"Mild", "Moderate", or "Severe" Carpal Tunnel Syndrome? Depends on Who You Ask: Analysis of Existing Classification Systems in 665 Hands.

OBJECTIVES: Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy in the body and impacts approximately 5% of the U.S. population costing nearly $5 billion/year. Electrodiagnostic (EDX) testing is considered the gold standard for CTS diagnosis. Classification systems exist that categorize CTS severity based on EDX findings. This investigation evaluated EDX findings across consecutive CTS severity categories within existing classification systems and consolidated classifications. METHODS: This retrospective study analyzed 665 hands from 468 patients undergoing EDX testing for suspected CTS. Complete classification systems and consolidated classifications were evaluated for discrimination capability across consecutive CTS severity categories based on EDX findings. Additional analysis evaluated the relationship of sex and age factors and CTS severity. RESULTS: Consolidated classifications demonstrated superior discrimination capability between consecutive CTS severity categories regardless of classification system used. Demographic factors significantly influenced EDX findings and categorization of CTS severity. CONCLUSIONS: This study underscores the value of consolidated classifications for enhancing discrimination between consecutive CTS severity categories based on EDX findings. Demographic factors should be considered when interpreting EDX findings for the purpose of categorizing CTS severity. Future research should refine existing classification systems and explore additional factors influencing CTS severity used to inform medical management.

Evaluation and resolution of many challenges of neural spike sorting: a new sorter.

We evaluate existing spike sorters and present a new one that resolves many sorting challenges. The new sorter, called "full binary pursuit" or FBP, comprises multiple steps. First, it thresholds and clusters to identify the waveforms of all unique neurons in the recording. Second, it uses greedy binary pursuit to optimally assign all the spike events in the original voltages to separable neurons. Third, it resolves spike events that are described more accurately as the superposition of spikes from two other neurons. Fourth, it resolves situations where the recorded neurons drift in amplitude or across electrode contacts during a long recording session. Comparison with other sorters on ground-truth data sets reveals many of the failure modes of spike sorting. We examine overall spike sorter performance in ground-truth data sets and suggest postsorting analyses that can improve the veracity of neural analyses by minimizing the intrusion of failure modes into analysis and interpretation of neural data. Our analysis reveals the tradeoff between the number of channels a sorter can process, speed of sorting, and some of the failure modes of spike sorting. FBP works best on data from 32 channels or fewer. It trades speed and number of channels for avoidance of specific failure modes that would be challenges for some use cases. We conclude that all spike sorting algorithms studied have advantages and shortcomings, and the appropriate use of a spike sorter requires a detailed assessment of the data being sorted and the experimental goals for analyses.NEW & NOTEWORTHY Electrophysiological recordings from multiple neurons across multiple channels pose great difficulty for spike sorting of single neurons. We propose methods that improve the ability to determine the number of individual neurons present in a recording and resolve near-simultaneous spike events from single neurons. We use ground-truth data sets to demonstrate the pros and cons of several current sorting algorithms and suggest strategies for determining the accuracy of spike sorting when ground-truth data are not available.

CORP: Standardizing methodology for assessing spontaneous baroreflex control of muscle sympathetic nerve activity in humans.

