Quantitative sudomotor axon reflex test (QSART): a new approach for testing distal sites

Validation of the Body Scan®, a new device to detect small fiber neuropathy by assessment of the sudomotor function: agreement with the Sudoscan®

Background

Sudomotor dysfunction is one of the earliest manifestations of small fiber neuropathy (SFN), reflecting the alteration of sympathetic C fiber innervation of the sweat glands. Among other techniques, such innervation can be assessed by measuring electrochemical skin conductance (ESC) in microsiemens (μS). In this study, ESC was measured at the feet to detect distal SFN. For this objective, the performance of a new device, the Body Scan® (Withings, France), intended for home use, was compared with that of a reference device, the Sudoscan® (Impeto Medical, France), which requires a hospital setting.

Methods

In patients with diabetes with or without neuropathy or non-diabetic patients with lower-limb neuropathy, the diagnostic performance of the Body Scan® measurement was assessed by calculating its sensitivity (Se) and specificity (Sp) to detect at least moderate SFN (Se70 and Sp70), defined by a value of feet ESC ≤ 70 μS and > 50 μS on the Sudoscan® measure, or severe SFN (Se50 and Sp50), defined by a value of feet ESC ≤ 50 μS on the Sudoscan® measure. The agreement between the two devices was assessed with the analysis of Bland-Altman plots, mean absolute error (MAE), and root mean squared error (RMSE) calculations. The repeatability of the measurements was also compared between the two devices.

Results

A total of 147 patients (52% men, mean age 59 years old, 76% diabetic) were included in the analysis. The sensitivity and specificity to detect at least moderate or severe SFN were: Se70 = 0.91 ([0.83, 0.96]), Sp70 = 0.97 ([0.88, 0.99]), Se50 = 0.91 ([0.80, 0.98]), and Sp50 = 0.99 ([0.94, 1]), respectively. The bias and 95% limits of agreement were 1.5 [-5.4, 8.4]. The MAE was 2.9 and the RMSE 3.8. The intra-sample variability was 2.0 for the Body Scan® and 2.3 for the Sudoscan®.

Conclusion

The ESC measurements provided by the Body Scan® were in almost perfect agreement with those provided by the reference device, the Sudoscan®, which validates the accuracy of the Body Scan® for the detection of SFN. By enabling simple, rapid, and autonomous use by the patient at home, this new technique will facilitate screening and monitoring of SFN in daily practice.

Clinical trial registration

ClinicalTrials.gov, identifier NCT05178459.

A simple non-contact optical method to quantify in-vivo sweat gland activity and pulsation

OBJECTIVE

Most methods for monitoring sweat gland activity use simple gravimetric methods, which merely measure the average sweat rate of multiple sweat glands over a region of skin. It would be extremely useful to have a method which could quantify individual gland activity in order to improve the treatment of conditions which use sweat tests as a diagnostic tool, such as hyperhidrosis, cystic fibrosis, and peripheral nerve degeneration.

METHODS

An optical method using an infrared camera to monitor the skin surface temperature was developed. A thermodynamics computer model was then implemented to utilize these skin temperature values along with other environmental parameters, such as ambient temperature and relative humidity, to calculate the sweat rates of individual glands using chemically stimulated and unstimulated sweating. The optical method was also used to monitor sweat pulsation patterns of individual sweat glands.

RESULTS

In this preliminary study, the feasibility of the optical approach was demonstrated by measuring sweat rates of individual glands at various bodily locations. Calculated values from this method agree with expected sweat rates given values found in literature. In addition, a lack of pulsatile sweat expulsion was observed during chemically stimulated sweating, and a potential explanation for this phenomenon was proposed.

CONCLUSION

A simple, non-contact optical method to quantify sweat gland activity in-vivo was presented.

SIGNIFICANCE

This method allows researchers and clinicians to investigate several sweat glands simultaneously, which has the potential to provide more accurate diagnoses and treatment as well as increase the potential utility for wearable sweat sensors.

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.

EZSCAN for undiagnosed type 2 diabetes mellitus: A systematic review and meta-analysis

OBJECTIVES

The EZSCAN is a non-invasive device that, by evaluating sweat gland function, may detect subjects with type 2 diabetes mellitus (T2DM). The aim of the study was to conduct a systematic review and meta-analysis including studies assessing the performance of the EZSCAN for detecting cases of undiagnosed T2DM.

