Application of a novel automatic duration method measurement based on the wavelet transform on pathological motor unit action potentials

ObjectiveTo evaluate a recently published automatic duration method based on the wavelet transform applied on normal and pathological motor unit action potentials (MUAPs).MethodsWe analyzed 313 EMG recordings from normal and pathological muscles during slight contractions. After the extraction procedure, 339 potentials were accepted for analysis: 68 from normal muscles, 124 from myopathic muscles, 20 from chronic neurogenic muscles, 83 from subacute neurogenic muscles and also 44 fibrillation potentials, as an example of very low duration muscular potentials. A “gold standard” of the duration positions (GSP) was obtained for each MUAP from the manual measurements of two senior electromyographists. The results of the novel method were compared to five well-known conventional automatic methods (CAMs). To compare the six methods, the differences between the automatic marker positions and the GSP for the start and end markers were calculated. Then, for the different groups of normal and pathological MUAPs, we applied: a one-factor ANOVA to compare their relative mean differences, the estimated mean square error (EMSE) and a Chi-square test about the rate of automatic marker placements with differences to the GSP greater than 5 ms, taken as gross errors.ResultsThe mean and the standard deviation of the differences, the EMSE and the gross errors for the novel method were smaller than those observed with the CAMs in the five different MUAP groups and significantly different in most of the cases.ConclusionsThe novel automatic duration method is more accurate than other available algorithms in normal and pathological MUAPs.SignificanceAccurate MUAP duration automatic measurement is an important issue in daily clinical practice.     

Signs of aging of the peripheral motor neurons based on electromyographic studies

Sixty healthy subjects of either sex aged from 15 to 75 years were examined. Electromyographic records were obtained by the one-step automatic histogram analysis method according to Hausmanowa-Petrusewicz and Kope?, and by the classic method of quantitative electromyography. In each case 4 muscles were examined: deltoid (Dlt), rectus m. of thigh (RF), short abducens m. of thumb (APB), short extensor of fingers (EDB). In both methods the mean duration of motor unit potential, the amplitude of single motor unit potential, the amplitude of effort record and the density of potentials were determined and correlated with age. The duration of motor unit potentials in the classic EMG record was correlated statistically significantly with the age in all muscles (in agreement with Buchthal). The number of parameters correlating with age and the significance of this correlation were highest in the records from lower extremity muscles, particularly in EDB. This could depend on age-related summation of subclinical signs of peroneal nerve damage, since this nerve is exposed to frequent microtraumas. However, in 4 examined healthy muscles the intensity of changes in EMG parameters correlating significantly with age seems to be related to the length of the muscles innervating them, and to the processes of ageing of the neuromuscular apparatus and blood vessels supplying it. Extensor muscle (EDB) innervated by motor neurons with longest axons may be the most sensitive indicator of the processes of ageing of peripheral motor neurons.     

多发性肌炎患者神经电生理特点分析

目的增进对多发性肌炎患者肌电图特点的认识,提高其检查的阳性率。方法对91例多发性肌炎患者进行肌电图(EMG)、神经传导速度测定。结果肌电图异常率为87.9%,肌源性损害者占79.1%,神经源性损害者占8.8%。其中插入电位延长、自发电位的阳性率分别为6%和52%,肱二头肌出现率较高,外展拇短肌出现率最低(p<0.05);运动单位电位(MUP)时限缩短的阳性率为71%,胫前肌出现率最高,外展拇短肌最低(p<0.05);MUP波幅降低的阳性率较低,仅为7%;多相波增多的阳性率为29%,胫前肌出现率最高,股四头肌最低(p<0.05);重收缩时波形异常的阳性率为26%,以股四头肌出现率最高;重收缩时峰值电压降低的阳性率为31%,胫前肌出现率最高,外展拇短肌最低(均p<0.05)。5例患者EMG呈神经源性损害,1例感觉神经传导速度减慢,2例运动神经传导速度减慢。肌电图正常组、肌源性损害组及神经源性损害组患者的病程、年龄无明显差异。结论 EMG对多发性肌炎诊断的阳性率为87.9%,其中以MUP时限缩短出现率最高为71%,其次为自发电位为52%。EMG异常最多见于肱二头肌、股四头肌和胫前肌。     

Turns amplitude analysis of the orbicularis oculi and oris muscles.

