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PubMed2006

The role of quantitative electromyography (EMG) in horses suspected of acute and chronic grass sickness.

REASONS FOR PERFORMING THE STUDY: Clinical evidence of motor neuron involvement in equine grass sickness (EGS) has not been reported. HYPOTHESIS: Quantitative electromyography (EMG) analysis can elucidate subtle changes of the lower motor neuron system present in horses with EGS, performed ante mortem. METHODS: Fourteen horses diagnosed clinically with acute, subacute or chronic EGS were examined and quantitative EMG performed. Previously published data on healthy horses and horses with proven lower motor neuron disease (LMND) were used as controls. In 8 horses post mortem examination was performed, and in 7 muscle biopsies of the lateral vastus muscle underwent histopathology and morphometry. RESULTS: Clinical electrophysiological evidence of neuropathy was present in 12 horses. Analysis of data from the first 4 horses resulted in 95% confidence intervals (CI) of nontransformed data for motor unit action potential (MUP) duration in subclavian, triceps and lateral vastus muscle of 11.0-13.7, 14.8-20.3 and 12.2-17.2 msecs, respectively, and for MUP amplitude 291-453, 1026-1892 and 957-1736 microV, respectively. For number of phases the 95% CI was 3.6-4.4, 2.9-3.6 and 2.9-3.4, respectively, and for number of turns 5.0-6.5, 4.3-5.3 and 3.7-4.6, respectively. No changes in duration of insertional activity were measured. Pathological spontaneous activity was observed in all horses. EGS as evidenced by degenerative changes in the autonomic ganglia in combination with minor degenerative changes of the spinal lower motor neurons was observed on post mortem examination in all 8 available autopsies. In muscle biopsies of 4 out of 7 horses changes consistent with slight neurogenic atrophy were found. CONCLUSIONS AND POTENTIAL RELEVANCE: EMG results demonstrated the presence of a neuropathy of skeletal muscles in all horses suspected to have EGS. The combination of clinical and electrophysiological evidence may aid differential diagnosis of neurogenic disease in cases of weight loss and colic.

Action Potentials↗
PubMed1994

Recording of single fiber electromyography in patients with peripheral facial palsy.

We determined muscle fiber density with single fiber electromyography (SFEMG) to discuss the condition of re-innervation after the recovery of facial movement in cases of peripheral facial palsy. Muscle fiber density was then compared with electroneurography (ENoG) which is thought to correlate with the severity of facial neuropathy in the early stage after the onset. The degree of neuropathy and subsequent recovery of innervation was also discussed. The subjects were 36 patients with peripheral facial palsy (30 patients with Bell's palsy and 6 with Hunt's syndrome), treated at our hospital, in whom ENoG could be recorded within 2 weeks after the onset. Muscle fiber density was determined after the recovery of facial movement. As a control, muscle fiber density was determined in 11 normal adults, and muscles on the healthy side in 23 patients with Bell's palsy. Muscle fiber density was 1.44 +/- 0.15 (mean +/- S.D.) in normal adults and 1.51 +/- 0.18 on the healthy side in patients, showing no significant difference. Data on the affected side were divided into 4 groups according to the minimum ENoG level within 2 weeks after onset and were compared with the normal group. In all cases with an ENoG level of 40% or more, muscle fiber densities were normal, and no significant differences were noted between the affected side and the healthy side. In cases with an ENoG level of less than 40%, muscle fiber density increased significantly with increasing severity of denervation. These findings suggest that collateral sprouting is absent in cases of peripheral facial palsy who show an ENoG level of 40% or more, or no wallerian degeneration.

Action Potentials↗
PubMed1986

Electromyography of human oesophageal smooth muscle.

The aim was to study whether electromyography (EMG) activity is synchronous with oesophageal motor activity as assessed by manometry from the same oesophageal site. Patients with different motor disorders of the oesophagus and control subjects were investigated. EMG recordings were made by means of a suction capsule with silver/silver chloride spike electrodes. Slow EMG waves synchronous with respiration were recorded from the lower oesophageal sphincter and intermittently from the body of the oesophagus. Edrophonium increased spike discharges; atropine diminished or abolished spike discharges after swallowing. Swallowing caused a burst of spiking activity which began immediately after deglutition. Continuous sips of water produced constant EMG activity but no peristaltic contractions as seen by manometry. In a patient with scleroderma and aperistalsis, swallowing elicited vigorous electrical activity. The different EMG findings without simultaneous contractions at manometry are interpreted as a response to a swallow by the longitudinal muscle of the oesophagus.