METHODOLOGY/PRINCIPAL FINDINGS

We searched for observational studies including diagnostic accuracy and performance results assessing EZSCAN for detecting cases of undiagnosed T2DM. OVID (Medline, Embase, Global Health), CINAHL and SCOPUS databases, plus secondary resources, were searched until March 29, 2017. The following keywords were utilized for the systematic searching: type 2 diabetes mellitus, hyperglycemia, EZSCAN, SUDOSCAN, and sudomotor function. Two investigators extracted the information for meta-analysis and assessed the quality of the data using the Revised Version of the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) checklist. Pooled estimates were obtained by fitting the logistic-normal random-effects model without covariates but random intercepts and using the Freeman-Tukey Arcsine Transformation to stabilize variances. Heterogeneity was also assessed using the I2 measure. Four studies (n = 7,720) were included, three of them used oral glucose tolerance test as the gold standard. Using Hierarchical Summary Receiver Operating Characteristic model, summary sensitivity was 72.0% (95%CI: 60.0%- 83.0%), whereas specificity was 56.0% (95%CI: 38.0%- 74.0%). Studies were very heterogeneous (I2 for sensitivity: 79.2% and for specificity: 99.1%) regarding the inclusion criteria and bias was present mainly due to participants selection.

CONCLUSIONS

The sensitivity of EZSCAN for detecting cases of undiagnosed T2DM seems to be acceptable, but evidence of high heterogeneity and participant selection bias was detected in most of the studies included. More studies are needed to evaluate the performance of the EZSCAN for undiagnosed T2DM screening, especially at the population level.

Distal Sensorimotor Neuropathy: Improvements in Diagnosis

Neurological complications of diabetes are common, affecting up to 50% of people with diabetes. In these patients, diabetic sensorimotor neuropathy (DSPN) is by far the most frequent complication. Detecting DSPN has traditionally been a clinical exercise that is based on signs and symptoms. However, the appearance of morphometric and neurophysiological techniques along with composite scoring systems and new screening tools has induced a paradigm change in the detection and stratification of DSPN and our understanding of its natural history and etiopathogenesis. These newer techniques have provided further evidence that changes in small nerve fiber structure and function precede large fiber changes in diabetes. Although useful, the challenge for the use of these new techniques will be their sensitivity and specificity when widely adopted and ultimately, their ability to demonstrate improvement when pathogenic mechanisms are corrected. Concurrently, we have also witnessed an emergence of simpler screening tools or methods that are mainly aimed at quicker detection of large fiber neuropathy in the outpatient setting. In this review, we have focused on techniques and tools that receive particular attention in the current literature, their use in research and potential use in the clinical environment.

Autonomic dysfunction assessed by EZSCAN and subclinical atherosclerosis

BACKGROUND

The present study aimed to explore the association between autonomic dysfunction and measurements of atherosclerosis in a middle-aged and elderly Chinese population.

METHODS

A population-based cross-sectional study was performed in Shanghai, China, from March to August 2010, with 5076 participants included in the analysis. Autonomic function was assessed by a novel EZSCAN test based on sudomotor function analysis. Carotid intima-media thickness (CIMT) was measured using B-mode ultrasonography and brachial-ankle pulse wave velocity (ba-PWV) was measured using an autonomic device. Participants were divided into three groups based on EZSCAN values: Group 1: EZSCAN 0-24; Group 2, EZSCAN 25-49; and Group 3, EZSCAN 50-100. These groups denoted autonomic dysfunction risk groups as follows: no risk, moderate risk and high risk, respectively.

RESULTS

The prevalence of elevated CIMT and ba-PWV increased markedly with increasing EZSCAN values (elevated CIMT 7.4%, 17.5%, and 29.7%, elevated ba-PWV 3.2%, 19.7%, and 36.5%, in Groups 1, 2, and 3, respectively; both Ptrend < 0.0001). Logistic regressions revealed that EZSCAN values ≥50 were associated with a non-significantly higher risk of elevated CIMT (odds ratio [OR] = 1.43; 95% confidence interval [CI] 0.98-2.07) and a significantly higher risk of elevated ba-PWV (OR = 2.16; 95% CI 1.25-3.71) compared with EZSCAN values <25, after controlling for conventional risk factors.

CONCLUSION

A higher EZSCAN value (≥50), an index of high autonomic dysfunction risk, was associated with an increased risk of elevated ba-PWV and CIMT. Such associations were partially explained by traditional atherosclerotic risk factors.

