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PubMed2004

Laryngeal electromyography: technical features.

Laryngeal Electromyography (LEMG) is an auxiliary diagnostic method used for the comprehension and diagnosis of different neurological diseases that compromise laryngeal function. The most common LEMG technique is the percutaneous insertion of needle electrodes guided by surface anatomical references. We describe techniques for inserting needle electrodes into the tireoaritenoideus (TA), cricotireoideus (CT), cricoaritenoideus lateralis (CAL) and cricoaritenoideus posterioris (CAP) muscles; these are used at UNICAMP laryngology ambulatory, we discuss difficulties found and their proposed solutions. All patients were submitted to otorhinolaryngological, phonoaudiological and laryngeal endoscopy before LEMG. The CAP approach, by digital rotation of the thyroid cartilage was found to be the most difficult, followed by the CAL approach. TA and CT approaches gave no major problems, except with some older and obese patients. A significant complication of the TA approach via thyroid cartilage was a hematoma in one patient which partially obstructed the laryngeal lumen.

Adolescent↗
PubMed2004

[Single-fibre electromyography].

Single-fibre electromyography (SF-EMG) is the most sensitive electrophysiological test for myasthenia gravis and other neuromuscular junction pathology. It is also useful in the assessment of motor unit morphology in some neuromuscular diseases. A special needle with a 25 microm recording surface is used to record the time-locked potentials of 2 muscle fibers belonging to the same motor unit. Jitter is the variability in the arrival time of action potentials to the recording surface between consecutive discharges. The junctional part of the jitter depends on the amount of Ach released and on the sensitivity of the postsynaptic membrane and is related to the safety margin of neuromuscular transmission. Thus, SF-EMG can detect subclinical impairment of neuromuscular transmission, which cause an increased jitter. However, an increased jitter is not specific of neuromuscular transmission disorders, because it may be due to unstable conduction in motor nerves and muscle fibers. It is the extrajunctional part of the jitter. SFEMG is performed either during slight voluntary contraction (volitional SFEMG) or by axonal stimulation (stimulated SFEMG). Jitter is expressed as the mean of the absolute consecutive differences (MCD) of the latency between the time-locked potentials (volitional SFEMG) or from the stimulus to the negative peak of the potential (stimulated SFEMG). Recording is judged abnormal when more than 10% of the collected pairs are abnormal. On the other hand, single use coaxial needle electrodes which are cheaper could be an alternative for neuromuscular transmission analysis, because the jitter analysed with this type of needle was found highly comparable to that analysed with SF electrode. Moreover, jitter measurements coupled with fiber density estimates provide valuable information on the pathophysiology of the motor units in various neuromuscular disorders.

Electromyography↗
PubMed2004

[Surface electromyography procedure].

Surface electromyography (SEMG) is not yet able to substitute needle EMG for diagnosing neuromuscular diseases in our current clinical neurophysiological practice. Several research groups have been working to reach this goal. Thus, we already have available, though imperfect and open to criticism, tools to apply SEMG to follow-up studies of neuromuscular diseases. There are enough scientific data to integrate validated tools into EMG equipment, to provide recommended electrodes and developed techniques and methods for recording and analysing all SEMG components, so that we could study the suggested standardised parameters in our clinical routine context. Independently of the accuracy of clinical indications for the chosen methods, the requirements of sensitivity, specificity and reproducibility should be as substantial for ENG as for needle or surface EMG. They suppose an equal demanding procedure in doing exams and interpreting results. The respective contribution of ENG and needle or surface EMG is still to be confirmed. Respective value and limitations of the force measurements by manual or quantitative testing, functional scales, SEMG or motor unit number counting are not yet evaluated in follow-up studies of neuromuscular diseases.

Clinical Protocols↗
PubMedDate not supplied

Single fiber electromyography in normal subjects: reproducibility, variability, and technical considerations.

We performed 59 single fiber electromyography (SFEMG) examinations on 33 patients with spasmodic torticollis, but no other medical or neurological disorder. 14 patients were studied serially (3 examinations over 12 weeks). There was excessive jitter (greater than 55 microseconds) in 14 of 1180 fiber pairs (1.1%). 7 of the 14 abnormal fiber pairs were found at single sites (1 in 20 sites studied). Abnormal jitter occurred at more than 2 of 20 sites in only two patients, both of whom head increased fiber density and were more than 70 years of age. Of the 14 abnormal fibers, subtle technical problems were discovered in 4: bimodal jitter (1); borderline amplitude of single fiber potential (1); and borderline rise time (2). 6 of the 14 jittering potentials were part of a triplet or quadruplet. 4 fibers with increased jitter occurred in pairs and these were seen only in patients over 70. One patient with quiescent non-tropical sprue was excluded from consideration because of increased mean jitter before injection and confirmed during 2 subsequent studies. Therefore, SFEMG is a valid and reliable technique that must be strictly interpreted according to existing guidelines, with special consideration to studies in older patients. Abnormal jitter is rarely found in normal muscle, however, when found, it usually occurs as part of a triplet or multiplet.

