Predictive power of motor unit potential parameters in anal sphincter electromyography

The diagnostic utility of motor unit potential (MUP) parameters is usually based exclusively on their diagnostic sensitivity, disregarding specificity. In the present study, advanced statistical methods were used to determine MUP parameters with the highest predictive power for the separation of neuropathic and normal external anal sphincter (EAS) muscles. Using multi-MUP analysis, 3,720 MUPs from 138 muscles of 52 patients with cauda equina lesion and 2,526 from 112 muscles of 64 controls were obtained. Only two principal components (PCs), which put weight on the MUP area and amplitude, were needed to explain all the data variability. On logistic and probit regression analyses, MUP area, duration, and number of turns gave results identical to all MUP parameters. Our results suggest that only these three MUP parameters are needed, and that they are as effective as PCs, in MUP analysis of chronic neuropathic EAS muscles. Reduced number of MUP parameters is expected to simplify MUP analysis and increase its specificity.     

Within-train neuromuscular propagation varies with torque in paralyzed human muscle

Electromyographic (EMG) recordings may serve an important role in predicting torque during repetitive activation of paralyzed muscle. We compared the initial M-wave to the subsequent M-waves of the same train under fatigued and recovered conditions in the paralyzed human soleus muscle. Sixteen individuals with chronic (n = 13) or acute paralysis (n = 3) had the tibial nerve activated before and after a repetitive supramaximal stimulation protocol. The mean within-train M-wave amplitude and median frequency increased approximately 20%, whereas the duration decreased approximately 15% compared with the initial M-wave of each train. During fatigue, there was a linear decrease in the difference between the initial M-wave amplitude and subsequent train ( approximately 20% to 8%). Following fatigue, this difference recovered to approximately 12%. The difference between the M-wave train average and the initial M-wave for amplitude, duration, and median frequency closely followed torque (Pearson correlations = 0.99, 0.94, and 0.98, respectively) during fatigue. We conclude that the difference between the later-occurring M-waves (average of the train) and initial M-wave is large when muscle torque is high and less when torque is low and, therefore, predicts torque during activation of paralyzed muscle. This difference in the within-train M-wave amplitude, duration, and median frequency may reflect a mechanical change, such as muscle shortening and increased muscle cross-sectional area during isometric contractions. Electromyographic feedback may assist in the optimization of neuromuscular electrical stimulation of paralyzed muscle.     

Surface EMG crosstalk between knee extensor muscles: experimental and model results

Surface electromyographic (EMG) crosstalk between vastus lateralis, vastus medialis, and rectus femoris muscles was evaluated by selective electrical stimulation of one muscle and recording from the stimulated and another muscle with linear surface arrays of eight electrodes. The ratio between the amplitude of the signals recorded over nonstimulated and stimulated muscles and their correlation coefficient were used as indices to quantify crosstalk. Single-differential and double-differential detection systems were used with interelectrode distances in the range 10-40 mm. The multichannel EMG signals clearly showed that crosstalk is largely due to nonpropagating potentials that correspond in time to the end of the propagation of the action potentials generated by the stimulated muscle. The crosstalk signal increased with increasing interelectrode distance and was statistically higher for single- than for double-differential recordings. The correlation-based indices of crosstalk were poorly correlated with the amplitude-based indices. Moreover, the characteristic spectral frequencies of the signals detected over the nonstimulated muscles were statistically higher than those from the stimulated muscles. A mathematical model of signal generation was used to explain the experimental findings. This study clarifies many controversial findings of past investigations and creates the basis for crosstalk interpretation, simulation, and reduction.     

