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1.
Moving forward: methodological considerations for assessing corticospinal excitability during rhythmic motor output in humans.
Lockyer, EJ, Compton, CT, Forman, DA, Pearcey, GE, Button, DC, Power, KE
Journal of neurophysiology. 2021;(1):181-194
Abstract
The use of transcranial magnetic stimulation to assess the excitability of the central nervous system to further understand the neural control of human movement is expansive. The majority of the work performed to-date has assessed corticospinal excitability either at rest or during relatively simple isometric contractions. The results from this work are not easily extrapolated to rhythmic, dynamic motor outputs, given that corticospinal excitability is task-, phase-, intensity-, direction-, and muscle-dependent (Power KE, Lockyer EJ, Forman DA, Button DC. Appl Physiol Nutr Metab 43: 1176-1185, 2018). Assessing corticospinal excitability during rhythmic motor output, however, involves technical challenges that are to be overcome, or at the minimum considered, when attempting to design experiments and interpret the physiological relevance of the results. The purpose of this narrative review is to highlight the research examining corticospinal excitability during a rhythmic motor output and, importantly, to provide recommendations regarding the many factors that must be considered when designing and interpreting findings from studies that involve limb movement. To do so, the majority of work described herein refers to work performed using arm cycling (arm pedaling or arm cranking) as a model of a rhythmic motor output used to examine the neural control of human locomotion.
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2.
Diagnosis and treatment of myasthenia gravis.
Mantegazza, R, Cavalcante, P
Current opinion in rheumatology. 2019;(6):623-633
Abstract
PURPOSE OF REVIEW This article provides an update on the most recent advances in diagnostic procedures and therapeutic approaches for myasthenia gravis, spanning from autoantibody and neuroelectrophysiological tests as diagnostic tools, to innovative and promising treatments based on biological drugs. RECENT FINDINGS Novel studies performed by cell-based assays (CBAs) indicate an improvement in the chance of identifying serum autoantibodies in myasthenic patients. Clinical trials on the use of biological drugs were recently concluded, providing important data on safety and efficacy of eculizumab, efgartigimod and amifampridine phosphate: the first, a complement blocker, showed long-term safety and efficacy in acetylcholine receptor (AChR)-positive myasthenic patients with refractory generalized disease; the second, the neonatal Fc receptor blocker, was well tolerated and clinically effective in both AChR-specific and muscle-specific kinase receptor (MuSK)-positive patients; the third, a blocker of presynaptic potassium channels, was found to be well tolerated and effective in MuSK-positive patients. SUMMARY CBAs can lead to a significant reduction of seronegative patients, improving myasthenia gravis diagnostic process. New biological drugs offer innovative approaches to treat myasthenic patients with generalized disease, promising to change the paradigm of treatment and to significantly enhance therapeutic success within a precision medicine framework.
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3.
The extraction of neural information from the surface EMG for the control of upper-limb prostheses: emerging avenues and challenges.
Farina, D, Jiang, N, Rehbaum, H, Holobar, A, Graimann, B, Dietl, H, Aszmann, OC
IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society. 2014;(4):797-809
Abstract
Despite not recording directly from neural cells, the surface electromyogram (EMG) signal contains information on the neural drive to muscles, i.e., the spike trains of motor neurons. Using this property, myoelectric control consists of the recording of EMG signals for extracting control signals to command external devices, such as hand prostheses. In commercial control systems, the intensity of muscle activity is extracted from the EMG and used for single degrees of freedom activation (direct control). Over the past 60 years, academic research has progressed to more sophisticated approaches but, surprisingly, none of these academic achievements has been implemented in commercial systems so far. We provide an overview of both commercial and academic myoelectric control systems and we analyze their performance with respect to the characteristics of the ideal myocontroller. Classic and relatively novel academic methods are described, including techniques for simultaneous and proportional control of multiple degrees of freedom and the use of individual motor neuron spike trains for direct control. The conclusion is that the gap between industry and academia is due to the relatively small functional improvement in daily situations that academic systems offer, despite the promising laboratory results, at the expense of a substantial reduction in robustness. None of the systems so far proposed in the literature fulfills all the important criteria needed for widespread acceptance by the patients, i.e. intuitive, closed-loop, adaptive, and robust real-time ( 200 ms delay) control, minimal number of recording electrodes with low sensitivity to repositioning, minimal training, limited complexity and low consumption. Nonetheless, in recent years, important efforts have been invested in matching these criteria, with relevant steps forwards.
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4.
Surface EMG of the masticatory muscles (part 2): fatigue testing, mastication analysis and influence of different factors.
