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PubMed1981

Single fiber electromyography. A method for the evaluation of motor axonopathy during toxicity studies in dogs.

In man, single fiber electromyography is used as a very sensitive indicator for the assessment of functional changes in motor nerves. The purpose of the present study was to adapt the above testing procedure to allow repeated investigations of dogs used in subchronic toxicity tests. Experiments were performed on anesthetized pure-bred beagle dogs. Action potentials from single muscle fibers in response to electrical stimulation of motor nerves were recorded with Medelec microelectrodes, amplified with a Medelec system and monitored on a Tektronic oscilloscope. Repeated electrical stimulation with pulses of 0.03 msec and 1 p.p.s. produced characteristic action potentials of single muscle fibers consisting of a positive, followed by a negative, deflection having a duration of from 500 to 800 microseconds altogether. Successive potentials occurred with a variable latency (the jitter) ranging from +/- 5 to 15 microseconds. Quantitative evaluation of the jitter will allow the clinical evaluation of motor axonopathies in dogs.

Action Potentials↗
PubMed1994

Electromyography of the internal anal sphincter performed under endosonographic guidance. Description of a new method.

PURPOSE: The aim of our study was to investigate internal anal sphincter electromyographic signals. METHODS: Electromyography of the internal anal sphincter was performed with platinum wire electrodes in six healthy volunteers (three males and three females), inserted under endosonographic guidance. Platinum wire electrodes were also inserted into the external anal sphincter. Activity of both the internal and external and sphincter in a 40-second period was measured. RESULTS: Internal anal sphincter median activity was 22.1 (range, 5.5-67.6) microV. Slow-wave activity was 47 cycles/minute (range, 34-55 cycles/minute). After inflation of a rectal balloon with air until a constant relaxation of the anal canal was obtained, a decrease in internal and sphincter activity to 15.9 (1.2-31.3) microV as well as a decrease in slow-wave activity to 34 cycles/minute (range, 27-40 cycles/minute) was found. The original internal anal sphincter EMG was resumed after deflation of the rectal balloon. External anal sphincter median activity was 3.1 (range, 0.77-18.6) microV. During inflation of the rectal balloon, a reflex increase in external sphincter EMG activity was found. With the rectal balloon fully inflated a part of this increase was still present, 11.0 (1.9-24.6) microV. In some of the subjects, this increased activity was superimposed on the internal anal sphincter recordings as well. During a voluntary squeeze it was not possible to identify internal anal sphincter activity due to activity of the external anal sphincter totally overriding the internal anal sphincter signal. CONCLUSION: Precise EMG recordings from the internal anal sphincter is possible with endosonographic guidance of the electrodes, except during voluntary squeezing of the external and sphincter.

Adult↗
PubMed1991

Assessment of noninvasive intra-anal electromyography to evaluate sphincter function.

Assessment of anal function is now regarded as an important aspect of the proctologic examination in assessment of patients with disordered defecation. Conventional electromyography is invasive and often not repeatable because of patient discomfort. Noninvasive surface intra-anal EMG was evaluated as a method of assessing sphincter function in 76 subjects. A significant correlation was found between intra-anal EMG and anal manometry at rest and during a maximum squeeze effort (P less than 0.01). Intra-anal EMG was found to be reproducible when evaluated by 2 independent observers (P less than 0.05) and may prove a reliable portable noninvasive method of assessing sphincter function.

Anal Canal↗
PubMed1997

Biofeedback retraining in patients with functional constipation and paradoxical puborectalis contraction: comparison of anal manometry and sphincter electromyography for feedback.

PURPOSE: This study was undertaken to assess the effect of biofeedback therapy in patients with constipation and paradoxical puborectalis contraction and to compare two different feedback modes. METHODS: Twenty-six patients were randomly allocated to either of two feedback modes: anal pressure using a manometry probe or anal sphincter electromyography (EMG) using surface electrodes. RESULTS: Six patients were unable to complete their training; ten patients were retrained using anal manometry and ten patients using EMG. The paradoxical puborectalis contraction disappeared after retraining with manometry feedback in eight of ten patients and with EMG feedback in ten of ten patients. A significant improvement in both bowel function and abdominal symptoms was found after training and a continued improvement at follow-up six months later. Six patients in the manometry group and nine in the EMG group experienced an overall improvement in symptoms. The two feedback methods did not differ in terms of efficacy. CONCLUSIONS: Our results suggest that biofeedback, using either manometry or EMG, is effective in improving symptoms and anorectal function caused by paradoxical puborectalis contraction.