Adult↗
PubMed2004

[Comprehensive prognostic value of spontaneous and evoked electromyography in laryngeal paralysis].

OBJECTIVE: To determine the comprehensive prognostic value of spontaneous and evoked electromyography (EMG) in laryngeal paralysis. METHODS: The characteristics of laryngeal EMG of 91 cases with unilateral vocal cord paralysis (VCP) after thyroid surgery were assessed. All cases were divided into four groups according to the interval of laryngeal EMG after onset, which were group one (2 months shorter, n = 13), group two (2 to 4 months, n = 23), group three (4 to 6 months, n = 36), group four (6 months longer, n = 19). The waveform morphology and the amplitude of laryngeal EMG and the highest evoked compound muscular active potential (CMAP) of thyroarytenoid muscles were examined and analyzed during voluntary tasks. The potential amplitude was showed by the percentage of that of the healthy lateral. The criterion of evaluation on evoked potential was attained by calculating statistical confidence interval. RESULTS: The highest evoked CMAP in group one was significantly lower than that of the others (P < 0.05), but no significant difference was observed between group two and group three (P > 0.05), so group two and group three were analyzed together. There were 2 recovered cases and 11 unrecovered cases in group one. On the basis of this criterion that a positive prognosis for laryngeal recovery was indicated when the evoked CMAP presented and there was no misdirect generated potential, correct prognostic rate was 92% (12/13). There were 11 recovered cases and 48 unrecovered cases in group two and three. The highest evoked CMAP was much higher in the recovered than in the unrecovered, significant difference was observed between them (P < 0.001). On the basis of the criterion that a positive prognosis for laryngeal recovery was indicated when the highest evoked CMAP was higher than 26. 4%, correct prognostic rate was 90% (53/59). On the basis of the criterion that a positive prognosis for laryngeal recovery was indicated when there was no misdirect generated potential and the highest evoked CMAP was higher than 26.4%, correct prognostic rate was 93% (55/59). When the interval from onset to laryngeal EMG recovering was longer than 6 months, none of these patients had return of vocal cord mobility whatever were the outcomes of laryngeal EMG. CONCLUSIONS: Correct prognostic rate can be improved if the prognosis of VCP in different courses is judged respectively by analyzing comprehensively spontaneous and evoked EMG.

Adult↗
PubMed2004

Laryngeal electromyography: contribution to vocal fold immobility diagnosis.

Laryngeal Electromyography (LEMG) is a diagnostic test commonly used in patients with vocal fold movement disorder. The aim of this study is to describe LEMG in patients with vocal fold immobility. A total of 55 dysphonic patients with vocal fold immobility diagnosed by laryngeal endoscopy were grouped according to probable clinical cause: 1) unknown; 2) traumatic; or 3) tumoral compression. They were submitted to LEMG by percutaneous insertion of concentric needle electrode. LEMG was conclusive in all patients and showed a majority with peripheral nerve injury. LEMG diagnosed peripheral nerve damage in 25 group 1, 12 group 2, and 11 group 3 patients. LEMG was normal in 4 patients, suggesting cricoarytenoid joint fixation. Central nervous system disorders was suggested in 2 and myopathic pattern in 1. As the major cause of vocal fold immobility is peripheral nerve damage, LEMG is an important test to confirm diagnosis.

Adolescent↗
PubMed2002

[The prognostic role of electromyography in vocal cord paralysis].

OBJECTIVE: To predict the recovery of vocal cord paralysis (VCP) by using electromyography (EMG). METHOD: The characteristics of EMG of 46 patients with unilateral VCP were assessed to determine the most useful factors in determining prognosis. The factors include the duration, amplitude, waveform morphology, root-mean-square, and time interval. RESULT: A positive prognosis for laryngeal recovery was indicated when the following EMG features were present in the immobile vocal fold during voluntary tasks if EMG was performed during 6 months of the onset of VCP: normal motor unit waveform morphology; no electrical silence. This predictive rate is 76%. When the root-mean-square value is greater than 26 microV, the predictive rate is 80%. On the basis of the criteria, all the prognostic rate is 84%. CONCLUSION: The results support the concept that EMG record is valuable in determining prognosis performed during 6 months of the onset of VCP.

