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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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Acosta I, Hofer M, Hilton-Jones D, Squier W, Brady S. Treatment resistance in inclusion body myositis: the role of mast cells. Neuromuscul Disord 2024; 41:20-23. [PMID: 38865916 DOI: 10.1016/j.nmd.2024.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Revised: 04/29/2024] [Accepted: 05/02/2024] [Indexed: 06/14/2024]
Abstract
Inclusion body myositis is the commonest acquired myopathy in those over 50 years of age. Although it is classified as an idiopathic inflammatory myopathy and the most frequent finding on muscle biopsy in inclusion body myositis is an endomysial inflammatory infiltrate, it is clinically distinct from other myositis, including a lack of response to immunosuppressive medication. Neurogenic changes are commonly reported in inclusion body myositis and inflammatory changes are observed in muscle following neurogenic injury. The objective of our study was to explore whether neurogenic inflammation plays a role in the pathogenesis of inclusion body myositis, possibly explaining its resistance to immunosuppression. The number of mast cells and presence of neuropeptides, substance P and calcitonin gene-related peptide, were assessed in 48 cases of inclusion body myositis, 11 cases of steroid responsive myositis, two cases of focal myositis associated with neurogenic injury, and ten normal controls. The number of mast cells in inclusion body myositis focal and myositis associated to neurogenic injury were significantly greater than that observed in steroid responsive myositis. Our findings suggest that neurogenic inflammation mediated through mast cells may play a role in the pathogenesis of inclusion body myositis, and focal myositis associated to neurogenic injury, and thus, explain in some part its lack of response to immunosuppressive treatments.
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Affiliation(s)
- I Acosta
- Neuropathology Department, John Radcliffe Hospital, Oxford University Hospitals Trust, Oxford OX3 9DU. United Kingdom; Translational neurology and neurophysiology laboratory (NODO lab), Advance clinical research centre (CICA). School of Medicine, Universidad de Chile, Providencia 7500787, Santiago Chile; Neurology and Psychiatry Department, Clínica Alemana Santiago, Vitacura, Santiago 7650568, Santiago Chile.
| | - M Hofer
- Neuropathology Department, John Radcliffe Hospital, Oxford University Hospitals Trust, Oxford OX3 9DU. United Kingdom
| | - D Hilton-Jones
- Oxford Muscle Service, Department of Neurology, John Radcliffe Hospital, Oxford University Hospitals Trust, Oxford OX3 9DU, United Kingdom
| | - W Squier
- Neuropathology Department, John Radcliffe Hospital, Oxford University Hospitals Trust, Oxford OX3 9DU. United Kingdom
| | - S Brady
- Oxford Muscle Service, Department of Neurology, John Radcliffe Hospital, Oxford University Hospitals Trust, Oxford OX3 9DU, United Kingdom
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Meldgaard M, Kristensen RS, Z'Graggen WJ, Tan SV, Søndergaard K, Qerama E, Andersen H, Fuglsang-Frederiksen A, Tankisi H. Muscle velocity recovery cycles in myopathy. Clin Neurophysiol 2023; 151:41-49. [PMID: 37148747 DOI: 10.1016/j.clinph.2023.04.001] [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: 12/09/2022] [Revised: 03/30/2023] [Accepted: 04/03/2023] [Indexed: 05/08/2023]
Abstract
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.
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Affiliation(s)
- M Meldgaard
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - R S Kristensen
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - W J Z'Graggen
- Departments of Neurology and Neurosurgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - S V Tan
- Department of Neurology and Neurophysiology, Guys and St Thomas' NHS Foundation Trust, London, UK
| | - K Søndergaard
- Department of Rheumatology, Aarhus University Hospital, Aarhus, Denmark
| | - E Qerama
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark; Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - H Andersen
- Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark; Department of Neurology, Aarhus University Hospital, Aarhus, Denmark
| | - A Fuglsang-Frederiksen
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark; Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - H Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark; Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark.