Adult↗
PubMed1985

A study of the pregnant uterus of the ewe and the goat using real-time ultrasound scanning and electromyography.

In this study of the pregnant uterus of the ewe and the pygmy goat, the simultaneous use of real-time ultrasound scanning and electromyography is introduced. In unanaesthetized animals it was possible to visualize the uterine wall, the placentomes, parts of the fetal skeleton, the fetal kidneys, different parts of the fetal stomach and several structures of the fetal heart and vascular system. From these features the intra-abdominal position of the fetus could be determined. It was observed that Episodes of Myometrial Electrical Activity (EMEA's), as registered by chronically implanted uterine surface electrodes, coincided with passive displacements of the fetus in the direction of the maternal pelvis. These passive displacements could clearly be discerned from active fetal body movements. In both species the number of active fetal movements was significantly reduced during and/or shortly after an EMEA. In one of the pygmy goats, in which three different types of movement were discerned, this reduction of fetal movements could be studied in more detail. It is concluded that real-time ultrasound scanning of the fetus in small ruminants might contribute to studies of the complex maternal-fetal interactions that exist during late gestation.

Animals↗
PubMed1993

Cinedefecography and electromyography in the diagnosis of nonrelaxing puborectalis syndrome.

A prospective study was undertaken to assess the correlation between electromyography (EMG) and cinedefecography (CD) for the diagnosis of nonrelaxing puborectalis syndrome (NRPR). Clinical criteria for NRPR included straining, incomplete evacuation, tenesmus, and the need for enemas, suppositories, or digitation. EMG criteria included failure to achieve a significant decrease in electrical activity of the puborectalis (PR) during attempted evacuation. CD criteria included either paradoxical contraction or failure of relaxation of the PR along with incomplete evacuation. In addition, other etiologies for incomplete evacuation, such as rectoanal intussusception or nonemptying rectocele, were excluded by proctoscopy and defecography in all cases. One hundred twelve patients with constipation, 81 females and 31 males, with a mean age of 59 (range, 12-83) years were studied by routine office evaluation, CD, and EMG. Forty-two patients (37 percent) had evidence of NRPR on CD (rectal emptying: none, 24; incomplete, 18). Twenty-eight of these patients (67 percent) also had evidence of NRPR on EMG. EMG findings of NRPR were present in 12 of 70 patients (17 percent) with normal rectal emptying. Conversely, 14 of 72 patients (19 percent) with normal PR relaxation on EMG had an NRPR pattern on CD. The sensitivity and specificity for the EMG diagnosis of NRPR were 67 percent and 83 percent, and the positive and negative predictive values were 70 percent and 80 percent, respectively. Conversely, if EMG is considered as the ideal test for the diagnosis of NRPR, CD had a sensitivity of 70 percent, a specificity of 80 percent, and positive and negative predictive values of 66 percent and 82 percent, respectively. In summary, sensitivity, specificity, and predictive values of EMG and CD are suboptimal. Therefore, a combination of these two tests is suggested for the diagnosis of NRPR.

Action Potentials↗
PubMed1993

Endoluminal ultrasound is preferable to electromyography in mapping anal sphincteric defects.

Assessment of complex sphincteric defects in patients with fecal incontinence by digital rectal examination and intraoperative dissection can be difficult in the presence of excessive scarring. Adjunctive investigation such as endoluminal ultrasound (ELUS) and needle electromyography (EMG) may provide objective evidence of the nature and extent of the sphincteric defects. In a series of 11 patients, ELUS of the anal canal with a 10-MHz transducer (focal zone of 1-4 cm) accurately detected defects in the external anal sphincter (EAS) in seven of seven patients, defects in the internal anal sphincter (IAS) in eight of eight patients, and integrity of both sphincters in two patients. These findings were confirmed by needle EMG of the EAS alone in five patients, by operative findings at a perineal sphincteroplasty operation in six patients, and by both in two patients. ELUS was associated with less pain than was needle EMG (pain score 4 vs. 10, 10 being most painful) and provided high-resolution radial images of both the EAS and the IAS. Thus, ELUS seems preferable to EMG in mapping anal sphincteric defects and can be a useful anatomic adjunct to physiologic studies of anorectal function in patients with fecal incontinence.

Adult↗
PubMed2003

Surface electromyography and mechanomyography recording: a new differential composite probe.

