Assessing the Motor Unit with Needle Electromyography

2009 ◽  
pp. 403-450 ◽  
Author(s):  
Devon I. Rubin
Keyword(s):  
Neuromuscular Junction ◽  
Peripheral Nerve ◽  
Motor Unit ◽  
Neuromuscular Diseases ◽  
Electric Activity ◽  
Great Sensitivity ◽  
Muscle Disease ◽  
Fine Needle ◽  
Needle Electromyography ◽  
Clinical Measures

Virtually all primary neuromuscular diseases result in changes in the electric activity recorded from muscle fibers. These changes can best be depicted using fine needle electrodes inserted into the muscle to record spontaneous and voluntary EMG. Thus, EMG can be used to distinguish among lower motor neuron, peripheral nerve, neuromuscular junction, and muscle disease with great sensitivity and some specificity. The sensitivity is usually greater than clinical measures; specificity in identifying the cause of the disease often requires muscle biopsy or other clinical measures. Although EMG is somewhat uncomfortable for patients because needles need to be inserted into the muscles, it generally is well tolerated by patients and provides a rapid, efficient means of testing the motor unit.

scholarly journals Bioengineered model of the human motor unit with physiologically functional neuromuscular junctions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Rowan P. Rimington ◽  
Jacob W. Fleming ◽  
Andrew J. Capel ◽  
Patrick C. Wheeler ◽  
Mark P. Lewis
Keyword(s):  
Neuromuscular Junction ◽  
Motor Neuron ◽  
Motor Unit ◽  
Motor Nerve ◽  
Motor Units ◽  
Extracellular Matrices ◽  
Synaptic Membrane ◽  
Type I ◽  
Dependent Manner ◽  
Human Motor

AbstractInvestigations of the human neuromuscular junction (NMJ) have predominately utilised experimental animals, model organisms, or monolayer cell cultures that fail to represent the physiological complexity of the synapse. Consequently, there remains a paucity of data regarding the development of the human NMJ and a lack of systems that enable investigation of the motor unit. This work addresses this need, providing the methodologies to bioengineer 3D models of the human motor unit. Spheroid culture of iPSC derived motor neuron progenitors augmented the transcription of OLIG2, ISLET1 and SMI32 motor neuron mRNAs ~ 400, ~ 150 and ~ 200-fold respectively compared to monolayer equivalents. Axon projections of adhered spheroids exceeded 1000 μm in monolayer, with transcription of SMI32 and VACHT mRNAs further enhanced by addition to 3D extracellular matrices in a type I collagen concentration dependent manner. Bioengineered skeletal muscles produced functional tetanic and twitch profiles, demonstrated increased acetylcholine receptor (AChR) clustering and transcription of MUSK and LRP4 mRNAs, indicating enhanced organisation of the post-synaptic membrane. The number of motor neuron spheroids, or motor pool, required to functionally innervate 3D muscle tissues was then determined, generating functional human NMJs that evidence pre- and post-synaptic membrane and motor nerve axon co-localisation. Spontaneous firing was significantly elevated in 3D motor units, confirmed to be driven by the motor nerve via antagonistic inhibition of the AChR. Functional analysis outlined decreased time to peak twitch and half relaxation times, indicating enhanced physiology of excitation contraction coupling in innervated motor units. Our findings provide the methods to maximise the maturity of both iPSC motor neurons and primary human skeletal muscle, utilising cell type specific extracellular matrices and developmental timelines to bioengineer the human motor unit for the study of neuromuscular junction physiology.

scholarly journals Inherited Defects of the ASC-1 Complex in Congenital Neuromuscular Diseases

2021 ◽  
Vol 22 (11) ◽  
pp. 6039
Author(s):  
Justine Meunier ◽  
Rocio-Nur Villar-Quiles ◽  
Isabelle Duband-Goulet ◽  
Ana Ferreiro
Keyword(s):  
Cell Cycle ◽  
Striated Muscle ◽  
Bone Fractures ◽  
Muscular Atrophy ◽  
Neuromuscular Diseases ◽  
Muscle Disease ◽  
Future Research ◽  
Muscle Involvement ◽  
Functional Studies ◽  
Monogenic Disorders