Adult↗
PubMed2004

Single fiber electromyography in 78 patients with amyotrophic lateral sclerosis.

BACKGROUND: Single fiber electromyography (SFEMG) is a sensitive technique for detecting abnormalities in neuromuscular transmission and is mainly used in the diagnosis of neuromuscular junction disorders, such as myasthenia gravis. While the process of denervation-reinnervation in amyotrophic lateral sclerosis (ALS) can also result in immature collateral nerve terminals and instability of neuromuscular transmission, the purpose of this study was to investigate the changes and clinical values of SFEMG in patients with ALS. METHODS: Volitional SFEMG was performed on the extensor digitorum communis (EDC) of 78 patients with ALS (men 52, women 26) who had been previously diagnosed by history, clinical features, and neurophysiological studies. The mean jitter, the percentage of jitter >55 micros, the impulse blocking percentage, and fiber density (FD) were determined. These results were compared to normal controls. In addition, the SFEMG indices were analyzed for correlations with the duration of ALS, the EDC strength score on the Medical Research Council (MRC) scale, and spontaneous activity detected by EMG studies. RESULTS: SFEMG indices were abnormal in all patients with ALS. Mean jitter ranged from 30 to 178 micros (mean 80.2 micros); the percentage of jitter >55 micros ranged from 5% to 100% (mean 60.5%). In addition, the impulse blocking percentage ranged from 0% to 90% (mean 28.1%) and FD ranged from 1.4 to 4.1 (mean 2.6). Mean jitter, the percentage of jitter >55 micros, and the blocking percentage in 57 patients with definite or probable ALS were significantly higher than in patients with possible or suspected ALS. MRC scores of the EDC negatively correlated with mean jitter, the percentage of jitter >55 micros, blocking percentage, and FD. CONCLUSIONS: SFEMG is the most sensitive tool for diagnosing definite or probable ALS. Increased jitter, blocking percentage, and FD can indicate the degree of immature collateral sprouts and motor end plates resulting from the progressive denervation and reinnervation associated with ALS, and may be helpful in evaluating prognosis.

Adolescent↗
PubMed2005

Nonlinear analysis of electromyography time series as a diagnostic tool for low back pain.

BACKGROUND: A number of studies have evaluated lumbar spinal muscle fatigue using the electromyography (EMG) signal. However, back muscle fatigue studies do not consistently report endurance levels for patients with or without low back pain (LBP). In this case report, we investigated a nonlinear analysis of EMG time series that characterizes their complexity. MATERIAL/METHODS: A 37-year-old male with chronic LBP and an age- and gender-matched volunteer were compared. The endurance of the erector spinae muscle was determined using a modified version of the isometric Sorensen fatigue test. Nonlinear time series analysis techniques reveal the presence of long-range, power-law correlations. After checking that the signal was stationary, the original time series of 60,000 entries was reduced to 6000 entries by averaging over 10 consecutive entries. RESULTS: There was a difference between the entropy time dependence exhibited by entropy time dependence exhibited by the healthy subject and the LBP subject. The entropy associated with the LBP subject saturates at very short-times--two orders of magnitude shorter than for the healthy subject. CONCLUSIONS: The characterization of the nonlinear time series in this case study provides a consistent measure of back muscle activities. It is important to understand the potential limitations before undertaking an EMG analysis in the field of ergonomics or biomechanics. Further studies are needed to investigate the characteristics of back muscles.

Adult↗
PubMed2004

[Surface electromyography signal classification using gray system theory].

A new method based on gray correlation was introduced to improve the identification rate in artificial limb. The electromyography (EMG) signal was first transformed into time-frequency domain by wavelet transform. Singular value decomposition (SVD) was then used to extract feature vector from the wavelet coefficient for pattern recognition. The decision was made according to the maximum gray correlation coefficient. Compared with neural network recognition, this robust method has an almost equivalent recognition rate but much lower computation costs and less training samples.

Electromyography↗
PubMed2004

[Analysis of surface electromyography on repetitive lifting task-induced fatigue of back muscles].

