Electromyography (EMG) assesses the anatomic motor unit (A‐MU), but knowledge of its anatomy, physiology, and changes with pathology is limited. The electrophysiological motor unit (E‐MU) and its ...motor unit potential (E‐MUP) represents a fraction of the A‐MU. Routine EMG assesses a limited number of E‐MUP waveform characteristics (metrics) and their magnitudes qualitatively scaled in a nonlinear manner. Another approach is quantitative EMG (QEMG), whereby 20+ E‐MUPs are extracted and both basic and derived metrics obtained and values expressed quantitatively. In diseased muscle, many E‐MUP metrics may be normal, which complicates diagnostic interpretation. In QEMG, E‐MUP metrics can be clustered and statistical analyses performed to assign probabilities that E‐MUPs (and the muscle) are normal, neuropathic, or myopathic. In this article we review what is known about the A‐MU, the restricted E‐MU, E‐MUP metrics, and what QEMG offers currently and in the future.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
2.
What Is in the Literature Bromberg, Mark B
Journal of clinical neuromuscular disease,
2024-Mar-01, 2024-03-00, 20240301, Volume:
25, Issue:
3
Journal Article
Peer reviewed
This issue of What is in the Literature focuses on the Guillain-Barré syndrome. Guillain-Barré syndrome is a monophasic illness, and there is new information about precipitating factors, changes in ...nerve conduction studies over time, potential biomarkers, optimal treatment, and features in uncommon patient populations.
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.
What Is in the Literature Bromberg, Mark B.
Journal of clinical neuromuscular disease,
12/2022, Volume:
24, Issue:
2
Journal Article
Peer reviewed
Open access
Abstract What is in the Literature focuses on chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), a neuropathy with challenges in diagnosis and treatment. A recent revision of ...diagnostic criteria (EFN/PNS criteria) has helped define clinical features of typical and atypical variants and what is not considered CIDP. Initiating pathologic factors is not known for typical CIDP or variants. New treatment approaches are based on immunologic mechanisms. Rare patients with a CIDP-like clinical pattern are found to have antibodies to proteins at and around the node of Ranvier and are not considered to be CIDP but a nodal-paranodopathy. Although occurring mainly in adults, CIDP also occurs in children. CIDP may have clinical and electrodiagnostic features that overlap with hereditary neuropathies, and the latter might show some response to treatment. Articles published in the past year that address these issues are discussed in this review.
Chronic inflammatory demyelinating polyradicoloneuropathy (CIDP) is a treatable form of neuropathy. Efforts to devise sets of electrodiagnostic (nerve conduction) criteria to distinguish primary ...demyelination from primary axonal neuropathies have been elusive, and at least 16 criteria have been proposed. Modifications to criteria frequently represent minor changes based on applying a set to a small number of patients with the clinical diagnosis of CIDP, whereas others are based on physiological changes related to demyelination and other pathophysiological features. The various modifications continue to result in limited sensitivity, likely related to the wide range of nerve conduction abnormalities among CIDP patients. Although some sets are appropriate for formal clinical drug trials, their complexity makes them difficult to apply in the clinic or electromyography laboratory. This study considers the evolution of the criteria, discusses their limitations, and ends with a simplified set of guidelines that can be applied in the clinic or laboratory. Muscle Nerve, 2011
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
6.
What Is in the Literature Bromberg, Mark B
Journal of clinical neuromuscular disease,
2022-Mar-01, 2022-03-00, 20220301, Volume:
23, Issue:
3
Journal Article
Peer reviewed
This issue of What Is in the Literature focuses on articles on amyotrophic lateral sclerosis over the past year. Amyotrophic lateral sclerosis remains a challenging disorder with progression to ...death. Within the past year, a phase 2 trial of a drug combination showed slowing in the rate of progression. While awaiting a phase 3 trial or approval by the Food and Drug Administration, selected articles that aid the diagnosis, contribute to care, or add to general knowledge about the disease are reviewed.
