Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ELECTROMYOGRAPHY”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,207 records · Page 67Linked to original sources
PubMed1982

Pathophysiology of fasciculations in ALS as studied by electromyography of single motor units.

Electromyographic potentials of fasciculations were studied in ten patients with amyotrophic lateral sclerosis (ALS). The EMG recordings were made from the extensor digitorum brevis muscle. The EMG recording was so selective that only one motor unit potential appeared on maximal voluntary effort and on supramaximal electrical stimulation of the peroneal nerve. In a series of fasciculations, the shapes of the EMG potentials varied, while in a series of voluntary twitch activations of electrical nerve stimulations the EMG potentials were mainly constant. Fasciculations were followed by antidromic impulses in the test unit axon as judged from collision tests, and they persisted after lidocaine blockades of the nerve to the muscle. The findings are compatible with a conclusion of distal multifocal triggering of fasciculation. Fasciculating motor units had voluntary firing properties close to those of normal low-threshold motor units. Widespread fasciculations were abolished by a nonparalytic dose of a synthetic curare derivative (Pavulon) and augmented by administration of neostigmine in two cases. The fasciculations in ALS thus have the same characteristics as experimental fasciculations evoked by cholinesterase inhibitors, and there is reason to believe that the underlying pathophysiological mechanism is similar in the two cases.

Amyotrophic Lateral Sclerosis↗
PubMed1987

Single fiber electromyography in chronic progressive external ophthalmoplegia.

We have reviewed the electromyographic (EMG) studies of 17 patients with chronic progressive external ophthalmoplegia (CPEO). In 13 of 17 patients, conventional concentric needle EMG demonstrated a "myopathic" pattern, usually predominating in the shoulder muscles. Single-fiber EMG showed increased jitter and/or blocking in at least one muscle in 13 of 16 patients. Jitter was increased in the frontalis muscle in 10 of 13 patients and in an arm muscle in 5 of 12. When both muscles were tested, jitter was greater in the frontalis muscle in 5 patients and in the arm muscle in 2. These observations demonstrate that it may be difficult to distinguish myasthenia gravis from CPEO by EMG. The frequency with which abnormal jitter is found in CPEO suggests that, in addition to a mild generalized myopathy, a primary defect in neuromuscular transmission may be present.

Chronic Disease↗
PubMed1990

Sonographic imaging of muscle contraction and fasciculations: a correlation with electromyography.

Precise quantitation of fasciculations with EMG is difficult because of their random location and discharge frequency in muscle. We studied the clinical value of real-time ultrasound in the study of normal voluntary muscle contraction and in the identification of fasciculations in 22 patients. Sonography effectively imaged fasciculations, demonstrating them in both resting and actively contracting extremity muscles and in less accessible muscles such as the tongue. In two instances ultrasound identified fasciculations not apparent on EMG. Analysis of the video images generated quantitative data on fasciculation duration (averaging 500 msec), size, and location and provided unique insight into the process of normal muscle contraction and motor unit physiology.

Electromyography↗
PubMed1990

AAEM minimonograph #34: polyneuropathy: classification by nerve conduction studies and electromyography.

Electrodiagnostic evaluation of patients with suspected polyneuropathy is useful for detecting and documenting peripheral abnormalities, identifying the predominant pathophysiology, and determining the prognosis for certain disorders. The electrodiagnostic classification of polyneuropathy is associated with morphologic correlates and is based upon determining involvement of sensory and motor fibers and distinguishing between predominantly axon loss and demyelinating lesions. Accurate electrodiagnostic classification leads to a more focused and expedient identification of the etiology of polyneuropathy in clinical situations.

Electromyography↗
PubMed1990

Quantitative electromyography in polymyositis: a reappraisal.

Manual analysis of motor unit action potentials (MUAPs) was performed in 33 patients with polymyositis of whom 16 were studied in the acute stage and 17 in the chronic stage. Contrary to common description of "myopathic potentials" as being of low amplitude, short duration, and polyphasic shape, the quantitated study revealed no difference as to amplitude of short duration MUAPs in patients and normal subjects though short-duration MUAP and short duration polyphasic potentials were 4 and 3 times, respectively, more common in patients than in controls. Although the mean duration of MUAPs usually was significantly shorter in polymyositis than in controls, the average scatter of MUAPs duration was the same in the 2 groups. The average incidence of polyphasic MUAPs was 4 times higher in patients than in controls, as was the incidence of those of long duration. To avoid misinterpretation of EMG findings due to an excess of polyphasic MUAPs, a greater number of individual potentials than usually recommended should be collected allowing a valid estimate of the mean duration of MUAPs of simple configuration.