The objective of the study was to develop a new surface probe for differential mechanomyographic (MMG) and electromyographic (EMG) recording. Differential amplification is commonly used in electromyography to improve the signal-to-noise ratio. A new composite probe was developed with two electrodes (EMG) and two identical piezo-electric membranes (MMG) to be positioned on muscle. The probe had two built-in fixed-gain differential amplifiers: one to amplify the electric signal and the other to amplify the vibration signal. A similar non-differential MMG probe was used for comparisons. Burst muscular activity was recorded using the non-differential and differential probes and was used to test the performance of the two probes in suppressing artifacts of non-muscular origin. Power spectrum analysis of signals from the two probes showed that differential amplification significantly improved the signal-to-noise ratio in MMG recordings and significantly suppressed artifacts (power difference > 90%). The composite probe allowed simultaneous differential recording of MMG and EMG signals from the same muscular site. It recorded muscular activity more efficiently than the non-differential probe and could therefore be useful in studying fatigue and neuromuscular diseases.

Artifacts↗
PubMed1989

Electromyography of the muscles of oropharyngeal swallowing: basic concepts.

Electromyography (EMG) has a valuable role in the evaluation of swallowing and its disorders, because it can assess the activity of individual muscles. Electromyographic kinesiology is a method for examining the physiology of swallowing. Analysis of individual myoelectric potentials is a technique for studying the integrity of the motor unit. This paper introduces the concepts of the motor unit, explains basic principles of EMG, and explores their relevance to the study of oropharyngeal swallowing. Several cases are presented to illustrate how EMG contributes to clinical diagnosis.

Deglutition↗
PubMed1996

Single-fibre laser Doppler flowmetry and electromyography for evaluating microcirculation in forearm muscle during static and continuous handgrip contractions.

A technique is described for intramuscular measurement of muscle blood flow in the forearm, by using a 0.5-mm thin optical single-fibre for laser Doppler flowmetry (LDF) inserted percutaneously. Continuous recordings were performed of the brachioradial muscle during an 11-min series of alternating 1-min periods of increased static contraction and rest determined by an electronic handgrip forcemeter and surface electromyography (EMG) of the muscle. Stepwise increased handgrip contractions were performed at 10%, 20%, 30%, 40% and 50% maximal voluntary contraction (MVC). This was followed by a similar series of continuous contractions. Finally, an endurance test was performed with a handgrip force of 50% MVC maintained for as long as possible. A group of ten healthy men of different ages was studied. Signal processing was done on line by computer. Successive increases in rootmean square (rms)-EMG and a fall in the mean power frequency (MPF) of the EMG spectrum occurred during the series of static contractions, which evoked perceived local fatigue in the forearm. Muscle blood flow recorded simultaneously showed no change from resting level during contractions at 10%, 20% and 30% MVC, while at 40% and 50% MVC mean increases of 150% and 200% were recorded. Blood flows measured during the rest periods showed large variability with no significant changes. This was also found after continuous contractions of the same intensities. The endurance time was 1.2-3.5 min (mean 2.4 min). Muscle blood flow showed mean increases of 214%, 256% and 229% of resting level each minute of the maintained contraction. Nevertheless, EMG signs of local fatigue developed, such as a rise in rms-EMG and a fall in MPF, and the subject experienced local fatigue. To conclude, this technique of percutaneous, continuous LDF recorded, at high sensitivity, the microcirculation at different fluxes and EMG-defined muscle activity.

Adult↗
PubMed1997

Selective electromyography of dorsal neck muscles in humans.

The patterns of activation of splenius capitis, semispinalis capitis, transversospinalis, and levator scapulae muscles were studied during various head-neck positions, movements, and isometric tests in 19 healthy human subjects. Myoelectric activities were recorded with intramuscular bipolar wire electrodes. Cervical computerized tomography of each subject was performed before the electromyography session in order to guide electrode insertion. Head motion was recorded using an electromechanical device. This report demonstrates that head motion results from a complex interaction of active muscular forces, passive ligamentous forces, and gravity. Splenius capitis has two main functions, i.e., cervical extension and ipsilateral rotation. Semi spinalis capitis and the transversospinalis are mainly extensors, and levator scapulae acts primarily on the shoulder girdle. Splenius capitis, semispinalis capitis, and transversospinalis play a subordinate part in ipsilateral tilting. In addition, most subjects' semispinalis capitis were gradually recruited during ipsilateral rotation. No signal was detected from the transversospinalis during rotation tests.

Adult↗
PubMed1998

Evaluation of the role of corpus cavernosum electromyography as a noninvasive diagnostic tool in male erectile dysfunction.