OBJECTIVE: Using surface electromyography (SEMG) technique to evaluate repetitive lifting task-induced fatigue of back muscles. METHODS: Thirteen volunteers lifted and lowered an 8 kg weight from floor to waist level for 100 times. Fatigue in the erector spinae muscles was quantified by comparing the frequency content of the EMG signal during static contractions performed before, and immediately after the 100 lifts. RESULTS: EMG average amplitude rose gradually during 100 lifts, the difference was significant at T10 right (P < 0.05) and L3 left (P < 0.01), the difference was not significant at T10 left and L3 right (P > 0.05). The median frequency intercept at T10 right, T10 left, L3 right, L3 left erector spinae muscles decreased by 2.0% (P > 0.05) 10.9% and 29.9% (P < 0.05), 27.9% (P < 0.01), respectively. The mean power frequency intercept decreased by 9% at L3 left erector spinae muscle (P < 0.05), the decrease was not statistically significant at other sites (P > 0.05). CONCLUSION: Repetitive lifting may induce measurable fatigue in the erector spinae muscles. Erector spinae muscle at L3 is more easily fatigued than at T10. Using the median frequency intercept to assess muscle fatigue is more sensitive than using mean power frequency intercept.

Adult↗
PubMed2005

Feasibility of electromyography-triggered neuromuscular stimulation as an adjunct to constraint-induced movement therapy.

BACKGROUND AND PURPOSE: The purpose of this case report is to explore the feasibility of electromyography-triggered neuromuscular stimulation (EMG-stim) as an adjunct to constraint-induced movement therapy (CIMT). CASE DESCRIPTION: The patient was a 72-year-old man, 10 years poststroke, who did not meet traditional CIMT criteria. The EMG-stim was applied to the wrist extensors of the patient's weaker arm for one half of the CIMT training hours. OUTCOMES: The intervention was feasible for this individual. Improvements were observed in motor behavior, quality and amount of use, muscle activity, wrist range of motion, and reaction time of the more-affected extremity. These improvements were paralleled by a change in the size and location of the extensor digitorum communis muscle representation in the primary motor cortex, as measured by transcranial magnetic stimulation mapping. DISCUSSION: These changes suggest that using EMG-stim as an adjunct to CIMT should be further investigated in individuals who have low functional abilities following stroke.

Aged↗
PubMed2005

[Diagnostic value of needle electromyography in patients with occupational polyneuropathy caused by vibration and functional overstrain].

The authors determined diagnostic and differential value of needle electromyography in workers with occupational diseases of upper limbs. Results prove differences in neuromotor disorders of hands: vibration disease usually involves spinal motoneurons, whereas functional overstrain is characterised by marked muscular suffering (myopathy, myodystrophy).

Adult↗
PubMedDate not supplied

Nerve conduction study, electromyography and somatosensory evoked potentials in non-Friedreich early onset cerebellar ataxia. A comparative study with Friedreich's ataxia and late onset cerebellar ataxia.

Electrophysiological findings in 14 patients with non-Friedreich early onset cerebellar ataxia are reported. Nerve conduction studies showed reduction of sensory action potential amplitudes in 7 cases associated in 3 with a decrease of sensory conduction velocities. Six subjects also exhibited a chronic neurogenic pattern to standard needle electromyography. Motor conduction velocities were normal in all cases; only two cases showed an increase in distal motor latencies. Short-latency somatosensory evoked potentials following median nerve stimulation revealed a prolonged central conduction time (N13-N20 interpeak latency) in 7 cases, compatible with supraspinal damage of the somatosensory pathways. These electrophysiological data are compared with those obtained in two reference groups of patients, respectively affected by Friedreich's ataxia and olivo-ponto-cerebellar atrophy.

Action Potentials↗
PubMed2005

Tensor veli palatini electromyography with surface electrode applied transnasally.

A new technique is proposed for paratubal electromyography, using a surface, non-invasive, electrode applied transnasally under nasopharyngoscope guidance. This electrode records activity of the tensor veli palatini muscle during swallowing. This technique is of interest for two reasons: endoscopic guidance offers the possibility to check correct positioning of the electrode recording at tensor veli palatini muscle level. Introduction of the non-invasive surface electrode is simple and not painful.

Electrodes↗
PubMedDate not supplied

Chaotic analysis of electromyography signal at low back and lower limb muscles during forward bending posture.

