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PubMed1991

Laryngeal electromyography.

Laryngeal electromyography (EMG) is simultaneously a powerful clinical and investigative tool. EMG may be diagnostic and prognostic in cases of laryngeal or vagus nerve injury and can differentiate between vocal cord fixation and paralysis. EMG also is being used to help unravel complex laryngeal neural and muscle physiology. Basic principles of EMG, techniques of EMG limited to three muscles--the thyroarytenoid, the posterior cricoarytenoid, and the cricothyroid, and pitfalls of this procedure are discussed within this article.

Electromyography↗

PubMedDate not supplied

[Electromyography in the evaluation of the functional state of the internal neuromuscular apparatus of the larynx in myasthenia].

Using needle transcutaneous electromyography of internal laryngeal muscles and kalymin tests, 40 patients with myasthenia of different forms were examined. It was found that patients with generalized and local pharyngeal-facial forms of the disease developed latent generalization of myasthenic injury. Characteristic changes can be used to determine the degree of disorders in the internal nervous-muscular apparatus of the larynx.

Adolescent↗

PubMed1991

[Contribution of early electromyography in the prognostic assessment of facial paralysis].

26 patients suffering from total facial palsy of different etiologies underwent an electromyography of the facial muscles between the 5th and 15th day, and were followed up for one year. The muscular activity in forced mimetics, the blink reflex, and the electric response latency were studied after stimulation of the stylomastoid foramen. Early EMG with detection of one or several motor units is a decisive factor in the final prognosis. The methodology and advantages of EMG are compared to those of electroneuronography.

Adolescent↗

PubMedDate not supplied

[Electromyography of the uterus in monitoring pregnancies with symptoms of premature labor].

Characteristics of uterine muscle action potentials in 100 gravidas with symptoms of preterm labor or imminent abortion (presence of contractions with cervical changes) from 18th till the 32nd weeks of pregnancy are analysed. Twenty four gravidas with uncomplicated pregnancy were monitored electromyographically from the 20th weeks until term, once a week. There was low electrical activity in uncomplicated pregnancies up to 7 days before labor. A similar trend was observed in pregnancies that were finished before term. But, in symptomatic pregnancies finished preterm, the index of uterine muscle electrical activity (expressed in the percentage of voltage plus frequency) was continuously, although not significantly, above the values in symptomatic and asymptomatic term pregnancies. In only 2 out of 18 (11.1%) before term terminated pregnancies and in 45 out of 82 (54.9%) in term accomplished pregnancies, was electrical silence was registered during clinical symptoms (p less than 0.01). In preterm accomplished pregnancies, higher voltages and more frequent occurrence of biphasic and polyphasic spikes were registered (p less than 0.05), although the single parameter was of no prognostic significance. With a successful tocolytic treatment, the index of uterine muscle electrical activity was significantly reduced (from 57.16 to 20.86, t = 2.52, p less than 0.02) and was similar to that registered in symptomatic term pregnancies subjected to no tocolytic treatment. Although intravenous tocolysis was shown diminish voltage and frequency, in preterm delivered pregnancies no reduction in electrical activity was observed. Uterine electromyography could be used as a predictor of successful or unsuccessful tocolytic treatment.

Action Potentials↗

PubMed1991

[An investigation of glottic movement and vocal cord evoked electromyography following unilateral cricoarytenoid joint injuries in rabbits].

The unilateral cricoarytenoid joints of rabbits were bluntly injured. Observations on glottic movement and vocal cord evoked electromyography were performed. The results confirm that injury of the cricoarytenoid joint always causes disturbances in ipsilateral vocal cord movement. But the evoked electrical activities of the ipsilateral vocal cord muscles were normal not only in acute stage but also in chronic stage. The above results may provide the experimental basis for clinical differentiation of disturbances in glottic movement.

Animals↗

PubMed1990

The value to the clinical neurologist of electromyography in the 1990s.

Increased knowledge in neurosciences and development of morphological and biochemical methods will continue to demand a greater sophistication of neurophysiological methods in relation to both recording and analysis. Today there are a number of EMG methods and parameters that have been proven useful in the laboratories where they have been developed. Wider use of these methods will improve the general quality of EMG studies, promote further understanding of pathological conditions and therefore be of value for the specialty of electromyography. Furthermore, even rather small computers are extremely helpful in improving analysis methods. The consistency, accuracy and possibilities of extracting new information offered by computer-aided analysis of neurophysiological signals will hopefully increase our understanding of muscle-nerve physiology and pathophysiology and improve the diagnostic yield of the methods used in the neurophysiology laboratory. Often the neurophysiological evaluation is inexpensive and can be carried out quickly and adds new facts to the picture. In summary, clinical neurophysiology continue to develop a number of sophisticated methods for better understanding of pathophysiological mechanisms. EMG describes the functional status of the central and peripheral nervous systems and is complementary to other techniques for evaluation of the patient with neurological disorders.