Corpus cavernosum electromyography (EMG) and its evolution: single potential analysis of cavernous electrical activity (SPACE) seem to be promising diagnostic methods in the evaluation of erectile dysfunction and smooth muscle integrity. Our study concentrates on the role of EMG in the evaluation of corpus cavernosum smooth muscles, using it as a noninvasive technique for demonstrating autonomic erectile dysfunction through their influence on recording SPACE and consequent proper selection of patients for different therapeutic modalities. A total of 80 male patients were examined for the feasibility of transcutaneous registration of cavernous electrical activity with a 2-channel electrophysiological unit (Evamatic 2000, Dantec) with two surface electrodes bilaterally placed on the penile shaft. Ten patients had normal erectile function, but complained of other urological symptoms. They served as the controls for normal electrical activity. Fifty patients with organic impotence of nonvascular (neurogenic) or vascular (venogenic, arteriogenic) aetiologies were subjected to EMG in both the flaccid and the erect state. On the basis of the EMG patterns the patients were divided into the following groups: 34 patients having normal tracing in both the flaccid and the erect state, and 21 patients showing abnormal patterns of waves with evidence of autonomic neurogenic dysfunction and incomplete smooth muscle relaxation. Of the latter 4 had long-standing diabetes mellitus and 4 had spinal injuries.

Adult↗
PubMed1989

The external anal sphincter. Relationship between anal manometry and anal electromyography and its clinical relevance.

Anal manometry and anal electromyography (EMG) were performed in 45 patients to evaluate the external anal sphincter. Their symptoms were soiling (N = 6), incontinence (N = 10), and obstipation (N = 19). Clinical diagnoses were previous anal surgery (N = 16), rectal prolapse--partial, total, intussusception (N = 16), puborectalis syndrome (N = 4), neurologic disorders (N = 3), and others (N = 6). The relationship between the maximum squeeze pressure (MSP) measured with anal manometry and the maximum (voluntary) contraction pattern (MCP) and signs of denervation (DEN) measured with anal EMG were examined. The correlation coefficient between MSP and MCP was 0.55 (P less than .001) and between MSP and DEN 0.13 (NS). A normal MSP always showed a normal MCP, a normal MCP showed an abnormal MSP in 43 percent only. In conclusion, the clinical value of anal EMG seems limited. Assessment of an additional anal EMG seems indicated in incontinent patients with previous anal surgery with a low MSP to estimate muscle function, whenever anal surgery is considered. Anal EMG during straining can easily confirm the clinical diagnosis of puborectalis syndrome.

Adolescent↗
PubMed1979

Endoscopic electromyography of the sphincter of Oddi.

Endoscopic electromyography of the human sphincter of ODDI has provided useful information for the patho-physiological studies on the choledocho-duodenal junction. The pattern and rhythm of the electromyogram observed on the spincter of ODDI were different from those of the duodenum recorded simultaneously in basal tracings of our initial four cases. In the half of other ten cases with consecutive tracings, the different pattern and rhythm of electromyograms between the sphincter of ODDI and the duodenum were also confirmed. It was possible, from our results, to speculate that the functional independence of the sphincter of ODDI from the duodenal wall muscles was in existence.

Adult↗
PubMed2000

Surface vs intramuscular laryngeal electromyography.

PURPOSE: To compare surface and intramuscular laryngeal electromyography (EMG) with adductor pollicis muscle EMG after 0.1 mgxkg(-1) cisatracurium. METHODS: This prospective study included ten patients undergoing surgery with risk of damage to the recurrent laryngeal nerve (RLN). The tracheas were intubated after fentanyl/propofol without the aid of muscle relaxation. A surface laryngeal electrode was attached to the tube and placed amidst the vocal cords; two straight needles were inserted endoscopically into the left lateral cricoarytenoid muscle. Single twitch stimulation of the left RLN (0.1 Hz) was performed transcutaneously; skin EMG of the left adductor pollicis muscle was performed at 0.1 Hz. After supramaximal stimulation for 10 min, 0.1 mgxkg(-1) cisatracurium was injected. Lag, onset time and peak effect were measured and compared. RESULTS: Good correlation (r = 0.9, 0.8, P < 0.005) and good comparability of the two methods of laryngeal EMG (mean difference and limits of agreement: 0 +/- 28 sec for lag time, -2 +/- 84 sec for onset time) was shown. The mean surface laryngeal lag and onset times were 67 +/- 22 sec and 198 +/- 72 sec, compared with the adductor pollicis muscle (98 +/- 30 sec and 242 +/- 59 sec) at P < 0.01. Peak effects at larynx (92 +/- 9%) and adductor pollicis muscle (95 +/- 3%) were similar. CONCLUSION: Surface laryngeal EMG is comparable to intramuscular laryngeal EMG to determine degree and onset of the neuromuscular blockade. Increasing muscle relaxation does not cause the surface electrode to lose contact with the vocal cords and therefore underestimate onset time and peak effect.