单纤维肌电图在糖尿病周围神经病变中的变化和意义探讨

目的观察单纤维肌电图(SFEMG)在糖尿病周围神经病变(DPN)中的变化,探讨DPN的发病机制。方法36例已作常规神经传导检测(NCS)的2型糖尿病患者,测定指总伸肌的颤抖和纤维密度(FD),并测量空腹血糖(FBG)、糖化血红蛋白(HbA1c)、总甘油三酯(TG)、总胆固醇(TC)、高密度脂蛋白胆固醇(HDL-C)、低密度脂蛋白胆固醇(LDL-C)、脂蛋白a[Lp(a)]、载脂蛋白A(Apo-A)、载脂蛋白B(Apo-B)及血压。结果在18例NCS异常者中,颤抖值均超出正常范围(11例伴阻滞),14例FD增加;18例NCS正常者中,有7例颤抖值增大(3例伴阻滞),5例FD增加。颤抖和FD呈正相关(r=0.7621,P<0.01),颤抖和FD均与糖化血红蛋白、TG、LDL-C、Lp(a)及舒张压呈正相关。结论SFEMG是DPN早期诊断的敏感手段,可发现亚临床神经病变。血糖、血压、血脂控制不良在DPN的发生和发展中起重要作用。     

免疫吸附治疗兔实验性自身免疫性重症肌无力

目的:观察全血灌流免疫吸附治疗兔实验性自身免疫性重症肌无力的疗效。方法:以电鳗乙酰胆碱受体α亚单位Ta125￣147段多肽为免疫源建立实验性自身免疫性重症肌无力动物模型,以球形纤维素为载体色氨酸为配基的吸附剂(IM-MG)进行全血灌流吸附治疗,观察治疗前后临床症状评分、抗体滴度及3,5,10Hz刺激频率下单纤维肌电图(SFEMG)腓肠肌平均连续波间值差异(MCD)的变化。结果:灌流2h,抗体最大吸附率为(50.73±7.67)%。临床无力症状相应改善,SFEMG示腓肠肌MCD从(23.00±4.14)μs(3Hz)、(28.00±4.07)μs(5Hz)和(30.88±5.06)μs(10Hz)明显地减少到(16.38±3.34)μs、(19.25±4.13)μs和(22.38±5.26)μs(均P<0.05)。结论:IM-MG全血灌流吸附治疗可能会成为重症肌无力的新型治疗方法。     

Masseter and temporalis muscle EMG levels and bite force in migraineurs

The purpose of this study was to compare absolute and proportional electromyography (EMG) levels in the masseter and temporalis muscles during performance of a variety of oral functions for migraineurs and age- and sex-matched controls. Both groups consisted of nine women and one man, with a mean age of 43 years (range, 29 to 51 years). Absolute resting EMG levels and those levels during swallowing and speech were not significantly different between the groups, but the levels of the group with migraine were significantly higher during maximum voluntary effort contractions on the anterior teeth and on the posterior teeth for both muscles. When expressed as a percentage of those levels obtained at maximal posterior contraction (ie, proportional levels), no difference in functional activity was demonstrated between groups. It was concluded that the two groups studied had similar levels of EMG activity in the masseter and temporalis muscles during the normal oral functions investigated, but that the group with migraine had higher levels of absolute EMG activity during anterior and posterior maximum voluntary contractions. Furthermore, the group with migraine demonstrated higher levels of anterior and posterior bite force, although not correlated with EMG levels.     

The electrodiagnostic examination of psychogenic swallowing disorders

The article discusses the usefulness and technique of investigation of suspected psychogenic dysphagia by surface electromyography (sEMG) of deglutition. Thirty-two patients with suspected psychogenic dysphagia (Group 1) and 40 healthy individuals (Group 2) were involved in the study. The timing, amplitude and graphic patterns of activity of the masseter, submental, infrahyoid and trapezius muscles were examined during voluntary single water swallows (“normal”), and continuous drinking of 100 cc of water. The muscle activity in oral, pharyngeal and initial oesophageal stages of swallowing was measured, and graphic records were evaluated in relation to timing and voltage. Globus hystericus was found in only 14 patients of the Group 1 (43.75%). The main sEMG pattern of psychogenic dysphagia is a lack of any pathologic changes of timing, voltage and graphic patterns of deglutition. In 28% of cases tension of skeletal muscles not involved in deglutition was observed during single swallowing (vs. 0% in controls). Psychogenic/hysteria-conversion dysphagia has no pathologic sEMG patterns associated with deglutition. Skeletal muscle tension during deglutition, being observed in some cases has no connection with the act of swallowing itself. Surface EMG, being non-invasive and non-radiographic, can be used for screening purposes for patients with dysphagia thus avoiding expensive and time-consuming investigation.     