Computers↗

PubMedDate not supplied

[Use of vecuronium and atracurium in continuous infusion. A comparative study using electromyography and accelerometry].

Vecuronium and atracurium, muscle relaxant agents of intermediate action, were administered in continuous infusion to 175 patients undergoing prolonged surgical operations with the purpose of achieving serum concentrations inducing maintained blocking of neuromuscular function. We used a 0.08 mg/kg or 0.5 mg/kg bolus intubation dose followed by a continuous infusion of vecuronium (72 patients) or atracurium (103 patients) 10 minutes after, at the necessary pace to maintain inhibition of neuromuscular transmission over 90%. Monitoring of relaxation was done by means of four supramaximal stimuli trains which were repeated every 20 seconds and applied to the cubital nerve. Composite electromyogram (electromyography) and thumb acceleration (mechanomyography-accelerometry) were simultaneously recorded. Infusion was interrupted 15 minutes before ending the operation; reversion occurred spontaneously in 143 patients and 32 patients had to be reversed with neostigmine. Beginning of action, total duration of infusion, infusion speed, and 25-75 spontaneous and after decurarization recovery index were measured. Initial dose allowed an easy tracheal intubation and the constant relaxation achieved with 0.068 mg/kg/h and 0.46 mg/kg/h infusion of vecuronium and atracurium was adequate for all operations. Spontaneous recovery is often adequate at the end of operations in carefully monitored patients. Both monitoring methods are useful for clinical evaluation of neuromuscular transmission.

Adolescent↗

PubMed1977

[Electromyography as a diagnostic aid (author's transl)].

Electromyography reflects the anatomical situation in the muscle parenchyma. Changes in the anatomical structure are present if the normal potential form breaks up into small amplitude or even polyphasic potentials (myopathy type) or increases into high amplitude, broad and coarsely fragmented potentials (chronic neuropathy with regeneration). The caliber and type of muscle fibers are expressed in the speed of conduction. Spontaneous activity suggests an increased excitability of the muscel fibers. Disturbances of neuromuscular transmission are detectable by direct stimulation of the muscle. Analysis of nerve conductivity permits the demonstration of diffuse (polyneuropathy type) or circumscribed (entrapment neuropathy type) nerve affections. The recording of the parameters mentioned is the domain of EMG.

Electromyography↗

PubMed1991

Detecting lower motor neuron dysfunction of the pharynx and larynx with electromyography.

This study assessed the utility of clinical electromyography (EMG) for detecting lower motor neuron (LMN) or upper motor neuron (UMN) dysfunction affecting the intrinsic muscles of the larynx and pharynx. Twenty-nine subjects were examined; their clinical diagnoses included perioperative nerve injury, cerebral infarction, and lateral medullary infarction. Resting activity, motor unit action potential (MUAP) morphology, and MUAP recruitment were evaluated in every case. Medical records (excluding EMG data) were analyzed for clinical evidence of LMN or UMN dysfunction in the intrinsic muscles of the larynx and pharynx. The diagnosis of LMN dysfunction rested on clinical data consistent with cranial nerve injury, poliomyelitis, Wallenberg syndrome, or unilateral bulbar palsy. Criteria for UMN dysfunction included previous cerebral (not brainstem) infarction or mass lesion or the presence of hemiparesis. Electromyographic abnormalities were significantly associated with LMN dysfunction (p less than .05), but they were not significantly associated with UMN dysfunction. Of the parameters tested, MUAP recruitment was the most sensitive (82%) and specific (92%).

Action Potentials↗

PubMed1991

Electromyography interference pattern decomposition.

Decomposition of an interference pattern enables examination of individual electromyography (EMG) motor units and their firing rates at more than minimal contraction forces. In this decomposition method, significant events with a constant occurrence (near motor unit action potentials) can be enhanced, and unwanted events (distant motor unit action potentials, artifacts) eliminated, by calculating the average accumulated change while sliding a fixed-width window along the digitized EMG interference pattern. Nonparametric statistical methods are then applied to these data to determine which information is significant at the .05 level. The exact duration of significant information is identified without the need for arbitrary thresholds and filters to eliminate unwanted information. Events are then classified into groups of similar events by comparing: (1) correlation coefficients, (2) point-to-point differences, (3) amplitudes, and (4) areas. The classification is further refined by the use of firing-rate information.