OBJECTIVE: The aim of the study was to determine whether 'clouds' from turns amplitude analysis obtained from the orbicularis oculi and oris muscles without force monitoring can be used to differentiate pathological processes affecting the face. METHODS: The interference pattern from orbicularis oculi and orbicularis oris was studied using a concentric needle electrode. Data-points from 20 normal subjects were plotted on a logarithmic scale of mean amplitude between turns versus turns/second, from which linear regression analysis defined the 95% confidence intervals. This enabled us to draw the boundaries of the normal cloud on a linear plot. Data-points from the interference pattern in two pathological cohorts, of 6 patients receiving botulinum toxin injections (representing a neurogenic model), and 6 patients with a muscle dystrophy (representing a myopathic model) were plotted against the normal cloud. These findings were compared and correlated with the mean durations obtained on motor unit action potential analysis from these same two facial muscles. RESULTS: The majority of patients receiving botulinum toxin injections into their facial muscles showed a pattern of high amplitude with low turns/s, or low amplitude with a low-to-normal range of turns/s in both facial muscles. These findings were associated with high-duration motor unit action potentials in most cases. In the myopathic group of patients 66% showed a pattern of low amplitude with low-to-normal range of turns/s in O oculi and O oris. This correlated with short-duration motor unit action potentials in both facial muscles. CONCLUSIONS: We have demonstrated that turns amplitude analysis without force monitoring can be used to study the interference pattern from facial muscles and can be applied to differentiate primary neurogenic from myopathic pathological processes. SIGNIFICANCE: Turns amplitude analysis without force monitoring in the facial muscles can be used as an effective and practical method of interference pattern analysis to complement findings from conventional motor unit action potential analysis.     

Electromyography and histopathology of muscle and spinal cord: Analysis of 105 skeletal muscles from 31 autopsy cases

The subject of our studies included 105 muscles from 31 cases; all cases had been subjected to detailed electromyographic examination before death, and histological studies could be made on the whole of the muscles and the spinal cords corresponding to them at autopsy. Histochemical methods were not applied. The diagnostic significance of EMG and muscle biopsy was investigated by making a comparison between the findings obtained by EMG and histological findings in muscles and spinal cords. The results are as follows:

1.

(1) All 25 muscles that were histologically found to contain groups of small fibres showed neurogenic changes in the EMG. However, among the muscles showing neurogenic changes in the EMG, some had no distinctly discernible groups of small fibres and contained only muscle fibres of different sizes, or scattered small fibres. These pathological findings in muscle could also be interpreted as neurogenic because the anterior horn cells of the corresponding spinal segments showed some morbid changes.     

Quantitative EMG of facial muscles in myasthenia patients with MuSK antibodies.

