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PubMed1997

The study of normal and abnormal neuromuscular transmission with single fibre electromyography.

The use of single fibre electromyography (SFEMG) in the study of neuromuscular transmission across individual motor endplates in situ is reviewed. The neuromuscular jitter can be studied both during voluntary contraction and electrical activation of the muscle fibre. The differences, pitfalls and advantages of these methods are discussed. Findings in myasthenia gravis and other disorders of the neuromuscular transmission are examined.

Electric Stimulation↗
PubMed1997

Laryngeal electromyography for the diagnosis and management of swallowing disorders.

Laryngeal electromyography has proved useful for the evaluation of neurologic disorders of the larynx. The techniques for this procedure are also well suited to investigate disorders of the pharyngeal phase of swallowing. The responses from the thyroarytenoid muscles, the cricothyroid muscles, and the cricopharyngeus muscle can offer information to aid in the diagnosis, prognosis, and in some cases, treatment of dysphagia. A general review of electromyographic responses with sample tracings from the larynx are included in this article.

Deglutition↗
PubMedDate not supplied

Experience with two types of electromyography monitoring electrodes during thyroid surgery.

PURPOSE: To prevent damage to the recurrent laryngeal nerve during thyroid or parathyroid surgery, spontaneous and evoked electromyography (EMG) can be used to locate the recurrent laryngeal nerve or determine when the nerve is being disturbed. Two commercial electrodes have been introduced to receive laryngeal EMG. This study compares the clinical performance of the two electrodes. PATIENTS AND METHODS: The Xomed-Treace endotracheal tube electrode (Xomed-Treace, Jacksonville, FL) and the RLN postcricoid laryngeal electrode (RLN Systems, Jefferson City, MO) were placed concomitantly in 11 patients during 14 surgical procedures. RESULTS: The RLN electrode provided feedback as to placement by providing a heart-beat artifact. The RLN electrode was found to be both more sensitive and more electrically noisy. On stimulation, the Xomed tube electrode produced generally higher EMG amplitudes, perhaps because of the different muscles they monitor. In one case, the Xomed tube failed to provide-EMG responses. Only at low electrical stimulation intensities could left and right vocalis muscles be identified with the Xomed tube. A laryngologist was needed to place the RLN electrode, whereas the attending anesthesiologist was able to place the Xomed tube. CONCLUSION: Both electrodes provided useful EMG information and helped confirm the location of the recurrent laryngeal nerve. Who will place the electrode, tumors extrinsic or intrinsic to the larynx, cost, and size requirements should be considered when choosing an electrode.

Electrodes↗
PubMed2002

Electromyography and ratings of lumbar muscle fatigue using a four-level staircase protocol.

OBJECTIVE: The purpose of the study was to explore whether a relationship existed between subject's experience and objective measurements of back-muscle fatigue in healthy subjects. This may be used as reference material later. DESIGN: Muscle fatigue in the lower back was measured in healthy subjects using a staircase protocol. BACKGROUND: Muscle fatigue measurement in the lower back is of importance when assessing patients with low-back pain. The subject's experience of muscle fatigue needs to be explored further. METHODS: Twenty healthy subjects with informed consent participated. Borg CR-10 scale responses and electromyography measurements were obtained from low-back muscles of the subjects following a staircase protocol with sustained contractions at 20%, 40%, 60%, and 80% of maximum voluntary contraction. RESULTS: A strong correlation was found between Borg ratings and force (r=0.83) and between slope and force (r= -0.72) but not between Borg ratings and slopes which was at best 0.43 (/r/< or =0.43). CONCLUSIONS: Although subjective ratings and slopes showed a low correlation; increases in force with a concomitant increase in fatigue was reflected both by the subjective ratings and the slope. One cannot use subjective ratings for prediction of the slope for this type of protocol. However, a more complete description of muscle fatigue needs both the slope and the Borg ratings. RELEVANCE: In clinical testing, both subjective and objective measures of muscle fatigue must be considered since they measure different aspects of muscle fatigue. The median frequency slope probably reflects "physical discomfort" but the Borg ratings add a factor of "lack of energy".

Adult↗
PubMed2001

Repetitive nerve stimulation and stimulation single fiber electromyography studies in rats intoxicated with single or mixed insecticides.