Action Potentials↗

PubMed1990

Quantitative surface electromyography (qEMG): applications in anaesthesiology and critical care.

During general anaesthesia and in lowered vigilance states such as after major trauma and during heavy sedation or analgesic medication, patients' ability to communicate with their surroundings is limited. Subjective intuitional interpretation may be the only means to ascertain a patient's emotional state, mood, and pain perception. Electromyographic detection and quantification of minimal and covert facial mimic muscle activity in anaesthesiology and critical care was an interesting concept worth further evaluation. In this study, the behaviour of quantitative surface-detected electromyographic activity (qEMG) was investigated during common anaesthetic events, post-operatively, and in volunteers as well as in experimental animals. A review of the methodology includes the necessary details for reproduction of the studies, including computerized processing of numerical data available in the commercial equipment. Results from the monitoring of 218 patients, seven volunteers and 31 rats are discussed. Conclusions are based on 32 testable null-hypotheses, the earlier documented literature and the author's own experience. The qEMG signal was derived from two electrodes placed on the frontal area and on the mastoid process behind the ipsilateral ear. After amplification, the signal was filtered to obtain a portion containing electrical activity between 60-300 Hz, which was considered to represent electromyographic activity. The signals were thereafter full-wave rectified and averaged with a 1-s time constant. The output of the processing unit consisted of a graphics display and a numeric computer output. A variety of clinical conditions and drug effects were studied in order to evaluate the method's applicability in research and in routine anaesthetic practice. The facial muscles turned out to be less sensitive to the effects of neuromuscular blocking drugs than the hand muscles, the normal monitoring site of neuromuscular transmission. Although muscle relaxants had a suppressing effect on spontaneous EMG activity, they did not abolish the ability of facial muscles to react to noxious stimuli. Also abdominal muscles retained this capability, though presumably through a different motor mechanism. Depolarizing and non-depolarizing neuromuscular blocking drugs had disparate effects on spontaneous EMG activity; succinylcholine seemed to facilitate the qEMG amplitude during recovery of the block. Quantitative surface electromyography revealed impending arousals during lightening anaesthesia, although this was not a consistent phenomenon. Inadequate anaesthesia was always reflected by an increase in facial qEMG, albeit this often was also evident to the naked eye. The arousal at the end of anaesthesia was always associated with an abrupt increase in facial qEMG activity, which often was preceded by a more gradual, predictive rise. Auditory stimulation was also effective in increasing qEMG.(ABSTRACT TRUNCATED AT 400 WORDS)

Anesthesia↗

PubMed1990

Use of electromyography for the diagnosis of equine hyperkalemic periodic paresis.

The use of electromyography (EMG) as a diagnostic aid for equine hyperkalemic periodic paresis (EHPP) was investigated in seven affected and seven control horses. Affected horses were confirmed positive for EHPP either by elevated serum potassium concentration with clinical signs of myotonia, or by inducing hyperkalemia and clinical signs using oral potassium chloride challenge. All horses were asymptomatic at the time EMG was performed, using bipolar fine wire needle electrodes. The myopotentials were recorded on magnetic tape and displayed on paper charts for analysis. Insertional and resting activity were recorded from the right supraspinatus, triceps, extensor carpi radialis and gluteal muscles in standing horses. Myotonic discharges were seen in six of seven affected horses but not in any of the controls. All seven affected horses and two control horses had prolonged insertional activity. Five out of seven affected horses and one control horse displayed spontaneous motor unit discharges unrelated to recording electrode movement. Myoelectrical potentials containing closely timed muscle potentials, i.e. doublets, were found in all affected horses, with four of seven affected horses also showing triplets. These potentials were not observed in any of the controls. No obvious difference in activity was observed among the four muscle sites tested. It is concluded that EMG is a safe and useful tool for diagnosing EHPP in horses not currently displaying clinical signs. Myotonic discharges and doublets appear to be the most diagnostically significant electromyographic abnormalities in EHPP affected horses.

Animals↗

PubMed1990

[Evaluation of abdominal motor blockade using surface integrated electromyography during bupivacaine spinal anesthesia].

