Concentric needle EMG versus macro EMG I. Relation in healthy subjects.

OBJECTIVES: The relation between motor unit action potentials (MUAPs) recorded via a macro needle electrode (MA-MUAP, MA-EMG) and MUAPs recorded via a concentric needle electrode (CN-MUAP, CN-EMG) is under debate. In particular it is not known to what degree CN-MUAP variables reflect the electrical properties of a motor unit. METHODS: CN-EMGs and MA-EMGs of the right brachial biceps muscle were recorded from 40 healthy subjects (23 women and 17 men) aged 17-83 years and CN-MUAP and MA-MUAP variables were cross-correlated. RESULTS: CN-MUAP duration was positively and significantly correlated with CN-MUAP area (r=0.52), rate of polyphasia (r=0.45), MA-MUAP amplitude (r=0.47) and MA-MUAP area (r=0.45). CN-MUAP amplitude was positively and significantly correlated with the rate of polyphasia (r=0.39) and the fibre density (r=0.45). CONCLUSIONS: CN-MUAP duration appropriately reflects the motor unit's electrical activity and may substitute MA-MUAP area and amplitude.     

98例神经肌肉病的临床、肌电图与病理研究

目的 探讨肌电图（EMG），肌活检对神经肌肉病的诊断价值。比较EMG，肌活检及初始临床诊断3者之间的关系。方法 将98例神经肌肉病分成肌病。重症肌无力和运动神经元病3组进行研究。结果 肌病组（80例），68.8%(55/80)肌活检，75%（60/80）EMG呈肌源性损害；重症肌无力组（10例）；针极EMG（不包括重视频率电刺激）及肌活检均未显示特异性改变；运动神经元病组（8例），75?/8）肌活检，100%（8/8）EMG呈神经源性损害。结论 肌活检对肌病明确诊断可提供直接信息。对运动神经元病只能做出神经源性损害结果。缺乏特异性。EMG对神经肌肉病只能做出分类诊断；单纯凭借初始临床资料易导致该类疾病误诊。     

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.     

Electromyography (EMG) accuracy compared to muscle biopsy in childhood

Reports show wide variability of electromyography (EMG) in detecting pediatric neuromuscular disorders. The study's aim was to determine EMG/nerve conduction study accuracy compared to muscle biopsy and final clinical diagnosis, and sensitivity for myopathic motor unit potential detection in childhood. Of 550 EMG/nerve conduction studies performed by the same examiner from a pediatric neuromuscular service, 27 children (ages 6 days to 16 years [10 boys; M:F, 1:1.7]) with muscle biopsies and final clinical diagnoses were compared retrospectively. Final clinical diagnoses were congenital myopathies (5 of 27,18%), nonspecific myopathies (biopsy myopathic, final diagnosis uncertain; 6 of 27, 22%), congenital myasthenic syndrome (3 of 27, 11%), juvenile myasthenia gravis (1 of 27, 4%), arthrogryposis multiplex congenita (2 of 27, 7%), hereditary motor and sensory neuropathy (1 of 27, 4%), bilateral peroneal neuropathies (1 of 27, 4%), and normal (8 of 27, 30%). There were no muscular dystrophy or spinal muscular atrophy patients. EMG/nerve conduction studies had a 74% agreement with final clinical diagnoses and 100% agreement in neurogenic, neuromuscular junction, and normal categories. Muscle biopsies concurred with final diagnoses in 87%, and 100% in myopathic and normal categories. In congenital myasthenic syndrome, muscle biopsies showed mild variation in fiber size in 2 of 3 children and were normal in 1 of 3. EMG sensitivity for detecting myopathic motor unit potentials in myopathies was 4 of 11 (36%), greater over 2 years of age (3 of 4, 75%), compared to infants less than 2 years (1 of 7, 14%), not statistically significant (P = .0879). EMGs false-negative for myopathy in infants < 2 years of age were frequently neurogenic (3 of 6, 50%). In congenital myopathies EMG detected myopathic motor unit potentials in 40%, with false-negative results neurogenic (20%) or normal (40%). Because our study has no additional tests for active myopathies, for example Duchenne muscular dystrophy genetic testing, our sensitivity for myopathies is lower than if we used a more global view. In conclusion, EMG detection rate of myopathic motor unit potentials at a young age was low, improving in children over 2 years of age. In neurogenic and neuromuscular junction disorders, the EMG has a very high detection rate. In children with mild to moderate neurogenic EMG findings and normal nerve conduction, a myopathy should always be considered.     

