THE ELECTROMYOGRAM IN MYOPATHY: ANALYSIS WITH THE AUDIO-FREQUENCY SPECTROMETER
THE ELECTROMYOGRAM IN MYOPATHY: ANALYSIS WITH THE AUDIO-FREQUENCY SPECTROMETER
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肌病中的肌电图：音频频谱仪分析
DOI：
10.1136/jnnp.15.4.219
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发表时间：
1952
影响因子：
11
通讯作者：
J. Walton
中科院分区：
文献类型：
--
作者：
J. Walton
尽管在大多数已确诊的肌营养不良症病例中，临床诊断是不言自明的，但偶尔也会出现难以确定肌肉萎缩是神经性还是肌病性的病例。Kugelberg（1949）和其他人的仔细研究表明，肌电图在进行这种基本区分方面可能具有相当大的价值，但在许多中心，诊断技术尚未建立。本文回顾了100例肌病的肌电图表现，并提出了一种频率分析法，以提高肌电图的诊断价值。通过应用这种分析技术在26名正常人和48名其他神经系统疾病患者的检查中获得的结果与肌病病例中注意到的结果进行了比较。然而，在讨论研究的方法和结果之前，有必要简要讨论一下所涉及的生理学原理和其他作者的发现。肌肉结构的单位是肌纤维;在正常情况下，肌纤维从不单独收缩，但在去神经支配后，可以从静息肌肉记录到单纤维或纤颤电位，其形式为持续时间约1毫秒的双相或双相尖峰（图1）（Weddell，Feinstein和Pattle，1944）。随意肌的正常意志活动由单个运动单位的异步收缩组成;每个单位由一个前角细胞及其运动神经元提供的肌纤维束组成。在电学上，单位纤维的活动平稳地叠加，产生单相、双相或三相波，即运动单位动作电位（图2），持续时间在4 ~ 10毫秒之间变化（Petersen和Kugelberg，1949）。因此，可以看出，在随意肌的持续收缩中，取决于合成干涉图案的复合波形的各个波的持续时间，放电的主频率将为每秒100到250个周期的量级。在前角细胞和下运动神经元近端部分的疾病中，很明显，由患病神经元提供能量的整个运动单位都将死亡，因此干扰模式将减少;最终，在许多神经元死亡后，针电极可以记录孤立的存活单位的活动，即Buchthal和Clemmesen（1941）的“单次放电”。在这些情况下，由于剩余的运动单位具有正常的持续时间，波形的主频率将不变。另一方面，在肌的原发性疾病（例如肌营养不良症）中，没有这种解剖学上的变性模式，个别肌纤维零星地死亡。因此，运动单位的纤维活动不再可能平滑地累加，因为该单位的某些成分将丢失，因此，许多多相电位被观察到（图3）。如果退化进一步发展，可能一个运动单位只剩下一根或两根神经纤维，并且可以自愿获得神经元电位。因此，预期来自收缩营养不良肌肉的放电的主频率将更接近每秒1,000个周期。Kugelberg（1949）检查了16例肌营养不良症，并对记录的运动单位电位进行了仔细测量。与142例神经病患者比较，证实肌病患者肱二头肌收缩时多相电位和减短或短时程电位的比例明显增加。此时应该指出的是，在正常肌肉的记录中发现了许多多相电位（Denslow和Hassett，1943年; Weddell等人，1944年）;在二头肌219 gest中，这一比例约为2%至4%。由正确的。
Despite the fact that in most established cases of muscular dystrophy the clinical diagnosis is selfevident, occasional cases arise in which it is difficult to decide whether muscular wasting is of neuropathic or myopathic origin. Careful work by Kugelberg (1949) and others has shown that electromyography may be of considerable value in making this fundamental distinction, but in many centres the techniques for diagnosis are not yet firmly established. In this paper the electromyographic findings in 100 cases of myopathy are reviewed, and a method of frequency analysis is described which appears to enhance the value of the electromyogram in diagnosis. The results obtained by applying this analytical technique in the examination of 26 normal subjects and 48 patients with other neurological disorders are compared with those noted in the cases of myopathy. Before discussing the methods and results of the investigation, however, it is essential to discuss briefly the physiological principles involved and the findings of other authors. The unit of muscle structure is the muscle fibre; under normal conditions muscle fibres never contract singly, but single fibre or fibrillation potentials can be recorded from resting muscle after denervation in the form of monophasic or diphasic spikes (Fig. 1) of about 1 millisecond duration (Weddell, Feinstein, and Pattle, 1944). Normal volitional activity of voluntary muscle is made up by the asynchronous contraction of individual motor units; each unit consists of the bundles of muscle fibres supplied by one anterior horn cell and its motor neuron. Electrically, the activity of the fibres of the unit summates smoothly to give a monophasic, diphasic, or triphasic wave, the motor unit action potential (Fig. 2), which varies between 4 and 10 milliseconds in duration (Petersen and Kugelberg, 1949). Hence it will be seen that in sustained contraction of voluntary muscle the dominant frequency of the electrical discharge, depending on the duration of the individual waves from which the complex wave form of the interference pattern is synthesized, will be of the order of 100 to 250 cycles per second. In disease of the anterior horn cell and the proximal part of the lower motor neuron it is clear that whole motor units, supplied by the diseased.neuron, will perish, and for this reason the interference pattern will be reduced; eventually after the death of many neurons a needle electrode may record the activity from isolated surviving units, the " single discharge" of Buchthal and Clemmesen (1941). Under these circumstances, since the remaining motor units are of normal duration, the dominant frequency of the wave form will be unchanged. In primary disease of the tnuscle, on the other hand (e.g. muscular dystrophy), no such anatomical pattern of degeneration obtains and individual muscle fibres die sporadically. No longer, therefore, is it possible for the activity of the fibres of a motor unit to summate smoothly, as some components of the unit will be missing, and for this reason many polyphasic potentials are seen (Fig. 3). If degeneration has proceeded further it may be that one or two fibres are all that remain of a motor unit and fibrillary potentials may be obtained on volition. Hence it will be expected that the dominant frequency of the electrical discharge from contracting dystrophic muscle will approach more nearly to 1,000 cycles per second. Kugelberg (1949) examined 16 cases of muscular dystrophy and carried out careful measurements of the motor unit potentials recorded. These findings were compared with those in 142 cases of neuropathy and it was confirmed that in the cases of myopathy a greatly increased proportion of polyphasic potentials and attenuated or short duration potentials was produced on contraction of the biceps brachii. It should be remarked at this juncture that a number of polyphasic potentials are to be found on recording from normal muscle (Denslow and Hassett, 1943; Weddell and others, 1944); the proportion is about 2 to 4% in the biceps 219 gest. P rocted by coright.