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Single fibre electromyography in the extensor digitorum communis muscle was studied in five patients with central core disease. The average number of muscle fibre action potentials belonging to the same motor unit was higher in patients than in healthy subjects of the same age. The increase in motor unit fibre density is consistent with increased terminal innervation ratio described in other papers about central core disease.
OBJECTIVE AND METHODS: Inclusion body myositis is said to have both myopathic and neurogenic features on electrophysiological tests. Twenty one studies from 20 patients with biopsy defined inclusion body myosis, 13 of whom had quantitative electromyography (qEMG), were reviewed to determine if this technique added diagnostic specificity (one patient had both needle EMG and a later study with qEMG before muscle biopsy). RESULTS: Excessive numbers of polyphasic motor unit potentials (MUPs) (> 12% per muscle) were seen in 11 of the 13 patients. In 10 of 13 patients, mean MUP duration was abnormally reduced (26% to 48%). In three patients, mean MUP duration was abnormally reduced only after polyphasic MUPs were excluded. In all 13 patients, the simple MUP duration was reduced. Myopathy was unequivocally diagnosed in all 13 studies that included qEMG; of the remaining eight patients, the conclusions of the electrophysiological studies without qEMG was myopathy (one), neurogenic (four) or non-diagnostic (three). CONCLUSIONS: There is no evidence of a neurogenic component in inclusion body myosis if qEMG is used. Quantitative EMG is often necessary to make an electrophysiological diagnosis of a myogenic disorder in patients with inclusion body myosis.
OBJECTIVE: To study the process of denervation-reinnervation in multifocal motor neuropathy with persistent conduction blocks in clinically affected and unaffected muscles. METHOD: Volitional single fibre electromyography (SFEMG) was performed in the extensor digitorum communis (EDC) of seven patients. The jitter, the fibre density, and the mean interpotential interval were determined. The results before and after treatment with intravenous immunoglobulin (IVIg) between the unaffected EDC and affected EDC examined during the same SFEMG session were also compared. In addition the values of jitter, fibre density, and mean interpotential interval were analysed for correlation with the strength score on the MRC scale, the duration of the neuropathy, the number of IVIg treatment periods, and the radial nerve conduction block values. RESULTS: Mean jitter, percentage of jitters >60 micros, and impulse blocking percentage, were higher than normal in both the affected EDCs and to a lesser degree in unaffected EDCs. Jitter decreased significantly after IVIg and correlated only with the MRC score. Fibre density and mean interpotential interval were higher than normal equally in the affected EDC and unaffected EDCs, but no correlation was found with strength, duration of the neuropathy, number of treatment periods, and conduction block values. CONCLUSION: The major finding is the presence of SFEMG abnormalities in clinically unaffected EDCs. This shows a process of denervation-reinnervation even in the absence of clinical symptoms, probably more frequent than commonly supposed in this neuropathy. The rapid clinical improvement after IVIg infusions could be due to remyelination after demyelination and to an interference of IVIg with the blocking effect of antibodies on the Na+ channels at the motor nerve endings.
Electromyography was used as an aid to the diagnosis of equine motor neuron disease in a conscious horse while it was under caudal epidural anaesthesia. A muscle biopsy was taken to confirm the diagnosis which was then supported by a postmortem examination.
This study examined the utility of electromyography and near-infrared spectroscopy (NIRS) in assessing m. erector spinae activity during the Biering-Sorensen Back Muscle Endurance (BSME) test. Six men and four women (27.0 +/- 7.1 years of age) performed the BSME test (time = 131.5 +/- 43.5 s). EMG was used to quantify neuromuscular activity of the right and left side at the L3 level, and root mean square was scaled for maximum value at the start of the exercise. NIRS was used to evaluate blood volume (BV) and oxygenation (OX) simultaneous with EMG bilaterally at the L3 level. There was a decrease to 49+/- 8% of initial median frequency (mean= 83 Hz) on both right and left sides when the exercise was 90% complete, and the slope of the median frequency/time relationship was significantly related to BSME time (r = 0.82). Group means for BV increased during back exercise while OX decreased and was significantly different between right and left sides of the lower back. However, large OX response differences among individuals and between right and left sides were noted. OX and median frequency were moderately related (r = 0.27-0.38). It appears that NIRS combined with EMG is a promising tool for assessing localized metabolic and neuromuscular activity during static contractions of the lower back.