EZSCAN™ a new technology to detect diabetes risk

Key to putting prevention of diabetes into practice is finding the people with increased risk. Several tools are currently in use: oral glucose tolerance test, fasting glucose measurement and a number of questionnaires to identify those with increased risk. Each has its own advantages and disadvantages. One new tool that can identify those with increased diabetes risk is the EZSCAN™. This new diagnostic device developed by Impeto Medical uses the sweat gland function to detect risk for insulin resistance and diabetes. The basic pathophysiology behind this technology is supported by the growing number of clinical studies worldwide which show a strong association between small nerve neuropathies to insulin resistance and diabetes risk. Because the EZSCAN™ test takes only three minutes to run, is non-invasive and easy to operate, it is an ideal diagnostic tool for both the medical and paramedical setting. Several applications are possible: the EZSCAN™ can be used to monitor insulin resistance-based treatment, to diagnose increased diabetes risk and to aid proposing diabetes prevention programmes. EZSCAN™ has the potential to become a very useful tool in diabetes risk diagnostics.

Horner's syndrome as a complication of thyroidectomy: report of a case

We report a case of Horner's syndrome (HS) occurring as a complication after total thyroidectomy. Horner's syndrome is characterized by myosis, eyelid ptosis, enophthalmos, and lack of sweating, with vascular dilatation of the lateral part of the face, caused by damage of the cervical sympathetic chain. We found only 28 other reports of HS developing after thyroidectomy, and only seven of these patients recovered completely. Of the 495 thyroidectomies performed at our hospital between 1997 and 2007, only one (0.2%) was complicated by the development of HS. The patient was a 35-year-old woman who underwent total thyroidectomy for Basedow-Graves' disease. Horner's syndrome manifested on postoperative day 2, but without anhydrosis or vascular dilatation of the face, and the symptoms resolved spontaneously 3 days later. The possible causes of HS after thyroidectomy include postoperative hematoma, ischemia-induced neural damage, and stretching of the cervical sympathetic chain by the retractor. The prompt and complete recovery of this patient suggests that the cervical sympathetic chain was damaged by retractor stretching.

A static handgrip method for distal quantitative sweat measurements

The quantitative sudomotor axon reflex test (QSART) measures sympathetic C fibre function when iontophoresed acetylcholine (Ach) evokes a measurable reliable sweat response. This study tests a novel, simplified method of sweat stimulation which accompanies hand dynamometry. In 34 healthy subjects we compared the standard sudomotor axon reflex test with a simplified method using static handgrip as sweat stimulus and recorded from the distal forearm, thumb and little finger tips. The standard method failed on technical grounds beyond the forearm. At the distal forearm, sweat rates were 313+/-140nl/min, representing a four-fold increase from baseline. Static handgrip induced sweat rates of 339+/-156 (thumb) and 296+/-139 (little finger)nl/min, representing a 1.7 and 1.6 fold increase from baseline. Static handgrip did not significantly alter distal forearm sweat secretion, and in females handgrip induced significantly less sweating over the thumb than in males. After dynamometry or Ach stimulation, over the three sites (thumb, little finger and forearm), the stimulated sweat secretion volumes were measured at 0.0278+/-0.021microl/cm(2)/min (thumb), 0.0204+/-0.020microl/cm(2)/min (little finger), and 0.0503+/-0.0283microl/cm(2)/min (forearm) after correction. Our study suggests the static handgrip method can be used to stimulate distal sweat production and may be of particular significance in investigating length-dependant neuropathies and assessing distal C fiber function.

Distal site testing of sympathetic skin response (big toe) in diabetic polyneuropathy

The aim of this study was to determine whether the sympathetic skin response (SSR) recorded from the big toe is more sensitive than standard SSR recorded from the sole for the detection of sudomotor fiber dysfunction in diabetic neuropathy. We recorded big toe SSR (SSRBT) and plantar SSR (SSRP) in 17 diabetic patients with non-disabling neuropathy (group A), 13 patients with disabling neuropathy (group B) and 30 age-matched normal controls. With regard to controls, SSRP amplitude was reduced only in group B. In contrast, SSRBT amplitude was reduced in both groups of patients (p<0.0001). In 8 patients in group B, SSRBT was not recordable while the SSRP still persisted. Our results suggest that SS-RBT is a more sensitive test than SSRP in detecting distal sudomotor failure in patients with diabetic neuropathy.