The study was undertaken to investigate abdominal motor blockade and compare sensory-motor differential blockade in bupivacaine spinal anesthesia by surface integrated electromyography (SIEMG). Seventeen physical status I adult male patients underwent lower limb surgery under spinal anesthesia were divided into two groups: hyperbaric bupivacaine (HB) group (n = 8) receiving 3 mL of 0.5% bupivacaine (8% glucose) and isobaric bupivacaine (IB) group (n = 9), 3 mL of 0.5% bupivacaine (glucose-free). Each patient was monitored with a blood pressure cuff, an ECG and a precordial stethoscope. Spinal anesthesia was performed at L3-4 interspace on the lateral position. Immediately following injection of bupivacaine, the patients were turned to the supine position and then simultaneous measurements of sensory blockade using pinprick, abdominal motor blockade at T6, T8, T10, T12 level using SIEMG and lower limb motor blockade using Bromage scale were made for 4 hours. Between two groups, there were no significant differences in terms of age, body weight, height as maximum level and mean times to maximum level of sensory blockade, abdominal motor blockade and lower limb motor blockade. The times of 2-segment regression of sensory blockade were 66.3 +/- 11.1 min in HB group and 115.6 +/- 31.3 min in IB group. The sensory-motor differential blockades were 4.6 +/- 0.5 segments and 4.8 +/- 2.1 segments in HB and IB groups, respectively. According to the linear regression analysis, the correlation between sensory blockade and abdominal motor blockade was better than the lower limb motor blockade and abdominal motor blockade. (Correlation coefficient (r): 0.893 vs 0.580 in HB group; 0.773 vs 0.366 in IB group).(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗

PubMed1990

Clinical electromyography. Principles and practice.

In this article the principles and practice of clinical EMG are described. The basic components of EMG instrumentation include specialized intramuscular recording electrodes, a preamplifier, amplifier, and displays. Displays are usually both visual and auditory, using the CRO and a loudspeaker, respectively. The motor unit is the functional unit of muscles and is the anatomic basis for clinical EMG. There are distinct sites along the motor unit pathway where pathologic changes may produce EMG abnormalities. These sites include (1) anterior horn cell; (2) spinal nerve root; (3) plexus; (4) peripheral nerve; (5) myoneural junction; and (6) muscle fiber. Normal EMG potentials in resting muscle (which is predominantly silent) include end-plate potentials and miniature end-plate potentials, which are present only in the region of the motor end plate. Individual motor unit potentials can be observed when a muscle contracts minimally. The morphology of motor unit potentials varies within a normal range, which is somewhat specific for each muscle, depending on its nerve-muscle fiber innervation ratio. Stronger contraction of a muscle produces an orderly recruitment of motor units, referred to as an interference pattern. In resting muscle the most commonly encountered abnormal potentials include (1) positive sharp waves, (2) fibrillation potentials, (3) fasciculation potentials, and (4) high frequency discharges. Abnormalities in motor unit morphology can be detected best in minimally contracting muscles. Polyphasic motor units contain more than four phases and constitute less than 15 per cent of all motor units in a given muscle. In myopathy the motor unit potentials are often polyphasic. They are of low amplitude and short duration. In neuropathy motor unit potentials may also be polyphasic; however, the size of the motor unit is either normal or of increased amplitude and duration depending on chronicity. Such findings in myopathy and neuropathy correlate with known pathoanatomic changes in these conditions. In myopathy the motor unit interference pattern will often be normal or enhanced despite clinical weakness in the muscle. In neuropathy the interference pattern will be reduced, and when neuropathy is severe a single large motor unit may produce a single motor unit pattern. Besides its application as a valuable aid in diagnosis of neuromuscular disorders, electromyography is also utilized for prognosis, determining the need for surgery, planning programs of rehabilitation, and providing evidence for medical legal purposes. Electromyographic findings most often serve as an adjunct to a thorough clinical evaluation of the patient. The electrophysiological data obtained may help support or rule out a specific clinical diagnosis.

Electrodes↗

PubMed1989

[Possibilities and limitations of electromyography in peripheral nerve lesions].

Besides the clinical examination, electromyography is the most important method in the diagnosis of peripheral nerve lesions. Together with the clinical findings it provides rather accurate information concerning the localisation, the severity and the type of a nerve lesion. However, one has to be aware of the limitations and the pitfalls of the method in order to prevent diagnostic errors. Besides a more general description of the diagnostic possibilities, the findings in traumatic nerve lesions and in entrapment neuropathies are discussed in more detail.