The use of spontaneous bursts of muscle sympathetic nerve activity (MSNA) to assess arterial baroreflex control of sympathetic nerve activity has seen increased utility in studies of both health and disease. However, methods used for analyzing spontaneous MSNA baroreflex sensitivity are highly variable across published studies. Therefore, we sought to comprehensively examine methods of producing linear regression slopes to quantify spontaneous MSNA baroreflex sensitivity in a large cohort of subjects (n = 150) to support a standardized procedure for analysis that would allow for consistent and comparable results across laboratories. The primary results demonstrated that 1) consistency of linear regression slopes was considerably improved when the correlation coefficient was above -0.70, which is more stringent compared with commonly reported criterion of -0.50, 2) longer recording durations increased the percentage of linear regressions producing correlation coefficients above -0.70 (1 min = 15%, 2 min = 28%, 5 min = 53%, 10 min = 67%, P < 0.001) and reaching statistical significance (1 min = 40%, 2 min = 69%, 5 min = 78%, 10 min = 89%, P < 0.001), 3) correlation coefficients were improved with 3-mmHg versus 1-mmHg and 2-mmHg diastolic blood pressure (BP) bin size, and 4) linear regression slopes were reduced when the acquired BP signal was not properly aligned with the cardiac cycle triggering the burst of MSNA. In summary, these results support the use of baseline recording durations of 10 min, a correlation coefficient above -0.70 for reliable linear regressions, 3-mmHg bin size, and importance of properly time-aligning MSNA and diastolic BP. Together, these findings provide best practices for determining spontaneous MSNA baroreflex sensitivity under resting conditions for improved rigor and reproducibility of results.

Utility of neuromuscular ultrasound in the investigation of common mononeuropathies in everyday neurophysiology practice.

INTRODUCTION: In everyday clinical neurophysiology practice, mononeuropathies are evaluated primarily by traditional electrodiagnostic testing. We sought to assess the additional benefit of neuromuscular ultrasound (US) in this scenario. METHODS: All consecutive mononeuropathies undergoing combined US and electrodiagnostic evaluation over a 23-mo period at a single neurophysiology practice were reviewed. Three independent examiners assessed how often US was: (a) "contributory" - enabling a definite diagnosis not made by electrophysiology alone and/or impacting on the therapeutic decision, (b) "confirmatory" of the electrodiagnostic findings, but not adding further diagnostic or therapeutic information, or (c) "negative" - missed the diagnosis. RESULTS: There were 385 studies included. US was "contributory" in 36%, "confirmatory" in 61% and "negative" in 3%. DISCUSSION: In this study of everyday neurophysiology practice, neuromuscular US contributed significant diagnostic or therapeutic information in over 1/3 of the investigations for common mononeuropathies. False negative US studies were uncommon in this setting.

Optimizing the operation of an electrodiagnostic laboratory during the COVID-19 pandemic: A 6-month single-center experience.

INTRODUCTION/AIMS: The initial surge of the coronavirus disease-2019 (COVID-19) pandemic in early 2020 led to widespread cancellation of elective medical procedures in the United States, including nonurgent outpatient and inpatient electrodiagnostic (EDx) studies. As certain regions later showed a downtrend in daily new cases, EDx laboratories have reopened under the guidance of the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM). In our reopening experience guided by the AANEM, we measured relevant outcomes to determine further workflow adaptations. We aimed to detail our experience and share the lessons learned. METHODS: We reviewed the clinical volumes, billing data, diagnosis distributions, and rates of COVID-19 exposure and transmission among patients and staff in our EDx laboratory during the first 6 months of reopening, starting on June 1, 2020. For context, we detailed the recent AANEM guidelines we adopted at our laboratory, supplemented by other consensus statements. RESULTS: We completed 816 outpatient studies from June 1 to December 1, 2020, reaching 97% of the total volume and 97% of total billing compared with the same time period in 2019. The average relative value units per study were similar. There were no major shifts in diagnosis distributions. We completed 10 of 12 requested inpatient studies during this period. There were no known COVID-19 transmissions between patients and staff. DISCUSSION: Our experience suggests that it is possible to safely operate an EDx laboratory under the guidance of the AANEM and other experts, with clinical volume and billing rates comparable to pre-pandemic baselines.

Utility of stimulus induced after discharges in the evaluation of peripheral nerve hyperexcitability: Old wine in a new bottle?