Patterns of fetal drinking behavior were quantified in five singleton fetuses (128 +/- 1 days gestation) by computer analysis of laryngeal-esophageal electromyography (EMG) and thoracic esophageal fluid flow. Esophageal flow was noted to be bidirectional with an average antegrade flow-to-retrograde flow ratio of 4.4 +/- 1.5. Retrograde esophageal flow coincided with diaphragmatic contractions, suggesting that inspiratory gastroesophageal pressure gradients may be operative. The regurgitated fluid was returned to the fetal rumen by thoracic esophageal contractions. Significant net fluid intake was noted during periods of primarily unidirectional antegrade esophageal flow. Fetuses swallowed an average of 35 +/- 9 ml/h during the 12-h study, extrapolating to an average daily volume of 840 +/- 224 ml. An EMG "propagated swallow" representing coordinated contractions of the thyrohyoid, nuchal esophagus, and thoracic esophagus averaged 43 +/- 3 swallows/h and was highly correlated with net esophageal flow. Nearly 60% of the total fluid intake occurred during "bouts" of propagated swallows, which represented only 8% of the study period. Bouts averaged 11.7 +/- 0.4 propagated swallows, lasted 2.1 +/- 0.2 min, and occurred every 27.6 +/- 1.7 min. Although EMG swallowing activity was similar, there were significant differences among fetuses in net esophageal fluid flow and volume per propagated swallow. We speculate that fetal fluid intake is dependent on the availability and physical properties of the swallowed fluid, whereas swallowing activity is primarily related to cortical maturation and thirst stimulation.
We have developed a new technique for diaphragmatic electromyography using an array of seven sequential electrode pairs at 1.0-cm spacing on an esophageal catheter. This array provides information about the spatial distribution of the electrical field generated by the diaphragm and reveals a sharply peaked variation of electrical potential with distance along the esophagus. The rectified and integrated information from each of the seven pairs is summed to give an approximation to the total electrical activity over the span of the array, providing a signal that is relatively insensitive to the position of the array over approximately 4 cm of catheter movement and removes the requirement for balloon stabilization of the catheter. With our array, we have confirmed the artifact in the evoked compound muscle action potential that seems to be related to diaphragmatic shape as reported by others who used supramaximal phrenic nerve stimulation, but the magnitude of this artifact (compared with the functional residual capacity level) was modest near functional residual capacity, averaging 12 +/- 14% (SD) for lung volumes 1.0 l above and -4 +/- 15% for lung volumes 1.0 l below functional residual capacity along the rib cage-abdomen relaxation line.
Electromyography (EMG) is commonly used to determine the electrical activity of skeletal muscle during contraction. To date, independent verification of the relationship between muscle use and EMG has not been provided. It has recently been shown that relaxation- (e.g., T2) weighted magnetic resonance images (MRI) of skeletal muscle demonstrate exercise-induced contrast enhancement that is graded with exercise intensity. This study was conducted to test the hypothesis that exercise-induced magnetic resonance (MR) contrast shifts would relate to EMG amplitude if both measures reflect muscle use during exercise. Both MRI and EMG data were collected for separate eccentric (ECC) and concentric (CON) exercise of increasing intensity to take advantage of the fact that the rate of increase and amplitude of EMG activity are markedly greater for CON muscle actions. Seven subjects 30 +/- 2 (SE) yr old performed five sets of 10 CON or ECC arm curls with each of four resistances representing 40, 60, 80, and 100% of their 10 repetition maximum for CON curls. There was 1.5 min between sets and 30 min between bouts (5 sets of 10 actions at each relative resistance). Multiple echo, transaxial T2-weighted MR images (1.5 T, TR/TE 2,000/30) were collected from a 7-cm region in the middle of the arm before exercise and immediately after each bout. Surface EMG signals were collected from both heads of the biceps brachii and the long head of the triceps brachii muscles. CON and ECC actions resulted in increased integrated EMG (IEMG) and T2 values that were strongly related (r = 0.99, P < 0.05) with relative resistance.(ABSTRACT TRUNCATED AT 250 WORDS)
A direct method for measuring force production of specific muscles during dynamic exercise is presently unavailable. Previous studies indicate that both intramuscular pressure (IMP) and electromyography (EMG) correlate linearly with muscle contraction force during isometric exercise. The objective of this study was to compare IMP and EMG as linear assessors of muscle contraction force during dynamic exercise. IMP and surface EMG activity were recorded during concentric and eccentric isokinetic plantarflexion and dorsiflexion of the ankle joint from the tibialis anterior (TA) and soleus (SOL) muscles of nine male volunteers (28-54 yr). Ankle torque was measured using a dynamometer, and IMP was measured via catheterization. IMP exhibited better linear correlation than EMG with ankle joint torque during concentric contractions of the SOL (IMP R2 = 0.97, EMG R2 = 0.81) and the TA (IMP R2 = 0.97, EMG R2 = 0.90), as well as during eccentric contractions (SOL: IMP R2 = 0.91, EMG R2 = 0.51; TA: IMP R2 = 0.94, EMG R2 = 0.73). IMP provides a better index of muscle contraction force than EMG during concentric and eccentric exercise through the entire range of torque. IMP reflects intrinsic mechanical properties of individual muscles, such as length-tension relationships, which EMG is unable to assess.
