Standards for quantification of EMG and neurography

Oral and topical analgesia in pediatric electrodiagnostic studies

INTRODUCTION/AIMS

Electrodiagnostic examinations, such as nerve conduction studies (NCS) and needle electromyography (EMG), are perceived as painful by children and their parents/guardians. Methods to reduce peri-procedural pain improve compliance and have neurocognitive and neuropsychiatric benefits. This study aimed to assess the efficacy of combined oral and topical analgesics (COTA), oral analgesics (OA), and placebo in reducing pain during NCS/EMG in children.

METHODS

We performed a double-blind, randomized, placebo-controlled trial on children presenting to our neurophysiology lab. Patients were stratified into two age groups (6M-6Y and 7Y-18Y) and randomized into three arms: COTA, OA, and placebo. Pain scores post-NCS/EMG were assessed using the Modified Behavioral Pain Scale (MBPS) and Faces Pain Scale-Revised (FPS-R).

RESULTS

One hundred thirteen participants were enrolled. A comparison of participants from both age groups combined revealed no significant differences in guardian FPS-R scores across all arms for NCS and EMG. A significant difference in the distribution of post-NCS FPS-R score severities in children aged 7Y-18Y was noted between OA and placebo (p = .007). EMG was more painful than NCS across all arms (p < .05). In children aged 6M-6Y undergoing at least 10 muscle samplings during EMG, those receiving COTA had significantly lower pain scores (p = .014).

DISCUSSION

This study reveals the complexity of pediatric pain perception during NCS/EMG and highlights that other methods to reduce experienced pain are required. Our findings suggest that procedural characteristics, such as number of muscles sampled, may influence the effectiveness of analgesia and serve as a foundation for future research aimed at optimizing pain management strategies.

A case control study of the relationship between persistent serum creatine kinase elevation and polyneuropathy

Creatine kinase (CK) has been associated with neuropathy, but the mechanisms are uncertain. We hypothesized that peripheral nerve function is impaired in subjects with persistent CK elevation (hyperCKemia) compared to age- and sex matched controls in a general population. The participants were recruited from the population based Tromsø study in Norway. Neuropathy impairment score (NIS), nerve conduction studies (NCS) and electromyography (EMG) in subjects with persistent hyperCKemia (n = 113; 51 men, 62 women) and controls (n = 128; 61 men, 67 women) were performed. The hyperCKemia group had higher NIS score than the controls (p = 0.050). NCS of the tibial nerve showed decreased compound motor action potential amplitude (p < 0.001), decreased motor conduction velocity (p < 0.001) and increased F-wave latency (p = 0.044). Also, reduced sensory amplitudes of the median, ulnar, and sural nerves were found. EMG showed significantly increased average motor unit potential amplitude in all examined muscles. CK correlated positively with glycated hemoglobin and non-fasting glucose in the hyperCKemia group, although not when controlled for covariates. The length dependent polyneuropathy demonstrated in the hyperCKemia group is unexplained, but CK leakage and involvement of glucose metabolism are speculated on.

Longitudinal Change in Serum Neurofilament Light Chain in Type 2 Diabetes and Early Diabetic Polyneuropathy: ADDITION-Denmark

OBJECTIVE

To investigate the longitudinal development of neurofilament light chain (NfL) levels in type 2 diabetes with and without diabetic polyneuropathy (+/-DPN) and to explore the predictive potential of NfL as a biomarker for DPN.

RESEARCH DESIGN AND METHODS

We performed retrospective longitudinal case-control analysis of data from 178 participants of the Anglo-Danish-Dutch Study of Intensive Treatment in People with Screen-Detected Diabetes in Primary Care-Denmark (ADDITION-Denmark) cohort of people with screen-detected type 2 diabetes. Biobank samples acquired at the ADDITION-Denmark 5- and 10-year follow-ups were analyzed for serum NfL (s-NfL) using single-molecule array, and the results were compared with established reference material to obtain NfL z-scores. DPN was diagnosed according to Toronto criteria for confirmed DPN at the 10-year follow-up.

RESULTS

s-NfL increased over time in +DPN (N = 39) and -DPN participants (N = 139) at levels above normal age-induced s-NfL increase. Longitudinal s-NfL change was greater in +DPN than in -DPN participants (17.4% [95% CI 4.3; 32.2] or 0.31 SD [95% CI 0.03; 0.60] higher s-NfL or NfL z-score increase in +DPN compared with -DPN). s-NfL at the 5-year follow-up was positively associated with nerve conduction studies at the 10-year follow-up (P = 0.02 to <0.001), but not with DPN risk. Areas under the curve (AUCs) for s-NfL were not inferior to AUCs for the Michigan Neuropathy Screening Instrument questionnaire score or vibration detection thresholds. Higher yearly s-NfL increase was associated with higher DPN risk (odds ratio 1.36 [95% CI 1.08; 1.71] per 1 ng/L/year).

CONCLUSIONS

Our findings suggest that preceding s-NfL trajectories differ slightly between those with and without DPN and imply a possible biomarker value of s-NfL trajectories in DPN.

Motor unit potential recruitment reference values in common upper and lower extremity muscles

OBJECTIVE

To define reference values for motor unit (MU) recruitment during needle EMG of six commonly examined muscles at low to moderate contraction.

METHODS

Needle examination was performed for each muscle in a total of 111 subjects without neuromuscular disorders. Fastest firing rates and recruitment ratios (RRs) were calculated in at least 5 sites within each muscle. Upper limits of normal based on 97th percentile for fastest MU firing rates and RRs were calculated for each muscle. The means of fastest firing rates were compared among muscles using the Friedman and Wilcoxon signed rank tests.

RESULTS

The upper limits of normal were 12-15 Hz for fastest firing rates and were slightly higher in the deltoid and triceps than the other muscles.

CONCLUSION

Firing rates >15 Hz recorded at multiple sites within a single muscle exceed the 97th percentile of normal subjects and may suggest reduced MU recruitment. In some muscles, rates >12 Hz might support mildly reduced recruitment. Recruitment ratios varied depending on number of firing MUs, whereas the fastest firing MU rate did not.

SIGNIFICANCE

The determination of reference values for fastest MU firing rates can help to identify mild reduction in recruitment with more accuracy.

Revisiting the compound muscle action potential (CMAP)

The compound muscle action potential (CMAP) is among the first recorded waveforms in clinical neurography and one of the most common in clinical use. It is derived from the summated muscle fiber action potentials recorded from a surface electrode overlying the studied muscle following stimulation of the relevant motor nerve fibres innervating the muscle. Surface recorded motor unit potentials (SMUPs) are the fundamental units comprising the CMAP. Because it is considered a basic, if not banal signal, what it represents is often underappreciated. In this review we discuss current concepts in the anatomy and physiology of the CMAP. These have evolved with advances in instrumentation and digitization of signals, affecting its quantitation and measurement. It is important to understand the basic technical and biological factors influencing the CMAP. If these influences are not recognized, then a suboptimal recording may result. The object is to obtain a high quality CMAP recording that is reproducible, whether the study is done for clinical or research purposes. The initial sections cover the relevant CMAP anatomy and physiology, followed by how these principles are applied to CMAP changes in neuromuscular disorders. The concluding section is a brief overview of CMAP research where advances in recording systems and computer-based analysis programs have opened new research applications. One such example is motor unit number estimation (MUNE) that is now being used as a surrogate marker in monitoring chronic neurogenic processes such as motor neuron diseases.

Optimization of Muscle Selection for Needle Electromyography in Isolated C6 Root Lesion: A Prospective Chart Review Study

OBJECTIVES

The aim of the study is to evaluate muscles with more prominent needle electromyographic findings to optimize needle electromyography screening of isolated C6 radiculopathy in patients with C6 root lesions.

DESIGN

This prospective clinical study was performed on 39 patients with isolated and unilateral cervical radiculopathy selected from all referrals of 1733 patients to the electrodiagnosis unit of the physical medicine and rehabilitation department of a tertiary medical center (from April 2021 to December 2021). The presence of fibrillation potentials, positive sharp waves, and/or neurogenic motor action potentials that occurred in isolation or combination with selected muscles was considered an abnormal finding.

RESULTS

Of 1733 referrals, 39 patients (18 males [46.1%] and 21 females [53.8%]), with a mean age of 49.7 ± 9.6 yrs, were found eligible. According to needle electromyography findings, the most involved muscles in C6 root lesion were pronator teres (100%), followed by extensor carpi radialis longus (94.8%), flexor carpi radialis (89.7%), brachioradialis (82%), infraspinatus (82%), supraspinatus (79.4%), deltoid (74.3%), biceps brachii (64.1%), extensor digitorum communis (33.3%), and triceps brachii (15.3%) muscles.

CONCLUSIONS

The pronator teres is the most involved muscle of patients diagnosed with C6 radiculopathy. It might be considered the key muscle for screening and accurate diagnosis of C6 root involvement.

