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Tankisi H, Bostock H, Tan SV, Howells J, Ng K, Z'Graggen WJ. Muscle excitability testing. Clin Neurophysiol 2024; 164:1-18. [PMID: 38805900 DOI: 10.1016/j.clinph.2024.04.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2023] [Revised: 04/22/2024] [Accepted: 04/22/2024] [Indexed: 05/30/2024]
Abstract
Conventional electrophysiological methods, i.e. nerve conduction studies and electromyography are suitable methods for the diagnosis of neuromuscular disorders, however, they provide limited information about muscle fibre membrane properties and underlying disease mechanisms. Muscle excitability testing is a technique that provides in vivo information about muscle fibre membrane properties such as membrane potential and ion channel function. Since the 1960s, various methodologies have been suggested to examine muscle membrane properties but technical difficulties have limited its use. In 2009, an automated, fast and simple application, the so-called multi-fibre muscle velocity recovery cycles (MVRC) has accelerated the use of muscle excitability testing. Later, frequency ramp and repetitive stimulation protocols have been developed. Though this method has been used mainly in research for revealing disease mechanisms across a broad range of neuromuscular disorders, it may have additional diagnostic uses; value has been shown particularly in muscle channelopathies. This review will provide a description of the state-of-the art of methodological and clinical studies for muscle excitability testing.
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Affiliation(s)
- H Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark; Institute of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark.
| | - H Bostock
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, WC1N 3BG London, United Kingdom
| | - S V Tan
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, WC1N 3BG London, United Kingdom; Department of Neurology and Neurophysiology, Guys and St Thomas' NHS Foundation Trust, London, United Kingdom
| | - J Howells
- Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, Australia
| | - K Ng
- Department of Neurology and Neurophysiology, Royal North Shore Hospital, St Leonards, NSW, Australia; University of Sydney, Camperdown, NSW, Australia
| | - W J Z'Graggen
- Departments Neurology and Neurosurgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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Lu Z, Chen M, Zong Y, Huang C, Li X, Zhou P. Sensitivity Analysis of CMAP Scan Step Index to Different Stimulation Parameters and Examination of Muscles Affected by Spinal Cord Injury. IEEE Trans Biomed Eng 2023; 70:2834-2840. [PMID: 37756167 PMCID: PMC11057332 DOI: 10.1109/tbme.2023.3266327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/29/2023]
Abstract
Step index (STEPIX) is a recently developed compound muscle action potential (CMAP) scan method for evaluating motor unit loss and remodeling changes. This study investigates the influence of different stimulation parameters during CMAP scan on STEPIX and its examination of muscles affected by spinal cord injury (SCI). CMAP scan of the first dorsal interosseous (FDI) muscle was performed using different stimulus pulse widths (0.1 ms, 0.2 ms) and different numbers of stimuli (500, 1000) in 12 neurologically intact subjects. STEPIX was derived from each CMAP scan of all subjects. A significantly higher STEPIX was obtained using 1000 stimuli than 500 stimuli, while no significant difference in STEPIX was observed using 0.1 and 0.2 ms stimulus pulse widths. STEPIX was further applied to process CMAP scans of the FDI muscle from 13 tetraplegia and 13 healthy control subjects using the same stimulation parameter setting (0.1 ms, 500 stimuli), along with other methods including MScanFit motor unit number estimation (MUNE) and D50. STEPIX was significantly lower for the SCI subjects compared with the healthy control subjects. STEPIX was significantly correlated with MscanFit MUNE and D50, but had a smaller relative width of the overlapping zone (WOZ%) between tetraplegic and healthy control groups compared with MScanFit MUNE and D50. The findings of the study highlight the importance of maintaining a consistent stimulation parameter setting in CMAP scan studies and confirm the usefulness of STEPIX as a convenient CMAP scan parameter for examination of motor unit number changes.