Hugger, S, Schindler, HJ, Kordass, B, Hugger, A
International journal of computerized dentistry. 2013;(1):37-58
Abstract
The second part of this review of the literature on the clinical significance of surface electromyography (EMG) of the masticatory muscles systematically examines the results of clinical studies in patients with temporomandibular disorders (TMD), preferably randomized controlled trials, investigating relevant aspects of EMG activity during prolonged chewing activity (fatigue effects), during the mastication process, and under the influence of different factors. Studies on the influence of factors such as gender, age, tooth status, orofacial morphology and (acute) pain, the significance of different occlusal relationships during static and dynamic occlusion, and the impact of changes in static occlusion on EMG activity of the masticatory muscles were included in the review.
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5.
Electrogastrography in adults and children: the strength, pitfalls, and clinical significance of the cutaneous recording of the gastric electrical activity.
Riezzo, G, Russo, F, Indrio, F
BioMed research international. 2013;:282757
Abstract
Cutaneous electrogastrography (EGG) is a non-invasive technique to record gastric myoelectrical activity from the abdominal surface. Although the recent rapid increase in the development of electrocardiography, EGG still suffers from several limitations. Currently, computer analysis of EGG provides few reliable parameters, such as frequency and the percentage of normal and altered slow wave activity (bradygastria and tachygastria). New EGG hardware and software, along with an appropriate arrangement of abdominal electrodes, could detect the coupling of the gastric slow wave from the EGG. At present, EGG does not diagnose a specific disease, but it puts in evidence stomach motor dysfunctions in different pathological conditions as gastroparesis and functional dyspepsia. Despite the current pitfalls of EGG, a multitasking diagnostic protocol could involve the EGG and the (13)C-breath testing for the evaluation of the gastric emptying time-along with validated gastrointestinal questionnaires and biochemical evaluations of the main gastrointestinal peptides-to identify dyspeptic subgroups. The present review tries to report the state of the art about the pathophysiological background of the gastric electrical activity, the recording and processing methodology of the EGG with particular attention to multichannel recording, and the possible clinical application of the EGG in adult and children.
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6.
The clinical and electrodiagnostic characteristics of Pompe disease with post-enzyme replacement therapy findings.
Hobson-Webb, LD, Dearmey, S, Kishnani, PS
Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology. 2011;(11):2312-7
Abstract
OBJECTIVE Pompe disease is a neuromuscular disorder that was progressive and fatal prior to enzyme replacement therapy (ERT). The advent of treatment has made early recognition imperative. Electrodiagnostic (EDx) studies represent a valuable diagnostic tool in Pompe disease, but there has been little contemporary data. METHODS The records of 29 patients with Pompe disease who had undergone EDx evaluation at Duke University Medical Center from 1999 to 2010 were reviewed. RESULTS Seventeen children and twelve adults comprised the group. The clinical characteristics of both groups did not differ from expected. Needle electromyography demonstrated spontaneous activity (SA) in 80% of children and 83% of adults. Myotonic discharges were found in 53% of children and 72% of adults, often isolated to the paraspinal muscles in adults. Eight patients had EDx studies performed after ERT with 3 showing improvement after therapy, despite clinical improvement in 6 of 8. CONCLUSIONS EDx studies remain a helpful tool in diagnosing Pompe disease, but do not appear to be sensitive for monitoring response to ERT based upon this limited sample. SIGNIFICANCE Paraspinal examination is necessary in adults with symptoms suggestive of Pompe disease, as abnormalities may be isolated to this region. Standard EDx studies are not sufficient to monitor early response to ERT and further research on potential biomarkers is needed.
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7.
Does the frequency content of the surface mechanomyographic signal reflect motor unit firing rates? A brief review.
Beck, TW, Housh, TJ, Johnson, GO, Cramer, JT, Weir, JP, Coburn, JW, Malek, MH
Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology. 2007;(1):1-13
Abstract
The purpose of this review is to examine the literature that has investigated the potential relationship between mechanomyographic (MMG) frequency and motor unit firing rates. Several different experimental designs/methodologies have been used to address this issue, including: repetitive electrical stimulation, voluntary muscle actions in muscles with different fiber type compositions, fatiguing and non-fatiguing isometric or dynamic muscle actions, and voluntary muscle actions in young versus elderly subjects and healthy individuals versus subjects with a neuromuscular disease(s). Generally speaking, the results from these investigations have suggested that MMG frequency is related to the rate of motor unit activation and the contractile properties (contraction and relaxation times) of the muscle fibers. Other studies, however, have reported that MMG mean power frequency (MPF) does not always follow the expected pattern of firing rate modulation (e.g. motor unit firing rates generally increase with torque during isometric muscle actions, but MMG MPF may remain stable or even decrease). In addition, there are several factors that may affect the frequency content of the MMG signal during a voluntary muscle action (i.e. muscle stiffness, intramuscular fluid pressure, etc.), independent of changes in motor unit firing rates. Despite the potential influences of these factors, most of the evidence has suggested that the frequency domain of the MMG signal contains some information regarding motor unit firing rates. It is likely, however, that this information is qualitative, rather than quantitative in nature, and reflects the global motor unit firing rate, rather than the firing rates of a particular group of motor units.
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8.