Small fiber neuropathy: a common and important clinical disorder

Small fiber neuropathy (SFN) is a neuropathy selectively involving small diameter myelinated and unmyelinated nerve fibers. Interest in this disorder has considerably increased during the past few years. It is often idiopathic and typically presents with peripheral pain and/or symptoms of autonomic dysfunction. Diagnosis is made on the basis of the clinical features, normal nerve conduction studies (NCS) and abnormal specialized tests of small nerve fibers. Among others, these tests include assessment of epidermal nerve fiber density, temperature sensation tests for sensory fibers and sudomotor and cardiovagal testing (QSART) for autonomic fibers. Unless an underlying disease is identified, treatment is usually symptomatic and directed towards alleviation of neuropathic pain.

Small-fiber neuropathy

Small-fiber neuropathy is a common disorder. It is often "idiopathic" and typically presents with painful feet in patients over the age of 60. Autoimmune mechanisms are often suspected, but rarely identified. Known causes of small-fiber neuropathy include diabetes mellitus, amyloidosis, toxins, and inherited sensory and autonomic neuropathies. Occasionally, small-fiber neuropathy is diffuse or multifocal. Depending on the type of small-fiber neuropathy, autonomic dysfunction can be significant or subclinical. Diagnosis is made on the basis of the clinical features, normal nerve conduction studies, and abnormal specialized tests of small-fiber function. These specialized studies include assessment of epidermal nerve fiber density as well as sudomotor, quantitative sensory, and cardiovagal testing. The sensitivities of these tests range from 59-88%. Each has certain advantages and disadvantages, and the tests may be complementary. Unless an underlying disease is identified, treatment is usually directed toward alleviation of neuropathic pain.

Comparison of SSR and QSART in early diabetic neuropathy--the value of length-dependent pattern in QSART

We evaluated postganglionic sympathetic function using the sympathetic skin response (SSR) and quantitative sudomotor axon reflex test (QSART) on the feet of 31 patients with early diabetic neuropathy and 20 age-matched normal controls. The amplitude of SSR and the sweat volume of QSART were significantly decreased in the diabetic patients. We evaluated the sensitivity of the tests in detecting autonomic failure. Out of 31 patients, 14 (45%) had abnormal SSR (14 absent; 17 present), while 16 of 31 patients (52%) had abnormal QSART (1 absent; 5 absolutely reduced and 10 showed a length-dependent pattern of reduction). More important than differences in sensitivity is the specificity of QSART, which specifically evaluates the postganglionic axon (instead of polysynaptic pathways in SSR) and provides quantitative data on the severity and pattern of autonomic deficit. In normal controls under 65 years of age, there was a significant correlation between the amplitude of SSR and the sweat volume of QSART. However, there was no significant relationship between these in diabetic patients. These results suggest that QSART can evaluate early diabetic neuropathy more precisely than SSR.

Complex regional pain syndrome type I in cancer patients

Complex regional pain syndrome type I (CRPS-I) is infrequently associated with various malignancies, and may lead to severe pain in already debilitated patients. The causal relationship between CRPS-I and paraneoplastic syndrome, controversies in diagnosis and treatment, and new treatment modalities are presented.

Redistribution of sudomotor responses is an early sign of sympathetic dysfunction in type 1 diabetes

Patients with diabetic neuropathy typically have decreased sweating in the feet but excessive sweating in the upper body. Previous studies of sudomotor function in diabetes have included patients with longstanding disease. The present study was designed to test for the early presence of sudomotor dysfunction and to characterize its relation to glycemic control and other aspects of peripheral nerve function. A total of 37 patients (10 males, 27 females) enrolled in a longitudinal study, in which autonomic function was evaluated annually for 3 years. Patients enrolled 2-22 months after the diagnosis of type 1 diabetes. Forty-one age- and sex-matched healthy control subjects were also studied. Sweat production in response to acetylcholine stimulation was dramatically increased in the forearm at the time of the first evaluation (1.67 +/- 0.24 micro/cm2 in the diabetic patients vs. 1.04 +/- 0.14 microl/cm2 in the control subjects, P < 0.05). Likewise, the ratio of sweating in the forearm to sweating below the waist was higher in the diabetic patients (0.553 +/- 0.07 microl/cm2) than in the control subjects (0.385 +/- 0.04 microl/cm2, P < 0.05). Forearm sweat was negatively associated with the renin-toprorenin ratio and vanillylmandelic acid (VMA) excretion (P < 0.025), tests of sympathetic nerve function. The ratio of sweating in the forearm to sweating in the foot was likewise increased in diabetic patients with poor glycemic control. We interpret this redistribution of sudomotor responses to be indicative of sympathetic nerve injury and conclude 1) that the sympathetic nervous system is especially vulnerable to the adverse effects of chronic hyperglycemia and 2) that sympathetic dysfunction can be detected very early in type 1 diabetes.