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Zong Y, Lu Z, Xu P, Chen M, Deng L, Li S, Zhang Y, Xie Q, Zhou P. MScanFit motor unit number estimation of abductor pollicis brevis: Findings from different experimental parameters. Front Aging Neurosci 2022; 14:953173. [PMID: 36325193 PMCID: PMC9621390 DOI: 10.3389/fnagi.2022.953173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 09/26/2022] [Indexed: 11/14/2022] Open
Abstract
MScanFit motor unit number estimation (MUNE) based on the recording of the compound muscle action potential (CMAP) scan has wide applications. This study evaluated the effect of different CMAP scan settings on MScanFit MUNE. CMAP scan of the abductor pollicis brevis (APB) muscle was performed in 10 healthy subjects at a United States (US) research center using different stimulus pulse widths (0.1, 0.2 ms) and total number of stimuli or steps (500, 1,000), and in 12 healthy subjects at a China research center using a 0.1 ms pulse width and 500 steps. MScanFit MUNE was derived using the default model parameters. A significantly higher MUNE was obtained using the shorter than longer pulse width; 84.70 ± 21.56 (500 steps) and 77.90 ± 27.62 (1,000 steps) at a pulse width of 0.1 ms vs. 67.60 ± 18.72 (500 steps) and 62.20 ± 15.82 (1,000 steps) at a pulse width of 0.2 ms (p < 0.05). However, MUNE was unrelated to the number of steps (500 vs. 1,000, p > 0.1). MUNE was significantly higher in persons studied in the China center (136.42 ± 32.46) than the US center (84.70 ± 21.56) despite each center using the same pulse widths and steps (p < 0.001). After excluding the ethnicity, age and experimenter factors, this significant difference is speculated to be partly related to different electrode size used in the two centers. The findings suggest that CMAP scan experimental parameters should remain consistent, so the MScanFit MUNE will not be compromised by non-physiological factors.
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Affiliation(s)
- Ya Zong
- Department of Rehabilitation Sciences, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zhiyuan Lu
- School of Rehabilitation Science and Engineering, University of Health and Rehabilitation Sciences, Qingdao, China
| | - Peipei Xu
- Department of Rehabilitation Sciences, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Maoqi Chen
- School of Rehabilitation Science and Engineering, University of Health and Rehabilitation Sciences, Qingdao, China
| | - Lianfu Deng
- Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases, Department of Orthopaedics, Ruijin Hospital, Shanghai Institute of Traumatology and Orthopaedics, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Sheng Li
- Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center at Houston, and TIRR Memorial Herman Hospital, Houston, TX, United States
| | - Yingchun Zhang
- Department of Biomedical Engineering, University of Houston, Houston, TX, United States
| | - Qing Xie
- Department of Rehabilitation Sciences, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- *Correspondence: Qing Xie,
| | - Ping Zhou
- School of Rehabilitation Science and Engineering, University of Health and Rehabilitation Sciences, Qingdao, China
- Ping Zhou,
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Tankisi DA, Alaydin HC, Boran E, Cengiz B. Feasibility and reliability of MScanFit motor unit number estimation in peroneus longus muscle. Muscle Nerve 2022; 66:503-507. [PMID: 35763284 DOI: 10.1002/mus.27667] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 06/16/2022] [Accepted: 06/18/2022] [Indexed: 11/08/2022]
Abstract
INTRODUCTION/AIM Motor unit number estimation (MUNE) methods may be valuable to detect motor involvement earlier than compound muscle action potential (CMAP) amplitude. The most recent MUNE method, MScanFit has been shown to have advantages compared to the previously described methods. However, MScanFit has only been applied in a few lower extremity muscles. We aimed in this study to examine the feasibility and reliability of MScanFit in peroneus longus muscle. METHODS Twenty healthy controls (16 males and 4 females, mean age: 36.05 ± 2.58) were examined twice within a 1-2 week interval. Fibular nerve was stimulated at the knee and CMAP scans were recorded from peroneus longus muscle. From this, MScanFit MUNE and size parameters were calculated as well as the CMAP amplitude. The reliability was examined using coefficient of variation (CV) and intraclass correlation coefficient (ICC). MUNE was correlated with CMAP amplitude using linear regression analysis. RESULTS The CV between sessions was higher for CMAP amplitude (11.63 ± 1.88 %) than MScanFit MUNE (3.13 ± 0.78%). Among the size parameters, mean unit amplitude (μV) showed the lowest CV (11.46 % ± 1.77). Using ICC, CMAP amplitude exhibited good reliability (0.787) whereas that of MScanFit MUNE was excellent (0.902). Reliability was good for all size parameters. There was no significant correlation between MScanFit MUNE and CMAP amplitude (R= 0.25, p>0.05). DISCUSSION MScanFit MUNE is feasible in the peroneus longus muscle with high test-retest reliability in healthy subjects. Studies in patients are needed to examine the sensitivity of this muscle in disease. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Deniz Alp Tankisi