The diagnostic yield of quantified electromyography and quantified muscle biopsy in neuromuscular disorders

Electromyography (EMG), histology, and histochemistry were related in 264 patients with neuromuscular disorders classified according to history and clinical and other laboratory findings. Electromyography and histological and histochemical abnormalities were divided in specific and nonspecific criteria. Specific histochemical criteria alone identified 28% of neurogenic lesions. Criteria of myopathy, obtained from the pattern of electrical activity during 30% of maximal effort, helped to delineate a myopathy when the only abnormality was an increased incidence of polyphasic potentials together with a pattern of full recuitment during maximal effort. Histology, histochemistry, or both, and EMG were concordant with clinical findings in 77% of 188 patients with myopathy and in 91% of 64 patients with neurogenic lesions. The electromyogram was concordant with the clinical classification in 87% of patients with myopathy and in 91% of patients with neurogenic impairment. The biopsy was in agreement with or contributed to the classification in 79% of patients with myopathy and in 92% of patients with neuropathy.     

Power spectrum analysis of the EMG pattern in normal and diseased muscles

The diagnostic value of analogue frequency analysis of EMG from patients with neuromuscular disorders has not been convincing. Using fast Fourier transformation it is today possible to obtain the EMG power spectrum on-line and with a better resolution. We examined the power spectrum of the EMG pattern of the brachial biceps muscle in 20 control subjects, 20 patients with myopathy, and 12 with neurogenic disorders. The electrical activity was sampled with a concentric needle electrode from 10 sites in each muscle. From each spectrum, mean power frequency, the power at 140 Hz, 1400 Hz, 2800 Hz and 4200 Hz relative to total power and the high/low ratio (1400/140) were obtained. The mean power frequency was higher at 10% than at 30% of maximal force. At a force of 30% of maximum the power spectrum analysis identified 55% and 64% of the patients with myopathy and neurogenic disorders, respectively. Although the diagnostic yield of the power spectrum analysis at a force of 10% of maximum was less than that at 30%, additional patients were identified at 10% increasing the diagnostic yield to 65% and 73% for patients with myopathy and neurogenic disorders, respectively. The best diagnostic parameters were the mean power frequency and the relative power at 1400 Hz.     

Analysis of EMG records obtained by using an "Anops" computer (their usefulness in the diagnosis of neuromuscular diseases

The studied group included 179 individuals: a control group of 82 subjects, myopathy patients (55) and neurogenic atrophy cases (42). The records were obtained from 4 muscles (biceps, 1st interosseous muscles, quadriceps muscle, anterior tibialis muscle) using the method of automatic EMG analysis and quantitative conventional method. The obtained results demonstrated that in the control group Anops analysis showed no significant differences in the electromyographic parameters of a given muscle in three age groups (15-30, 31-45 and 46-60 years). The values of the mean duration of single potentials were calculated by the automatic method and in the control group they were shorter (by a mean value of 15%) than the mean duration of these potentials calculated by the conventional method. In cases of neuromuscular diseases the obtained measurements differentiated the normal records from the pathological ones, and myogenic from neurogenic lesions. The EMG parameters in the automatic analysis differentiating most evidently normal EMG from pathological EMG were: amplitude and mean duration of single potentials. These results seem to demonstrate the usefulness of automatic analysis of EMG records.     

Turns-amplitude analysis of the electromyographic recruitment pattern disregarding force measurement. II. Findings in patients with neuromuscular disorders.

Turns-amplitude analysis of the electromyographic recruitment pattern was performed on-line in the brachial biceps muscle of 46 patients with neuromuscular disorders using the mean amplitude as an indicator of force. The parameters, peak-ratio (PR) and number of time intervals (TI) from 0 to 1.5 ms, were increased in patients with myopathy. In patients with neurogenic involvement, the characteristic pattern was a decreased PR and a decreased incidence of TI between 0 and 1.5 ms. The results indicate that the two parameters supplement each other as some of the patients were identified only by one or the other. In patients with myopathy, the method had a higher diagnostic yield than the individual motor unit action potential analysis. The method is objective, fast, and reliable.     