Myths and Methodologies: Understanding the health impact of head down bedrest for the benefit of older adults and astronauts. Study protocol of the Canadian Bedrest Study

Weightlessness during spaceflight can harm various bodily systems, including bone density, muscle mass, strength and cognitive functions. Exercise appears to somewhat counteract these effects. A terrestrial model for this is head-down bedrest (HDBR), simulating gravity loss. This mirrors challenges faced by older adults in extended bedrest and space environments. The first Canadian study, backed by the Canadian Space Agency, Canadian Institutes of Health Research, and Canadian Frailty Network, aims to explore these issues. The study seeks to: (1) scrutinize the impact of 14-day HDBR on physiological, psychological and neurocognitive systems, and (2) assess the benefits of exercise during HDBR. Eight teams developed distinct protocols, harmonized in three videoconferences, at the McGill University Health Center. Over 26 days, 23 participants aged 55-65 underwent baseline measurements, 14 days of -6° HDBR, and 7 days of recovery. Half did prescribed exercise thrice daily combining resistance and endurance exercise for a total duration of 1 h. Assessments included demographics, cardiorespiratory fitness, bone health, body composition, quality of life, mental health, cognition, muscle health and biomarkers. This study has yielded some published outcomes, with more forthcoming. Findings will enrich our comprehension of HDBR effects, guiding future strategies for astronaut well-being and aiding bedrest-bound older adults. By outlining evidence-based interventions, this research supports both space travellers and those enduring prolonged bedrest.

Estimation of the number of motor units in the human extensor digitorum brevis using MScanFit

OBJECTIVE

Our aim was to determine the number and size parameters of EDB motor units in healthy young adults using MScanFit, a novel approach to motor unit number estimation (MUNE). Since variability in MUNE is related to compound muscle action potential (CMAP) size, we employed a procedure to document the optimal EDB electromyographic (EMG) electrode position prior to recording MUNE, a neglected practice in MUNE.

METHODS

Subjects were 21 adults 21-44 y. Maximum CMAPs were recorded from 9 sites in a 4 cm2 region centered over the EDB and the site with the largest amplitude was used in the MUNE experiment. For MUNE, the peroneal nerve was stimulated at the fibular head to produce a detailed EDB stimulus-response curve or "MScan". Motor unit number and size parameters underlying the MScan were simulated using the MScanFit mathematical model.

RESULTS

In 19 persons, the optimal recording site was superior, superior and proximal, or superior and distal to the EDB mid-belly, whereas in 3 persons it was proximal to the mid-belly. Ranges of key MScanFit parameters were as follows: maximum CMAP amplitude (3.1-8.5 mV), mean SMUP amplitude (34.4-106.7 μV), mean normalized SMUP amplitude (%CMAP max, 0.95-2.3%), largest SMUP amplitude (82.7-348 μV), and MUNE (43-103). MUNE was not related to maximum CMAP amplitude (R2 = 0.09), but was related to mean SMUP amplitude (R2 = -0.19, P = 0.05).

CONCLUSION

The EDB CMAP was highly sensitive to electrode position, and the optimal position differed between subjects. Individual differences in EDB MUNE were not related to CMAP amplitude. Inter-subject variability of EDB MUNE (coefficient of variation) was much less than previously reported, possibly explained by better optimization of the EMG electrode and the unique approach of MScanFit MUNE.

TDP-43-M323K causes abnormal brain development and progressive cognitive and motor deficits associated with mislocalised and increased levels of TDP-43

TDP-43 pathology is found in several neurodegenerative disorders, collectively referred to as "TDP-43 proteinopathies". Aggregates of TDP-43 are present in the brains and spinal cords of >97% of amyotrophic lateral sclerosis (ALS), and in brains of ∼50% of frontotemporal dementia (FTD) patients. While mutations in the TDP-43 gene (TARDBP) are usually associated with ALS, many clinical reports have linked these mutations to cognitive impairments and/or FTD, but also to other neurodegenerative disorders including Parkinsonism (PD) or progressive supranuclear palsy (PSP). TDP-43 is a ubiquitously expressed, highly conserved RNA-binding protein that is involved in many cellular processes, mainly RNA metabolism. To investigate systemic pathological mechanisms in TDP-43 proteinopathies, aiming to capture the pleiotropic effects of TDP-43 mutations, we have further characterised a mouse model carrying a point mutation (M323K) within the endogenous Tardbp gene. Homozygous mutant mice developed cognitive and behavioural deficits as early as 3 months of age. This was coupled with significant brain structural abnormalities, mainly in the cortex, hippocampus, and white matter fibres, together with progressive cortical interneuron degeneration and neuroinflammation. At the motor level, progressive phenotypes appeared around 6 months of age. Thus, cognitive phenotypes appeared to be of a developmental origin with a mild associated progressive neurodegeneration, while the motor and neuromuscular phenotypes seemed neurodegenerative, underlined by a progressive loss of upper and lower motor neurons as well as distal denervation. This is accompanied by progressive elevated TDP-43 protein and mRNA levels in cortex and spinal cord of homozygous mutant mice from 3 months of age, together with increased cytoplasmic TDP-43 mislocalisation in cortex, hippocampus, hypothalamus, and spinal cord at 12 months of age. In conclusion, we find that Tardbp M323K homozygous mutant mice model many aspects of human TDP-43 proteinopathies, evidencing a dual role for TDP-43 in brain morphogenesis as well as in the maintenance of the motor system, making them an ideal in vivo model system to study the complex biology of TDP-43.

Functional Limitations and Exercise Intolerance in Patients With Post-COVID Condition: A Randomized Crossover Clinical Trial

Importance

Many patients with post-COVID condition (PCC) experience persistent fatigue, muscle pain, and cognitive problems that worsen after exertion (referred to as postexertional malaise). Recommendations currently advise against exercise in this population to prevent symptom worsening; however, prolonged inactivity is associated with risk of long-term health deterioration.

Objective

To assess postexertional symptoms in patients with PCC after exercise compared with control participants and to comprehensively investigate the physiologic mechanisms underlying PCC.

Design, Setting, and Participants

In this randomized crossover clinical trial, nonhospitalized patients without concomitant diseases and with persistent (≥3 months) symptoms, including postexertional malaise, after SARS-CoV-2 infection were recruited in Sweden from September 2022 to July 2023. Age- and sex-matched control participants were also recruited.

Interventions

After comprehensive physiologic characterization, participants completed 3 exercise trials (high-intensity interval training [HIIT], moderate-intensity continuous training [MICT], and strength training [ST]) in a randomized order. Symptoms were reported at baseline, immediately after exercise, and 48 hours after exercise.

Main Outcomes and Measures

The primary outcome was between-group differences in changes in fatigue symptoms from baseline to 48 hours after exercise, assessed via the visual analog scale (VAS). Questionnaires, cardiopulmonary exercise testing, inflammatory markers, and physiologic characterization provided information on the physiologic function of patients with PCC.

Results

Thirty-one patients with PCC (mean [SD] age, 46.6 [10.0] years; 24 [77%] women) and 31 healthy control participants (mean [SD] age, 47.3 [8.9] years; 23 [74%] women) were included. Patients with PCC reported more symptoms than controls at all time points. However, there was no difference between the groups in the worsening of fatigue in response to the different exercises (mean [SD] VAS ranks for HIIT: PCC, 29.3 [19.5]; controls, 28.7 [11.4]; P = .08; MICT: PCC, 31.2 [17.0]; controls, 24.6 [11.7]; P = .09; ST: PCC, 31.0 [19.7]; controls, 28.1 [12.2]; P = .49). Patients with PCC had greater exacerbation of muscle pain after HIIT (mean [SD] VAS ranks, 33.4 [17.7] vs 25.0 [11.3]; P = .04) and reported more concentration difficulties after MICT (mean [SD] VAS ranks, 33.0 [17.1] vs 23.3 [10.6]; P = .03) compared with controls. At baseline, patients with PCC showed preserved lung and heart function but had a 21% lower peak volume of oxygen consumption (mean difference: -6.8 mL/kg/min; 95% CI, -10.7 to -2.9 mL/kg/min; P < .001) and less isometric knee extension muscle strength (mean difference: -37 Nm; 95% CI, -67 to -7 Nm; P = .02) compared with controls. Patients with PCC spent 43% less time on moderate to vigorous physical activity (mean difference, -26.5 minutes/d; 95% CI, -42.0 to -11.1 minutes/d; P = .001). Of note, 4 patients with PCC (13%) had postural orthostatic tachycardia, and 18 of 29 (62%) showed signs of myopathy as determined by neurophysiologic testing.

Conclusions and Relevance

In this study, nonhospitalized patients with PCC generally tolerated exercise with preserved cardiovascular function but showed lower aerobic capacity and less muscle strength than the control group. They also showed signs of postural orthostatic tachycardia and myopathy. The findings suggest cautious exercise adoption could be recommended to prevent further skeletal muscle deconditioning and health impairment in patients with PCC.

Trial Registration

ClinicalTrials.gov Identifier: NCT05445830.

Tongue electrical impedance myography correlates with functional, neurophysiologic, and clinical outcome measures in long-term oropharyngeal cancer survivors with and without hypoglossal neuropathy: An exploratory study

BACKGROUND

This pilot study analyzed correlations between tongue electrical impedance myography (EIM), standard tongue electromyography (EMG), and tongue functional measures in N = 4 long-term oropharyngeal cancer (OPC) survivors.

METHODS

Patients were screened for a supportive care trial (NCT04151082). Hypoglossal nerve function was evaluated with genioglossus needle EMG, functional measures with the Iowa oral performance instrument (IOPI), and multi-frequency tissue composition with tongue EIM.

RESULTS

Tongue EIM conductivity was higher for patients with EMG-confirmed cranial nerve XII neuropathy than those without (p = 0.005) and in patients with mild versus normal EMG reinnervation ratings (16 kHz EIM: p = 0.051). Tongue EIM correlated with IOPI strength measurements (e.g., anterior maximum isometric lingual strength: r2  = 0.62, p = 0.020).

CONCLUSIONS

Tongue EIM measures related to tongue strength and the presence of XII neuropathy. Noninvasive tongue EIM may be a convenient adjunctive biomarker to assess tongue health in OPC survivors.