Animals↗
PubMed1979

Sagittal splitting of the mandibular ramus. Electromyography and radiologic follow-up study of temporomandibular joint function in 44 patients.

A follow-up study was performed on 44 patients operated with sagittal splitting of the mandibular ramus for correction of a mandibular protrusion. The study included clinical examination, electromyography and masticatory efficiency test as well as radiography of the temporomandibular joint. The maximum opening capacity and protrusion of the mandible decreased one to three years after the operation. The activity of the temporal muscle decreased in rest position after the operation. Masticatory efficiency was unchanged. The position of the condyle in the fossa was unchanged postoperatively, while a posterior and superior condylar movement occurred during the fixation period. Normalization of the condylar position tended to occur one year after the operation. In 37 of 86 condyles, a double contour was seen on the postesuperior margin of the condyle one year after the operation. Possible mechanism behind the development of the new condylar bone layer is discussed.

Electromyography↗
PubMed1992

Muscle performance, electromyography and fibre type composition in fibromyalgia and work-related myalgia.

Muscle performance and fibre type composition were investigated in women with fibromyalgia, work-related trapezius myalgia and healthy volunteers. Each subject performed 100 repetitive shoulder flexions using an isokinetic dynamometer during simultaneous registration of surface electromyography. A biopsy from the trapezius muscle was obtained. The groups differed neither in mechanical performance nor in fibre type proportions. An inability to relax between contractions was found in all registered muscles in patients with fibromyalgia. The patients with work-related myalgia displayed an inability to relax only in the myalgic trapezius muscle. An inability to relax during repetitive movements might play an important role both in initiating and upholding muscle pain.

Adult↗
PubMed1976

Orbicularis oculi reflex and facial muscle electromyography. Pre- and postoperative evaluation of posterior fossa space-occupying lesions.

The electrically evoked orbicularis oculi reflex was analyzed in 26 patients with proven posterior fossa space-occupying lesions (11 cerebellopontine angle and 15 cerebellar hemispheric masses). In the former group, although only six had clinical evidence of trigeminal or facial involvement, the reflex analysis showed both nerves to be involved in all. Electromyography (EMG) of the orbicularis oculi showed profound denervation of this muscle while only minimal abnormalities of the masseter were seen. The sensory component of the trigeminal nerve was always more involved than its motor component and this was a reliable guide as to the upward and medial extension of the tumor, especially in the absence of clinical localizing signs. In the 15 patients with cerebellar masses, six with masses located posteriorly and entirely within the confines of the cerebellum had normal studies. In eight, the mass was located anteriorly, and fifth nerve involvement could be detected in all by EMG, although only two patients had clinical evidence of such involvement. One patient with dysfunction of the central reflex arc had EMG evidence of an intraventricular dermoid tumor abutting the pons, later confirmed at surgery. Thus, an invaluable body of diagnostic and prognostic data can be obtained by this nontraumatic and simple electrodiagnostic procedure.

Brain Neoplasms↗
PubMed2000

Continuous electromyography monitoring of motor cranial nerves during cerebellopontine angle surgery.

OBJECT: Electromyography (EMG) monitoring is expected to reduce the incidence of motor cranial nerve deficits in cerebellopontine angle surgery. The aim of this study was to provide a detailed analysis of intraoperative EMG phenomena with respect to their surgical significance. METHODS: Using a system that continuously records facial and lower cranial nerve EMG signals during the entire operative procedure, the authors examined 30 patients undergoing surgery on acoustic neuroma (24 patients) or meningioma (six patients). Free-running EMG signals were recorded from muscles targeted by the facial, trigeminal, and lower cranial nerves, and were analyzed off-line with respect to waveform characteristics, frequencies, and amplitudes. Intraoperative measurements were correlated with typical surgical maneuvers and postoperative outcomes. Characteristic EMG discharges were obtained: spikes and bursts were recorded immediately following the direct manipulation of a dissecting instrument near the cranial nerve, but also during periods when the nerve had not yet been exposed. Bursts could be precisely attributed to contact activity. Three distinct types of trains were identified: A, B, and C trains. Whereas B and C trains are irrelevant with respect to postoperative outcome, the A train--a sinusoidal, symmetrical sequence of high-frequency and low-amplitude signals--was observed in 19 patients and could be well correlated with additional postoperative facial nerve paresis (in 18 patients). CONCLUSIONS: It could be demonstrated that the occurrence of A trains is a highly reliable predictor for postoperative facial palsy. Although some degree of functional worsening is to be expected postoperatively, there is a good chance of avoiding major deficits by warning the surgeon early. Continuous EMG monitoring is superior to electrical nerve stimulation or acoustic loudspeaker monitoring alone. The detailed analysis of EMG-waveform characteristics is able to provide more accurate warning criteria during surgery.