脂肪累积肌肉病的病理和肌电图改变之间的关系

目的探讨脂肪累积性肌肉病和线粒体脂肪累积性肌肉病的肌肉活检病理改变和肌电图改变之间的关系。方法对33例肌活检确诊患者的肌肉病理改变分为单纯脂肪累积性肌肉病和线粒体-脂肪累积性肌肉病两组,对比两者肌纤维内脂肪沉积的程度以及肌电图改变的差异。结果33.3%为线粒体-脂肪累积性肌肉病,66.7%为单纯脂肪累积性肌肉病。前者肌纤维内脂肪沉积程度显著,7例出现小组样分布的小角状萎缩的肌纤维,后者脂肪沉积的程度相对轻,只有3例患者出现小角状萎缩的肌纤维。在前者81.8%的患者肌电图为肌源性损害、18.2%为混合性损害、45.5%合并周围神经损害。在后者59.1%的患者出现肌源性损害、13.6%出现混合或神经源损害、27.3%肌电图正常、22.7%合并周围神经损害。结论和单纯脂肪累积性肌肉病比较,线粒体-脂肪累积性肌肉病的脂肪滴沉积程度更显著以及更多的患者出现肌纤维萎缩,更易导致骨骼肌的电生理改变以及合并周围神经损害。     

Vulnerability of lower brachial myotomes in motor neurone disease: A clinical and single fibre EMG study

Single fibre EMG was used to study the motor unit fibre density in the right biceps brachii, extensor digitorum communis and first dorsal interosseous muscles of 15 patients with motor neurone disease, with different patterns of initial weakness. There was an inverse relationship between strength and fibre density in these muscles. Abnormalities were more marked in patients whose initial symptom was arm weakness, but collateral reinnervation was not as effective as in other neurogenic disorders. These findings are consistent with a hypothesis that motor neurone disease begins segmentally, or at a discrete level within the motor system, before becoming generalised. The single fibre EMG fibre density is a useful quantitative technique for sequential assessment of patients with neurogenic disorders.     

Origin of ICU acquired paresis determined by direct muscle stimulation

BACKGROUND: Acquired diffuse paresis in an intensive care unit (ICU) can result from critical illness myopathy or polyneuropathy. Clinical examination and conventional neurophysiological techniques may not distinguish between these entities. OBJECTIVE: To assess the value of direct muscle stimulation (DMS) to differentiate myopathic from neuropathic process in critically ill patients with diffuse severe muscle weakness. METHODS: 30 consecutive patients with ICU acquired diffuse motor weakness were studied. Responses of the right deltoid and tibialis anterior muscles to DMS and to motor nerve stimulation (MNS) were studied and compared with results of conventional nerve conduction studies and concentric needle electromyography (EMG). An original algorithm was used for differential diagnosis, taking into account first the amplitude of the responses to DMS, then the MNS to DMS amplitude ratio, and finally the amplitude of the sensory nerve action potentials recorded at the lower limbs. RESULTS: Evidence of neuropathy and myopathy was found in 57% and 83% of the patients, respectively. Pure or predominant myopathy was found in 19 patients. Other results were consistent with neuromyopathy (n = 5) and pure or predominant neuropathy (n = 2). Four patients had normal results with stimulation techniques, but spontaneous EMG activity and raised plasma creatine kinase suggesting necrotic myopathy. CONCLUSIONS: A neurophysiological approach combining DMS and conventional techniques revealed myopathic processes in a majority of ICU patients. Reduced muscle fibre excitability may be a leading cause for this. The diagnosis of myopathy in ICU acquired paralysis can be established by a combination of DMS, needle EMG, and plasma creatine kinase.     

Integrated electrical activity and number of zero crossings during a gradual increase in muscle force in patients with neuromuscular diseases

In the brachial biceps muscle of 17 patients with myopathy and of 14 patients with neurogenic disorders the integrated electrical activity and number of zero crossings per unit time were analysed in 3 sites of each muscle every 100 msec during a gradual increase in force from zero to maximum within 10 sec. The analysis of integrated electrical activity could not discriminate between patients with myopathy and patients with neurogenic disorders. The slope of the linear relation between the square root of integrated electrical activity and force expressed in kilograms was increased in 44% of the patients with myopathy and in 64% of the patients with neurogenic disorders. The increase in slope may be due to increase in the ratio of electrical activity and force of individual motor units. The integrated electrical activity related to a force of 40% of maximum was decreased in about two-thirds of patients with myopathy and in about half of the patients with neurogenic disorders. This decrease in integrated electrical activity may be due to random loss of muscle fibres or to loss of whole motor units respectively. The integrated electrical activity was linearly related to mean amplitude between potential reversals per unit time (turns). The number of zero crossings was increased in 29% of the patients with myopathy and decreased in 70% of the patients with neurogenic disorders at a force of 30% of maximum. The number of zero crossings was linearly related to turns.(ABSTRACT TRUNCATED AT 250 WORDS)     