Cerebrospinal fluid and blood exosomes as biomarkers for amyotrophic lateral sclerosis; a systematic review

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal motor neuron disease. Due to the limited knowledge about potential biomarkers that help in early diagnosis and monitoring disease progression, today's diagnoses are based on ruling out other diseases, neurography, and electromyography examination, which takes a time-consuming procedure.

METHODS

PubMed, ScienceDirect, and Web of Science were explored to extract articles published from January 2015 to June 2023. In the searching strategy following keywords were included; amyotrophic lateral sclerosis, biomarkers, cerebrospinal fluid, serum, and plama.

RESULTS

A total number of 6 studies describing fluid-based exosomal biomarkers were included in this study. Aggregated proteins including SOD1, TDP-43, pTDP-43, and FUS could be detected in the microvesicles (MVs). Moreover, TDP-43 and NFL extracted from plasma exosomes could be used as prognostic biomarkers. Also, downregulated miR-27a-3p detected through exoEasy Maxi and exoQuick Kit in the plasma could be measured as a diagnostic biomarker. Eventually, the upregulated level of CORO1A could be used to monitor disease progression.

CONCLUSION

Based on the results, each biomarker alone is insufficient to evaluate ALS. CNS-derived exosomes contain multiple ALS-related biomarkers (SOD1, TDP-43, pTDP-43, FUS, and miRNAs) that are detectable in cerebrospinal fluid and blood is a proper alternation. Exosome detecting kits listed as exoEasy, ExoQuick, Exo-spin, ME kit, ExoQuick Plus, and Exo-Flow, are helpful to reach this purpose.

Therapeutic effect of knee extension exercise with single-joint hybrid assistive limb following total knee arthroplasty: a prospective, randomized controlled trial

The single-joint hybrid assistive limb (HAL-SJ), an exoskeletal robotic suit, offers functional improvement. In this prospective randomized controlled trial, we investigated the therapeutic effects of knee extension exercises using the HAL-SJ after total knee arthroplasty (TKA). Seventy-six patients with knee osteoarthritis were randomly assigned to HAL-SJ or conventional physical therapy (CPT) groups. The HAL-SJ group underwent exercise using the HAL-SJ for 10 days postoperatively, in addition to CPT; the CPT group underwent only CPT. Pain intensity and active and passive knee extension angles were evaluated preoperatively and on postoperative days 1-10 and weeks 2 and 4. Performance tests and Knee Injury and Osteoarthritis Outcome Scores (KOOS) were evaluated preoperatively and at postoperative weeks 2 and 4. Statistical analysis showed that the HAL-SJ group significantly improved active and passive knee extension angles compared with the CPT group. The HAL-SJ group showed immediate improvement in active knee extension angle through day 5. There were no significant differences in results between the performance tests and KOOS. Knee extension exercises with the HAL-SJ improved knee pain and the angle of extension in the acute phase after TKA.

Multiparametric Quantitative MRI of Peripheral Nerves in the Leg: A Reliability Study

BACKGROUND

Patients with polyneuropathies typically have demyelination and/or axonal degeneration in peripheral nerves. Currently, there is a lack of imaging biomarkers to track the changes in these pathologies.

PURPOSE

To develop and evaluate the reliability of a multiparametric quantitative magnetic resonance imaging (qMRI) method of peripheral nerves in the leg.

STUDY TYPE

Prospective.

SUBJECTS

Seventeen healthy volunteers (36.2 ± 13.8 years old, 9 males) with 10 of them scanned twice for test-retest.

FIELD STRENGTH/SEQUENCE

3 T, three-dimensional gradient echo and diffusion tensor imaging.

ASSESSMENT

A qMRI protocol and processing pipeline was established for quantifying the following nerve parameters that are sensitive to myelin and axonal pathologies: magnetization transfer (MT) ratio (MTR), MT saturation index (MTsat), T2 *, T1 , proton density (PD), fractional anisotropy (FA), and mean/axial/radial diffusivities (MD, AD, and RD). The qMRI protocol also measures the volume of nerve fascicles (fVOL) and the fat fraction (FF) of muscles.

STATISTICAL TESTS

The intersession reproducibility and inter-rater reliability of each qMRI parameter were assessed by Bland-Altman analysis and intraclass correlation coefficient (ICC). Pairwise Pearson correlation analyses were performed to investigate the intrinsic association between qMRI parameters. Distal-to-proximal variations were evaluated by paired t-tests with Bonferroni-Holm multiple comparison corrections. P < 0.05 was considered statistically significant.

RESULTS

The MTR, MTsat, T2 *, T1 , PD, FA, AD, and fVOL of the sciatic and tibial nerves, and the FF of leg muscles, had an overall good-to-excellent test-retest agreement (ICC varying from 0.78 to 0.99). All the qMRI parameters had good-to-excellent inter-rater reliability (ICC > 0.80). The data demonstrated a pattern of distal-to-proximal changes of an increased nerve MTsat and FA, and a decreased nerve T1 , PD, MD, and RD, as well as a significantly increased muscle FF.

DATA CONCLUSION

The proposed multiparametric qMRI method of the peripheral nerves is highly reproducible and provided healthy control data which will be used in developing monitoring biomarkers in patients with polyneuropathies.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 2.

Comparison of muscle ultrasound and needle electromyography findings in neuromuscular disorders

INTRODUCTION/AIMS

Needle electromyography (EMG) and muscle ultrasound can be used to evaluate patients with suspected neuromuscular disorders. The relation between muscle ultrasound pathology and the corresponding needle EMG findings is unknown. In this study we compared the results of concurrent ultrasound and needle EMG examinations in patients suspected of a neuromuscular disorder.

METHODS

Retrospective data from 218 patients with pairwise ultrasound and EMG results of 796 muscles were analyzed. We compared overall quantitative and visual muscle ultrasound results to EMGs with neurogenic and myopathic abnormalities and assessed the congruency of both methods in the different clinical diagnosis categories.

RESULTS

In muscles of patients with a neuromuscular disorder, abnormalities were found with EMG in 71.8%, and quantitative and visual muscle ultrasound results were abnormal in 19.3% and 35.4% respectively. In muscles with neurogenic EMG abnormalities, quantitative and visual muscle ultrasound results were abnormal in 18.9% versus 35.6%, increasing up to 43.7% versus 87.5% in muscles with the most pronounced signs of denervation. Congruency of EMG and ultrasound was better for more proximal and cranial muscles than for muscles in the hand and lower limb.

DISCUSSION

Needle EMG and muscle ultrasound typically produce disparate results and identify different aspects of muscle pathology. Muscle ultrasound seems less suited for detecting mild neurogenic abnormalities. As the severity of neurogenic needle EMG abnormalities increased, muscle ultrasound abnormalities were also increasingly found. Visual analysis seems better suited than grayscale quantification for detecting neurogenic abnormalities.

Controversies in Sleep Apnea

This chapter discusses controversies in diagnosis and management of obstructive sleep apnea (OSA), with particular focus on surgical management to improve quality of life. Though OSA is a complex disorder that affects millions of people worldwide, its management remains controversial among clinicians. Gaps in understanding its pathophysiology, long-term health consequences, diagnostic methods, and treatment strategies exist. While continuous positive airway pressure (CPAP) therapy is considered the gold standard for moderate to severe obstructive sleep apnea (OSA), its adherence rate is often low, and its efficacy in improving outcomes beyond symptom reduction and quality of life improvement is uncertain. As such, surgical intervention may be an alternative for specific patient populations. Additionally, the type of surgical intervention may depend on individual patient needs, anatomic features, as well as preferences.

The role of electrodiagnosis in focal neuropathies

Electrodiagnostic (EDX) testing plays an important role in confirming a mononeuropathy, localizing the site of nerve injury, defining the pathophysiology, and assessing the severity and prognosis. The combination of nerve conduction studies (NCS) and needle electromyography findings provides the necessary information to fully assess a nerve. The pattern of NCS abnormalities reflects the underlying pathophysiology, with focal slowing or conduction block in neuropraxic injuries and reduced amplitudes in axonotmetic injuries. Needle electromyography findings, including spontaneous activity and voluntary motor unit potential changes, complement the NCS findings and further characterize chronicity and degree of axon loss and reinnervation. EDX is used as an objective marker to follow the progression of a mononeuropathy over time.

Vascularized versus Free Nerve Grafts: An Experimental Study on Rats

BACKGROUND

Vascularized nerve grafts (VNGs) have been proposed as a superior alternative to free nerve grafts (FNGs) for complex nerve defects. A greater regenerative potential has been suggested by clinical and experimental studies, but conclusive evidence is still lacking.

METHODS

In this experimental study, 10 adult male Wistar rats received a non-vascularized orthotopic sciatic nerve graft on their right side, and a vascularized orthotopic sciatic nerve graft nerve on their left side. Functional outcome following nerve regeneration was evaluated through electrodiagnostic studies, target muscles weight and histomorphology, and data of VNGs and FNGs were compared.

RESULTS

The results of this study showed a significant difference in the motor unit number of Gastrocnemius Medialis (GM) estimated by MUNE in the VNG side compared to the FNG side. No other significant differences in axonal regeneration and muscle reinnervation were evident at either electrodiagnostic, histomorphology studies or muscle weight.

CONCLUSIONS

This experimental model showed slight differences in nerve regeneration between VNGs and FNGs, but cannot support a high clinical advantage for VNGs. The results of this study show that VNGs are not strongly superior to FNGs in the rat model, even in avascular beds. Clinical advantages of VNGs are likely to be limited to extensive and thick nerve defects and can only be assessed on experimental model with bigger animals. Also, we showed that the MUNE technique provided a reliable and reproducible evaluation of functional outcomes in the rat sciatic nerve and defined a reproducible protocol for functional evaluation of muscle reinnervation.

