-subject variability but is limited by technical demands. The thermoregulatory sweat test comprises topographic sweat pattern analysis of the ventral skin surface and allows differentiating preganglionic from postganglionic sudomotor damage when combined with a small fiber test such as QSART. The sympathetic skin response also belongs to the more established techniques and is used in lie detection systems due to its high sensitivity for sudomotor responses to emotional stimuli. However, its clinical utility is limited by high variability of measurements, both within and between subjects. Newer and, therefore, less widely established techniques include silicone impressions, quantitative direct and indirect axon reflex testing, sensitive sweat test, and measurement of electrochemical skin conductance. The spoon test does not allow a quantitative assessment of the sweat response but can be used as bedside-screening tool of sudomotor dysfunction. While new autonomic sudomotor function testings have been developed and studied over the past decades, the most were well-studied and established techniques QSART and TST remain the gold standard of sudomotor assessment. Combining these techniques allows for sophisticated analysis of neurally mediated sudomotor impairment. However, newer techniques display potential to complement gold standard techniques to further improve their precision and diagnostic value.

Advantages of early diagnosis of diabetic neuropathy in the prevention of diabetic foot ulcers

AimsTo evaluate the utility of the sudomotor function test (SFT) as a clinical tool in the Risk Stratification System of diabetic patients and to demonstrate the earlier detection of the risk of developing diabetic foot ulcers (DFU) compared to the standard clinical tests. MethodsProspective follow-up study on 263 patients enrolled consecutively over 3.5 years. Diabetic patients without active DFU were classified according to the International Working Group Risk Stratification System (RSS) and categorized according to the results of the Semmes-Wenstein Monofilament (SWM) and biothesiometer measurements or the SFT. The main outcome evaluated was the development of DFU. ResultsMedian follow-up was 42 [38–44] months. Sixty patients (22.8%) developed DFU after a median of 6.2 [3–17] months. Ten patients that were included in the no-risk group (group 0) based on the SWM and biothesiometer results developed DFU. Thus the sensitivity of this approach was 83.33% and the specificity was 50.47%. Based on the SFT results, all patients that developed DFU were included in the correct risk group. This approach had 100% sensitivity and 31.53% specificity. Regarding the diagnostic accuracy of the two Methods, the respective AUC values were 0.776 (95% CI 0.702–0.849) and 0.816 (95% CI 0.757–0.874). ConclusionsSFT improved RSS in diabetic patients in a specialized diabetic foot unit. SFT categorized patients correctly according to the risk of developing DFU.

A device to measure secretion of individual sweat glands for diagnosis of peripheral neuropathy.

There is a need for quantitative, precise assessment of small fiber peripheral nerve function. We tested a customized camera device and protocol designed to quantify secretions of individual sweat glands (SGs). Testing was performed on 178 healthy controls and 20 neuropathy subjects. Sweating was stimulated on a 2.25 cm2 skin area by iontophoresis of pilocarpine. The camera imaged sweat from 50 to 400 sweat ducts. We calculated secretion rate of individual SGs, total sweat volume, and number of secreting SGs at four body sites. Neuropathy subjects were tested at the two distal sites to demonstrate the device's capability to detect abnormal sudomotor function. Normal ranges were calculated for each body site. Neuropathy subjects had lower sweat rates per SG, lower total sweat, and lower SG density. The normal values decreased with advancing age, were lower in females, and differed between body sites. There was good agreement with repeat testing. The device provides reliable, precise quantitative measures of sweat secretion from single SGs for characterization of sudomotor nerve function in healthy control subjects and in subjects with known peripheral neuropathy. The test combines the capabilities of existing tests of sudomotor function while providing additional capabilities.

Sudoscan is an effective screening method for asymptomatic diabetic neuropathy in Chinese type 2 diabetes mellitus patients.