Laryngeal muscle electromyography (EMG) and measures of the behavior of the respiratory system have been made during spontaneous laughter in two groups of subjects. The smaller group also had a direct measure of tracheal pressure during this behavior. Laryngeal adductors such as the thyroarytenoid (TA) and lateral cricoarytenoid (LCA) exhibited brief high-amplitude bursts of activity, at a rate of approximately 5 Hz, which were usually associated on a 1 : 1 basis with the sound bursts (ha ha ha) of laughter. The laryngeal abductor, posterior cricoarytenoid (PCA), also showed bursts of activity that were out of phase with TA and LCA. The cricothyroid (CT) was only weakly, if at all, modulated during the bursting activity of the other laryngeal muscles. Tracheal pressure usually exhibited positive pressure pulses during laughter that were often, but not always, temporally correlated to the bursts of laryngeal adductor EMG activity. Such pressure modulations appeared to precisely determine when-and if-phonation was produced during the laugh. During laughter, laryngeal EMG is highly stereotyped both within and between subjects. In most instances, this activity appears to be supported by coordinated pulses of tracheal pressure. The periaqueductal gray (PAG) has been shown in animal studies to produce emotionally indicative vocalizations, in which the laryngeal and respiratory system are coordinated. Therefore, it is suggested that the PAG is involved with the production of laughter.
OBJECTIVES: Incontinence after radical prostatectomy is addressed to sphincter damage and/or bladder dysfunction. Taking into account a high cure rate of incontinence by pelvic floor biofeedback treatment, the search for further mechanisms of a complex physiological concept seems feasible. METHODS: To characterize pelvic floor function, 18 patients were prospectively evaluated before and after radical prostatectomy by clinical neurourological tests, urodynamics and needle/surface electromyography (EMG). RESULTS: In all patients (mean age 62 years) investigations were completed successfully. The outcomes of neurourological investigations (sacral reflexes, voluntary pelvic floor contraction and relaxation) and needle EMG showed no significant changes in the pre-/postoperative comparison. Only by using surface EMG polygraphy change of activation patterns during pelvic floor contraction (decreased mean and medium frequency) could be found. CONCLUSION: In patients without preexisting bladder dysfunction and with a basically normal operative and postoperative course, fine motoric changes of pelvic floor function are the main finding. This cannot be explained by a pure anatomical approach. Neurophysiological events, like a barrage of nociceptive information, caused by surgical dissection and an inflammatory reaction due to the healing process, contribute to altered processing within the central nervous system. The appreciation of these mechanisms, well studied in neuroscience and pain research, offers a better understanding of surgery-related short- and longterm morbidity after pelvic surgery, i.e., urinary incontinence and erectile dysfunction.
In stereotactic pallidotomy for Parkinson's disease, care must be taken to avoid internal capsule injury while maximizing improvement of rigidity and tremor. In 21 patients, intraoperative electromyography (EMG) was used to assess stimulation thresholds required for capsular responses and to monitor muscle tone and tremor. Surface EMG electrodes were placed on the face and multiple muscle groups of the extremities. The stimulation and lesion electrode was introduced via MRI-guided stereotaxis toward a point 2-3 mm anterior to the midcommissural point, 5-6 mm inferior to the AC-PC plane, and 21-22 mm lateral to the midline. Exact targets were modified according to MRI-visualized anatomy. With stimulation at 5 and 50 Hz, thresholds for detection of EMG responses were usually seen at 4-5 mA. EMG responses were consistently seen prior to visual observation of muscle activity. Timing of EMG response relative to stimulus aided in differentiating stimulus-related movement from spontaneous tremor. Resting spontaneous EMG activity was seen to decrease as rigidity was improved by incremental lesion production. EMG activity related to tremor was recorded; tremor decrease by lesion production was documented by EMG recording. Patient cooperation with physiologic testing during stimulation and lesion production may become limited. Intraoperative EMG monitoring provides an adjunct to improve reliability of assessment of capsular stimulation and rigidity while providing documentation of lesion impact on rigidity and tremor.