Systematic Review of the Clinical Characteristics and Management of Isaac Syndrome

OBJECTIVES

Isaac syndrome (IS) is a condition characterized by peripheral nerve hyperexcitability caused by voltage-gated potassium channel (VGKC)-complex antibodies. Muscle twitching, stiffness, hypertrophy, and dysautonomic characteristics, such as hyperhidrosis, are common manifestations. The syndrome can be autoimmune or paraneoplastic, with thymoma being a common cause of paraneoplastic IS. Furthermore, this condition could be handed down from one generation to another. However, there is limited information regarding outcomes, relapses, associated syndromes, associated malignancies (other than thymoma), and treatment options. Despite its rarity, there remains a need for effective management strategies for patients with IS. To address this gap, we conducted a systematic review to summarize the most common and effective treatments of IS in immunomodulatory agents and symptomatic medications, as well as to describe outcomes, relapses, and associated malignancies. Altogether, this review serves to guide clinical practice recommendations for IS and highlight areas for further research.

METHODS

We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol to conduct a systematic review of cases reposted through the PubMed and Google Scholar databases. The terms "Isaac Syndrome" and "Acquired Neuromyotonia" were used. The Joanna Briggs Institute's critical appraisal tool was used to evaluate the quality of the included studies.

RESULTS

We identified 61 case reports and 4 case series, comprising a total of 70 patients with IS (mean age at onset: 42.5 ± 18 years, and 69% were males). Fourteen cases reported relapses. Thymoma was the most common malignancy associated with IS, followed by lymphoma. Among various serum antibodies, voltage-gated potassium channel-complex antibodies were the most reported antibodies elevated in IS (reported in 38 patients and elevated in 21 patients [55.2%]), followed by acetylcholine ganglionic receptor antibodies, which were reported in 30% of patients (n = 21) and were elevated in 5 cases. The most common electromyography findings were myokymic discharges (n = 22), followed by fasciculations (n = 21) and neuromyotonia (n = 19). For treatment, combining anticonvulsants such as carbamazepine with immunotherapy therapy showed the best results in controlling the symptoms. Among immunotherapy therapies, the combination of plasma exchange plus intravenous high-dose steroids achieved the best results in the acute treatment of IS ([n = 6], with improvement noted in 83.3% [n = 5] of cases). Among the symptomatic treatments with anticonvulsants, carbamazepine was the most efficacious anticonvulsant in treatment of IS, with an average effective dosing of 480 mg/day (carbamazepine was used in 32.3% of acute treatment strategies [n = 23], with improvement noted in 73.9% [n = 17] of cases).

CONCLUSIONS

IS a rare neuromuscular syndrome that tends to affect middle-aged men. These patients should be screened for thymoma and other malignancies such as lymphomas. The management of IS symptoms can be challenging, but based on our review, the combination of multiple immunosuppressives such as IV steroids and plasmapheresis with anticonvulsants such as carbamazepine seems to achieve the best results.

Double-sided asymmetric method for automated fetal heart rate baseline calculation

The fetal heart rate (FHR) signal is used to assess the well-being of a fetus during labor. Manual interpretation of the FHR is subject to high inter- and intra-observer variability, leading to inconsistent clinical decision-making. The baseline of the FHR signal is crucial for its interpretation. An automated method for baseline determination may reduce interpretation variability. Based on this claim, we present the Auto-Regressed Double-Sided Improved Asymmetric Least Squares (ARDSIAsLS) method as a baseline calculation algorithm designed to imitate expert obstetrician baseline determination. As the FHR signal is prone to a high rate of missing data, a step of gap interpolation in a physiological manner was implemented in the algorithm. The baseline of the interpolated signal was determined using a weighted algorithm of two improved asymmetric least squares smoothing models and an improved symmetric least squares smoothing model. The algorithm was validated against a ground truth determined from annotations of six expert obstetricians. FHR baseline calculation performance of the ARDSIAsLS method yielded a mean absolute error of 2.54 bpm, a max absolute error of 5.22 bpm, and a root mean square error of 2.89 bpm. In a comparison between the algorithm and 11 previously published methods, the algorithm outperformed them all. Notably, the algorithm was non-inferior to expert annotations. Automating the baseline FHR determination process may help reduce practitioner discordance and aid decision-making in the delivery room.

Serum neurofilament light chain - A potential biomarker for polyneuropathy in type 2 diabetes?

AIMS

To investigate the relationship between neurofilament light chain (NfL) and the presence and severity of diabetic polyneuropathy (DPN).

METHODS

We performed cross-sectional analysis of data from 178 participants of the ADDITION-Denmark cohort of people with screen-detected type 2 diabetes and 32 healthy controls. Biobank serum samples were analyzed for NfL using single-molecule array. DPN was defined by Toronto criteria for confirmed DPN. Original and axonal nerve conduction study (NCS) sum z-scores were used as indicators of the severity of DPN and peripheral nerve damage.

RESULTS

39 (21.9%) participants had DPN. Serum NfL (s-NfL) was significantly higher in participants with DPN (18.8 ng/L [IQR 14.4; 27.9]) than in participants without DPN (15.4 ng/L [IQR 11.7; 20.1]). There were no unadjusted s-NfL differences between controls (17.6 ng/L [IQR 12.7; 19.8]) and participants with or without DPN. Higher original and axonal NCS sum z-scores were associated with 10% higher s-NfL (10.2 and 12.1% [95% CI's 4.0; 16.8 and 6.6; 17.9] per 1 SD). The AUC of s-NfL for DPN was 0.63 (95% CI 0.52; 0.73).

CONCLUSIONS

S-NfL is unlikely to be a reliable biomarker for the presence of DPN. S-NfL is however associated tothe severity of the nerve damage underlying DPN.

The Rise Slope of the Compound Sensory Nerve Action Potential in Normal and Pathological Human Nerves

In spite of the diagnostic importance of the early phase of the sensory nerve action potential (SNAP), reliable electrodiagnostic metrics for this part of the recorded waveform are lacking. The average rise slope of the SNAP appreciates the steepness of the initial negative deflection of the waveform, which might be a useful metric for the first part of the potential. Sural nerve sensory neurography was performed in patients with various axonal neuropathies, and median nerve sensory studies were carried out in patients with carpal tunnel syndrome. Age-matched healthy individuals served as controls. The rise slope was compared to conventional SNAP parameters such as conduction velocity, latency, duration, and rise time. Overall, 537 sensory studies were prospectively analyzed. The rise slope of the sural SNAP demonstrated superior classification performance in terms of sensitivity (92.5%), specificity (97%), and area under the receiver operating characteristic curve (0.986), as compared to conventional SNAP parameters. Its diagnostic power was similarly excellent in median nerve studies, whereas here a slightly better classification performance was obtained by SNAP latency and conduction velocity. The average rise slope appears to do justice to the tight interplay between amplitude and rise time of the initial negative spike deflection, outperforming many conventional measures. This composite metric proved high diagnostic potency in particular with regard to axonal sensory nerve dysfunction.

Quantitative sensory testing and skin biopsy findings in late-onset ATTRv presymptomatic carriers: Relationships with predicted time of disease onset (PADO)

INTRODUCTION

Hereditary transthyretin amyloidosis polyneuropathy (ATTRv-PN) presymptomatic carriers often show preclinical abnormalities at small fiber-related diagnostic tests. However, no validated biomarker is currently available to use for presymptomatic carriers' follow-up, thus helping therapeutic decision making. Our study aimed at assessing nerve conduction study (NCS), quantitative sensory testing (QST), and skin biopsy parameters in a large cohort of late-onset ATTRv presymptomatic carriers and to evaluate whether they correlated with predicted age of disease onset (PADO).

METHODS

Late-onset ATTRv presymptomatic carriers were consecutively enrolled and underwent NCS, QST, and skin biopsy with intraepidermal nerve fiber density (IENFD) evaluation from a distal and a proximal site. Douleur Neuropathique-4 (DN4) and Small Fiber Neuropathy-Symptoms Inventory (SFN-SIQ) were used to assess painful and small fiber neuropathy-related symptoms. PADO and time-to-PADO (delta-PADO) were estimated for each carrier, and correlations with diagnostic test measures were analyzed.

RESULTS

Forty presymptomatic ATTRv subjects were enrolled. Twenty carriers (50%) had distal IENFD reduction, with a non-length-dependent distribution in 73% of cases. Eleven subjects (27.5%) had cold and/or warm detection threshold (CDT and/or WDT) abnormalities at QST. Delta-PADO positively correlated with sural sensory nerve action potential (SNAP) amplitude (r = .416, p = .004), and z-values of QST parameters like CDT (r = .314, p = .028), WDT (r = -.294, p = .034), and mechanical detection threshold (MDT; r = -.382, p = .012). Simple linear regression models showed a linear relation between delta-PADO and sural SAP, CDT, and MDT.

CONCLUSIONS

Our findings confirm that IENFD reduction and QST abnormalities may occur early in ATTRv presymptomatic carriers, often with a non-length-dependent pattern. However, only sural SAP amplitude and QST parameters correlated with delta-PADO, suggesting that serial combined QST and NCS evaluation could be useful in ATTRv presymptomatic carriers' follow-up.