Adult↗
PubMed2006

Use of surface electromyography to assess and select patients with idiopathic dystonia for bilateral pallidal stimulation.

OBJECT: The object of this study was to identify a preoperative physiological index by using surface electromyography (EMG) signals that would correlate with clinical outcome in dystonic patients following bilateral pallidal stimulation. METHODS: In 14 patients with spasmodic torticollis, generalized dystonia, and myoclonic dystonia, surface EMG signals were recorded from the most affected muscle groups. Although the dystonia affected different body segments, the EMG signals in all patients could be decomposed into bursting and sustained components. Subsequently, a ratio of the EMG amplitude was calculated between the two components and then correlated with clinical outcome. Patients who experienced rapid improvement following bilateral pallidal stimulation had a significantly higher EMG ratio compared with those who did not. Furthermore, a significant correlation was found between the EMG ratio and clinical improvement during the 12-month period following pallidal stimulation. CONCLUSIONS: The authors concluded that surface EMG studies could be used to predict the clinical outcome of and to select patients for pallidal stimulation for dystonia.

Adult↗
PubMed2005

Palsies of the fifth cervical nerve root after cervical decompression: prevention using continuous intraoperative electromyography monitoring.

OBJECT: A desire to prevent complications resulting from spinal surgery led to the development of intraoperative monitoring. Intraoperative electromyography (EMG) provides useful diagnostic information regarding nerve root function during spinal and peripheral nerve surgeries. The C-5 nerve root is considered particularly vulnerable to injury during cervical surgery. Despite advances in techniques, the incidence of postoperative C-5 palsy has not changed. METHODS: The authors reviewed prospectively collected data obtained in 161 patients who underwent 171 cervical procedures. In 116 procedures, operative monitoring was modified to include continuous C-5 EMG from the deltoid muscle. In cases in which spontaneous C-5 activity occurred, an appropriate change in operative manipulation was made. A historical control group consisted of a retrospective review of 55 procedures that were monitored using conventional techniques. In the retrospective cohort, four (7.3%) of 55 patients presented after undergoing surgery for C-5 nerve root palsy. In each patient conventional monitoring revealed unremarkable findings. In the prospective cohort, intraoperative spontaneous EMG activity necessitated a change in either positioning or operative technique in three cases. Only one patient (0.9%) experienced postoperative C-5 palsy. Postoperative C-5 palsy occurred in no patient in whom there was no intra-operative evidence of root irritation (p < 0.03, chi-square test). CONCLUSIONS: The incidence of postoperative C-5 palsies was reduced from 7.3% to 0.9% due to intraoperative continuous EMG monitoring. No patient suffered a postoperative C-5 palsy when intraoperative evidence of root irritation was absent.

Case-Control Studies↗
PubMed2006

Muscle fatigue in women with primary biliary cirrhosis: Spectral analysis of surface electromyography.

AIM: To evaluate the myoelectric manifestations of peripheral fatigability in patients with primary biliary cirrhosis in comparison to healthy subjects. METHODS: Sixteen women with primary biliary cirrhosis without comorbidity and 13 healthy women matched for age and body mass index (BMI) completed the self-reported questionnaire fatigue impact scale. All subjects underwent surface electromyography assessment of peripheral fatigability. Anterior tibial muscle isometric voluntary contraction was executed for 20 s at 80% of maximal voluntary isometric contraction. During the exercise electromyographic signal series were recorded and root mean square (expression of central drive) as well as mean and median of electromyographic signal frequency spectrum (estimates of muscle fatigability) were computed. Each subject executed the trial two times. EMG parameters were normalized, then linear regression was applied and slopes were calculated. RESULTS: Seven patients were fatigued (median fatigue impact scale score: 38, range: 26-66) and 9 were not fatigued (median fatigue impact scale score: 7, range: 0-17). The maximal voluntary isometric contraction was similar in patients (82, 54-115 N) and controls (87, 74-101 N), and in patients with high (81, 54-115 N) and low fatigue impact scale scores (86, 65-106 N). Root mean square as well as mean and median of frequency spectrum slopes were compared with the Mann-Whitney U test, and no significant difference was found between fatigued and non-fatigued patients and controls. CONCLUSION: No instrumental evidence of peripheral fatigability can be found in women with primary biliary cirrhosis but no comorbidity, suggesting that fatigue in such patients may be of central origin.