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Ruijs TQ, Koopmans IW, de Kam ML, Tannemaat MR, Groeneveld GJ, Heuberger JAAC. Muscle velocity recovery cycles as pharmacodynamic biomarker: Effects of mexiletine in a randomized double-blind placebo-controlled cross-over study. Clin Transl Sci 2022; 15:2971-2981. [PMID: 36281627 PMCID: PMC9747120 DOI: 10.1111/cts.13418] [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: 06/02/2022] [Revised: 08/09/2022] [Accepted: 09/04/2022] [Indexed: 01/26/2023] Open
Abstract
Measuring muscle velocity recovery cycles (MVRCs) is a method to obtain information on muscle cell excitability, independent of neuromuscular transmission. The goal was to validate MVRC as a pharmacodynamic (PD) biomarker for drugs targeting muscle excitability. As proof-of-concept, sensitivity of MVRC to detect effects of mexiletine, a voltage-gated sodium channel (Nav ) blocker, was assessed. In a randomized, double-blind, two-way crossover study, effects of a single pharmacologically active oral dose of 333 mg mexiletine was compared to placebo in 15 healthy male subjects. MVRC was performed predose, and 3- and 5-h postdose using QTrac. Effects of mexiletine versus placebo were calculated using a mixed effects model with baseline as covariate. Mexiletine had significant effects on MVRC when compared to placebo. Early supernormality after five conditioning stimuli was decreased by mexiletine (estimated difference -2.78% [95% confidence interval: -4.16, -1.40]; p value = 0.0003). Moreover, mexiletine decreased the difference in late supernormality after five versus one conditioning stimuli (5XLSN; ED -1.46% [-2.26, -0.65]; p = 0.001). These results indicate that mexiletine decreases the percentage increase in velocity of the muscle fiber action potential after five conditioning stimuli, at long and short interstimulus intervals, which corresponds to a decrease in muscle membrane excitability. This is in line with the pharmacological activity of mexiletine, which leads to use-dependent NaV 1.4 blockade affecting muscle membrane potentials. This study shows that effects of mexiletine can be detected using MVRC in healthy subjects, thereby indicating that MVRC can be used as a tool to demonstrate PD effects of drugs targeting muscle excitability in early phase drug development.
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Affiliation(s)
- Titia Q. Ruijs
- Centre for Human Drug ResearchLeidenThe Netherlands,Leiden University Medical CentreLeidenThe Netherlands
| | - Ingrid W. Koopmans
- Centre for Human Drug ResearchLeidenThe Netherlands,Leiden University Medical CentreLeidenThe Netherlands
| | | | | | - Geert Jan Groeneveld
- Centre for Human Drug ResearchLeidenThe Netherlands,Leiden University Medical CentreLeidenThe Netherlands
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Suetterlin KJ, Männikkö R, Matthews E, Greensmith L, Hanna MG, Bostock H, Tan SV. Excitability properties of mouse and human skeletal muscle fibres compared by muscle velocity recovery cycles. Neuromuscul Disord 2022; 32:347-357. [PMID: 35339342 PMCID: PMC7614892 DOI: 10.1016/j.nmd.2022.02.011] [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] [Received: 07/11/2021] [Revised: 01/27/2022] [Accepted: 02/22/2022] [Indexed: 11/21/2022]
Abstract
Mouse models of skeletal muscle channelopathies are not phenocopies of human disease. In some cases (e.g. Myotonia Congenita) the phenotype is much more severe, whilst in others (e.g. Hypokalaemic periodic paralysis) rodent physiology is protective. This suggests a species' difference in muscle excitability properties. In humans these can be measured indirectly by the post-impulse changes in conduction velocity, using Muscle Velocity Recovery Cycles (MVRCs). We performed MVRCs in mice and compared their muscle excitability properties with humans. Mouse Tibialis Anterior MVRCs (n = 70) have only one phase of supernormality (increased conduction velocity), which is smaller in magnitude (p = 9 × 10-21), and shorter in duration (p = 3 × 10-24) than human (n = 26). This abbreviated supernormality is followed by a period of late subnormality (reduced velocity) in mice, which overlaps in time with the late supernormality seen in human MVRCs. The period of late subnormality suggests increased t-tubule Na+/K+-pump activity. The subnormal phase in mice was converted to supernormality by blocking ClC-1 chloride channels, suggesting relatively higher chloride conductance in skeletal muscle. Our findings help explain discrepancies in phenotype between mice and humans with skeletal muscle channelopathies and potentially other neuromuscular disorders. MVRCs are a valuable new tool to compare in vivo muscle membrane properties between species and will allow further dissection of the molecular mechanisms regulating muscle excitability.