Cardiovascular autonomic neuropathy in patients with type 2 diabetes with and without sensorimotor polyneuropathy

BACKGROUND AND AIMS

Cardiovascular autonomic neuropathy (CAN) in patients with diabetes is associated with poor prognosis. We aimed to assess signs of CAN and autonomic symptoms and to investigate the impact of sensorimotor neuropathy on CAN by examining type 2 diabetes patients with (DPN [distal sensorimotor polyneuropathy]) and without distal sensorimotor polyneuropathy (noDPN) and healthy controls (HC). Secondarily, we aimed to describe the characteristics of patients with CAN.

METHODS

A population of 374 subjects from a previously described cohort of the Danish Centre for Strategic Research in Type 2 Diabetes (DD2) were included. Subjects were examined with the Vagus™ device for the diagnosis of CAN, where two or more abnormal cardiovascular autonomic reflex tests indicate definite CAN. Autonomic symptoms were assessed with Composite Autonomic Symptom Score 31 (COMPASS 31) questionnaire. DPN was defined according to the Toronto consensus panel definition.

RESULTS

Definite CAN was present in 22% with DPN, 7% without DPN and 3% of HC, and 91% of patients with definite CAN had DPN. Patients with DPN and definite CAN reported higher COMPASS 31 scores compared to patients with noDPN (20.0 vs. 8.3, p < 0.001) and no CAN (22.1 vs. 12.3, p = 0.01). CAN was associated with HbA1c and age in a multivariate logistic regression analysis but was not associated with IEFND or triglycerides.

INTERPRETATION

One in five patients with DPN have CAN and specific CAN characteristics may help identify patients at risk for developing this severe diabetic complication. Autonomic symptoms were strongly associated with having both DPN and CAN, but too unspecific for diagnosing CAN.

Fully automated F-wave corridor extraction and analysis algorithm for F-wave analyses and MUNE studies

F-waves are used in motor unit number estimation (MUNE) studies, which require rapid dedicated software to perform calculations. The aim of this study is to define a mathematical method for a fully automated F-wave extraction algorithm to perform F-wave and MUNE studies while performing baseline corrections without distorting traces. Ten recordings from each class, such as healthy controls, polio patients and ALS patients, were included. Submaximal stimuli were applied to the median and ulnar nerves to record 300 traces from the abductor pollicis brevis and abductor digiti minimi muscles. The autocorrelation function and the signal of sum of all traces were used to find the location for the maximum amplitude of the F-waves. F-waves were revealed by using a cutting window. Linear line estimation was preferred for baseline corrections because it did not cause any distortion in the traces. The algorithm automatically revealed F-waves from all 30 recordings in accordance with the locations marked by a neurophysiologist. The execution of the algorithm was less than 2 (usually < 1) minutes when 300 traces were analyzed. Mean sMUP amplitudes and MUNE values are important for differentiating healthy controls from patients. Moreover, F-wave parameters belonging to polio patients on whom there was a relatively low number of studies conducted were also evaluated.

A scoping review of current and emerging techniques for evaluation of peripheral nerve health, degeneration, and regeneration: part 1, neurophysiology

Peripheral neuroregeneration research and therapeutic options are expanding exponentially. With this expansion comes an increasing need to reliably evaluate and quantify nerve health. Valid and responsive measures that can serve as biomarkers of the nerve status are essential for both clinical and research purposes for diagnosis, longitudinal follow-up, and monitoring the impact of any intervention. Furthermore, such biomarkers can elucidate regeneration mechanisms and open new avenues for research. Without these measures, clinical decision-making falls short, and research becomes more costly, time-consuming, and sometimes infeasible. As a companion to Part 2, which is focused on non-invasive imaging, Part 1 of this two-part scoping review systematically identifies and critically examines many current and emerging neurophysiological techniques that have the potential to evaluate peripheral nerve health, particularly from the perspective of regenerative therapies and research.

Muscle velocity recovery cycles in myopathy

OBJECTIVE

To understand the pathophysiology of myopathies by using muscle velocity recovery cycles (MVRC) and frequency ramp (RAMP) methodologies.

METHODS

42 patients with quantitative electromyography (qEMG) and biopsy or genetic verified myopathy and 42 healthy controls were examined with qEMG, MVRC and RAMP, all recorded from the anterior tibial muscle.

RESULTS

There were significant differences in the motor unit potential (MUP) duration, the early and late supernormalities of the MVRC and the RAMP latencies in myopathy patients compared to controls (p < 0.05 apart from muscle relatively refractory period (MRRP)). When dividing into subgroups, the above-mentioned changes in MVRC and RAMP parameters were increased for the patients with non-inflammatory myopathy, while there were no significant changes in the group of patients with inflammatory myopathy.

CONCLUSIONS

The MVRC and RAMP parameters can discriminate between healthy controls and myopathy patients, more significantly for non-inflammatory myopathy. MVRC differences with normal MRRP in myopathy differs from other conditions with membrane depolarisation.

SIGNIFICANCE

MVCR and RAMP may have a potential in understanding disease pathophysiology in myopathies. The pathogenesis in non-inflammatory myopathy does not seem to be caused by a depolarisation of the resting membrane potential but rather by the change in sodium channels of the muscle membrane.

Vocal Cord Paralysis and Feeding Difficulties as Early Diagnostic Clues of Congenital Myasthenic Syndrome with Neonatal Onset: A Case Report and Review of Literature

Herein, we present a newborn female with congenital vocal cord paralysis who required a tracheostomy in the neonatal period. She also presented with feeding difficulties. She was later diagnosed with a clinical picture of congenital myasthenia, associated with three variants of the MUSK gene: the 27-month follow-up was described. In particular, the c.565C>T variant is novel and has never been described in the literature; it causes the insertion of a premature stop codon (p.Arg189Ter) likely leading to a consequent formation of a truncated nonfunctioning protein. We also systematically collected and summarized information on patients' characteristics of previous cases of congenital myasthenia with neonatal onset reported in the literature to date, and we compared them to our case. The literature reported 155 neonatal cases before our case, from 1980 to March 2022. Of 156 neonates with CMS, nine (5.8%) had vocal cord paralysis, whereas 111 (71.2%) had feeding difficulties. Ocular features were evident in 99 infants (63.5%), whereas facial-bulbar symptoms were found in 115 infants (73.7%). In one hundred sixteen infants (74.4%), limbs were involved. Respiratory problems were displayed by 97 infants (62.2%). The combination of congenital stridor, particularly in the presence of an apparently idiopathic bilateral vocal cord paralysis, and poor coordination between sucking and swallowing may indicate an underlying congenital myasthenic syndrome (CMS). Therefore, we suggest testing infants with vocal cord paralysis and feeding difficulties for MUSK and related genes to avoid a late diagnosis of CMS and improve outcomes.

Median nerve ultrasound cross sectional area and wrist-to-forearm ratio in relation to carpal tunnel syndrome related axonal damage and patient age

Objective

Primary objective was to retrospectively examine the effects of patient age and carpal tunnel syndrome (CTS) related axon loss on median nerve (MN) high resolution ultrasound (HRUS) in younger and older patients. HRUS parameters evaluated in this study were MN cross sectional area at the wrist (CSA) and wrist-to-forearm ratio (WFR).

Methods

The material comprised 467 wrists of 329 patients. The patients were categorized into younger (<65 years) and older (≥65 years) groups. Patients with moderate to extreme CTS were included in the study. Axon loss of the MN was assessed by needle EMG and graded by the interference pattern (IP) density. The association between axon loss and CSA and WFR was studied.

Results

The older patients had smaller mean CSA and WFR values compared to the younger patients. CSA correlated positively to the CTS severity only in the younger group. However, WFR correlated positively to CTS severity in both groups. In both age groups, CSA and WFR correlated positively with IP reduction.

Conclusions

Our study complemented recent findings on the effects of patient age on the CSA of the MN. However, although the MN CSA did not correlate with the CTS severity in older patients, the CSA increased in respect to the amount of axon loss. Also, as a new result, we presented the positive association of WFR with CTS severity among older patients.

Significance

Our study supports the recently speculated need for different MN CSA and WFR cut-off values for younger and older patients in assessing the severity of CTS. With older patients, WFR may be a more reliable parameter to assess the CTS severity than the CSA. CTS related axonal damage of the MN is associated to additional nerve enlargement at the carpal tunnel intel site.

Assessing Corneal Confocal Microscopy and Other Small Fiber Measures in Diabetic Polyneuropathy

BACKGROUND AND OBJECTIVES

Damage to small nerve fibers is common in diabetic polyneuropathy (DPN), and the diagnosis of DPN relies on subjective symptoms and signs in a combination with objective confirmatory tests, typically electrophysiology or intraepidermal nerve fiber density (IENFD) from skin biopsy. Corneal confocal microscopy (CCM) has been introduced as a tool to detect DPN. However, it is unclear if CCM can reliably be used to diagnose DPN and how the technique compares with other commonly used measures of small fiber damage, such as IENFD, cold detection threshold (CDT), and warm detection threshold (WDT). Therefore, we assessed and compared the use of CCM, IENFD, CDT, and WDT in the diagnosis of DPN in patients with type 2 diabetes.

METHODS

In this cohort study, the participants underwent detailed neurologic examination, electrophysiology, quantification of IENFD, CCM, and quantitative sensory testing. Definition of DPN was made in accordance with the Toronto criteria for diabetic neuropathy (without relying on IENFD and thermal thresholds).