The function of the neuromuscular transmission in rats dosed with phoxim (P), methomyl (M), fenvalerate (F), and mixtures of P+M and P+F was studied by using both the stimulation single fiber electromyography (SSFEMG) and repetitive nerve stimulations (RNS) to determine the single muscle fiber action potential and compound muscle action potential (CMAP) respectively. The results showed that the mean consecutive difference (MCD) in SSFEMG was significantly prolonged in P, P+M and P+F intoxicated rats during the presence of myasthenia, but not in rats dosed with F and M when stimuli were given at 10 Hz or 20 Hz, thus indicating a transmission blocking at the neuromuscular junction (NMJ) induced by P. The frequency of neuromuscular transmission abnormalities detected by SSFEMG was significantly higher than those detected by RNS. This study demonstrated that the neuromuscular junction (NMJ) blocking is more frequently seen in P, P+M and P+F poisoning than in M and F poisoning, and that SSFEMG is a more sensitive electrophysiological method than RNS for detecting neuromuscular transmission blockage in myasthenia rats with acute insecticides poisoning.

Acetylcholinesterase↗
PubMed2003

The value of corpus cavernosum electromyography in erectile dysfunction: current status and future prospect.

In the last decade, several investigators have tried to develop corpus cavernosum electromyography (CC-EMG) as a direct clinical method to evaluate the state of the penile autonomic innervation and the cavernous smooth muscle. Both basic and clinical studies have shown promising results. However, its application as a diagnostic tool with clinical relevance was hindered by insufficient knowledge of cavernous smooth muscle electrophysiology, lack of standardization, technical and practical difficulties and problems in the interpretation of the results. Recently, the European Commission created the so-called COST Action B18 (corpus cavernosum EMG in erectile dysfunction), aiming to strengthen the coordination of the European research groups and give the development of CC-EMG a new impetus. This review presents an overview of the physiological background, the current status of CC-EMG, and discusses possibilities for further developments.

Electromyography↗
PubMed1999

Changes of trapezius muscle blood flow and electromyography in chronic neck pain due to trapezius myalgia.

Chronic neck pain may increase the transmitter activity of neuropeptides in the upper cervical medulla causing impairment of the blood flow in the local muscle because of a lack of vasodilatatory substances excreted axonally. We have been using a new single-fibre technique for clinical determination of the microcirculation (LDF) in the trapezius muscles in relation to electromyography (EMG). This study pertains to the 76 patients (46 women and 30 men) who received a final diagnosis of chronic trapezius myalgia out of a total series of 300 cases with chronic neck pain which had been remitted to the National Insurance Administration Hospital in Tranås, Sweden, because their complaints interfered with their working ability. The purpose was to derive more objective medical information upon which to base rehabilitation. Sixty percent had continuous pain and 40% had pain after physical effort, or at work. Twenty healthy women volunteered to participate as a normal control group. The right and left trapezius muscles of all individuals were examined simultaneously with laser-Doppler flowmetry (LDF) and surface EMG during a fatiguing series of stepwise-increased contractions, each of 1 min duration with 1 min rest in between. The most painful side was compared with the opposite side in all patients and, in the female patients, also with the right shoulder of the healthy control women. The patients showed consistently low local blood flow in the painful side. The difference was statistically significant at low contraction intensities. Muscle tension was somewhat elevated, as evidenced by a slight increase of the rms-EMG that was statistically significant at high contraction intensities. The mean power frequency (MPF) of the EMG showed no change. The lowered local blood flow was not explained by a changed intramuscular pressure which is low in the trapezius during ordinary activities that do not normally impair the local blood flow (Larsson, S-E., Cai, H. and (Oberg, P.A., Microcirculation in the upper trapezius muscle during varying levels of static contraction, fatigue and recovery in healthy women. A study using percutaneous laser-Doppler flowmetry and surface electromyograpy, Eur. J. Appl. Physiol., 66 (1993) 483-488). We conclude that an impaired regulation of the microcirculation in the local muscle is of central importance in chronic trapezius myalgia, causing nociceptive pain which can be differentiated objectively from neuralgic neck-shoulder pain by the atraumatic technique described.

Adult↗
PubMed1986

[Urinary stress incontinence in women: contribution of electromyography of the striated urethral sphincter].

Fourteen women within their menopausal period and suffering from stress urinary incontinence were studied. Electromyographic studies show that sphincter weakness is almost constant (9/14), usually associated with a bladder instability and/or a lack in abdominal urethral transmission, both conditions being known as possible causes of urinary stress incontinence. However, neurological causes at the origin of urinary stress incontinence, such as neurogenous sphincter, may be found (3/14). Electromyography, coupled with urodynamic evaluation, therefore presents itself as the most accurate method for a good assessment of correct pathophysiology in urinary stress incontinence and thereby for good therapeutic prescription.

Adult↗
PubMed2003

Muscle ultrasonography and electromyography correlation for evaluation of floppy infants.