A clinical and neurophysiological study of scorpion envenomation in Assiut, Upper Egypt

Scorpion envenomation (SE) represents an agonizing problem in many countries, especially in rural areas. This clinical and neurophysiological study aimed to determine the relative frequency of scorpion envenomation in the Assiut area, in Upper Egypt. Full clinical evaluation was carried out for all children ≤18 y of age included in the study. Electroencephalography (EEG), electromyography (EMG) and motor conduction velocity measurements were carried out for a variable number of children. SE was recorded in 302 cases per year in this area. Of these, 78.5% were ≤18 y of age. SE occurred most commonly during the summer months. Clinical evaluation revealed that SE results in marked autonomic manifestations, principally sinus tachycardia (78.1%), vomiting (70.5%) and hyperthermia (53.2%). It also results in many neuropsychiatric manifestations, such as agitation and restlessness (17.7%) and disturbance of consciousness (8.0%). Electroencephalographic study of 184 cases of SE in paediatric patients aged ≤18 y revealed abnormalities in 77.7%. Study of mean distal latency and motor conduction velocity revealed that patients had a significantly shorter distal latency and a more rapid motor conduction velocity compared with the control group. This was true for both the inflicted limb and the contralateral limb. Most of the complications of SE are due to irritability of the central and peripheral nervous systems.     

Observations on intra-abdominal pressure and patterns of abdominal intra-muscular activity in man

Cresswell , A. G., Grundström , H. & Thorstensson , A. 1992. Observations on intra-abdominal pressure and patterns of abdominal intra-muscular activity in man. Actri Physiol Scand 144 , 409418. Received 16 July 1 991 , accepted 11 October 1991. ISSN 0001–6772. Department of Physiology III, Karolinska Institute, and Department of Radiology, Danderyd Hospital, Stockholm, Sweden. The aim was to investigate possible relationships between activities of the individual muscles of the ventrolateral abdominal wall and the development of pressure within the abdominal cavity. Intra-muscular activity was recorded bilaterally from transversus abdominis, obliquus internus, obliquus externus and rectus abdominis with fine-wire electrodes guided into place using real-time ultrasound. Intra-abdominal pressure was measured intragastrically using a micro tip pressure transducer. Six males were studied during loading and movement tasks with varied levels of intra-abdominal pressure. During both maximal voluntary isometric trunk flexion and extension, transversus abdominis activity and intra-abdominal pressure remained constant, while all other abdominal muscles showed a marked reduction during extension. When maximal isometric trunk flexor or extensor torques were imposed upon a maximal Valsalva manoeuvre, transversus abdominis activity and intra-abdominal pressure remained comparable within and across conditions, whereas obliquus internus, obliquus externus and rectus abdominis activities either markedly increased (flexion) or decreased (extension). Trunk twisting movements showed reciprocal patterns of activity between the left and right sides of transversus abdominis, indicating an ability for torque development. During trunk flexion-extension, transversus abdominis showed less distinguished changes of activity possibly relating to a general stabilizing function. In varied pulsed Valsalva manoeuvres, changes in peak intra-abdominal pressure were correlated with mean amplitude electromyograms of all abdominal muscles, excluding rectus abdominis. It is concluded that the coordinative patterns shown between the muscles of the ventrolateral abdominal wall are task specific based upon demands of movement, torque and stabilization. It appears that transversus ahdominis is the abdominal muscle whose activity is most consistently related to changes in intra-abdominal pressure.