RESULTS

A total of 214 patients with at least probable DPN, 63 patients without DPN, and 97 controls without diabetes were included. Patients with DPN had lower CCM measures (corneal nerve fiber length [CNFL], nerve fiber density, and branch density), IENFD, CDT, and WDT compared with patients without DPN (p ≤ 0.001, <0.001, 0.002, p < 0.001, p = 0.003, and <0.005, respectively), whereas there was no difference between controls and patients with diabetes without DPN. All 3 CCM measures showed a very low diagnostic sensitivity with CNFL showing the highest (14.4% [95% CI 9.8-18.4]) and a specificity of 95.7% (88.0-99.1). In comparison, the sensitivity of abnormal CDT and/or WDT was 30.5% (24.4-37.0) with a specificity of 84.9% (74.6-92.2). The sensitivity of abnormal IENFD was highest among all measures with a value of 51.1% (43.7-58.5) and a specificity of 90% (79.5-96.2). CCM measures did not correlate with IENFD, CDT/WDT, or neuropathy severity in the group of patients with DPN.

DISCUSSION

CCM measures showed the lowest sensitivity compared with other small fiber measures in the diagnosis of DPN. This indicates that CCM is not a sensitive method to detect DPN in recently diagnosed type 2 diabetes.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that CCM measures aid in the detection of DPN in recently diagnosed type 2 diabetics but with a low sensitivity when compared with other small fiber measures.

Quantitative muscle magnetic resonance imaging depicts microstructural abnormalities but no signs of inflammation or dystrophy in post-COVID-19 condition

BACKGROUND AND PURPOSE

Post-COVID-19 condition (PCC) has high impact on quality of life, with myalgia and fatigue affecting at least 25% of PCC patients. This case-control study aims to noninvasively assess muscular alterations via quantitative muscle magnetic resonance imaging (MRI) as possible mechanisms for ongoing musculoskeletal complaints and premature exhaustion in PCC.

METHODS

Quantitative muscle MRI was performed on a 3 Tesla MRI scanner of the whole legs in PCC patients compared to age- and sex-matched healthy controls, including a Dixon sequence to determine muscle fat fraction (FF), a multi-echo spin-echo sequence for quantitative water mapping reflecting putative edema, and a diffusion-weighted spin-echo echo-planar imaging sequence to assess microstructural alterations. Clinical examination, nerve conduction studies, and serum creatine kinase were performed in all patients. Quantitative muscle MRI results were correlated to the results of the 6-min walk test and standardized questionnaires assessing quality of life, fatigue, and depression.

RESULTS

Twenty PCC patients (female: n = 15, age = 48.8 ± 10.1 years, symptoms duration = 13.4 ± 4.2 months, body mass index [BMI] = 28.8 ± 4.7 kg/m² ) were compared to 20 healthy controls (female: n = 15, age = 48.1 ± 11.1 years, BMI = 22.9 ± 2.2 kg/m² ). Neither FF nor T2 revealed signs of muscle degeneration or inflammation in either study groups. Diffusion tensor imaging (DTI) revealed reduced mean, axial, and radial diffusivity in the PCC group.

CONCLUSIONS

Quantitative muscle MRI did not depict any signs of ongoing inflammation or dystrophic process in the skeletal muscles in PCC patients. However, differences observed in muscle DTI depict microstructural abnormalities, which may reflect potentially reversible fiber hypotrophy due to deconditioning. Further longitudinal and interventional studies should prove this hypothesis.

Not myopathic, but autonomic changes in patients with long-COVID syndrome: a case series

INTRODUCTION

Neurological sequelae following SARS-CoV-2 infection still represent a serious concern both for neurologists and neuroscientists. In our paper, we investigated pain, myalgia, and fatigue as symptoms in long-COVID patients with an electrophysiological approach, comprising the evaluation of sympathetic skin responses (SSRs) and quantitative electromyography (qEMG).

MATERIALS AND METHODS

Twelve patients were enrolled (mean age, 47.7 ± 11.6 years), referred to our attention because of myalgia, pain, or muscle cramps, which persisted about 6 months after the diagnosis of SARS-CoV-2 infection. They underwent conventional electroneurography (ENG), needle electromyography (EMG), and SSRs; moreover, qEMG was performed by sampling at least 20 motor unit potentials (20-30 MUPs) during weak voluntary contraction in deltoid and tibialis anterior muscles. The mean duration, amplitude, and percentage of polyphasic potentials were assessed and compared with healthy and age-matched volunteers.

RESULTS

ENG did not disclose significant changes compared to healthy subjects; needle EMG did not reveal denervation activity. In addition, qEMG showed MUPs similar to those recorded in healthy volunteers in terms of polyphasia (deltoid: p = 0.24; TA: p = 0.35), MUP area (deltoid: p = 0.45; TA: p = 0.44), mean duration (deltoid: p = 0.06; TA: p = 0.45), and amplitude (deltoid: p = 0.27; TA: p = 0.63). SSRs were not recordable from lower limbs in seven patients (58%) and from the upper ones in three of them (25%).

CONCLUSION

Our data suggest an involvement of the autonomic system, with a focus on cholinergic efferent sympathetic activity, without any evidence of myopathic changes.

Myopathy as a cause of Long COVID fatigue: Evidence from quantitative and single fiber EMG and muscle histopathology

OBJECTIVE

To describe neurophysiological abnormalities in Long COVID and correlate quantitative electromyography (qEMG) and single fiber EMG (sfEMG) results to clinical scores and histopathology.

METHODS

84 patients with non-improving musculoskeletal Long COVID symptoms were examined with qEMG and sfEMG. Muscle biopsies were taken in a subgroup.

RESULTS

Mean motor unit potential (MUP) duration was decreased in ≥ 1 muscles in 52 % of the patients. Mean jitter was increased in 17 % of the patients in tibialis anterior and 25 % in extensor digitorum communis. Increased jitter was seen with or without myopathic qEMG. Low quality of life score correlated with higher jitter values but not with qEMG measures. In addition to our previously published mitochondrial changes, inflammation, and capillary injury, we show now in muscle biopsies damage of terminal nerves and motor endplate with abundant basal lamina material. At the endplate, axons were present but no vesicle containing terminals. The post-synaptic cleft in areas appeared atrophic with short clefts and coarse crests.

CONCLUSIONS

Myopathic changes are common in Long COVID. sfEMG abnormality is less common but may correlate with clinical scores. sfEMG changes may be due to motor endplate pathology.

SIGNIFICANCE

These findings may indicate a muscle pathophysiology behind fatigue in Long COVID.

Investigation of gait, balance and lower extremity muscle activity during walking in patients with cervical spondylotic myelopathy using wearable sensors

BACKGROUND CONTEXT

Cervical spondylotic myelopathy (CSM) is a degenerative disease caused by cervical cord compression and can lead to the significant impairment of motor function including gait and balance disturbances and changes in lower extremity muscle activity.

PURPOSE

This study aimed to characterize gait, balance and lower extremity muscle activity in patients with CSM compared to age-matched healthy controls (HCs) using wearable sensors in the clinical setting.

STUDY DESIGN

Non-Randomized, prospective cohort study.

PATIENT SAMPLE

10 CSM patients and 10 age-matched HCs were recruited for this study.

OUTCOME MEASURES

Gait and balance function parameters contained spatial temporal parameters, step regularity (SR1), stride regularity (SR2) and harmonic ratio (HR). EMG muscle activity parameters included time to peak and peak value during loading, stance, and swing phase.

METHODS

In this study, parameters of gait and balance function were extracted using triaxial accelerometer attached to the spinous processes of Lumbar 5 while participants performed an overground walking at a self-preferred speed. Moreover, muscular activity was simultaneously recorded via sEMG sensors attached to tibialis anterior (TA), rectus femoris (RF), bicep femoris (BF) and gastrocnemius lateral (GL). Independent sample t-test was used to find the differences between CSM patients and HCs.

RESULTS

Gait analysis showed cadence, step length and walking speed were statistically significantly lower in CSM patients than HCs. Stride time was significantly higher for CSM patients in comparison to HCs. Lower root mean square ratio (RMSR) of acceleration in the mediolateral (ML) direction, HR in the anteroposterior (AP) direction, SR1 in the AP direction and SR2 in all three directions were observed in CSM patients. For muscle activity analysis, EMG RMS for TA and RF during loading phase and RMS for GL during midstance phase was significantly lower for CSM patients, while significantly higher value was observed for RF RMS during midstance phase and GL RMS during swing phase in CSM patients.

CONCLUSION

Our pilot study shows that wearable sensors are able to detect the changes of gait, balance and lower extremity muscle activities of CSM patients in the clinical setting. This pilot study sets the stage for future researches on the diagnosis and monitor progression of CSM disease using wearable technology.

Functional and morphometric assessment of small-fibre damage in late-onset hereditary transthyretin amyloidosis with polyneuropathy: the controversial relation between small-fibre-related symptoms and diagnostic test findings

INTRODUCTION

We aimed at investigating whether functional and morphometric tests assessing small-fibre damage, ie quantitative sensory testing, Sudoscan and skin biopsy, reliably reflect neuropathic pain and autonomic symptoms in patients with late-onset hereditary transthyretin amyloidosis with polyneuropathy (ATTRv-PN).

METHODS

In 30 patients with late-onset ATTRv-PN, we collected quantitative sensory testing, Sudoscan and skin biopsy with assessment of intraepidermal, piloerector muscle and sweat gland nerve fibre density. We then correlated these functional and morphometric parameters with neuropathic pain and autonomic symptoms as assessed with the Neuropathic Pain Symptom Inventory (NPSI) and Composite Autonomic Symptom Score-31 (COMPASS-31).