Aims/IntroductionThe aim of the present study was to use the sudomotor function test, Sudoscan, as a screening method for the evaluation of asymptomatic diabetic distal symmetric polyneuropathy in Chinese type 2 diabetes patients. As a result, more attention could be paid to those asymptomatic patients who could be easily neglected and underdiagnosed in everyday clinic.Materials and MethodsA total of 394 Chinese type 2 diabetes patients were enrolled and tested for symptoms and clinical signs of neuropathy using the Neurological Symptom Score, Neuropathy Disability Score, and vibration perception threshold. Sudoscan was carried out, and the results were collected as the measurement of the electrochemical skin conductance of both hands and feet.ResultsIn the present study, we found that the abnormal rate of Sudoscan results in patients with asymptomatic neuropathy was higher than those without neuropathy and those with symptomatic neuropathy. This study also showed that lower electrochemical skin conductance at the feet was significantly associated with increasing symptoms, Neurological Symptom Score (r = −0.124, P < 0.05), Neuropathy Disability Score (r = −0.3, P < 0.01) and vibration perception threshold value (r = −0.18, P < 0.05). Logistic analysis showed that age (odds ratio 1.042, 95% confidence interval 1.014−1.071, P < 0.05) and feet electrochemical skin conductance levels (odds ratio 0.98, 95% confidence interval 0.962–0.993, P < 0.01) were independently associated with diabetic distal symmetric polyneuropathy.ConclusionsSudoscan might be a promising tool to screen asymptomatic diabetic distal symmetric polyneuropathy in Chinese patients with type 2 diabetes mellitus.

46. Peripheral nerve: Target of inflammatory, infectious and mal-nutritional diseases. Electrodiagnostic studies, role in diagnosis

The prevalence of peripheral neuropathy in the general population is 2.4% and increases with age to an estimated 8% in older than 55 years. Electrodiagnostic (EDX) studies play a key role in the evaluation of patients with peripheral neuropathies. Nerve Conduction Studies (NCSs) and Electromyography (EMG) are useful to confirm the presence of peripheral neuropathy, exclude mimickers such as mononeuropathies or radiculopathies, localize the disorder, assess its severity, confirm the type of fiber affected and the underlying pathophysiology, all of these factors allow us to narrow the differential diagnosis and perform an accurate treatment when is possible. EMG/NCSs assess the function and integrity of large, myelinated A beta nerve fibers. They do not assess small nerve fibers. As such, normal findings do not exclude a small-fiber peripheral neuropathy). A number of autonomic tests can evaluate possible small-fiber peripheral neuropathies (tests of sudomotor function, heart rate variability), that are most useful in neuropathies with notable autonomic impairment. EDX studies often can define the underlying pathophysiology (demyelination or axonal) and usually can differentiate between a primary demyelinating and a primary axonal neuropathy. Because of this noninvasive differentiation, nerve biopsy is almost never required.

Normative Values for Electrochemical Skin Conductances and Impact of Ethnicity on Quantitative Assessment of Sudomotor Function.

Sudomotor dysfunction is one of the earliest pathophysiologic abnormalities in diabetes. Sudoscan™ (Impeto Medical, Paris, France) was developed as a noninvasive, rapid, and quantitative assessment of sudomotor function and has been shown to be sensitive in the detection of neuropathy. This global collaborative analysis aimed to establish reference values in healthy subjects of different ethnic groups, age, and gender, to define factors potentially affecting results, and to provide standardization of the methodology. Data from 1,350 generally healthy study participants who underwent sudomotor function testing were collected and analyzed. The relationship between age, height, weight, gender, glycemic and lipid profiles, ethnicity, and hand and foot electrochemical skin conductance (ESC) was assessed among subgroups of participants. Lower mean hands and feet ESC values were observed in African American, Indian, and Chinese subjects (P < 0.0001). No participant discomfort or safety concern was reported in 1,376 tests. No significant difference in ESC was observed between women and men at the hands (75 [57-87] vs. 76 [56-89] μS; P = 0.35) or feet (83.5 [71-90] vs. 82.5 [70-91] μS; P = 0.12). The coefficient of correlation between right and left side ESC was r = 0.96, P < 0.0001 for hands and r = 0.97, P < 0.0001 for feet. A significant but weak correlation was observed between ESC and age: for hands, r = -0.17, P < 0.0001; for feet, r = -0.19, P < 0.0001. A normative reference range was established in whites showing that there was no effect of sex or body mass index and a slight decrease in ESC with age. Ethnicity influenced ESC scores, but additional studies are necessary to validate this effect and determine its mechanism and impact on nerve function.

Quick, non-invasive and quantitative assessment of small fiber neuropathy in patients receiving chemotherapy.

