Which Method for Diagnosing Small Fiber Neuropathy?

Abstract

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.

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

“…In the course of ATTRv, up to 75% of patients develop symptoms of AN, affecting the cardiovascular, gastrointestinal, and genitourinary systems. Amyloid AN can be very disabling with a high morbidity and mortality rate and an increased risk of sudden death 23–25 . The assessment of sudomotor dysfunction using ESC measurement could help in the follow‐up of cardiac AN as evidenced in previous studies 26–28 .…”

“…Amyloid AN can be very disabling with a high morbidity and mortality rate and an increased risk of sudden death. [23][24][25] The assessment of sudomotor dysfunction using ESC measurement could help in the follow-up of cardiac AN as evidenced in previous studies. [26][27][28] Our study revealed that ESC measurement, a rapid and simple test, may be of important clinical value in the context of cardiac amyloidosis by predicting a functional deterioration (cardiac decompensation) when fESC decreases.…”

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

“…The performance of the SID(TAN) method was the best (0.755) if we take AUC(P D , P F ) minus AUC(P F , τ) in Table 4 as the background suppressibility. Our results indicate that the AUC(P D , P F )/accuracy of all four methods, SID, SID(TAN), MSE and SAM, were 0.82/75% which implies that all four methods can provide clinicians with useful information for a diagnosis (comparison of noninvasive neurophysiological examinations of small-nerve fibers evaluation shown in Table 5 [39,[57][58][59]). In addition, we used the average spectral signatures of healthy subjects as the comparison benchmark, so we found that the SAM method had the highest normal plantar skin detectability and the SID(TAN) method had the best ability to detect abnormal plantar skin from the results in Table 4.…”

Insights From Invasive Cardiopulmonary Exercise Testing of Patients With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

“…Regarding small-fiber metrics, we used the very small single-site distal skin biopsies recommended as required for SFN research, given 91% specificity, ease of performance, and widespread accessibility to mail-in pathology interpretation. 47 However, tradeoffs include lower sensitivity (58%) 47 than more comprehensive testing such as autonomic function testing, which is not endorsed because of lower specificity, higher complexity of administration and interpretation, and limited availability. 27 Another reason for low sensitivity is that axonal degeneration is an end-stage change, whereas earlier small fiber malfunction also contributes but is harder to quantify.…”