Limited literature is available on stimulus induced after discharges (SIAD) in patients with peripheral nerve hyperexcitability (PNH). The aim of the study was to examine the diagnostic utility of SIAD in the diagnosis and monitoring of primary PNH disorders. In this retrospective study, we studied 26 patients who were admitted with a diagnosis of primary PNH to the department of Neurology from January 2013 to April 2019. Their clinical profile, immunological characteristics were extracted from the database and nerve conduction studies were relooked for the presence of SIAD. 76% of patients in the primary PNH cohort had SIAD with 90% of them being voltage-gated potassium channel complex antibody positive; predominantly against contactin-associated protein-2 antigen and rest being paraneoplastic. There was also resolution of SIAD following treatment indicating reversible hyperexcitability. SIAD is a sensitive marker for Primary PNH syndrome with monitoring and diagnostic implications.

Quality measures in electrodiagnosis: Carpal tunnel syndrome-An AANEM Quality Measure Set.

Carpal tunnel syndrome (CTS) is a common neuromuscular condition and a major cause of work-related disability. As healthcare in the United States transitions toward a value-based system from fee-for-service, quality measures assume importance in the evaluation of care provided. This report from the American Association of Neuromuscular & Electrodiagnostic Medicine Quality Improvement Committee provides an introduction to quality measures and outlines a quality measurement set for the electrodiagnosis of CTS. The measures attempt to standardize technical requirements for electrodiagnostic (EDX) studies of CTS, the criteria for diagnosing median neuropathy at the wrist and assessing its severity, and the role of operative EDX testing. The assumption is that implementation of these measures will improve the accuracy of CTS diagnosis when EDX is performed, help exclude mimics, and, therefore, improve care of patients with CTS with the ultimate goal of improving outcomes. Postimplementation assessment of outcomes will refine these measures.

Quality of electrodiagnostic testing for carpal tunnel syndrome: adherence to quality measures.

INTRODUCTION: Research has shown that quality of health-care services is often suboptimal. Little is known about the quality of electrodiagnostic testing. METHODS: We prospectively recruited 477 adults with workers' compensation claims for carpal tunnel syndrome (CTS) from 30 occupational health clinics and evaluated whether electrodiagnostic testing adhered to five process-oriented quality measures. RESULTS: Among patients who had surgery for CTS, nearly all underwent recommended preoperative electrodiagnostic testing (measure #1, 170 of 174, 97.7%). Most electrodiagnostic tests included essential components (measure #2, 295 of 379, 77.8%). However, few reports documented skin temperature (measure #3, 93 of 379, 24.5%) and criteria were seldom met for interpreting test findings as consistent with CTS (measure #4, 41 of 284, 14.4%) or "severe" CTS (measure #5, 8 of 46, 17.4%). DISCUSSION: Most patients underwent testing before surgery, but test quality was often suboptimal. This work lays the groundwork for future efforts to monitor and improve the quality of electrodiagnostic testing for CTS.

Lowering the cutoff value for increment increases the sensitivity for the diagnosis of Lambert-Eaton myasthenic syndrome.

BACKGROUND: Increment of compound muscle action potential amplitude is a diagnostic hallmark of Lambert-Eaton myasthenic syndrome (LEMS). Making a diagnosis can be challenging, therefore, a proper cutoff for abnormal increment is highly relevant for improved recognition of this rare disease. METHODS: We determined the sensitivity and specificity of 60% and 100% cutoff values in all consecutive patients who underwent increment testing in our hospital from 1999 to 2016. RESULTS: We included 156 patients, 63 with LEMS and 93 without LEMS. Sensitivity of a 60% cutoff for increment testing was 77.8% (95% confidence interval 65.5%-87.3%) and 58.7% (45.6%-71.0%) for 100%. Specificity was 98.9% (94.2%-100%) and 100% (96.1%-100%) using a threshold of 60% and 100%, respectively. CONCLUSIONS: Lowering the cutoff value for abnormal increment to 60% greatly increases sensitivity to diagnose LEMS without an overt loss in specificity.

The quality of electrodiagnostic tests for carpal tunnel syndrome: Implications for surgery, outcomes, and expenditures.