Chemotherapy-induced peripheral neurotoxicity (CIPN) is a common, potentially severe and dose-limiting adverse effect; however, it is poorly investigated at an early stage due to the lack of a simple assessment tool. As sweat glands are innervated by small autonomic C-fibers, sudomotor function testing has been suggested for early screening of peripheral neuropathy. This study aimed to evaluate Sudoscan, a non-invasive and quantitative method to assess sudomotor function, in the detection and follow-up of CIPN. Eighty-eight patients receiving at least two infusions of Oxaliplatin only (45.4%), Paclitaxel only (14.8%), another drug only (28.4%) or two drugs (11.4%) were enrolled in the study. At each chemotherapy infusion the accumulated dose of chemotherapy was calculated and the Total Neuropathy Score clinical version (TNSc) was carried out. Small fiber neuropathy was assessed using Sudoscan (a 3-min test). The device measures the Electrochemical Skin Conductance (ESC) of the hands and feet expressed in microSiemens (µS). For patients receiving Oxaliplatin mean hands ESC changed from 73 ± 2 to 63 ± 2 and feet ESC from 77 ± 2 to 66 ± 3 µS (p < 0.001) while TNSc changed from 2.9 ± 0.5 to 4.3 ± 0.4. Similar results were observed in patients receiving Paclitaxel or another neurotoxic chemotherapy. During the follow-up, ESC values of both hands and feet with a corresponding TNSc < 2 were 70 ± 2 and 73 ± 2 µS respectively while they were 59 ± 1.4 and 64 ± 1.5 µS with a corresponding TNSc ≥ 6 (p < 0.0001 and p = 0.0003 respectively). This preliminary study suggests that small fiber neuropathy could be screened and followed using Sudoscan in patients receiving chemotherapy.

Seasonal acclimation in sudomotor function evaluated by QSART in healthy humans.

The quantitative sudomotor axon reflex testing (QSART) is a classic test of routine postganglionic sudomotor function. We investigated sudomotor function by QSART after summer (July 2012) and winter (January 2013) seasonal acclimation (SA) in the Republic of Korea. QSART with acetylcholine (ACh) iontophoresis were performed to determine directly activated (DIR) and axon reflex-mediated (AXR1, 2) sweating rate. Onset time of axon reflex, activated sweat gland density (ASGD), activated sweat gland output (ASGO), tympanic and skin temperatures (Tty, Tsk), basal metabolic rate (BMR), and evaporative loss volume changes were measured. Tympanic and mean body temperature (Tb; calculated from Tty, Tsk) were significantly lower after summer-SA than that of winter-SA. Sweat onset time was delayed during winter-SA compared to that after summer-SA. BMR, AXR(1), AXR(2), and DIR sweat rates, ASGD and ASGO, and evaporative loss volume were significantly diminished after winter-SA relative to after summer-SA. In conclusion, changes in sweating activity measured by QSART confirmed the involvement of the peripheral nervous system in variation of sudomotor activity in seasonal acclimation.

The New Age of Sudomotor Function Testing: A Sensitive and Specific Biomarker for Diagnosis, Estimation of Severity, Monitoring Progression, and Regression in Response to Intervention.

Sudorimetry technology has evolved dramatically, as a rapid, non-invasive, robust, and accurate biomarker for small fibers that can easily be integrated into clinical practice. Though skin biopsy with quantitation of intraepidermal nerve fiber density is still currently recognized as the gold standard, sudorimetry may yield diagnostic information not only on autonomic dysfunction but also enhance the assessment of the small somatosensory nerves, disease detection, progression, and response to therapy. Sudorimetry can be assessed using Sudoscan™, which measures electrochemical skin conductance (ESC) of hands and feet. It is based on different electrochemical principles (reverse iontophoresis and chronoamperometry) to measure sudomotor function than prior technologies, affording it a much more practical and precise performance profile for routine clinical use with potential as a research tool. Small nerve fiber dysfunction has been found to occur early in metabolic syndrome and diabetes and may also be the only neurological manifestation in small fiber neuropathies, beneath the detection limits of traditional nerve function tests. Test results are robust, accomplished within minutes, require little technical training and no calculations, since established norms have been provided for the effects of age, gender, and ethnicity. Sudomotor testing has been greatly under-utilized in the past, restricted to specialized centers capable of handling the technically demanding and expensive technology. Yet, evaluation of autonomic and somatic nerve function has been shown to be one of the best estimates of cardiovascular risk. Evaluation of sweating has the appeal of quantifiable non-invasive determination of the integrity of the peripheral autonomic nervous system, and can now be accomplished rapidly at point of care clinics with the determination of ESC, allowing intervention for morbid complications prior to permanent structural nerve damage. We review here sudomotor function testing technology, the research evidence accumulated supporting the clinical utility of measuring ESC, the medical applications of sudorimetry now available to physicians with this device, and clinical vignettes illustrating its use in the clinical decision-making process.