The present study aims to perform further investigation on muscular activity during forward bending posture by applying a nonlinear dynamic (chaotic) analysis method. The objective is to determine the characteristics of the low back and lower limb muscle electromyography (EMG) signal under chaotic analysis while maintaining a certain posture. Twelve subjects were asked to maintain postures of six stages in bending angles from 0 to 180 degrees, and the EMG signals of erector spinae (ES) at L1 and L5 levels, hamstrings, and gastrocnemius were recorded. Two important concepts to characterize deterministic chaos, Correlation Dimension (D2) and Lyapunov Exponents (lambda, LE), were applied to observe the chaotic characteristic of the EMG signals, and the results were also compared to the FFT based total power value. The EMG signals in all observed muscles during bending posture showed results of positive LE and high D2 at 5.5 to 7.5, which led us to classify EMG as a high dimension chaotic signal. The result obtained showed that the correlation dimension could be used as a reliable method to compare the EMG signal in various postures (or muscle contraction conditions). However, Lyapunov exponents did not show a significant difference of comparison result thus leading to the conclusion that LE could not be a reliable measure for high dimension chaotic system, such as an EMG signal. It was also shown that in both light and deep bending, the EMG signal of the low back muscles was of the same complexity level due to the D2 result. It was evident that somehow the low back muscle remained loaded in all bending stages which was contrary to the hypothesis that the low back muscle was less active during the deep bending, as was the case in most of the previous studies. The reason of such phenomenon was elucidated with use of the theory of muscular functional differentiation, including corticalization and spinalization.

Adult↗
PubMed2006

[Characteristics of surface electromyography and work load of the forearm extensors in repetitive wrist extending].

OBJECTIVE: To evaluate the influence of the frequency, the weight and the motion angle on the stress and the fatigue of the forearm extensors in repetitive wrist extending at low force loading level with surface electromyography (SEMG). METHODS: Sixteen male college student volunteers were recruited for the experiment. Eight tasks of wrist extending were performed for 20 minutes respectively in given weight (1.96, 4.90 N), frequency (8.0, 33.3 moves/minute) and motion angle (45 degrees, 90 degrees). The static wrist extending at the level of 20% maximum voluntary contraction (MVC) were performed before and after each task for 2 up to 3 seconds, and the SEMG signals of extensor carpi ulnaris muscle (ECU) and extensor digitorum (ED) were recorded and analyzed. RESULTS: The weight loading level was approximately equal to 1.40% or 3.50% of the MVC force. The mean power frequency (MPF) and the median frequency (MF) were decreased with the increase of 3 kinds of loading levels. The decrease of MPF of the muscle ED was significant (P < 0.05 or P < 0.01). The MF was decreased with the increase of angle and weight loading levels (P < 0.05 or P < 0.01). The root mean square (RMS) value of SEMG could be divided into 3 or 4 groups with significant difference. All three kinds of loads had positive correlation with amplitude of SEMG according to the stepwise regression analysis. CONCLUSION: The fatigue level of ED is the highest. The primary load factor for the forearm extensors is the frequency followed by the weight and the angle. MF, MPF and RMS can be used as sensitive indexes for evaluating the stress and the fatigue of the forearm extensors during repetitive performance at lower force loading level.

Adolescent↗
PubMed2006

[Mechanism of post-stroke reflex sympathetic dystrophy: study with needle electromyography].

OBJECTIVE: To explore the mechanism of post-stroke reflex sympathetic dystrophy (RSD) patients electromyographic abnormality and confirm its clinical value. METHODS: Fifty patients with first-onset stroke, aged 33 - 78, including 30 with RSD and 20 without RSD, underwent needle electromyography (EMG) to test the nerve conduction velocity (NCV) and sensory nerve conduction velocity (SCV) of bilateral median nerves, and the number and position of spontaneous EMG activity of bilateral short abductor muscles of thumb and abductor muscles little finger. RESULTS: The median nerve compound muscle action potential (CMAP) amplitude of the affected upper extremities of the RSD group was 8.6 mV +/- 2.9 mV, significantly lower than that of the non-RSD group (13.2 mV +/- 4.6 mV, P < 0.01). The incidence of spontaneous electrical potential of the RSD group was 100%; significantly higher than hat of the non-RSD group (65%, P < 0.001). The quantity of spontaneous EMG activity on the short abductor muscles of thumb and abductor muscles little finger was increased in the RSD group (P < 0.01). The motor nerve conduction velocity and electrophysiological presentation of sensory nerve of these 2 groups were all normal and without significant differences between them. CONCLUSION: Partial axonal degeneration occurs on the distal motor never fibers of the affected upper extremity of the RSD patients, which may be related to subsequent peripheral nerve injury after central nerve system impairment.

Adult↗