INTRODUCTION: The quality of electrodiagnostic tests may influence treatment decisions, particularly regarding surgery, affecting health outcomes and health-care expenditures. METHODS: We evaluated test quality among 338 adults with workers' compensation claims for carpal tunnel syndrome. Using simulations, we examined how it influences the appropriateness of surgery. Using regression, we evaluated associations with symptoms and functional limitations (Boston Carpal Tunnel Questionnaire), overall health (12-item Short Form Health Survey version 2), actual receipt of surgery, and expenditures. RESULTS: In simulations, suboptimal quality tests rendered surgery inappropriate for 99 of 309 patients (+32 percentage points). In regression analyses, patients with the highest quality tests had larger declines in symptoms (-0.50 point; 95% confidence interval [CI], -0.89 to -0.12) and functional impairment (-0.42 point; 95% CI, -0.78 to -0.06) than patients with the lowest quality tests. Test quality was not associated with overall health, actual receipt of surgery, or expenditures. DISCUSSION: Test quality is pivotal to determining surgical appropriateness and associated with meaningful differences in symptoms and function.

Utility and practice of electrodiagnostic testing in the pediatric population: An AANEM consensus statement.

Nerve conduction studies and needle electromyography, collectively known as electrodiagnostic (EDX) studies, have been available for pediatric patients for decades, but the accessibility of this diagnostic modality and the approach to testing vary significantly depending on the physician and institution. The maturation of molecular diagnostic approaches and other diagnostic technologies such as neuromuscular ultrasound indicate that an analysis of current needs and practices for EDX studies in the pediatric population is warranted. The American Association of Neuromuscular & Electrodiagnostic Medicine convened a consensus panel to perform literature searches, share collective experiences, and develop a consensus statement. The panel found that electrodiagnostic studies continue to have high utility for the diagnosis of numerous childhood neuromuscular disorders, and that standardized approaches along with the use of high-quality reference values are important to maximize the diagnostic yield of these tests in infants, children, and adolescents.

A new method to define cutoff values in nerve conduction studies for carpal tunnel syndrome considering the presence of false-positive cases.

BACKGROUND: Nerve conduction studies (NCS) are useful tools for diagnosing carpal tunnel syndrome (CTS). Establishing the normal values is the first step required for utilizing NCS for diagnosis. Previous epidemiological studies demonstrated the presence of fairly large number of false-positive subjects regarding NCS among control population, which has not been properly considered in past studies. This study proposed a new method to address this issue. METHODS: Non-diabetic 144 CTS patients were retrospectively enrolled using clinically defined inclusion criteria. Controls consisted of 73 age-matched volunteers without hand symptoms. Six NCS parameters were evaluated including peak-latency difference by the thumb method (thumbdif) and that by the ring-finger method (ringdif). The Youden index of the receiver operator characteristic curve was used both to judge the sensitivity of a parameter and to identify false-positive cases that were thought to have subclinical median neuropathy at the wrist. The linear function of six parameters was constructed, and the coefficient for each parameter was variously changed. RESULTS: When the Youden index took on the maximum value, seven control subjects (10%) were identified as false-positive and were excluded from the calculation of normal values. The most sensitive parameter before exclusion was thumbdif, whereas ringdif became the most sensitive after exclusion. The cut-off value for ringdif was 1.15 ms before exclusion, but was 0.37 ms after exclusion. CONCLUSION: This method can be widely applied to solve the statistical problem when the gold standard is lacking, and the outside reference standard is not completely reliable.

Electrodiagnostic reference data for motor nerve conduction studies in Saudi Arabia.