Adult↗
PubMed1991

Dynamic electromyography in active and limited walking below-knee amputees.

Walking electromyography was performed in 12 below-knee amputees, who were amputated for peripheral vascular insufficiency. All were at least 1 year post-surgery and had no problems with the fit of their prostheses. Seven were community walkers and five were limited household ambulators. The quadriceps and hamstring muscles exhibited electrical activity during 60% and 64.7% of the gait cycle, respectively, in the active walkers, compared with 44.6% and 53.8% in the limited walkers. Quadriceps muscle activity was initiated almost 10% earlier in the active walkers, while hamstring muscle initiation was similar in both groups. The active walkers were able to maintain quadriceps and increase hamstring muscle activity to compensate for their absent ankle motors, while the limited walkers showed decreased activity in both muscle group. The results of this preliminary study suggest that the dysvascular limited walking below-knee amputee does not use the quadriceps and hamstring muscles for propulsion during walking, and does not appear to reap the benefits of knee joint preservation.

Aged↗
PubMed1983

Immediate effects of positioning devices on the normal and spastic hand measured by electromyography.

There is a continuing controversy in the literature and in clinical practice about whether positioning devices are effective in decreasing spasticity and, if so, which type is most effective. In this study, the immediate effects of a volar resting splint, a finger spreader, a firm cone, and no device were compared on eight normal and four hemiplegic subjects. Electromyography (EMG) was used to measure flexor muscle activity of the tested forearm while the subjects squeezed a grasp meter with the contralateral hand and during the following relaxation period. Results showed significantly greater EMG activity for the finger spreader compared to no device in the flexor carpi radialis of normal subjects during the grasping period. Hemiplegic subjects did not show significantly less EMG activity when using positioning devices compared to no device. In fact, the volar splint appeared to increase the EMG activity while the subjects were grasping.

Electromyography↗
PubMedDate not supplied

An electromyography study of wrist extension orthoses and upper-extremity function.

OBJECTIVE: This study examined the effect of commonly used long and short styles of commercially produced wrist extension orthoses on the activity of the proximal muscles of the shoulder and elbow and on wrist flexor and extensor muscle activity. METHOD: While 17 women between 22 and 40 years of age (M = 26.6) performed a specified movement wearing each of the two styles of orthosis and without an orthosis, their motor unit recruitment of five proximal joint muscle groups, wrist extensors, and wrist flexors was measured by surface electromyography. RESULTS: Motor unit recruitment was significantly greater in both orthosis conditions for four of five proximal muscles and for wrist flexors. There were no significant differences between the short and long orthosis conditions for proximal muscle groups. CONCLUSION: Wearing a wrist extension orthosis appears to place additional stress on the proximal joint musculature beyond that found without splint use. The study has implications for the prescription of wrist extension orthoses, especially for patients whose proximal joints are already compromised.

Adult↗
PubMed1992

[Clinical significance of urinary flow pattern--based on combined uroflowmetry and external sphincter electromyography].

We performed combined uroflowmetry and external sphincter electromyography in 108 patients (87 males and 21 females); 16 serving as normal controls, 49 with benign prostatic hyperplasia, 16 with overactive type of neurogenic bladder, 27 with underactive type of neurogenic bladder. Urinary flow pattern was classified into 5 categories. All of urinary flow patterns of normal controls showed pattern A which had the form of a bell. EMG showed complete suppression during micturition followed by a few intermittent increases in amplitude. Urinary flow patterns of BPH patients were distributed widely from pattern A to E. Intermittent increases in EMG amplitude during a late phase of micturition were characteristic in patients with BPH. We must pay attention to sex differences to evaluate urinary flow pattern because it could be influenced by abdominal pressure such as stressing or Créde maneuver in female patients with an underactive type of neurogenic bladder.

Adult↗
PubMed1993

[Quantitative electromyographic analysis of the external urethral sphincter using automatic decomposition electromyography on normal subjects].

Motor unit action potentials (MUPs) of the external urethral sphincter muscle during cystometry were analysed on six normal males. Electrodes were of concentric needle type having the exposed tip surface of 0.07 mm2, and the potential changes were analysed by automatic decomposition electromyography (ADEMG), for isolation and characterization of unit discharges. Number of analysed units was as follows: Two at rest, 4 at first desire to void, and 6 at maximum desire to void. Number of the recorded units and the firing rate were increased along with the degree of bladder filling. Average MUP figures as follows: Amplitude of 206 microV, 8.3 msec. duration, and 5.4 Hz firing rate at rest; 246 microV, 9.7 msec and 7.3 Hz at first desire to void; 277 microV. 9.7 msec and 7.2 Hz at maximum desire to void, respectively. It is concluded that external urethral sphincter maintains its urinary continence by excitation of the neuromuscular units, and by the increase in the firing rate of individual MUP during bladder filling.