OBJECTIVE: Our aim was to study the pathophysiological process leading to facial muscle atrophy in 13 patients with MuSK antibody positive myasthenia gravis (MuSK-MG), and to compare with findings from 12 acetylcholine receptor antibody positive myasthenia patients (AChR-MG), selected because they suffered from the same degree of disease severity and required similar treatment. METHODS: Motor unit action potential (MUAP) and interference pattern analysis from orbicularis oculi (O oculi) and orbicularis oris (O oris) muscles were studied using a concentric needle electrode, and compared with findings in 20 normal subjects, 6 patients receiving botulinum toxin injections (representing a neurogenic model) and 6 patients with a muscle dystrophy (representing a myopathic model). The techniques and control data have been reported previously. RESULTS: The mean MUAP durations for O oculi and O oris were significantly reduced (p<0.001) in both MG cohorts when compared with healthy subjects, and were similar to those in the myopathic control group. They were significantly different from those obtained from the neurogenic control group (p<0.001 for both O oculi and O oris). The MUAP findings in O oculi occurred independently from neuromuscular blocking on single fibre EMG (SFEMG) in the same muscle. On turns amplitude analysis (TAA), 50% of MuSK-MG patients and 42% of AChR-MG patients had a pattern in O oculi which was similar to that in the myopathic control group, and 62% of MuSK-MG patients and 50% of AChR-MG patients had a pattern in O oris that was also similar to that in the myopathic control group. The TAA findings for O oculi and O oris in both MG cohorts were different from those obtained from the neurogenic control group. CONCLUSIONS: Facial muscle atrophy in MuSK-MG patients is not neurogenic and the pathophysiological changes are akin to a myopathic process. The selected AChR-MG patients also show evidence of a similar pathophysiological process in the facial muscles albeit to a lesser degree. SIGNIFICANCE: We propose that muscle atrophy in MuSK-MG is a myopathic process consisting of either muscle fibre shrinkage or loss of muscle fibres from motor units. The duration of disease and long-term steroid treatment may be further contributory factors.     

Scanning EMG in normal muscle and in neuromuscular disorders.

The spatial distribution of motor units in normal subjects and in patients with neurogenic and myogenic conditions was studied. The possibilities and the difficulties in quantifying the records are discussed. Normal values are presented for the brachial biceps and anterior tibial muscles. The results are compared to the previous multielectrode studies. The findings in pathological conditions compared to normals are evaluated. The scanning EMG verified the rearrangement of muscle fibres in abnormal muscles. The most striking finding was the presence of long polyphasic sections in abnormal muscles. However, this parameter did not differentiate neurogenic from myogenic cases. The length of the motor unit cross-section did not differ significantly in the abnormal muscles compared to normal. Thus, the size of motor unit territory does not seem to be a useful parameter to detect pathology. Scanning EMG gives a new dimension to exploring the motor unit characteristics not attainable by conventional methods and provides important information towards a better understanding of concentric needle EMG. Examples are shown from healthy subjects and from patients with neuromuscular diseases, both for the different parameters and special phenomena.     

Fibre density,amplitudes of macro-EMG motor unit potentials and conventional EMG recordings from the anterior tibial muscle in patients with amyotrophic lateral sclerosis

Summary Fibre density and amplitudes of macro-EMG motor unit potentials were studied and compared with conventional EMG in the anterior tibial muscles from 51 patients with amyotrophic lateral sclerosis. The fibre density was increased in 46 muscles. Increased amplitudes of macro-EMG motor unit action potentials were found in 46 muscles, while the mean duration of motor unit potentials recorded with a concentric needle electrode was prolonged in only 26 muscles. Changes in the packing density of muscle fibres of surviving motor units are thought to influence the different electrophysiological parameters in different ways.     

Turns-amplitude analysis at different sampling frequencies.

In the EMG interference pattern the number of potential reversals of more than 100 microV (i.e., turns) measured may be low if a low sampling frequency is used. This might be more pronounced in a myopathic muscle with small short potentials than in a control muscle, resulting in a decreased diagnostic yield. The influence of sampling frequencies from 6 to 200 kHz on the turns, mean amplitude and ratio of turns to mean amplitude analysed on the interference pattern at a force of 30% of maximum was examined at 10 sites in each of 5 control muscles, 5 myopathic muscles and 5 neurogenic muscles (i.e., 150 sites in all). In this small group of muscles low sampling frequency did not tend to reduce the diagnostic yield of the measurements. Proper reproducibility was obtained with sampling frequencies down to 17 kHz. However, due to systematic errors, measurements obtained with sampling frequencies below 25 kHz require comparable control values or compensations for errors. As time intervals between turns (not studied here) have a skew distribution with many small time intervals a sampling frequency of 50 kHz or higher is probably required.     