Electromyography↗

PubMed1989

[Mechanomyography and electromyography--2 competing methods of relaxometry using vecuronium].

The recording of the evoked twitch tension has been the established reference method to quantitate neuromuscular blockade. The evoked compound electromyogram has been introduced later as a clinically more convenient alternative. We compared both methods in 20 patients in whom cumulative dose response curves of vecuronium and the time constants of weaning neuromuscular blockade were determined. The evoked twitch tension was slightly more sensitive in detecting residual neuromuscular blockade than the EMG. No significant differences between the two methods were found in the cumulative 90% blocking dose, the duration of block and the recovery time (25%-75%). These results are in agreement with communications of previous authors using different nondepolarizing muscle relaxants. In the absence of abnormal conditions such as neuromuscular disorders and hypothermia, recording of evoked electromyography is a clinically satisfactory method to quantitate neuromuscular blockade.

Adult↗

PubMed1989

Esophageal electromyography in scleroderma patients with functional dysphagia.

Simultaneous recordings of myoelectric and manometric activities of the esophagus were made in two groups of patients with scleroderma. Group A consisted of patients who suffered from functional dysphagia that had appeared recently, and who had a normal size esophagus when examined radiographically. Patients in group B had complained of functional dysphagia for several years and showed a dilated hypotonic esophagus on x-ray. A control group of five normal subjects was also examined in the same manner. The study was carried out by means of a peroral probe with two pairs of suction-needle electrodes and two manometric side-hole catheters positioned at the same levels as the electrodes. Standard manometric examination of the esophagus was carried out in all patients. Normal subjects after each deglutition showed a propagated burst of spikes in correspondence with the ascending phase of the peristaltic wave, whereas, in the period between deglutitions, rare spikes and no pressure waves were recorded. Group A patients were characterized by the frequent appearance during the interdeglutitive period of spontaneous rhythmic sequences or bursts of spikes associated with pressure waves. In these patients, repetitive nonpropagated spike bursts with a higher than normal amplitude and duration were observed after deglutitions in association with high-amplitude nonpropagated repetitive pressure waves similar to those observed in diffuse esophageal spasm (DES). Five of the seven group B patients showed spike bursts and pressure waves with both amplitude and duration markedly lower than normal. The remaining two patients from group B presented no spike bursts or pressure waves at all. Standard manometry demonstrated findings equivalent to those obtained via electromyography (EMG) in all patients of group B and in only two patients of group A. In conclusion, the functional dysphagia of patients with scleroderma can be attributed to two different motor disorders. The first one is characterized by disorganized myoelectric hyperactivity and may have a manometric appearance similar to that of diffuse spasm. The second one is characterized by a marked decrease in myoelectric activity and corresponds to the classic manometric finding of scleroderma involvement of the esophagus. Both these myoelectric patterns seem to be related to subsequent stages of esophageal scleroderma involvement.

Adult↗

PubMed1979

[Significance of electromyography of the diaphragm in respiratory physiopathology].

Adequate electromyographic method are available in order to record the electrical activity of the vertebral (oesophageal surface electrodes) and the right or left costal (concentric needle electrodes) parts of the diaphragm and in order to stabilize the EMG's base line (rejection of the electrical movement's artefacts by means of RC filters). The electromyographic patterns of the agonistic and antagonistic activity of the diaphragm in normal subjects have been clearly defined in different circumstances such as quiet ventilation and hyperventilation. Disturbances of the ventilatory diaphragmatic activity have been demonstrated by electromyography in different diseases: broncho-pneumopathies; supraspinal disorders, myopathies. In normal subjects, global motor responses of the diaphragm to the electrical stimulation of each phrenic nerve can be easily recorded with surface electrodes located in the oesophageal hiatus or placed over the lower intercostal spaces. The phrenic nerve conduction times was measured in 30 normal adults. The average value of this parameter was 7,5 +/- 0,53 msec for excitation on the right side and 8,2 +/- 0,71 on the left. The measurement of the phrenic nerve conduction time seems to provide a sensitive index of involvement of the nerve in diaphragmatic dyskinesias. Prolongation of conduction time was demonstrated in phrenic lesions of various aetiologies such as: peripheral polyneuropathies, traumatic sequelae, mediastinal tumors, phrenic neuritis or idiopathic diaphragmatic paresis. Electrical phrenic stimulation and prostigmin have permitted to establish the diagnosis of myasthenic bloc of the phrenodiaphragmatic transmission.

Adolescent↗