Denervation was assessed in 89 spinal muscular atrophy (SMA) 1, 2, and 3 subjects via motor unit number estimation (MUNE) and maximum compound motor action potential amplitude (CMAP) studies, and ...results correlated with SMN2 copy, age, and function. MUNE and maximum CMAP values were distinct among SMA subtypes (p < 0.05). Changes in MUNE and maximum CMAP values over time were dependent on age, SMA type, and SMN2 copy number. SMN2 copy number less than 3 correlated with lower MUNE and maximum CMAP values (p < 0.0001) and worse functional outcomes. As SMN2 copy number increases, so does functional status (p < 0.0001). Change in MUNE longitudinally over the time intervals examined in this study was not statistically significant for any SMA cohort. However, a decline in maximum CMAP over time was apparent in SMA2 subjects (p = 0.049). Age‐dependent decline in MUNE and maximum CMAP was apparent in both SMA 1 (p < 0.0001) and SMA 2 (p < 0.0001) subjects, with age as an independent factor regardless of type. Maximum CMAP at the time of the initial assessment was most predictive of functional outcome (p < 0.0001). Prospective longitudinal studies in four prenatally diagnosed infants demonstrated significant progressive denervation in association with symptomatic onset or functional decline. These data highlight the potential value of such measures in increasing our understanding of pathophysiological factors involved in denervation in SMA. Ann Neurol 2005;57:704–712
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
ABSTRACT
Introduction: Numerous methods for motor unit number estimation (MUNE) have been developed. The objective of this article is to summarize and compare the major methods and the available data ...regarding their reproducibility, validity, application, refinement, and utility. Methods: Using specified search criteria, a systematic review of the literature was performed. Reproducibility, normative data, application to specific diseases and conditions, technical refinements, and practicality were compiled into a comprehensive database and analyzed. Results: The most commonly reported MUNE methods are the incremental, multiple‐point stimulation, spike‐triggered averaging, and statistical methods. All have established normative data sets and high reproducibility. MUNE provides quantitative assessments of motor neuron loss and has been applied successfully to the study of many clinical conditions, including amyotrophic lateral sclerosis and normal aging. Conclusions: MUNE is an important research technique in human subjects, providing important data regarding motor unit populations and motor unit loss over time. Muscle Nerve 50: 884–893, 2014
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
9.
What is in the Literature Bromberg, Mark B
Journal of clinical neuromuscular disease,
2021-Jun-01, 2021-06-00, 20210601, Volume:
22, Issue:
4
Journal Article
Peer reviewed
This edition of What is in the Literature focuses on chronic immune neuropathies as they represent treatable conditions. There are formal criteria to solidify the diagnosis of chronic inflammatory ...demyelinating polyradiculoneuropathy (CIDP), but patients are encountered who have clinical and electrodiagnostic features of CIDP but do not fulfill diagnostic criteria. These patients are addressed in recent publications. CIDP (and variants) and other forms of immune-mediated neuropathies (multifocal motor neuropathy) are responsive early on to treatment, but long-term factors are less well described, and a number of publications focus on extended consequences. Acute immune neuropathies have been described in the setting of viral illness, and recent publications look at the question as to whether they are associated with the COVID-19 pandemic. Finally, idiopathic sensory neuropathies are the most common polyneuropathy, and consensus efforts to codify features into subtypes can be used clinically for a more precise diagnosis.
Abstract Motor unit number estimation (MUNE) is a unique electrophysiologic technique that can provide a numeric estimate of the number of axons innervating a muscle or group of muscles. The first ...technique was first described in 1971, and since then different techniques have been developed to address specific methodologic issues. The field was reviewed in this journal in 2001, and this update covers new information and uses of MUNE over the past five years. These include models of muscles that allow evaluation of MUNE techniques and comparisons between techniques. There have been further investigations of specific technical aspects of MUNE. Modifications to MUNE techniques have been offered that permit more rapid acquisition of data. MUNE has been used in clinical situations to elucidate the pathophysiology features of axonal loss in a number of disorders. There is now more experience with MUNE as endpoint measures in clinical trials.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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