Floppiness in an infant may have a number of different etiologies from disorders of the brain to spinal cord lesions, neuropathies, neuromuscular junction disorders and myopathies. In this study we aimed to investigate the correlation of muscle ultrasonography (US) and electromyography (EMG) in the diagnosis of floppy infants. The study encompassed 41 floppy infants aged 2-24 months. The muscle US and EMG examinations were performed without awareness of the clinical diagnosis. The final diagnosis was established by molecular genetic tests or muscle/nerve biopsy. The neurogenic group consisted of 16 infants according to their US and EMG findings. Fifteen of them had spinal muscular atrophy proven by genetic analysis and one had polyneuropathy diagnosed by nerve biopsy. Six infants were in the myopathic group according to their muscle US and EMG results. All of them underwent muscle biopsy and microscopic examination revealed five congenital muscular dystrophy and one glycogen storage disease. In two infants the US and EMG data conflicted. Their biopsies were also insufficient for the diagnosis. Seventeen infants had normal US and EMG findings but pathologic cranial magnetic resonance imaging or metabolic/genetic tests. They were considered in the group of central hypotonia. Our results suggest a high concordance of US and EMG findings in the diagnostic work-up of neurogenic and myopathic disorders.

Child, Preschool↗
PubMed1988

An electromyography in spastic diplegia.

To evaluate the pathologic state accurately and objectively, fifteen patients with spastic diplegia were examined with surface electromyography (EMG) of the rectus femoris, medial hamstring, anterior tibial and gastrocnemius muscles. Seven showed disturbed reciprocal innervation (disturbed group) and 8 showed reciprocal innervation (non disturbed group). The disturbance of reciprocal innervation on EMG showed a positive correlation with delay in onset of crawling by 10 months (p less than 0.05), a low level of motor development (p less than 0.005) and more abnormal CT findings. Four patients in the disturbed group showed various abnormalities in X-rays of the hips. Surface EMG findings of crawling muscle may be useful for understanding the pathologic state of crawling in spastic diplegia.

Cerebral Palsy↗
PubMed2002

The clinical electromyography examination. An overview.

Clinical electromyography (EMG) is the electrophysiological study of nerve and muscle. The terminology of the electrodiagnostic and needle electromyographic is confusing. The scope of the EMG studies, preparation of patient, referral process and recommended procedures are discussed. Report generation is a major function of the electromyographer. It should include tabulated nerve conduction studies and needle EMG findings along with brief history, summary of findings, and impression.

Electromyography↗
PubMed2003

Electromyography of scoliotic patients treated with a brace.

When a brace is used to correct spinal deviation, patients may seek to ease the discomfort from the pressure exerted by the orthosis by actively recruiting specific trunk muscles. The effect of bracing on trunk electromyography (EMG) has been reported in only one study where a limited number of electrodes were placed mainly in the thoracic region. Our hypothesis was that a multi-electrode mapping of the activity of the thoracic, lumbar, and abdominal trunk muscles would provide a more representative picture of the muscular reaction in response to bracing. With a larger number of EMG measuring sites, the presence of any brace-induced trunk muscle activity should be detected. Therefore, EMG signals of 11 adolescent idiopathic scoliosis patients who had been undergoing Boston brace treatment for 0.7-3 years were collected during four isometric tasks to evaluate the response of trunk muscles in the minutes following the application of the brace. Twenty-two pairs of bipolar electrodes were used to measure the EMG signals of the main superficial trunk muscles during four isometric tasks. EMG signals of trunk muscles were compared in braced and unbraced conditions. Brace-induced increases in EMG activity were significant in 43% of the individual measurements and in three of the four tasks for the group mean values. Increases were greater in the lumbar area, especially on the convex side of the secondary (lumbar) curve. These results thus suggest that immediately following the application of the brace, significant muscular responses can be observed in some patients.

Abdominal Muscles↗
PubMed2004

Practice parameter: laryngeal electromyography (an evidence-based review).

This paper reports on an evidence-based review of laryngeal electromyography (EMG) as a technique for use in the diagnosis, prognosis, and treatment of laryngeal movement disorders, including the laryngeal dystonias, vocal fold paralysis, and other neurolaryngological disorders. The authors performed a systematic review of the medical literature from 1944 through 2001 on the clinical application of EMG to laryngeal disorders. Thirty-three of the 584 articles met the predefined inclusion criteria. The evidence demonstrated that in a double-blind treatment trial of botulinum toxin versus saline, laryngeal EMG used to guide injections into the thyroarytenoid muscle in persons with adductor spasmodic dysphonia was beneficial. A cross-over comparison between laryngeal EMG-guided injection and endoscopic injection of botulinum toxin into the posterior cricoarytenoid muscle in abductor spasmodic dysphonia found no significant difference between the two techniques and no significant treatment benefit. Based on the evidence, laryngeal EMG is possibly useful for the injection of botulinum toxin into the thyroarytenoid muscle in the treatment of adductor spasmodic dysphonia. There were no evidence-based data sufficient to support or refute the value of laryngeal EMG for the other uses investigated, although there is extensive anecdotal literature suggesting that it is useful for each of them. There is an urgent need for evidence-based research addressing other applications in the use of laryngeal EMG for other applications.