The "Functional -QEMG" method -- a substantial progress in electromyography (EMG)

In contradistinction to the traditional quantitative EMG, our new "Functional-QEMG" method provides new information about structural and functional changes in the whole population of active motor units (MUs) in various neuromuscular disorders. Individual motor unit action potentials (MUAPs) and the interference pattern (IP) recordings are analyzed not as complementary measurements but as one integral test. Such a complex of EMG signals is submitted to a non-linear dynamic analysis determining interrelationships between an active MU size and its functional properties. Structural changes in MU size represent the primary destructive process, while the resulting changes in MU functional properties due to a compensatory mechanism (a secondary restorative process) provide new and very useful diagnostic information. All EMG data are processed online and automatically classified by a special computer-assisted diagnostic program as either a normal or pathological (myogenic or neurogenic) EMG recording. At the same time severity of muscle damage is assessed. This article illustrates how both the efficacy and limitations of compensatory mechanisms are related to structural damage in various neuromuscular disorders. The "Functional-QEMG" method application in clinical practice for over ten years has evidenced that this new approach is a turning point in improving the EMG diagnosis. This automatic method provides online reliable answers to most of the questions facing an electromyographer in daily routine investigations.     

Muscle velocity recovery cycles in neurogenic muscles

ObjectiveTo examine muscle membrane properties in neurogenic muscles using Muscle Velocity Recovery Cycles (MVRCs).MethodsForty-seven patients referred to Nerve Conduction Studies (NCS) and Electromyography (EMG) for peroneal nerve entrapment neuropathy were prospectively included. The patients were categorized as peroneal nerve entrapment neuropathy across knee (n = 22), L5-radiculapathy (n = 10), normal NCS/EMG (n = 9) and other disorders (n = 6) using NCS/EMG and neuroimaging results. Strength in anterior tibial muscle was measured by Medical Council Scale (MRC) and disease duration was recorded. In addition to conventional NCS/EMG, all subjects were examined with MVRCs in anterior tibial muscle. This provided parameters of muscle relative refractory period (MRRP) and early supernormality (ESN) and late supernormality (LSN). The results were compared with 29 age-matched healthy control subjects.ResultsMRRP was prolonged and ESN and LSN were reduced in neurogenic muscles. MRRP, ESN and LSN correlated to MRC and incidence of spontaneous activity but not to motor unit potential parameters or disease duration.ConclusionsMVRC changes provide in vivo evidence of depolarization in intact human muscle fibres that could underlie reduced muscle excitability and hence weakness in neurogenic muscles.SignificanceMVRCs appear to be a useful technique for revealing disease mechanism in a broad range of neuromuscular diseases.     

Evaluation of an automated method for analysing the electromyogram.

An automated system, incorporating the ANOPS-101 mini-computer, has been used to analyse the EMG. The vastus medialis (VM) and biceps brachii (BB) muscles were studied in 28 controls, 16 patients with myopathies, and in 26 patients with denervating disorders. For each muscle mean values were computed for the durations and numbers of phases of muscle action potentials; the mean density and amplitude of the deflections in the interference pattern were also measured. A higher incidence of abnormalities could be detected in myopathic than in neuropathic disorders; for both conditions the incidence was significantly greater in BB than in VM. For the diagnosis of denervation the most useful measurement was that of potential duration; for the detection of myopathies amplitude determinations were also very useful. The present results have been compared with those of other published studies in which automatic EMG analysis has been employed.     