Action Potentials↗
PubMed1991

AAEM minimonograph #11: Needle examination in clinical electromyography.

The physiologic and histologic principles underlying clinical electromyographic studies are briefly reviewed as an introduction to the normal and abnormal findings in human subjects. Technical aspects of recordings as well as the specific types of discharges and their significance are discussed.

Action Potentials↗
PubMed1991

Concentric macro electromyography.

Concentric EMG electrodes can record from a few (10 to 15) muscle fibers of a motor unit (MU). Macro EMG, is able to record from the majority of muscle fibers in the MU. The macro EMG electrode uses a single fiber action potential (SFAP) on one channel to trigger the time locked cannula (macro) response on the other channel. To study the concentric motor unit action potential (MUAP), alongside the macro potential, we built a needle electrode combining concentric and macro recording surfaces. The study of 240 motor units in 10 healthy subjects with the single fiber (SF macro) and concentric macro (conmac) electrodes revealed no significant differences between macro potentials areas and amplitudes obtained with either electrode. The ability to study a small and a large section of the motor unit simultaneously offers insights into the local or global nature of motor unit changes not otherwise available to the electromyographer. It also reveals which concentric parameters correlate best with the macro potential and, can even be of great help with the newer EMG signal decomposition techniques; by identifying each motor unit by its concentric and macro waveform simultaneously, it will allow for the "marking" of these motor units helping to reduce the risk of their misclassification when the concentric MUAP is used alone.

Action Potentials↗
PubMed1991

Role of electromyography in amyotrophic lateral sclerosis.

We reviewed the role of electrodiagnostic testing in amyotrophic lateral sclerosis (ALS) in a large ALS clinic. Over 31 months, 133 patients with a clinical diagnosis of ALS were tested. In most, nerve conduction studies were normal, and needle electrode examination showed active denervation in the upper and lower limbs or the limbs and bulbar muscles (Lambert's criteria). However, 50 of 133 patients did not fulfill Lambert's criteria at presentation because of abnormal nerve conduction studies (11 patients), abnormal F-wave latencies (6 patients), or insufficiently distributed fibrillation potentials (40 patients). This study reveals that a large proportion of patients with a clinical diagnosis of ALS fail to have classical findings on initial electrodiagnostic studies, and reveals several caveats of electrodiagnostic testing in these patients: (1) Conduction studies may be unreliable in motor nerves with markedly low compound muscle action potential (CMAP) amplitudes. (2) Sensory nerve action potential (SNAP) amplitudes may be abnormal in a small percentage of otherwise typical ALS patients. However, better controls for elderly subjects are needed. (3) Needle electrode examination may not show widespread active denervation early in the disease. (4) Some patients may have a mild polyneuropathy. (5) The classic diagnostic criteria may need to be modified to allow earlier acceptance of many ALS patients into therapeutic trials.

Action Potentials↗
PubMed1993

Acoustic myography compared to electromyography during isometric fatigue and recovery.

This study compared the acoustic (RMS-AMG) to electromyographic (RMS-EMG) signal, median frequency of EMG power spectrum (Fm), and quadriceps torque during isometric fatiguing contraction (FC) and recovery. Seven subjects were tested for strength (MVC) and then, on separate days, maintained 20%, 40%, or 80% MVC to exhaustion followed by MVC testing at regular intervals. Throughout FC, RMS-EMG significantly (P < 0.05) increased and Fm significantly (P < 0.05) decreased during all trials; RMS-AMG significantly (P < 0.05) increased only during the 20% and 40% trials. During recovery, MVC and RMS-EMG recovered most slowly after the 20% trial and most rapidly after the 80% trial; Fm and RMS-AMG recovered by 90 seconds after all trials. RMS-AMG reflects RMS-EMG during low but not high levels of FC. Recovery of strength is most depressed following FC at lower relative levels of torque. We conclude that RMS-AMG behaves differently than RMS-EMG, torque, and Fm during FC and recovery.

Acoustics↗
PubMed1993

Paraspinal mapping: quantified needle electromyography in lumbar radiculopathy.