RESULTS

50% of patients showed small-fibre damage in the form of a pure small-fibre neuropathy, 47% in the context of a mixed fibre neuropathy with small and large fibre involvement. All patients complained of at least one autonomic symptom and 60% had neuropathic pain. Whereas quantitative sensory testing and Sudoscan parameters correlated with neuropathic pain and autonomic symptoms as assessed by NPSI and COMPASS-31, intraepidermal, piloerector muscle and sweat gland nerve fibre density quantification did not.

CONCLUSIONS

Our findings indicate that functional test parameters reliably reflect neuropathic pain and autonomic symptoms related to small-fibre damage. These findings might help to identify clinically useful biomarkers to assess patient follow-up.

Heterozygous Seryl-tRNA Synthetase 1 Variants Cause Charcot-Marie-Tooth Disease

OBJECTIVE

Despite the increasing number of genes associated with Charcot-Marie-Tooth (CMT) disease, many patients currently still lack appropriate genetic diagnosis for this disease. Autosomal dominant mutations in aminoacyl-tRNA synthetases (ARSs) have been implicated in CMT. Here, we describe causal missense mutations in the gene encoding seryl-tRNA synthetase 1 (SerRS) for 3 families affected with CMT.

METHODS

Whole-exome sequencing was performed in 16 patients and 14 unaffected members of 3 unrelated families. The functional impact of the genetic variants identified was investigated using bioinformatic prediction tools and confirmed using cellular and biochemical assays.

RESULTS

Combined linkage analysis for the 3 families revealed significant linkage (Zmax LOD = 6.9) between the genomic co-ordinates on chromosome 1: 108681600-110300504. Within the linkage region, heterozygous SerRS missense variants segregated with the clinical phenotype in the 3 families. The mutant SerRS proteins exhibited reduced aminoacylation activity and abnormal SerRS dimerization, which suggests the impairment of total protein synthesis and induction of eIF2α phosphorylation.

INTERPRETATION

Our findings suggest the heterozygous SerRS variants identified represent a novel cause for autosomal dominant CMT. Mutant SerRS proteins are known to impact various molecular and cellular functions. Our findings provide significant advances on the current understanding of the molecular mechanisms associated with ARS-related CMT. ANN NEUROL 2023;93:244-256.

Quantitative electrodiagnosis of the motor unit

Electromyography (EMG) focuses on assessment of the motor unit (MU), and a given muscle has several hundred MUs, each innervating hundreds of muscle fibers. Assessment is limited by the recording radius of electrodes, 1-2 fibers with single-fiber electrodes and 7-15 fibers with concentric or monopolar electrodes. Routine qualitative EMG studies rely on observing MUs in free-run mode and qualitatively estimating common metrics. In contrast, quantitative EMG (QEMG) applied to routine studies includes assessment of individual MUs by software available in modern EMG machines with extraction of discrete values for common metrics, and also derived metrics. This results in greater precision and statistical interpretation. Other QEMG techniques assess muscle fiber density within the MU and time variability at the neuromuscular junction. The interference pattern can also be assessed. The number of MUs innervating a muscle can be estimated. Advanced signal processing, called near-fiber EMG, allows for extraction of underlying muscle fiber contributions to MU waveforms. It is also possible to use QEMG to make statistical probabilities of the state of a muscle as to whether normal, myopathic, or neuropathic. Time to acquire QEMG data is minimal. QEMG is most useful in situations where pathology is uncertain.

miR-31-5p as a Potential Circulating Biomarker and Tracer of Clinical Improvement for Chronic Inflammatory Demyelinating Polyneuropathy

Background

MicroRNAs are endogenous, small noncoding RNA molecules that play a pivotal role in the regulation of gene expression. MicroRNAs are involved in many biological processes such as proliferation, cell differentiation, neovascularization, and apoptosis. Studies on microRNA expression may contribute to a better understanding of the pathomechanism of chronic inflammatory demyelinating polyneuropathy (CIDP) and consequently enable the development of new therapeutic measures using antisense miRNAs (antagomirs). In this study, we evaluated the level of miR-31-5p in the serum of patients with CIDP and its correlation with the miR-31-5p level and clinical presentation and electrophysiological and biochemical parameters.

Methods

The study group consisted of 48 patients, mean age 61.60 ± 11.76, who fulfilled the diagnostic criteria of a typical variant of CIDP. The expression of miR-31-5p in patient serum probes was investigated by droplet digital PCR. The results were correlated with neurophysiological findings and the patient's clinical and biochemical parameters.

Results

The mean copy number of miRNA-31 in 100 μl serum was 1288.64 ± 2001.02 in the CIDP group of patients, while in the control group, it was 3743.09 ± 4026.90. There was a significant positive correlation (0.426) between IgIV treatment duration and miR-31-5p expression. Patients without IgIV treatment showed significantly lower levels of miR-31 compared to the treated group (259.44 ± 304.02 vs. 1559.48 ± 2168.45; p = 0.002). The group of patients with body weight > 80 kg showed statistically significantly lower levels of miRNA-31-5p than the patients with lower body weight (934.37 ± 1739.66 vs. 1784.62 ± 2271.62, respectively; p = 0.014). Similarly, the patients with elevated cerebrospinal fluid (CSF) protein levels had significantly higher miRNA-31-5p expression than those with normal protein levels (1393.93 ± 1932.27 vs. 987.38 ± 2364.10, respectively; p = 0.044).

Conclusion

The results may support the hypothesis that miR-31-5p is strongly involved in the autoimmune process in CIDP. The positive correlation between higher miR-31-5p levels and duration of IVIg treatment may be an additional factor explaining the efficacy of prolonged IVIg therapy in CIDP.

Motor unit recruitment and firing rate at low force of contraction

INTRODUCTION/AIMS

A prevailing concept of motor unit (MU) recruitment used for calculating recruitment ratio (RR) suggests a progressive linear increase in firing rate (FR). The objective of this study is to assess its validity.

METHODS

Concentric needle electromyography (EMG) recordings were made in normal muscle and abnormal muscle of patients with neurogenic findings. Signals recorded at low force were visually decomposed to study MU FR at onset, recruitment of a second MU, and recruitment of more MUs with further increases in force.

RESULTS

We observed one to six MUs discharging at a rate < 15 Hz in normal muscles at low force. The MU FR was 5-8 Hz at onset. With increasing force, FR increased by 3-5 Hz and then idled at <15 Hz while other MUs were recruited. The recruitment frequency (RF) and RR had low sensitivity and were abnormal mainly in moderately to severely weak muscles.

DISCUSSION

Our data are consistent with FR analysis results described by other investigators. It does not support a progressive linear increase in MU FR with recruitment. A revised model for MU recruitment at low effort during gradual increase in force is presented. On subjective assessment, the FR of the fastest firing MU can help detect MU loss in neurogenic processes.

Expanded clinical spectrum of oculopharyngodistal myopathy type 1

INTRODUCTION/AIMS

Heterozygous CGG repeat expansions in low-density lipoprotein receptor-related protein 12 (LRP12) have recently been identified as a cause of oculopharyngodistal myopathy (OPDM), and the disease is designated as OPDM type 1 (OPDM1). In contrast to broadening of our knowledge on the genetic background of OPDM, what we know of the clinical phenotype of genetically confirmed OPDM1 remains limited.

METHODS

This investigation was a single-center case series study of OPDM consisting of ten patients from seven families. Repeat-primed polymerase chain reaction and Southern blot analyses were performed to confirm the CGG repeat expansions in LRP12. Clinical findings were retrospectively reviewed.

RESULTS

Seven patients from five families were identified as having CGG repeat expansions in LRP12. We found a high prevalence of axial muscle involvement, such as neck muscle weakness (6/7) and fatty infiltration in the rectus abdominis muscle, as revealed by computed tomography (5/5). We identified patients with very subtle oculopharyngeal symptoms, mimicking isolated distal myopathy. Muscle specimens were collected from the biceps brachii and tibialis anterior muscles of three patients. Myopathic changes were more severe with more atrophic fibers forming clusters in the tibialis anterior than the biceps brachii muscles of these three patients. No rimmed vacuoles were observed in the biceps brachii muscles in two of the three patients.

DISCUSSION

This study shows the expanded clinical spectrum of OPDM1, highlighting the importance of axial muscle evaluation in OPDM1. Considering patients with very subtle oculopharyngeal symptoms, genetic analysis of LRP12 should be considered in patients with isolated distal myopathy.

Optically pumped magnetometers detect altered maximal muscle activity in neuromuscular disease

Optically pumped magnetometers (OPM) are quantum sensors that enable the contactless, non-invasive measurement of biomagnetic muscle signals, i.e., magnetomyography (MMG). Due to the contactless recording, OPM-MMG might be preferable to standard electromyography (EMG) for patients with neuromuscular diseases, particularly when repetitive recordings for diagnostic and therapeutic monitoring are mandatory. OPM-MMG studies have focused on recording physiological muscle activity in healthy individuals, whereas research on neuromuscular patients with pathological altered muscle activity is non-existent. Here, we report a proof-of-principle study on the application of OPM-MMG in patients with neuromuscular diseases. Specifically, we compare the muscular activity during maximal isometric contraction of the left rectus femoris muscle in three neuromuscular patients with severe (Transthyretin Amyloidosis in combination with Pompe’s disease), mild (Charcot-Marie-Tooth disease, type 2), and without neurogenic, but myogenic, damage (Myotonia Congenita). Seven healthy young participants served as the control group. As expected, and confirmed by using simultaneous surface electromyography (sEMG), a time-series analysis revealed a dispersed interference pattern during maximal contraction with high amplitudes. Furthermore, both patients with neurogenic damage (ATTR and CMT2) showed a reduced variability of the MMG signal, quantified as the signal standard deviation of the main component of the frequency spectrum, highlighting the reduced possibility of motor unit recruitment due to the loss of motor neurons. Our results show that recording pathologically altered voluntary muscle activity with OPM-MMG is possible, paving the way for the potential use of OPM-MMG in larger studies to explore the potential benefits in clinical neurophysiology.