OBJECTIVE: To determine nerve conduction studies (NCS) reference data for motor nerves and F-waves in the upper and lower limbs of healthy subjects in Saudi Arabia. METHODS: This is a cross-sectional study conducted between May 2015 and June 2019. Healthy subjects without neurological or systemic diseases were recruited. Motor NCS were performed following a standard protocol. Pearson correlations were employed between NCS parameters and age, gender, height, weight, and body mass index. Reference data were generated using the percentile method. RESULTS: A total of 127 subjects were recruited for the upper limb studies and 137 for the lower limb studies. Quantile regression models were generated to estimate compound muscle action potential amplitude (adjusted for age), as well as F-wave minimal latency (adjusted for height). The estimated reference limits of distal motor latency (ms) and conduction velocity (m/s) for the different nerves were, respectively, 3.7 and 50 for the median nerve, 3.3 and 50 for the ulnar nerve, 5.8 and 40 for the tibial nerve, and 5.0 and 40 for the fibular nerve. CONCLUSION: The reference data for motor NCS parameters and F-wave minimal latency are generally comparable with those of Western countries. However, minimal differences were observed. The underrepresentation of the older age group warrants future studies. The reference data for motor NCS parameters and F-wave minimal latency are generally comparable with those of Western countries. However, minimal differences were observed. The underrepresentation of the older age group warrants future studies.

Bipolar disorder in the balance.

Bipolar disorder (BD) is a severe mood disorder that lacks established electrophysiological, neuroimaging or biological markers to assist with both diagnosis and monitoring disease severity. This study's aim is to describe the potential of new neurophysiological features assistive in BD diagnosis and severity measurement utilizing the recording of electrical activity from the outer ear canal called Electrovestibulography (EVestG). From EVestG data sensory vestibulo-acoustic features were extracted from a single supine-vertical translation stimulus to distinguish 50 depressed and partly remitted/remitted bipolar disorder patients [18 symptomatic (BD-S, MADRS > 19), 32 reduced symptomatic (BD-R, MADRS ≤ 19)] and 31 age and gender matched healthy individuals (controls). Six features were extracted from the measured firing pattern interval histogram and the extracted shape of the average field potential response. Five of the six features had low but significant correlations (p < 0.05) with the MADRS assessment. Using leave-one-out-cross-validation, unbiased parametric and non-parametric classification routines resulted in 75-79%, 84-86%, 76-85% and 79-82% accuracy for separation of control from BD, BD-S and BD-R as well as BD-S from BD-R groups, respectively. The main limitation of this study was the inability to fully disentangle the impact of prescribed medication from the responses recorded. A mix of stationary and movement evoked EVestG features produced good discrimination between control and BD patients whether BD-S or BD-R. Moreover, BD-S and BD-R appear to have measurably different pathophysiological manifestations. The firing pattern features used were dissimilar to those observed in a prior major depressive disorder study.

AANEM policy statement on electrodiagnosis for distal symmetric polyneuropathy.

Electrodiagnostic (EDX) studies are often very helpful in the diagnosis and management of patients who have or are suspected to have Distal Symmetric Polyneuropathy (DSP). However, EDX studies may not be appropriate in every situation. There are five common scenarios in which EDX studies are likely to be beneficial: (1) determining primary and alternative diagnoses; (2) determining severity, duration and prognosis of disease; (3) evaluating risk of associated problems; (4) determining the effect of medications; and (5) evaluating the effect of toxic exposures. Muscle Nerve 57: 337-339, 2018.

Hereditary neuropathy with liability to pressure palsy in patients under 30 years old: Neurophysiological data and proposed electrodiagnostic criteria.

INTRODUCTION: In young patients with mononeuropathy who lack family history and precipitating factors, hereditary neuropathy with liability to pressure palsy (HNPP) may be a possibility. Our objective is to propose neurophysiological criteria for HNPP in patients <30 years of age. METHODS: We conducted a national multicenter retrospective clinical and neurophysiological study in patients under 30 with genetically confirmed HNPP. RESULTS: All of the 51 patients included in the study had at least 1 demyelinating pattern in 2 asymptomatic nerves, and 3 abnormalities were found in almost 90%, including slowed motor nerve conduction velocity across the elbow in at least 1 ulnar nerve (97.5%), increased distal motor latency (DML) in at least 1 fibular nerve (95.8%), and increased DML in both median nerves (89%). Age influenced DML slightly only in the fibular nerve. DISCUSSION: Dissemination of nerve involvement in HNPP incites to perform a complete nerve conduction study. including bilateral ulnar, fibular, and median nerves. Muscle Nerve 57: 217-221, 2018.