- Department of Neurology, Gazi University Faculty of Medicine, Beşevler, Ankara, Turkey
| | - Halil Can Alaydin
- Department of Neurology, Gazi University Faculty of Medicine, Beşevler, Ankara, Turkey
| | - Evren Boran
- Department of Neurology, Gazi University Faculty of Medicine, Beşevler, Ankara, Turkey
| | - Bulent Cengiz
- Department of Neurology, Gazi University Faculty of Medicine, Beşevler, Ankara, Turkey
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Zong Y, Lu Z, Chen M, Deng L, Xie Q, Zhou P. Motor Unit Number Estimation of the Second Lumbrical Muscle in Human Hand. Front Physiol 2022; 13:854385. [PMID: 35283764 PMCID: PMC8911217 DOI: 10.3389/fphys.2022.854385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 02/02/2022] [Indexed: 11/13/2022] Open
Abstract
The number of motor units of the lumbrical muscles in human hand has not been explored. The objective of this study was to fill this gap by estimating the number of motor units in the second lumbrical muscle. Compound muscle action potential scan of the second lumbrical muscle was performed in 12 healthy subjects, with 10 of them being tested on two separate occasions. Motor unit number estimation (MUNE) was derived from the MScanFit program. The average MUNE of the second lumbrical muscle was 41.6 ± 2.1 (mean ± standard error) from 12 subjects in the first test, and 42.0 ± 2.2 from 10 of the 12 subjects in the retest, demonstrating excellent measurement reliability. Findings of the study provide novel information about the motor unit number of the second lumbrical muscle in human hand. The relatively low motor unit number in the muscle can facilitate motor unit investigations, especially at high level muscle activation.
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Affiliation(s)
- Ya Zong
- Department of Rehabilitation Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zhiyuan Lu
- Faculty of Rehabilitation Engineering, University of Health and Rehabilitation Sciences, Qingdao, China
| | - Maoqi Chen
- Faculty of Rehabilitation Engineering, University of Health and Rehabilitation Sciences, Qingdao, China
| | - Lianfu Deng
- Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint Diseases, Department of Orthopaedics, Shanghai Institute of Traumatology and Orthopaedics, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Qin Xie
- Department of Rehabilitation Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Ping Zhou
- Faculty of Rehabilitation Engineering, University of Health and Rehabilitation Sciences, Qingdao, China
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Itani M, Gylfadottir S, Krøigård T, Gaist L, Holbech JV, Kristensen AG, Karlsson P, Möller S, Tankisi H, Gaist D, Jensen TS, Finnerup NB, Sindrup SH. Comparison of diabetic and idiopathic sensory polyneuropathies with respect to nerve fibre affection and risk factors. BMJ Neurol Open 2022; 4:e000247. [PMID: 35360409 PMCID: PMC8921860 DOI: 10.1136/bmjno-2021-000247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 02/14/2022] [Indexed: 11/20/2022] Open
Abstract
Background and purpose Chronic distal sensory or sensorimotor polyneuropathy is the most common pattern of polyneuropathy. The cause of this pattern is most often diabetes or unknown. This cross-sectional study is one of the first studies to compare the demographics, cardiovascular risk factors and clinical characteristics of diabetic polyneuropathy (DPN) with idiopathic polyneuropathy (IPN). Methods Patients with DPN were included from a sample of 389 patients with type 2 diabetes mellitus (T2DM) enrolled from a national cohort of patients with recently diagnosed T2DM (Danish Centre for Strategic Research in Type 2 Diabetes cohort). Patients with IPN were included from a regional cohort of patients with symptoms of polyneuropathy referred for workup at a combined secondary and tertiary neurological centre (database cohort). Results A total of 214 patients with DPN were compared with a total of 88 patients with IPN. Patients with DPN were older (67.4 vs 59 years) and had a longer duration of neuropathy symptoms. Patients with DPN had greater body mass index (32 vs 27.4 kg/m2) and waist circumference (110 cm vs 97 cm); higher frequency of hypertension diagnosis (72.9% vs 30.7%); lower total cholesterol, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol levels; and a higher prevalence of use of statins (81.8% vs 19.3%). DPN was associated with a slightly higher autonomic score and total score on the Neuropathy Symptom Score; lower frequency of hyperalgesia, allodynia and decreased vibration on quantitative sensory testing; lower intraepidermal nerve fibre density count and higher frequency of small-fibre neuropathy. Conclusion DPN and IPN showed clear differences in neuropathy characteristics, indicating that these two entities are to be regarded as aetiologically and pathogenetically distinct.