In the diagnosis of low back pain, the presence of a high percentage of false positive findings on radiologic imaging studies has lead to a more definitive role for electrodiagnosis as a confirmatory test. The paraspinal muscles are a crucial part of the electrodiagnostic examination for radiculopathy. To date, no technique for paraspinal evaluation has been validated. Based on previously documented anatomical techniques, we have designed a method of paraspinal examination termed "paraspinal mapping" (PM). Electromyographic (EMG) needles are placed in five carefully chosen locations and inserted in multiple directions. Individual scores for these insertions are added to determine a total PM sensitivity score. The first 50 studies using PM were compared to peripheral EMG, imaging studies, and pain drawings. Results indicate that the technique is easy to perform. Sensitivity scores relate well with these tests. In this limited and uncontrolled population, PM had higher sensitivity for abnormalities than either peripheral EMG or imaging studies. Because of the anatomical validity of PM, future studies may show it to be useful in localizing the level of radiculopathy independently from peripheral EMG, and to support clinical findings and imaging studies.

Electromyography↗
PubMed1994

Cranial nerve conduction and needle electromyography in patients with acoustic neuromas: a model of compression neuropathy.

Of 45 patients with acoustic neuromas (0.3-5.0 cm), 73% had facial nerve impairment on electrophysiologic testing, but only 16% had facial weakness. Cranial nerve conduction was the most sensitive measurement, especially prolongation of the ipsilateral R1 latency of the blink reflex compared with that of the contralateral reflex. The severity of nerve conduction abnormality was highly correlated with tumor size. Our results confirm and quantitate the sensitivity of nerve action potential latency in response to chronic nerve compression.

Adult↗
PubMed1995

Dynamic electromyography and muscle biopsy changes in a 4-year follow-up: study of patients with a history of polio.

Eighteen patients who had had polio 29-56 years prior to the first investigation were studied on two occasions, 4 years apart. Isokinetic and isometric strength measurements and Macro EMG were performed in 28 legs. Muscle biopsy specimens were obtained on both occasions from 11 legs. On average the muscle strength was 56% of control values at the first examination, and decreased by another 8% during the observation period. The muscle fiber area was increased compared to that of controls and did not change significantly. Macro EMG, comprising muscle fiber area and number of muscle fibers, and/or single fiber EMG showed clear signs of reinnervation in all legs. The motor units at the first examination were increased 11-fold, on average, compared with age-matched control values. During the observation period, reinnervation continued and the size of motor units increased by another 56% as a result of ongoing denervation, that is, loss of neurons. This compensation was particularly pronounced in patients with stable conditions. The parameters studied did not reveal any definite pattern predicting future development of new muscle weakness in individual subjects.

Adenosine Triphosphatases↗
PubMed2002

Standardization of anal sphincter electromyography: quantification of continuous activity during relaxation.

AIM: Sphincter motor units (MUs) are continuously firing during relaxation. The quantification of this activity is a potentially useful electromyographic (EMG) parameter related to the number of MUs innervating the muscle and the level of motor neuron excitation. The aim of the present study was to develop a reliable, quantitative measure of continuous sphincter muscle activity during relaxation. METHODS: EMG activity was analyzed during relaxation, 1 minute after insertion of the concentric needle electrode into four sites in the external anal sphincter (EAS) muscle. In 10 control subjects, 8 interference pattern samples were obtained by "turn/amplitude" analysis. In 35 control subjects, a multi-MUP count of continuously firing motor unit potentials (MUPs) was used, quadruplets with scores of 0-6 obtained, and the lower reference limits (95th percentile) calculated. This approach was then evaluated in 57 patients (182 muscles) with cauda equina or conus medullaris lesion (CECML) and 7 patients (13 muscles) with "idiopathic fecal incontinence." RESULTS: The lower reference ("outlier") limits for MUP count were 0 0 6 6 and 0 1 2 2 for the subcutaneous, and 0 0 0 6 and 0 0 1 1 for the deeper EAS muscles. Both patient groups had a significantly diminished number of continuously firing MUPs, which was below the reference range in 43% of the EAS muscles from CECM patients and in 85% of muscles from patients with idiopathic fecal incontinence. In patients with CECML, the decrease in MUP count correlated with the severity of the lesion, as defined by the sensory deficit. CONCLUSIONS: MUP count in sphincter muscles during relaxation is technically feasible, and it is a promising tool, particularly in patients with idiopathic fecal incontinence.

Adult↗