Defects in transcriptional and cell cycle regulation have emerged as novel pathophysiological mechanisms in congenital neuromuscular disease with the recent identification of mutations in the TRIP4 and ASCC1 genes, encoding, respectively, ASC-1 and ASCC1, two subunits of the ASC-1 (Activating Signal Cointegrator-1) complex. This complex is a poorly known transcriptional coregulator involved in transcriptional, post-transcriptional or translational activities. Inherited defects in components of the ASC-1 complex have been associated with several autosomal recessive phenotypes, including severe and mild forms of striated muscle disease (congenital myopathy with or without myocardial involvement), but also cases diagnosed of motor neuron disease (spinal muscular atrophy). Additionally, antenatal bone fractures were present in the reported patients with ASCC1 mutations. Functional studies revealed that the ASC-1 subunit is a novel regulator of cell cycle, proliferation and growth in muscle and non-muscular cells. In this review, we summarize and discuss the available data on the clinical and histopathological phenotypes associated with inherited defects of the ASC-1 complex proteins, the known genotype–phenotype correlations, the ASC-1 pathophysiological role, the puzzling question of motoneuron versus primary muscle involvement and potential future research avenues, illustrating the study of rare monogenic disorders as an interesting model paradigm to understand major physiological processes.

scholarly journals Motor Unit Number Estimation in Neuromuscular Disease

2008 ◽  
Vol 35 (2) ◽  
pp. 153-159 ◽  
Author(s):  
Omid Rashidipour ◽  
K. Ming Chan
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Motor Unit ◽  
Neuromuscular Disease ◽  
Muscular Atrophy ◽  
Neuromuscular Diseases ◽  
Neuronal Loss ◽  
Response To Treatment ◽  
Motor Unit Number Estimation ◽  
Electrophysiological Method ◽  
Lateral Sclerosis

Motor unit number estimation (MUNE) is an electrophysiological method designed to quantify motor unit loss in target muscles of interest. Most of the techniques are noninvasive and are therefore well suited for longitudinal monitoring. In this brief review, we describe the more commonly used techniques and their applications in amyotrophic lateral sclerosis, poliomyelitis, spinal muscular atrophy and hereditary sensorimotor neuropathies. Findings in some of these studies offer important pathophysiological insights. Since conventional electrophysiologic methods are not sensible measures of motor neuronal loss, MUNE could play a potentially important role in the diagnosis, monitoring of disease progression and response to treatment in neuromuscular diseases in which motor unit loss is a major feature.

Electrodiagnostic Findings in Neuromuscular Disorders

2018 ◽  
Author(s):  
Bashar Katirji
Keyword(s):  
Neuromuscular Junction ◽  
Peripheral Nerve ◽  
Myasthenia Gravis ◽  
Nerve Conduction ◽  
Neuromuscular Disorders ◽  
Nerve Conduction Studies ◽  
Anterior Horn Cell ◽  
Peripheral Neuropathies ◽  
Peripheral Nerve Lesions ◽  
Myasthenic Syndrome

Neuromuscular disorders are often classified into four major categories: anterior horn cell disorders, peripheral neuropathies, neuromuscular junction disorders and myopathies. This chapter discusses the electrodiagnostic and clinical EMG findings in these various neuromuscular disorders. Peripheral neuropathies are subdivided into focal mononeuropathies, radiculopathies, plexopathies and generalized peripheral polyneuropathies. Focal peripheral nerve lesions and generalized peripheral polyneuropathies may be axonal or demyelinating, and manifest quite distinctly on nerve conduction studies. Neuromuscular junction disorders may be presynaptic, as seen with the Lambert-Eaton myasthenic syndrome, or postsynaptic, as seen with myasthenia gravis.

Motor unit anatomy and physiology

2017 ◽  
Author(s):  
Matthew Pitt
Keyword(s):  
Quantitative Analysis ◽  
Motor Unit ◽  
Interference Pattern ◽  
Theoretical Explanation ◽  
Motor Unit Potential ◽  
Amplitude Analysis ◽  
Anatomy And Physiology ◽  
Needle Electromyography ◽  
Accurate Quantitative Analysis ◽  
Recruitment Order

This chapter focuses on the signals recorded with needle electromyography (EMG) and the measurement of their specific parameters. These parameters include duration, amplitude, number of phases, and stability. The concept of the electrophysiologic biopsy and the explanation of unusual findings seen on EMG are introduced. In relation to the interference pattern, discussions of the firing rate, recruitment order, and interference pattern are given. Moving from the theoretical explanation of the findings, the problems of the accurate quantitative analysis of the motor unit potential are discussed and measures to improve quantification, particularly in children, are highlighted. The importance of filter settings, the storage of signals, and the different ways of collecting and analysing the potentials are all covered. This section finishes with discussion of the normative range for motor unit duration, and concludes with the automatic analysis of the interference pattern, including turns/amplitude analysis, number of short segments measurement, and envelope analysis.

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