Macro EMG in neuromuscular diseases]

The aim of this study is the introducing of macro-emg method as electrophysiological test used in diagnosis of neuromuscular diseases. The macro motor unit potentials (macro MUPs) obtained by recording macroelectrode (modified single-fibre electrode) represents temporal and spatial summation of individual single fiber action potentials belonging to whole motor unit territory--so the uptake area is larger for macroelectrode than for the concentric electrode, commonly used in emg routine work, when central main complex is generated only from less than 15 muscle fibers [10, 12, 13]. Additional information obtained by macro-emg method is spatial organisation of muscle fibers within the motor unit, so-called fiber density (F.D) In our study macro-emg examinations were performed in 20 healthy subjects, aged 21-55, without signs and symptoms of neuromuscular disorders. Macro MUPs were recorded using special programme for macro-emg and performed on electromyograph Counterpoint. 37 muscles (20 BB and 17 RF) were examined, and median values of amplitude, area of macro MUPs and F.D. in healthy subjects of different age were analyzed. Mean values of median for amplitude and area of macro MUPs in BB and RF muscles show respectively--148 microV, 382 microV x ms, and 319 microV, 763 microV x ms. Parameters of macro MUPs obtained in healthy subjects were compared to results obtained in 10 patients with myopathy and lower motor neuron lesion. Our results have confirmed the value of macro-emg method for investigating of the pathophysiological changes in motor units in neurogenic disorders, in myopathy the study should be continued.     

Longitudinal fibre splitting in neurogenic muscular disorders--its relation to the pathogenesis of "myopathic" change.

In 15 patients with neurogenic muscular disorders, including cases of motor neuron disease, Wohlfart-Kugelberg-Welander disease, Davidenkow's scapuloperoneal syndrome, peripheral neuropathy and traumatic neuropathies, muscle biopsies were carried out, usually after EMG or single fibre EMG investigation. Enzyme histochemical and electronmicroscopic techniques were used to study longitudinal fibre splitting and its quantitative relation to the general changes in the biopsies. In 9 cases serial sections were used to study the longitudinal extent and character of fibre splitting. Longitudinal fibre splitting was found in 14 cases. It was prominent in Type 1 fibres, and in those biopsies in which hypertrophy was most marked. It was often associated with central migration of sarcolemmal nuclei. Ultrastructurally there was evidence that splitting consisted of mechanical disruption of the myofibrillar pattern, followed by an active process of membrane formation. We suggest that longitudinal splitting of muscle fibres, induced by overload of poorly innervated, hypertrophied fibres, can account for many of the "myopathic" changes found in neurogenic muscular disorders.     

Comparison of electrophysiological and histochemical methods for assessing the spatial distribution of muscle fibres of a motor unit within muscle

The spatial distribution of muscle fibres of a motor unit has been examined in patients with a variety of neuromuscular disorders using the fibre density (FD) technique of single fibre EMG and the enclosed fibre count (EFC) method, and the results of the two approaches compared. Agreement between the findings occurred in 64% of cases; an increase in both parameters was seen only in neurogenic conditions. FD was found to be more sensitive to minor disturbances of motor unit architecture as seen in myopathies and mild neurogenic states, and this factor together with sampling differences accounted for most of the discrepancies between the two methods. The finding of normal FD and EFC values in the presence of fibre type disproportion helped to exclude reinnervation as the cause by confirming the predominantly diffuse distribution of muscle fibres.     

Electrical muscle activity during a gradual increase in force in patients with neuromuscular diseases

The electrical activity of the brachial biceps muscle from 31 patients with neuromuscular diseases were quantified during a gradual increase in force from zero to maximum within 10 sec. In patients with myopathy the ratio of potential reversals per 100 msec (turns) to mean amplitude was increased more often at 10% and 20% of maximum force than at greater force (i.e., in four-fifths of the patients). Similarly, the mean amplitude as a function of turns was more diagnostic at low than at high force, possibly due to an affection of low threshold motor units. In 14 patients with neurogenic disorders turns was decreased in nearly two-thirds of the patients at a force of 20% and 30% of maximum. In muscles where the force is easily determined it is suggested to quantitate the electrical activity during constant forces of 10% and 30% of maximum. In muscles where the force is difficult to determine the analysis of the ratio of turns to mean amplitude should be performed when motor unit potentials begin to interfere.     