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Affiliation(s)
- Mustapha Itani
- Research Unit for Neurology, Department of Neurology, Odense University Hospital, Odense, Denmark
- Clinical Medicine, University of Southern Denmark, Odense, Denmark
| | - Sif Gylfadottir
- Danish Pain Research Center, Clinical Medicine, Aarhus University, Aarhus, Denmark
- Neurology, Aarhus Universitetshospital, Aarhus, Denmark
| | - Thomas Krøigård
- Research Unit for Neurology, Department of Neurology, Odense University Hospital, Odense, Denmark
- Clinical Medicine, University of Southern Denmark, Odense, Denmark
| | - Laura Gaist
- Research Unit for Neurology, Department of Neurology, Odense University Hospital, Odense, Denmark
| | - Jakob Vormstrup Holbech
- Research Unit for Neurology, Department of Neurology, Odense University Hospital, Odense, Denmark
| | | | - Pall Karlsson
- Danish Pain Research Centre, Department of Clinical Medicine, Core Center for Molecular Morphology, Aarhus Universitet, Aarhus, Denmark
| | - Sören Möller
- OPEN, Odense University Hospital, Odense, Denmark
- Clinical Research, University of Southern Denmark, Odense, Denmark
| | - Hatice Tankisi
- Clinical Neurophysiology, Aarhus Universitetshospital, Aarhus, Denmark
| | - David Gaist
- Research Unit for Neurology, Department of Neurology, Odense University Hospital, Odense, Denmark
- Clinical Medicine, University of Southern Denmark, Odense, Denmark
| | - Troels S Jensen
- Danish Pain Research Center, Clinical Medicine, Aarhus University, Aarhus, Denmark
- Neurology, Aarhus Universitetshospital, Aarhus, Denmark
| | - Nanna Brix Finnerup
- Neurology, Aarhus Universitetshospital, Aarhus, Denmark
- Danish Pain Research Center, Department of Clinical Medicine, Aarhus Universitet, Aarhus, Denmark
| | - Søren Hein Sindrup
- Research Unit for Neurology, Department of Neurology, Odense University Hospital, Odense, Denmark
- Clinical Medicine, University of Southern Denmark, Odense, Denmark
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Sørensen DM, Bostock H, Ballegaard M, Fuglsang-Frederiksen A, Graffe CC, Grötting A, Jones K, Kallio M, Krarup C, Krøigård T, Lupescu T, Maitland S, Moldovan M, Nilsen KB, Pugdahl K, Santos MO, Themistocleous AC, Zlateva SS, Ööpik M, Tankisi H. Assessing inter-rater reproducibility in MScanFit MUNE in a 6-subject, 12-rater "Round Robin" setup. Neurophysiol Clin 2021; 52:157-169. [PMID: 34906430 DOI: 10.1016/j.neucli.2021.11.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 11/20/2021] [Accepted: 11/20/2021] [Indexed: 11/16/2022] Open
Abstract
OBJECTIVE To assess the inter-rater reliability of MScanFit MUNE using a "Round Robin" research design. METHODS Twelve raters from different centres examined six healthy study participants over two days. Median, ulnar and common peroneal nerves were stimulated, and compound muscle action potential (CMAP)-scans were recorded from abductor pollicis brevis (APB), abductor digiti minimi (ADM) and anterior tibial (TA) muscles respectively. From this we calculated the Motor Unit Number Estimation (MUNE) and "A50", a motor unit size parameter. As statistical analysis we used the measures Limits of Agreement (LOA) and Coefficient of Variation (COV). Study participants scored their perception of pain from the examinations on a rating scale from 0 (no pain) to 10 (unbearable pain). RESULTS Before this study, 41.6% of the raters had performed MScanFit less than five times. The mean MUNE-values were: 99.6 (APB), 131.4 (ADM) and 126.2 (TA), with LOA: 19.5 (APB), 29.8 (ADM) and 20.7 (TA), and COV: 13.4 (APB), 6.3 (ADM) and 5.6 (TA). MUNE-values correlated to CMAP max amplitudes (R2-values were: 0.463 (APB) (p<0.001), 0.421 (ADM) (p<0.001) and 0.645 (TA) (p<0.001)). The average perception of pain was 4. DISCUSSION MScanFit indicates a high level of inter-rater reliability, even with only limited rater experience and is overall reasonably well tolerated by patients. These results may indicate MScanFit as a reliable MUNE method with potential as a biomarker in drug trials.