Relationships between the Clinical Test Results and Neurophysiological Findings in Patients with Thoracic Outlet Syndrome

A thoracic outlet syndrome (TOS) is the type of brachial plexus disorder most difficult to objectively assess using a clinical examination and differential diagnosis. Its symptoms can be frequently misdiagnosed, especially among others with cervical disc-root conflicts, plexopathies, and peripheral neuropathies. In this study, we aim to identify the correlations between positive Doppler ultrasonography results indicating pathological changes in the subclavian flow velocity, clinical tests, and chosen clinical neurophysiology recordings as proposed alternative or supplementary diagnostic tools for evaluating TOS patients. Sixty TOS patients with positive Doppler ultrasonography and Roos test results and sixty healthy people as a control group were bilaterally examined, and the results were compared. Pain intensity was assessed using a visual analogue scale (VAS). Sensory perceptions within C4–C8 dermatomes were assessed with Von Frey filament (FvF) tests. The activity of motor units in the proximal and distal muscles of the upper extremities was evaluated using surface electromyography (sEMG) during maximal contractions before and after a provocative raised hands test (RHT). An electroneurography (ENG) was used to evaluate the transmission of nerve impulses peripherally. Motor evoked potential (MEP) recordings, induced by the over-vertebral magnetic stimulation of the C5–C7 neuromeres, were used to examine motor transmissions from the cervical motor centres to the upper extremities muscles. The results revealed a relationship between positive Doppler test scores and pathological changes in the subclavian flow velocity through the results of the following diagnostic tools: a VAS score of 1.9 was detected on average, superficial sensory perception abnormalities were found in the innervation areas of the ulnar nerves detected by FvF tests, a decrease in the amplitudes of sEMG recordings was seen in distal rather than proximal muscles (especially following the RHT), a decrease in the motor and sensory peripheral transmissions of nerve impulses in the median, ulnar and cutaneous anterobrachial median nerves was seen, as well as MEP amplitudes recorded from the abductor pollicis brevis muscle. The provocative RHT combined with sEMG and MEP recordings can be considered accurate and objective clinical neurophysiology tools that could supplement the commonly used clinical tests. Such an approach may result in a more precise neurogenic TOS diagnostic algorithm.

GABA facilitates spike propagation through branch points of sensory axons in the spinal cord

Movement and posture depend on sensory feedback that is regulated by specialized GABAergic neurons (GAD2⁺) that form axo-axonic contacts onto myelinated proprioceptive sensory axons and are thought to be inhibitory. However, we report here that activating GAD2⁺ neurons directly with optogenetics or indirectly by cutaneous stimulation actually facilitates sensory feedback to motor neurons in rodents and humans. GABA_A receptors located at or near nodes of Ranvier of sensory axons cause this facilitation by preventing spike propagation failure at the many axon branch points, which is otherwise common without GABA. In contrast, GABA_A receptors are generally lacking from axon terminals and so cannot inhibit transmitter release onto motor neurons, unlike GABA_B receptors that cause presynaptic inhibition. GABAergic innervation near nodes and branch points allows individual branches to function autonomously, with GAD2⁺ neurons regulating which branches conduct, adding a computational layer to the neuronal networks generating movement and likely generalizing to other central nervous system axons.

Predictors of Step Length from Surface Electromyography and Body Impedance Analysis Parameters

Step length is a critical hallmark of health status. However, few studies have investigated the modifiable factors that may affect step length. An exploratory, cross-sectional study was performed to evaluate the surface electromyography (sEMG) and body impedance analysis (BIA) parameters, combined with individual demographic data, to predict the individual step length using the GAITRite® system. Healthy participants aged 40−80 years were prospectively recruited, and three models were built to predict individual step length. The first model was the best-fit model (R2 = 0.244, p < 0.001); the root mean square (RMS) values at maximal knee flexion and height were included as significant variables. The second model used all candidate variables, except sEMG variables, and revealed that age, height, and body fat mass (BFM) were significant variables for predicting the average step length (R2 = 0.198, p < 0.001). The third model, which was used to predict step length without sEMG and BIA, showed that only age and height remained significant (R2 = 0.158, p < 0.001). This study revealed that the RMS value at maximal strength knee flexion, height, age, and BFM are important predictors for individual step length, and possibly suggesting that strengthening knee flexor function and reducing BFM may help improve step length.

Force and electromyography reflections of sensory action-effect weighting during pinching

Ideomotor theories suggest that different action-effects are not equally important in goal-directed actions, and that task-relevant information are weighted stronger during the representation of actions. This stronger weighting of task-relevant action-effects might also enable to utilize them as retrieval cues of the corresponding motor patterns. The aim of the present study was to investigate how the consistent presence or absence of a sound action-effect influenced the retrieval of the motor components of a simple, everyday action (pinching) as reflected by the pattern of force application and surface electromyogram (sEMG) recorded from the abductor pollicis brevis (APB) and first dorsal interosseous (FDI). Participants applied pairs of pinch impulses to a force sensitive resistor (FSR). The presence or absence of a sound action-effect and the between-action interval (BAI, 2 or 4 s) were manipulated blockwise, whereas the target force level (low or high) was randomly cued from trial to trial. When actions resulted in a sound, force and sEMG activity were reduced. This effect was more pronounced for low target force level trials, which is compatible with a stronger weighting of the sound action-effect when the intensity of the tactile and proprioceptive action-effects is low. Surprisingly, the FDI activity was more variable within actions pairs in the 2 s BAI conditions, which suggests that action pairs separated by the longer time interval might have been represented differently from those separated by the shorter interval.

EMG und Neurografie – ein Update

Elektromyografie (EMG) und Elektroneurografie (ENG) gelten als bewährte Methoden, deren Anfänge aber schon Jahrzehnte zurückliegen. In dieser Arbeit werden jüngere Entwicklungen beschrieben und die Rolle von EMG und ENG in wichtigen Situationen diskutiert, nämlich bei traumatische Nervenläsionen, Nervenkompressionssyndromen, Polyneuropathien, Motoneuronerkrankungen, Myopathien, neuromuskulären Transmissionsstörungen und bei muskulärer Überaktivität.

Deep Learning-Based Surface Nerve Electromyography Data of E-Health Electroacupuncture in Treatment of Peripheral Facial Paralysis

This study was aimed at exploring the application value of electroacupuncture in the treatment of peripheral facial palsy using surface nerve electromyogram (EMG) image data based on deep learning. The surface nerve EMG recognition model was constructed based on multiview convolutional neural network, and the differences between it and the traditional single-view convolutional neural network were analyzed. Meanwhile, the influence of the multiview aggregation method based on pooling of view and decision fusion on facial recognition accuracy was compared and analyzed. 150 patients with peripheral facial paralysis were randomly divided into the control group (n = 70, basic treatment) and treatment group (n = 80, basic treatment + electroacupuncture). After 4 weeks of treatment, the therapeutic effect was evaluated by surface EMG parameters based on Horsfall-Barratt (H-B) scale and multiview convolutional neural network. The results showed that the face recognition accuracy of multiview convolutional neural networks was significantly higher than that of all single-view convolutional neural networks. The multiview aggregation network proposed in this research had a higher accuracy in facial recognition than the pooling of the view method and decision fusion-based multiview aggregation method. According to the evaluation results of H-B scale, the number of patients who recovered, significantly effective, effective, and ineffective in the control group was 39, 17, 3, and 11, respectively. The number of patients in the treatment group who recovered, significantly effective, effective, and ineffective was 51, 15, 9, and 5, respectively. Total effective rate of patients in the control group was 84.29%, and that of the treatment group was 93.75%, which was significantly higher than the control group (P < 0.05). According to surface EMG assessment results, compared with the control group, the mean root mean square (RMS), median frequency (MF), and mean power frequency (MPF) of the buccal and frontalis muscles in the treatment group increased significantly (P < 0.05). Compared with that before treatment, the mean buccal and frontalis RMS of patients in the control and treatment groups increased significantly after treatment (P < 0.05). In conclusion, electroacupuncture treatment could significantly improve the muscle strength of patients with peripheral facial paralysis.

Estimating the motor unit number of the flexor carpi ulnaris muscle with MScanFit MUNE

INTRODUCTION/AIMS

MScanFit motor unit number estimation (MUNE) is a promising method for motor unit estimation and is reported to have good reliability in distal and small muscles. In this study, we investigated the reliability of MScanFit MUNE in a proximal forearm muscle, the flexor carpi ulnaris.

METHODS

Twenty healthy volunteers were included in this study and 15 participants were re-evaluated in a second session. The ulnar nerve was stimulated at the elbow and a compound muscle action potential (CMAP) scan from the flexor carpi ulnaris (FCU) muscle was recorded from each arm. CMAP, MUNE and other motor unit parameters were obtained. Reproducibility was evaluated using intraclass correlation coefficients.

RESULTS

The average MUNE from 40 FCU muscles was 90.9 (SD: 16.4). MScanFit MUNE and CMAP were not significantly different between the dominant and non-dominant sides. The intraclass correlation coefficient indicated good reliability between sessions for each side (0.81 and 0.8 respectively).

DISCUSSION

Our results indicate that MScanFit MUNE is a feasible method with good reproducibility for MUNE of the FCU muscle. This article is protected by copyright. All rights reserved.