Action Potentials↗
PubMed1999

Pelvic floor muscle surface electromyography. Reliability and clinical predictive validity.

OBJECTIVE: To study the reliability and clinical predictive validity of pelvic floor muscle surface electromyography (sEMG) for use in early detection and prophylaxis of urogynecologic disorders. STUDY DESIGN: Fifty-seven women ranging from 19 to 69 years of age completed a written questionnaire and underwent digital pelvic examination followed by pelvic floor muscle sEMG using an intravaginal sensor. Thirty-seven subjects underwent repeat evaluations one week or more later. RESULTS: sEMG data demonstrated significant test-retest reliability (P < .001) and significant clinical predictive validity (P < .05) for undifferentiated urinary incontinence, stress incontinence, urge incontinence, menstrual status and parity on both initial and repeat examinations. CONCLUSIONS: Pelvic floor muscle sEMG is reliable and consistently predictive of several important clinical status variables, suggesting that it can be a useful tool in early at-risk detection and prophylactic intervention for disorders of pelvic floor muscle laxity. Recent advances in sEMG technology make it cost-effective, convenient, noninvasive and easy to learn and administer by assisting staff. This technology is a powerful complementary tool for digital assessment of pelvic floor muscles and should be considered for use in gynecologic practice.

Adult↗
PubMedDate not supplied

[A comparative study of 2 methods of neuromuscular function monitoring, electromyography and acceleromyography, during anesthesia in children].

The responses of m. adductor pollici to TOF stimulation of the ulnar nerve were recorded by electromyography (EMG) and acceleromyography (AMG) in 36 children aged 2-12 years with ASA classes I-II during 36 planned surgeries. In 14 children myoplegia was attained by intravenous bolus and infusion atracurium (Tracrium) and in 22 by cisatracurium (nimbex). The data on the function of this muscle after the initial bolus injection of myoplegics do not provide reliable information on the function of the larynx and respiratory muscles during intubation and do not allow a conclusion on the possibility of endotracheal intubation. The threshold sensitivities of EMG and AMG recording of the neuromuscular function starting from the fifth minute after the myorelaxant injection till the end of anesthesia are different. EMG permits evaluating the recovery of neuromuscular conduction early after the infusion of myoplegics; complete recovery of the block is shown virtually simultaneously by AMG and EMG. EMG as a more accurate method is preferable for research, while AMG is a simpler and stable method, preferable for routine practice.

Age Factors↗
PubMed1999

[Prognostic value of preoperative electromyography for outcome of lumbosacral radiculopathy of discal origin].

OBJECTIVES: To assess the prognostic value of preoperative electromyography (EMG) for long-term outcome in patients who undergo surgery for discal radiculalgia at the lumbar level. PATIENTS AND METHODS: Thirty-seven patients who underwent surgery less than 6 weeks after the EMG were selected among a pool of 384 patients suffering from discal radiculalgia at the lumbar level who had had an EMG at our hospital since 1980. Among these 37 patients, 30 were contacted by telephone for an interview on outcome after a mean 42.1 +/- 22 month follow-up. RESULTS: Five out of 30 patients reported limitation for walking, 8/30 motor weakness, 14/30 had sensorial deficits, 12/30 had frequent or incapacitating radiculalgia, and 16/30 reported paresthesia. Patients were more satisfied with pain outcome (good or very good results in 22/30 patients (73%)) than with functional outcome (good or very good results in 20/30 patients (66%)). Preoperative EMG abnormalities (observed in 22/30 cases) were not correlated with patient age or duration of sciatica. The patients whose preoperative EMG was abnormal did not later report more paresthesia (11/20 versus 5/10) or severe radiculalgia (7/20 versus 5/10) than the others. Conversely, they complained more frequently of motor weakness (7/20 versus 1/10), but their global opinion about long-term outcome of surgery was not worse good or very good results for 15/20 patients with abnormal EMG (75%) versus 7/10 (70%) of those whose preoperative EMG was normal. CONCLUSION: This study shows that a normal EMG does not preclude surgical cure of discal sciatica. The results of preoperative EMG do not predict the long-term outcome after surgery: indeed they are only correlated with motor weakness (7/20 versus 1/10), but not with residual pain and functional outcome.

Adult↗