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Affiliation(s)
| | - Hugh Bostock
- Insitute of Neurology, Queen Square House, London, United Kingdom
| | - Martin Ballegaard
- Deparment of Clinical Neurology, Zealand University Hospital, Roskilde, Denmark
| | | | | | - Arnstein Grötting
- Department of Clinical Neurophysiology, St. Olav Hospital, Trondheim, Norway
| | - Kelvin Jones
- Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Canada
| | - Mika Kallio
- Department of Clinical Neurophysiology, Oulu University Hospital, Oulu, Finland
| | - Christian Krarup
- Department of Clinical Neurophysiology, Rigshospitalet, Copenhagen, Denmark
| | - Thomas Krøigård
- Department of Neurology, Odense University Hospital, Denmark
| | - Tudor Lupescu
- Department of Neurology, Agrippa Ionescu Hospital, Bucharest, Romania
| | - Stuart Maitland
- Newcastle Biomedical Research Centre, Newcastle upon Tyne, United Kingdom
| | - Mihai Moldovan
- Department of Clinical Neurophysiology, Rigshospitalet, Copenhagen, Denmark
| | | | - Kirsten Pugdahl
- Department of Clinical Neurophysiology, Aarhus University Hospital, Denmark
| | - Miguel Oliveira Santos
- Department of Neurosciences and Mental Health, Hospital de Santa Maria, Lisbon, Portugal
| | | | | | - Merle Ööpik
- Deparment of Clinical Neurology, Zealand University Hospital, Roskilde, Denmark
| | - Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Denmark.
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The role of potassium in muscle membrane dysfunction in end-stage renal disease. Clin Neurophysiol 2021; 132:3125-3135. [PMID: 34740043 DOI: 10.1016/j.clinph.2021.09.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 08/15/2021] [Accepted: 09/01/2021] [Indexed: 12/24/2022]
Abstract
OBJECTIVE Uremic myopathy is a condition seen in end-stage renal disease (ESRD), characterized by muscle weakness and muscle fatigue, in which the pathophysiology is uncertain. The aim of this study was to assess the role of abnormal serum constituents in ESRD patients by relating them to the excitability properties of the tibialis anterior muscle, at rest and during electrically induced muscle activation, by recording muscle velocity recovery cycles (MVRC) and frequency ramp responses. METHODS Eighteen ESRD patients undergoing hemodialysis were evaluated by blood sample, MVRC, and frequency ramp (before and near the end of dialysis treatment), quantitative electromyography, and nerve conduction studies. Patients were compared to 24 control subjects. RESULTS In patients, muscle relative refractory period, early supernormality, late supernormality after 5 conditioning stimuli, and latency of the last of 15 and 30 frequency ramp pulses were strongly associated with potassium levels (p < 0.01), showing depolarization before and normalization in the end of hemodialysis. CONCLUSIONS In ESRD patients, the muscle membrane is depolarized, mainly due to hyperkalemia. SIGNIFICANCE Since normal muscle fatigue has been attributed to potassium-induced depolarization, it seems likely that this mechanism is also a major cause of the exaggerated muscle fatigue and weakness in ESRD patients.