ISCEV guide to visual electrodiagnostic procedures.

Clinical electrophysiological testing of the visual system incorporates a range of noninvasive tests and provides an objective indication of function relating to different locations and cell types within the visual system. This document developed by the International Society for Clinical Electrophysiology of Vision provides an introduction to standard visual electrodiagnostic procedures in widespread use including the full-field electroretinogram (ERG), the pattern electroretinogram (pattern ERG or PERG), the multifocal electroretinogram (multifocal ERG or mfERG), the electrooculogram (EOG) and the cortical-derived visual evoked potential (VEP). The guideline outlines the basic principles of testing. Common clinical presentations and symptoms are described with illustrative examples and suggested investigation strategies.

It's time to move on from the bell curve.

The bell curve was first described in the 18th century by de Moivre and Gauss to depict the distribution of binomial events, such as coin tossing, or repeated measures of physical objects. In the 19th and 20th centuries, the bell curve was appropriated, or perhaps misappropriated, to apply to biologic and social measures across people. For many years we used it to derive reference values for our electrophysiologic studies. There is, however, no reason to believe that electrophysiologic measures should approximate a bell-curve distribution, and empiric evidence suggests they do not. The concept of using mean ± 2 standard deviations should be abandoned. Reference values are best derived by using non-parametric analyses, such as percentile values. This proposal aligns with the recommendation of the recent normative data task force of the American Association of Neuromuscular & Electrodiagnostic Medicine and follows sound statistical principles. Muscle Nerve 56: 859-860, 2017.

Proper performance of autonomic function testing.

INTRODUCTION: The aim of this position statement is to provide a recommendation from experts at the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) on the proper performance of autonomic testing. METHODS: The AANEM Professional Practice Committee and selected AANEM members reached a consensus based on expert opinion on the training required to perform autonomic testing and the appropriate performance of such tests. RESULTS: Individuals without sufficient medical education in autonomic disorders are unqualified to interpret the data generated or to coordinate the findings with other clinical information in order to reach a clinical diagnosis. CONCLUSIONS: The AANEM strongly recommends that autonomic testing procedures be performed by physicians with comprehensive knowledge of neurologic and autonomic disorders to ensure precise interpretation and diagnosis at the completion of the testing. The same physician should obtain a relevant history and physical examination and should directly supervise and interpret the data on-site and in real time. Muscle Nerve 55: 3-4, 2017.

Comparison of four different nerve conduction techniques of the superficial fibular sensory nerve.

INTRODUCTION: There are many different nerve conduction study (NCS) techniques to study the superficial fibular sensory nerve (SFSN). We present reference distal latency values and comparative data regarding 4 different NCS for the SFSN. METHODS: Four different NCS techniques, Spartan technique, Izzo techniques (medial and intermediate dorsal cutaneous branches), and Daube technique, were performed on (114) healthy volunteers. A total of 108 subjects with 164 legs were included. RESULTS: The mean latency of the Spartan technique was longest (3.9 ± 0.3 ms) while the Daube technique was the shortest (3.6 ± 0.7 ms). The mean amplitude of the Daube technique displayed the highest (15.2 ± 8.2 µV) with the Spartan technique having the lowest (8.7 ± 4.2 µV). Among the absent sensory nerve action potentials (SNAPs), the Spartan technique was absent only twice (1.2%) and the Izzo Medial technique was absent more than the other techniques (2.9%). CONCLUSIONS: All 4 techniques were reliable methods for obtaining the superficial fibular nerve SNAP, present in 95% of individuals. Muscle Nerve 56: 458-462, 2017.