Quantitative electromyography of the external anal sphincter in Parkinson's disease and multiple system atrophy

The distinction of multiple system atrophy (MSA) from Parkinson's disease (PD) can be difficult, especially early in the disease. In MSA degeneration of sacral anterior horn cells (Onuf's nucleus) results in denervation-reinnervation of anal and urethral sphincter muscles, which can be recognized as neurogenic electromyographic (EMG) changes of motor unit potentials. Sphincter EMG has therefore been recommended as a test for distinguishing MSA from PD. Our results confirm the presence of marked neurogenic EMG changes of the external anal sphincter muscle in patients with probable MSA compared to healthy controls. However, in patients with probable PD, our quantitative EMG data show a scatter from normal to marked neurogenic changes and the degree of EMG abnormality is correlated to the duration of the disease. Thus an abnormal sphincter EMG cannot be taken as a strong indicator of MSA rather than PD in the individual patient, especially in long-standing cases.     

EMG power spectrum, turns-amplitude analysis and motor unit potential duration in neuromuscular disorders

The diagnostic value of power spectrum analysis of the needle EMG pattern at a force of 30% of maximum was compared to that of turns-amplitude analysis and to that of manual measurements of motor unit potential (MUP) duration in the brachial biceps muscle of 20 patients with myopathy and 11 patients with neurogenic disorders. In myopathy the power spectrum analysis had the same diagnostic value as the turns-amplitude analysis and MUP duration measurements and the 3 methods supplemented each other. In patients with neurogenic disorders the diagnostic value of the power spectrum analysis as well as that of the turns-amplitude analysis were lesser than that of MUP duration measurement. In diseased muscles the amount of high frequencies increased with increasing ratio of turns to mean amplitude while there was no relation between the power spectrum and the MUP changes. The results suggest that the power spectrum analysis of EMG can be used as a diagnostic tool in patients with neuromuscular disorders.     

Standardization of anal sphincter electromyography: normative data.

OBJECTIVES: Electromyography (EMG) of the external anal sphincter (EAS) is important in the evaluation of conus/cauda lesions, the differential diagnosis of parkinsonism and anal incontinence. The aim of our study was to establish normative data in a sufficiently large group of healthy subjects, using a rigorously standardized examination technique. METHODS: Sixty-four subjects (aged 19-83 years) without pelvic or neurological disorders were included. Motor unit potentials (MUPs)/interference pattern (IP) samples were obtained from the EAS using multi-MUP and turn/amplitude analyses, respectively. The effect of age, gender, parity, and constipation on MUP/IP parameters was studied. For MUP parameters the lower/upper limits for mean values, and 'outlier' limits, and for IP parameters normal 'clouds' were calculated. RESULTS: From 112 muscles 15-30 MUPs were sampled. As no effect of evaluated factors on mean values could be demonstrated, common reference values were calculated. Lower/higher limits for mean values were: amplitude 148/661 microV, duration 3.2/7.8 ms, area 87/625 microVms, and number of phases 2. 3/3.7. 'Outlier' limits for individual MUPs were: amplitude 84/1315 microV, duration 1.6/13.8 ms, area 46/1222 microVms, number of phases 2/6. From 95 muscles 2706 IP samples were obtained. CONCLUSIONS: The presented normative data should allow valid quantitative EMG of the EAS muscle in patients.     

Normal and myopathic propagation of surface motor unit action potentials

With the aid of a computer-assisted multichannel EMG system, the propagation of motor unit action potentials is analysed during isometric voluntary muscular contraction under normal and myopathic conditions. A linear array of 30 surface electrodes is fixed above the biceps brachii muscle, parallel to the longitudinal muscle axis and centered over the end-plate zone. The EMG is simultaneously recorded on all channels and displays the propagation of surface potentials on both sides of the innervation band. The mean muscle fibre conduction velocity is computed by a cross-correlation technique. Five adult patients in a late stage of progressive muscular dystrophy show a highly altered propagation behaviour of motor unit action potentials without a time shift between potentials of adjacent electrodes. A mathematical model is described which predicts such a behaviour and suggests that it must be due to a pathological longitudinal spread of end-plates in this patient group. In 5 boys with Duchenne muscular dystrophy and only moderate impairment of the biceps muscle the mean muscle fibre velocity was reduced (2.81 +/- 0.34 m/sec) compared to 17 healthy subjects (4.42 +/- 0.37 m/sec). Each myopathic patient examined could be separated clearly from the group of healthy subjects on the basis of the surface EMG analysis.     