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Affiliation(s)
- K J Suetterlin
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, United Kingdom; AGE Research Group, NIHR Newcastle Biomedical Research Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust and Newcastle University, Newcastle upon Tyne, United Kingdom.
| | - R Männikkö
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, United Kingdom
| | - E Matthews
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, United Kingdom; Atkinson Morley Neuromuscular Centre, Department of Neurology, St Georges University Hospitals NHS Foundation Trust, London, United Kingdom
| | - L Greensmith
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, United Kingdom
| | - M G Hanna
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, United Kingdom
| | - H Bostock
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, United Kingdom
| | - S V Tan
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, United Kingdom; Department of Neurology and Clinical Neurophysiology, Guy's & St Thomas' NHS Foundation Trust and Institute of Psychiatry, Psychology & Neuroscience, Division of Neuroscience, King's College London, United Kingdom
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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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Hochstrasser A, Rodriguez B, Söll N, Bostock H, Z'Graggen WJ. Effect of intermittent high-frequency stimulation on muscle velocity recovery cycle recordings. J Neurophysiol 2021; 126:736-742. [PMID: 34288792 DOI: 10.1152/jn.00213.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The technique of multifiber muscle velocity recovery cycle recordings was developed as a diagnostic tool to assess muscle membrane potential changes and ion channel function in vivo. This study was undertaken to assess the impact of intermittent high-frequency stimulation on muscle velocity recovery cycle components and to study whether the changes can be modified by endurance training. We recorded muscle velocity recovery cycles with 1 and 2 conditioning stimuli in the left tibialis anterior muscle in 15 healthy subjects during intermittent 37-Hz stimulation and analyzed its effects on the different phases of supernormality. Recordings were conducted before and after 2-wk endurance training. Training effect was assessed by measuring the difference in endurance time, peak force, and limb circumference. Muscle velocity recovery cycle recordings during intermittent high-frequency stimulation were successfully recorded in 12 subjects. Supernormality for interstimulus intervals shorter than 15 ms (early supernormality) was maximally reduced at the beginning of repetitive stimulation and recovered during stimulation. Supernormality for interstimulus intervals between 50 and 150 ms (late supernormality) showed a delayed decrease and stayed significantly reduced after high-frequency stimulation. Training had no significant effect on any of the measured parameters, but we found that training induced changes in peak force correlated positively with baseline changes of early supernormality. Our results support the hypothesis that early supernormality represents membrane potential, which depolarizes in the beginning of high-frequency stimulation. Late supernormality probably reflects transverse tubular function and shows progressive changes during high-frequency stimulation with delayed normalization.NEW & NOTEWORTHY A conditioning impulse in human muscle fibers induces a prolonged phase of increased velocity (also called supernormality) with two phases related to an early and late afterpotential. We investigated the effects of intermittent 37-Hz stimulation on muscle fiber supernormality and found that the early and late phases of supernormality changed differently, and that the late phase may reflect the ionic interactions responsible for the counter-regulation of muscle fatigue.