AIM OF STUDY: To assess the utility of laryngeal electromyography (EMG) as a diagnostic method for patients with immobile vocal folds and to evaluate its possible role as a prognostic indicator in the management of those cases. METHODOLOGY: The study included 35 patients with unilateral vocal fold immobility (VFI) and 10 normal controls. All patients were subjected to full history taking and thorough clinical examination and radiological investigations. Laryngeal EMG was performed for all the patients and controls. RESULTS: The specificity of EMG was 100%, while the sensitivity was 65.7% in detecting VFI. Seventeen cases (74%) with abnormal EMG data had a combined lesion of recurrent and superior laryngeal nerves and 6 cases (26%) had isolated recurrent laryngeal nerve lesion. In both groups there was no statistical difference as regards the position of the paralyzed vocal fold in either paramedian or lateral positions. Clinical follow-up with indirect laryngoscopy, 6 months later, revealed recovery in 10 of the 25 cases (40%). None of the recovered patients showed abnormal EMG data at presentation, while 13 out of 15 cases of non-recovered patients showed abnormal EMG data, i.e. the specificity of EMG was 100%, while the sensitivity was 86.6% in predicting recovery in patients with VFI. The quantitative analysis of the interference pattern was more sensitive (65.7 and 86.6%) than the conventional methods of analysis (60 and 80%) in detecting and predicting recovery in patients with immobile vocal folds, respectively. CONCLUSION: The clinical use of laryngeal EMG is an efficient and objective test in the study of patients with immobile vocal folds and in predicting recovery of those cases. It is also a useful tool in the diagnostic algorithm in vocal fold paralysis.
Thirty-two patients with hemifacial spasm were treated with 61 botulinum toxin (BT) injections. Some patients had post-BT lower facial paresis (LFP+group) while others did not suffer this side effect (LFP-group). Abnormal electromyography (EMG) recordings were more frequent in the LFP+ group (6/11) than in the LFP- group (3/21; p < 0.05). This result suggests that an EMG performed before any BT injection could detect the patients with a higher risk for this side effect. The first dose of BT might be lowered in such cases.
The effects of steroids on normal end-plate in vivo were evaluated in man by using single-fiber electromyography (SFEMG). SFEMG was performed on voluntarily activated extensor digitorium communis muscle under basal conditions and 1 week later an intramuscular injection of 4 mg betamethasone per day was administered for 7 days. Ten patients with low back pain were examined. Steroid therapy did not induce any statistically significant variation either of the mean jitter value or of the percentage of recordings with abnormally high jitter. The results of this study do not give evidence of a direct effect of steroids on normal neuromuscular junction.
OBJECTIVES: To assess the effects of autonomic nerve damage on the basis of cavernous electrical changes. METHODS: A study was carried out on the cavernous electrical activity in healthy volunteers (controls) and impotent patients after radical cystoprostatectomy using a specific electromyographical device, the 'SPACE-recorder 7500'. RESULTS: A significant reduction in the amplitude of potentials was recorded after pharmacological stimulation in both the controls and impotent patients. The healthy controls showed amplitude values which were significantly higher than the impotent patients after radical cystectomy (715 +/- 141 vs. 381 +/- 227 microV, p < 0.01). After 'nerve-sparing' radical cystectomy with a mean amplitude similar to controls (500-700 microV), the patients showed rigid erections after injection of intracavernous drugs in a high percentage of cases. CONCLUSION: In our experience, corpora cavernosa electromyography seems a reliable method which can directly point out damage in the cavernous smooth muscle and the penile autonomic nerves.
In this paper, parametric modeling of surface electromyography (EMG) algorithms that facilitates automatic SEMG feature extraction and artificial neural networks (ANN) are combined for providing an integrated system for the automatic analysis and diagnosis of myopathic disorders. Three paradigms of ANN were investigated: the multilayer backpropagation algorithm, the self-organizing feature map algorithm and a probabilistic neural network model. The performance of the three classifiers was compared with that of the old Fisher linear discriminant (FLD) classifiers. The results have shown that the three ANN models give higher performance. The percentage of correct classification reaches 90%. Poorer diagnostic performance was obtained from the FLD classifier. The system presented here indicates that surface EMG, when properly processed, can be used to provide the physician with a diagnostic assist device.
We report our experience with intraoperative laryngeal electromyography (L-EMG) using direct laryngoscopy and placement of monopolar electrodes under general anesthesia in the evaluation and management of laryngeal dysfunction in pediatric patients. In this series of case studies, we present clinical data on 30 pediatric patients with known or suspected anatomic or neurologic laryngotracheal disorders evaluated with placement of shielded monopolar electrodes into the thyroarytenoid muscles during direct laryngoscopy under general anesthesia. Diagnoses included congenital vocal fold paralysis (VFP), laryngotracheal stenosis, cerebral palsy, laryngeal tumors, traumatic vocal fold dysfunction, and postsurgical VFP. The impact of L-EMG on patient management was assessed. We found that L-EMG objectively supported clinical findings, but provided new objective data relevant toward management recommendations in only a few selected pediatric patients with new-onset vocal fold paralysis or paresis or infiltrative laryngeal tumors, and in selected postsurgical cases involving decannulation decisions. The prognostic utility of L-EMG in newborns with congenital VFP has not been established. A normal L-EMG recording indicates an intact neuromuscular axis, but does not guarantee vocal fold mobility or guarantee muscle function in a partially denervated or deconditioned muscle. The potential for false-negative recordings is the major limitation of this technique.