A case of type 1 muscle fibre hypotrophy and internal nuclei.

A 14 year old boy was diagnosed as suffering from type 1 muscle fibre hypotrophy with internal nuclei. On histological examination of a biopsied muscle, there was selective hypotrophy of type 1 muscle fibre with internal nuclei, and focal degenerative changes were seen in a few type 1 fibres. The small type 1 fibres were arranged in small or large groups in one bundle. An EMG study of moderately weak muscles revealed low amplitude and short duration motor unit potentials as well as normal potentials and no spontaneous discharges. The H reflexes were abnormally low in amplitude comapred with the M response. The histological and electrophysiological findings suggested that the type 1 fibre involvement in the present case may have a neurogenic basis. It is likely that the clinical features of the reported cases are too variable for a single clinical entity.     

An analysis of mandibular movement trajectories and masticatory muscle EMG activity during drinking in the guinea pig

Electromyographic (EMG) activity of the anterior digastric, lateral pterygoid, and deep masseter muscles as well as the associated jaw movements during drinking were studied in the awake guinea pig. Drinking was characterized by rhythmic, vertically directed jaw movements with little or no associated lateral movements. The jaw opening phase of each cycle was associated with bilaterally synchronized EMG activity in the digastric and lateral pterygoid muscles, and the jaw closing phase with bilaterally synchronized activity in the masseter muscles. The mean EMG burst durations (+/- 1 S.E.) in the digastric and masseter muscles were 164.2 +/- 14.93 ms and 94.3 +/- 26.44 ms, respectively. The digastric muscle EMG burst duration was significantly correlated with drinking cycle time and with masseter muscle EMG onset; on the other hand, masseter muscle EMG burst duration was not correlated with cycle time. These patterns of EMG activity and jaw movement trajectories are similar to those induced by apomorphine in the ketamine-anesthetized guinea pig.     

Diagnostic yield of the analysis of the pattern of electrical activity of muscle and of individual motor unit potentials in neurogenic involvement.

The pattern of electrical activity and the properties of individual motor unit potentials were analysed in the flexor muscles of the forearm of 15 patients with motor neurone disease and 15 patients with a lesion of the brachial plexus. The best diagnostic yield from the pattern of electrical activity was obtained when the force was 30% of maximum: The number of spikes (turns/15 s) was diminished in 70% of the patients; none showed the increase in turns characteristic of myopathy. The decrease in the number of turns was often associated with an increased incidence of long time intervals between turns and with an increased amplitude between turns. The mean duration of individual motor unit potentials was prolonged in 78% of the patients; none showed the decrease in mean duration characteristic of myopathy. Prolongation of the mean duration of motor unit potentials produced by cooling of normal muscle, led to a decrease in the number of turns. This suggested that the diminished number of turns in neurogenic involvement was due mainly to the prolonged duration of motor unit potentials.     

肌萎缩侧索硬化症152例下胸段脊旁肌肌电图特点

目的探讨下胸段脊旁肌肌电图在肌萎缩侧索硬化症(ALS)诊断中的应用价值。方法总结152例确诊ALS患者的临床及电生理资料,观察下胸段脊旁肌肌电图的特点,并分析其与病程、年龄、首发部位、呼吸困难、胸锁乳突肌肌电图、舌肌肌电图的相关性。结果152例ALS中,下胸段脊旁肌肌电图出现自发电位者125例(82．24%)；胸锁乳突肌肌电图呈神经源性损害83例(55．33%),其中出现自发电位者45例。通过Logistic多元回归分析提示脊旁肌肌电图与病程、年龄有关,而与首发部位、呼吸困难无明显相关性。结论脊旁肌肌电图与ALS患者的病程及年龄有关,且下胸段脊旁肌肌电图方便易行,在ALS中诊断价值较大。