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Affiliation(s)
- Annie Hochstrasser
- Department of Neurology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
| | - Belén Rodriguez
- Department of Neurosurgery, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
| | - Nicole Söll
- Department of Neurosurgery, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
| | - Hugh Bostock
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, United Kingdom
| | - Werner J Z'Graggen
- Department of Neurology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland.,Department of Neurosurgery, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
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Tankisi A, Pedersen TH, Bostock H, Z'Graggen WJ, Larsen LH, Meldgaard M, Elkmann T, Tankisi H. Early detection of evolving critical illness myopathy with muscle velocity recovery cycles. Clin Neurophysiol 2021; 132:1347-1357. [PMID: 33676846 DOI: 10.1016/j.clinph.2021.01.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 12/29/2020] [Accepted: 01/19/2021] [Indexed: 11/19/2022]
Abstract
OBJECTIVE To investigate the sensitivity of muscle velocity recovery cycles (MVRCs) for detecting altered membrane properties in critically ill patients, and to compare this to conventional nerve conduction studies (NCS) and quantitative electromyography (qEMG). METHODS Twenty-four patients with intensive care unit acquired weakness (ICUAW) and 34 healthy subjects were prospectively recruited. In addition to NCS (median, ulnar, peroneal, tibial and sural nerves) and qEMG (biceps brachii, vastus medialis and anterior tibial muscles), MVRCs with frequency ramp were recorded from anterior tibial muscle. RESULTS MVRC and frequency ramp parameters showed abnormal muscle fiber membrane properties with up to 100% sensitivity and specificity. qEMG showed myopathy in 15 patients (63%) while polyneuropathy was seen in 3 (13%). Decreased compound muscle action potential (CMAP) amplitude (up to 58%) and absent F-waves (up to 75%) were frequent, but long duration CMAPs were only seen in one patient with severe myopathy. CONCLUSIONS Altered muscle fiber membrane properties can be detected in patients with ICUAW not yet fulfilling diagnostic criteria for critical illness myopathy (CIM). MVRCs may therefore serve as a tool for early detection of evolving CIM. SIGNIFICANCE CIM is often under-recognized by intensivists, and large-scale longitudinal studies are needed to determine its incidence and pathogenesis.
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Affiliation(s)
- A Tankisi
- Department of Anaesthesiology and Intensive Care, Aarhus University Hospital, Aarhus, Denmark
| | - T H Pedersen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - H Bostock
- Institute of Neurology, University College London, Queen Square House, London, United Kingdom
| | - W J Z'Graggen
- Departments of Neurology and Neurosurgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - L H Larsen
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - M Meldgaard
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - T Elkmann
- Department of Anaesthesiology and Intensive Care, Aarhus University Hospital, Aarhus, Denmark
| | - H Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark; Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark.
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Tankisi H. Still much to explore in nerve excitability testing despite 20 years of experience. Clin Neurophysiol 2020; 131:2734-2735. [PMID: 33012638 DOI: 10.1016/j.clinph.2020.09.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 09/08/2020] [Indexed: 11/26/2022]
Affiliation(s)
- H Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark; Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.
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Neuropathy in sporadic inclusion body myositis: A multi-modality neurophysiological study. Clin Neurophysiol 2020; 131:2766-2776. [PMID: 32928695 DOI: 10.1016/j.clinph.2020.07.025] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2020] [Revised: 07/09/2020] [Accepted: 07/22/2020] [Indexed: 02/03/2023]
Abstract
OBJECTIVE Sporadic inclusion body myositis (sIBM) has been associated with neuropathy. This study employs nerve excitability studies to re-examine this association and attempt to understand underlying pathophysiological mechanisms. METHODS Twenty patients with sIBM underwent median nerve motor and sensory excitability studies, clinical assessments, conventional nerve conduction testing (NCS) and quantitative thermal threshold studies. These results were compared to established normal controls, or results from a normal cohort of older control individuals. RESULTS Seven sIBM patients (35%) demonstrated abnormalities in conventional NCS, with ten patients (50%) demonstrating abnormalities in thermal thresholds. Median nerve motor and sensory excitability differed significantly in sIBM patients when compared to normal controls. None of these neurophysiological markers correlated significantly with clinical markers of sIBM severity. CONCLUSION A concurrent neuropathy exists in a significant proportion of sIBM patients, with nerve excitability studies revealing changes possibly consistent with axolemmal depolarization or concurrent neuronal adaptation to myopathy. Neuropathy in sIBM does not correlate with muscle disease severity and may reflect a differing tissue response to a common pathogenic factor. SIGNIFICANCE This study affirms the presence of a concurrent neuropathy in a large proportion of sIBM patients that appears independent of the severity of myopathy.
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Tankisi H. Muscle velocity recovery cycles: An evolving technique for assessing muscle fiber membrane properties. Clin Neurophysiol 2019; 130:2268-2269. [PMID: 31694794 DOI: 10.1016/j.clinph.2019.09.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Accepted: 09/09/2019] [Indexed: 10/25/2022]
Affiliation(s)
- H Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Palle Juul-Jensens Boulevard 165, 8200 Aarhus N, Denmark.
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