Investigations of back muscle fatigue by simultaneous 31P MRS and surface EMG measurements.
Rzanny, R, Grassme, R, Reichenbach, JR, Scholle, HC, Kaiser, WA
Biomedizinische Technik. Biomedical engineering. 2006;(5-6):305-13
Abstract
Investigations of back muscle fatigue are important for understanding the role of muscle strain in the development of low back pain. The aim of this contribution is to review the two main techniques used for in vivo investigations of metabolic and electrophysiological changes, namely magnetic resonance phosphorous spectroscopy ((31)P MRS) and surface electromyography (SEMG), and to report some of our recent results on simultaneous measurements using these techniques during isometric back-muscle contraction in volunteers. Since it appears that electrophysiological and metabolic factors are simultaneously involved in the processes of fatigue and muscle recovery during load application, simultaneous acquisition of complete information is quite promising for obtaining new insights into the metabolic origin of electrophysiological changes or vice versa. Performing these measurements simultaneously, however, is more intricate owing to the occurrence of signal artifacts caused by mutual signal interferences of both techniques. Besides these mutual disturbances, further experimental difficulties are related to spatial limitations within the bore of clinical whole-body high-field magnetic resonance (MR) systems (1.5 T) and the sensitivity of MR measurements to motion-induced artifacts. Our own experimental results are presented, and problems that occur using both techniques simultaneously, as well as possibilities to resolve them, are discussed. The results shed light on the interrelation of electrophysiological and metabolic changes during fatigue of the back muscle while performing an exercise.
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9.
[Isaacs' syndrome. Diagnosis and differential diagnosis of neuromyotonia].
Fischer, D, Schröder, R
Der Nervenarzt. 2004;(6):531-5
Abstract
Neuromyotonia is a clinical and electrophysiological syndrome of spontaneous muscle fiber activity due to hyperexcitability of peripheral nerve origin causing generalised, visible myokymia and muscular cramps. Electromyography shows abnormal doublet and triplet discharges of high intraburst frequency as well as myokymic and neuromyotonic discharges. Fasciculations and fibrillation potentials are common. Most commonly, neuromyotonia is an acquired immune-mediated disorder (Isaacs' syndrome) showing elevated antibody levels against presynaptic, voltage-gated, potassium channels. Some of these patients have additional autonomic (hyperhidrosis) and/or CNS symptoms similar to those from limbic encephalitis (referred to then as Morvan's syndrome). We report on a patient with Isaacs' syndrome and discuss the clinical and electrophysiological features, pathophysiology, diagnosis, and differential diagnosis of diseases with peripheral nerve hyperexcitability.
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10.
Surface electromyographic studies of swallowing in normal subjects: a review of 440 adults. Report 2. Quantitative data: amplitude measures.
Vaiman, M, Eviatar, E, Segal, S
Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery. 2004;(5):773-80
Abstract
OBJECTIVES Surface electromyographic (EMG) studies were performed on 420 normal adults to establish normative database for muscle activity's amplitude during swallowing and drinking clinically useful for ENT department. STUDY DESIGN Prospective observational study of healthy volunteers. METHODS Parameters evaluated during swallowing include the EMG activity of the orbicularis oris, masseter, submental, and infrahyoid muscle groups covered by platysma (range, mean, SD). Four tests were examined including voluntary swallow of saliva ("dry" swallow), voluntary single water swallows as normal (variable volume of a bolus), voluntary single swallows of fixed amount of water (20 mL), and continuous drinking of 100 mL of water. Activity of the above-mentioned muscles during swallowing was measured for groups of adults of different age groups. Groups included volunteers and were separated into age groups as follows: ages 18-30, 31-40, 41-50, 51-60, 61-70, and 70+ years of age. RESULTS Normative data for electric muscle activity (mean +/- SD; range, in microV) during single swallowing and continuous drinking are established for healthy adults. The range of submental group activity during swallows showed a significant decrease with the age, whereas the range of masseter activity changed insignificantly (1-dimensional analysis of variance, SPSS, Chi-square criterion, 95% confidence interval). There were no significant changes in mean muscle activity between different age groups. These parameters represent activities required for normal deglutition, and can be used to identify abnormalities in ENT patients, and provide a basis for comparison of swallowing performance both within and between patients. These measurements can be performed in a simple way, cause no discomfort, do not use radiation, and are noninvasive. The relevance and clinical utility of new and alternative measures, in particular, are discussed. CONCLUSIONS In single swallow tests range of electric activity of involved muscles is more informative than its mean. In the continuous drinking test, the mean electric activity is the only electric variance that can be evaluated. Orbicularis oris muscle activity is not important when reflex phase of a swallow is evaluated. Surface EMG of swallowing is a simple and reliable method for evaluation of swallowing with a low level of discomfort during the examination. The method can be easily used in outpatient ENT departments for quick evaluation of patients. The normative amplitude data can be used for comparison purposes in preoperaive and postoperative stages and in EMG monitoring during ENT treatment.