Electromyography↗
PubMed1998

Comparison of acceleromyography and electromyography in vecuronium-induced neuromuscular blockade with xenon or sevoflurane anesthesia.

STUDY OBJECTIVES: To compare acceleromyography (AMG) and electromyography (EMG) with xenon or sevoflurane anesthesia during vecuronium-induced neuromuscular blockade. DESIGN: Prospective randomized study. SETTING: University hospital. PATIENTS: 28 ASA physical status I and II adult patients presenting for elective surgery. INTERVENTIONS: Patients received vecuronium for neuromuscular blockade and either xenon (n = 11) or sevoflurane (n = 17) anesthesia. MEASUREMENTS AND MAIN RESULTS: The first twitch depression, which was expressed as a ratio of the first twitch to that obtained before the blocking drug was administered (T1/Tc), was measured simultaneously by AMG and EMG. T1/Tc as measured by AMG consistently demonstrated greater depression than that by EMG during recovery. The limits of agreement were unacceptably wide, suggesting that T1/Tc obtained by AMG is a poor predictor of T1/Tc as measured by EMG. Such relations were not affected by the anesthetic (xenon or sevoflurane) used. CONCLUSION: AMG and EMG-cannot be used interchangeably with either xenon or sevoflurane anesthesia.

Acceleration↗
PubMed2002

Respective value of pudendal nerve terminal motor latency and anal sphincter electromyography in neurogenic fecal incontinence.

Fecal incontinence may be related to a neurogenic injury. Electrodiagnostic tests including pudendal nerve terminal motor latency (PNTML) and external anal sphincter electromyography (AEMG) have been proposed to reveal anal nerve damage. The aim of this study was to assess the respective value of PNTML and AEMG in the diagnosis of fecal incontinence. This study included 80 women (range 23-85 years) with fecal incontinence secondary to obstetrical and/or surgical trauma. They were evaluated by performing PNTML and AEMG. The electrophysiological results were compared and interpreted in the light of anorectal manometry (ARM) results. Electrodiagnostic test abnormalities were found in 64 of 80 patients (80%), including 28 patients with abnormal results for both tests and 36 patients with only one abnormal test. Overall, a neurogenic AEMG pattern was found in 64% of patients and a prolonged PNTML in 51%. No correlation was found between PNTML value and either AEMG grade or ARM parameters, while AEMG grade strongly correlated with squeeze pressure measured by ARM. This study showed that AEMG and PNTML did not give redundant information and allowed to explicit the mechanisms of neurogenic fecal incontinence. We found that AEMG was more sensitive and more closely related to the anal functional status (ARM parameters) than PNTML. These electrodiagnostic tests, particularly AEMG as performed in everyday practice, are useful in the assessment of neurogenic fecal incontinence.

Adult↗
PubMed1997

[Signal processing in electromyography: a review].

Automatic analysis of electromyography (EMG), signals, first operated in 1950 with analogic machines, steeply expanded from 1980 when fast computers and worthwhile programs became available. On-line measurement of response area and latency, averaging of low amplitude waves, fast sorting of motor unit potential shape parameters, computation of the "jitter" between two muscle fibers, turns/amplitude and spectral analysis of interferential pattern records, are some examples of programs currently offered in modern EMG machines. Other techniques are still reserved for research purposes: scanning EMG, decomposition of nerve and muscle compound potentials, measurement of the threshold and firing rate of motor units, trace analysis using tracking models. Finally, the credit for artificial intelligence systems (knowledge based systems, fuzzy logic, neuronal networks) is still not clearly stated.

Artifacts↗
PubMed1997

Electromyography in myopathy.

Electromyography (EMG) is the most common procedure for screening patients with myopathies and remains the most important technique for assessing the course of the disease over time. Fibrillation potentials, positive sharp waves, myotonic or complex repetitive discharge, as well as polyphasic potentials are non specific and can occur in both myopathic and neurogenic lesions. The most sensitive and specific parameter for myopathy in conventional EMG is the decreased duration of motor unit potentials (MUP), but this can also be seen in disorders of the terminal motor fibers or the neuromuscular junction. More advanced techniques such as single fiber EMG, macro EMG, scanning EMG and turns/amplitude analysis have opened additional possibilities for analysis of the motor unit and the interference pattern, by which both the sensitivity to early changes and specificity for myopathic alterations is increased. The importance of combining different techniques to improve diagnostic yield and specificity is stressed.

Electromyography↗