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Model-Based Analysis of Muscle Strength and EMG-Force Relation with respect to Different Patterns of Motor Unit Loss. Neural Plast 2021; 2021:5513224. [PMID: 34257638 PMCID: PMC8245245 DOI: 10.1155/2021/5513224] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 05/02/2021] [Accepted: 06/01/2021] [Indexed: 01/07/2023] Open
Abstract
This study presents a model-based sensitivity analysis of the strength of voluntary muscle contraction with respect to different patterns of motor unit loss. A motor unit pool model was implemented including simulation of a motor neuron pool, muscle force, and surface electromyogram (EMG) signals. Three different patterns of motor unit loss were simulated, including (1) motor unit loss restricted to the largest ones, (2) motor unit loss restricted to the smallest ones, and (3) motor unit loss without size restriction. The model outputs including muscle force amplitude, variability, and the resultant EMG-force relation were quantified under two different motor neuron firing strategies. It was found that motor unit loss restricted to the largest ones had the most dominant impact on muscle strength and significantly changed the EMG-force relation, while loss restricted to the smallest motor units had a pronounced effect on force variability. These findings provide valuable insight toward our understanding of the neurophysiological mechanisms underlying experimental observations of muscle strength, force control, and EMG-force relation in both normal and pathological conditions.
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Kristensen AG, Gylfadottir S, Itani M, Kuwabara S, Krøigård T, Khan KS, Finnerup NB, Andersen H, Jensen TS, Sindrup S, Tankisi H. Sensory and motor axonal excitability testing in early diabetic neuropathy. Clin Neurophysiol 2021; 132:1407-1415. [PMID: 34030050 DOI: 10.1016/j.clinph.2021.02.397] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 01/30/2021] [Accepted: 02/01/2021] [Indexed: 11/16/2022]
Abstract
OBJECTIVE The aim of the present study was to gain insight into the pathophysiology of diabetic polyneuropathy (DPN) and examine the diagnostic value of sensory and motor axonal excitability testing. METHODS One hundred and eleven type 2 diabetics with and without DPN (disease duration: 6.36 ± 0.25 years) and 60 controls were included. All participants received a thorough clinical examination including Michigan Neuropathy Screening Instrument (MNSI) score, nerve conduction studies (NCS), and sensory and motor excitability tests. Patients were compared by the likelihood of neuropathy presence, ranging from no DPN (17), possible/probable DPN (46) to NCS-confirmed DPN (48). RESULTS Motor excitability tests showed differences in rheobase and depolarizing threshold electrotonus measures between NCS-confirmed DPN group and controls but no changes in hyperpolarising threshold electrotonus or recovery cycle parameters. Sensory excitability showed even less changes despite pronounced sensory NCS abnormalities. There were only weak correlations between the above motor excitability parameters and clinical scores. CONCLUSIONS Changes in excitability in the examined patient group were subtle, perhaps because of the relatively short disease duration. SIGNIFICANCE Less pronounced excitability changes than NCS suggest that axonal excitability testing is not of diagnostic value for early DPN and does not provide information on the mechanisms.
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Affiliation(s)
- A G Kristensen
- Department of Clinical Neurophysiology, Aarhus University Hospital, Denmark; Danish Pain Research Center, Department of Clinical Medicine, Aarhus University, Denmark
| | - S Gylfadottir
- Danish Pain Research Center, Department of Clinical Medicine, Aarhus University, Denmark; Department of Neurology, Aarhus University Hospital, Denmark
| | - M Itani
- Department of Neurology, Odense University Hospital, Denmark
| | - S Kuwabara
- Department of Neurology, Graduate School of Medicine, Chiba University, Japan
| | - T Krøigård
- Department of Neurology, Odense University Hospital, Denmark
| | - K S Khan
- Department of Neurology, Aarhus University Hospital, Denmark
| | - N B Finnerup
- Danish Pain Research Center, Department of Clinical Medicine, Aarhus University, Denmark; Department of Neurology, Aarhus University Hospital, Denmark
| | - H Andersen
- Department of Neurology, Aarhus University Hospital, Denmark
| | - T S Jensen
- Danish Pain Research Center, Department of Clinical Medicine, Aarhus University, Denmark; Department of Neurology, Aarhus University Hospital, Denmark
| | - S Sindrup
- Department of Neurology, Odense University Hospital, Denmark
| | - H Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Denmark.
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Tankişi H. MScanFit motor unit number estimation: A novel method for clinics and research. NEUROL SCI NEUROPHYS 2021. [DOI: 10.4103/nsn.nsn_30_21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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