Surface EMG and Myosonography in the Detection of Fasciculations: A Comparative Study

Surface electromyography (EMG) and muscle sonography both facilitate the detection of fasciculations. This study was conducted to evaluate the prevalence of fasciculations in 10 lower extremity muscles in 58 subjects 47 ± 18 years of age without and 54 patients 52 ± 15 years of age with various neuromuscular diseases (3 with inflammatory myopathy, 15 with lower motor neuron disease, 22 with acquired and 11 with hereditary motor and sensory neuropathy (HMSN), and 3 with adrenomyeloneuropathy). When each muscle was screened by means of myosonography for 10 seconds, fasciculations were found in up to 8 muscles in 11 control subjects (19%) and in up to 10 muscles in 41 patients (76%). Within the same recording period surface EMG revealed fasciculations in 5 control subjects (9%) and 30 patients (56%), whereas during a recording time of 20 minutes fasciculations were detected in 55 (95%) control subjects and all patients. An amplitude of 400 µV proved to be the optimum cutoff between fasciculations for healthy subjects and patients with neuromuscular disease (accuracy, 74%). Myosonography allowed differentiation of both groups with an accuracy of 79%. Surface EMG was more liable to artifacts than myosonography. The average interval between subsequent fasciculations cannot be used to differentiate patients with acquired and hereditary polyneuropathy and with lower motor neuron disease. Long-term surface EMG recording indicates fasciculations to occur in almost all patients with neuromuscular disease and the vast majority of healthy subjects. Muscle ultrasonography was more convenient and reliable than surface EMG in differentiating patients and healthy subjects.     

肌电图干扰相自动分析在神经源性和肌源性损害中的应用

目的 探讨肌电图干扰相自动分析（QIP技术在神经源性和肌源性疾病中的应用价值。方法 记录40例健康人、20例神经源损害和20例炎性肌病患者的肱二头肌在不同强度自主收缩时运动单位动作电位的反折数（NT）与平均波幅（MA）的比值，并以“云图”的方式表示。结果 神经疾病组和肌病组QIP阳性率分别为75%和65%，前者表现为NT：MA比值降低，后者表现为NT：MA比值升高。QIP的异常与临床上肌肉无力的程度有关。中重度肌肉无力的阳性率分别为89%和80%，高于轻度肌肉无力组。结论 尽管该方法不如常规同心圆针电极肌电图（EMG）敏感，但操作简单，重复性好，可作为初步筛选和疗铲判断的客观指标。     

Muscle biopsy correlated with electromyography. Study of 100 cases

To find what the correlation is and verify if it is possible to avoid extensive electromyographic examination, studying only one muscle, 100 patients with neuromuscular disorders (58 primary myopathies, 32 neurogenic disorders and 10 myotonic dystrophies) were submitted to quantified electromyography (EMG) and muscle biopsy (MB) with fresh-frozen section plus histochemistry in the same muscle, but on the opposite side. The EMG was abnormal in 98% and MB in 93% of the cases. EMG and MB had a concordance of 84.3% in the neurogenic disorders and 84.77% in the primary myopathies. A correlation of 80% was obtained between all MB and EMG (including the cases of myotonic dystrophies), regarding the origin of the pathogenic process (p less than 0.01). The EMG had 5% inconsistencies and the MB 11%, with respect to the pathogenic process. When the myotonic dystrophy was separated from the primary myopathies and from the denervation disorders, a complete concordance was found in all MB and had only 3.4% inconsistencies in the denervation disorders and 3.1% in the primary myopathies.     

EMG, single fibre EMG and sacral reflexes in assessment of sacral nervous system lesions.

EMG of pelvic floor muscles, single fibre EMG of external anal sphincter and both bulbocavernosus and anal reflexes were investigated in 31 men without sacral nervous system lesions and in 12 patients with neurogenic erectile impotence, of whom one had slight loss of sensitivity to pinprick in the lower sacral dermatomes. EMG and single fibre EMG abnormalities have been found concomitantly in eight patients and six of these had also prolonged bulbocavernosus reflex latencies. In two patients the prolonged bulbocavernosus reflex latency was the only abnormality. Single fibre EMG of anal sphincter muscle seems to be superfluous in routine evaluation of sacral nervous system lesions.