Aged↗
PubMed1997

[Electromyography study and follow-up of bilateral recurrent laryngeal nerve paralysis after thyroid gland operations].

Bilateral recurrent laryngeal nerve (RLN) palsies result in dyspnea and often require further surgery to secure an adequate airway for safe respiration. The present study was devised to determine a predictive value of laryngeal electromyography (LEMG) and if it has therapeutic consequences. In a retrospective study of 63 patients with bilateral recurrent laryngeal nerve palsies after thyroid gland surgery we compared the results of LEMG from the thyroarytenoid muscles with the spontaneous recovery rate of vocal cord mobility. A tracheostomy had to be performed in 18 patients because of unsafe dyspnea, while a unilateral lateral cord fixation had to be carried out in 20 patients. Primary thyroidectomies as treatment for benign goiters showed spontaneous normalization of unilateral or bilateral vocal cord mobility in 75% of cases versus 36% after revision thyroidectomies. Single LEMG correctly predicted prognosis in 78% of patients. In all, LEMG was found to be of value in the assessment of bilateral recurrent laryngeal nerve palsies. Findings also showed that a lateral cord fixation should be planned after a 9-month waiting period. When a patient refuses a tracheostomy lateral cord fixation can be performed at an earlier time, with the use of repeated LEMGs to predict whether or not a corrective surgery.

Adult↗
PubMed1998

Can electromyography predict the prognosis of transverse myelitis?

The role of clinical and magnetic resonance imaging (MRI) features on the prognosis of acute transverse myelitis has been studied, but the role of electromyography (EMG) changes, although reported, has not been investigated. Seventeen patients with acute transverse myelitis were subjected to clinical evaluation, MRI scanning and concentric needle EMG. The outcome was defined on the basis of a 3-month Barthel Index (BI) score as good or poor. The EMG changes in these groups were compared. All of the patients had complete paraplegia (power grade 0), except 1 who had grade III power. Mild upper limb weakness was present in 6 patients. Joint position and vibration sense were impaired in the lower limbs, and a horizontal limit to sensory loss to pinprick was present in all of the patients. Spinal MRI was abnormal in 12 of 14 patients. EMG of the lower limb muscles in the acute stage (within 15-30 days of onset) revealed fibrillations or sharp waves or both in 11 patients. At 3-month follow-up, the lower limb power had improved in 8 and upper limbs in all 6 patients. The EMG changes also improved in 6 patients; fibrillations either disappeared or were markedly reduced. The motor unit potentials (MUPs) were of long duration, polyphasic with reduced recruitment. In 5 patients, however, no MUPs could be recorded and fibrillations persisted. Lower limb hypotonia and fibrillations on EMG were significantly related to the 3-month outcome. EMG evidence of denervation in the lower limb muscles in acute transverse myelitis suggests a poor outcome as assessed by 3-month Barthel index score.

Adolescent↗
PubMed2002

Development of muscle fatigue as assessed by electromyography and mechanomyography during continuous and intermittent low-force contractions: effects of the feedback mode.

The goal of the present study was to investigate the significance of low-force continuous or intermittent static contraction and feedback mode (visual or proprioceptive) on the development of muscle fatigue as assessed by electromyography (EMG) and mechanomyography (MMG). Visual (force control) and proprioceptive (displacement control) feedback was investigated during intermittent (6 s contraction, 4 s rest) and continuous static contractions at 10% and 30% of the maximum voluntary contraction (MVC). Mean force, force fluctuation, rating of perceived exertion and root mean square (RMS) and mean power frequency (MPF) of the EMG and MMG signals were analysed. The general pattern for MMG RMS and EMG RMS values and the rating of perceived exertion was an increase with contraction time, while the EMG MPF values decreased ( P<0.05). The increase in RMS values was generally more pronounced for the MMG compared with the EMG, while the decrease in MPF values was more consistent for the EMG compared with the MMG signal. During the intermittent contractions, the main effect was on MPF for both EMG and MMG. Lower force fluctuation and larger rating of perceived exertion ( P<0.05), greater slopes of EMG and MMG RMS and MPF values versus time were observed with proprioceptive feedback compared with visual feedback. The findings suggest that (1) the EMG and MMG signals give complementary information about localised muscle fatigue at low-level contraction: they responded differently in terms of changes in the time and frequency domain during continuous contraction, while they responded in concert in the frequency domain during intermittent contractions, and (2) the different centrally mediated motor control strategies used during fatiguing contraction may be dependent upon the feedback modality.

Adult↗