Guidelines for single fiber EMG

This document is the consensus of international experts on the current status of Single Fiber EMG (SFEMG) and the measurement of neuromuscular jitter with concentric needle electrodes (CNE – CN-jitter). The panel of authors was chosen based on their particular interests and previous publications within a specific area of SFEMG or CN-jitter. Each member of the panel was asked to submit a section on their particular area of interest and these submissions were circulated among the panel members for edits and comments. This process continued until a consensus was reached. Donald Sanders and Erik Stålberg then edited the final document.     

Single fiber macro versus concentric trigger macro EMG: a comparison of methods.

The values obtained from two different macro EMG methods were compared, and found to be different. Normally, macro electromyography (EMG) is performed with a modified single fiber (SF) needle using the SF potential as a trigger; a new method recommends a modified concentric needle and triggers on the concentric EMG signal. The concentric macro EMG has a 40% to 50% smaller amplitude and area values than data obtained with a SF macro EMG needle. The different values are the result of variant spatial relationships of the respective needles to the motor unit under study, and may be due to a recruitment-dependent bias resulting from different trigger properties of the two methods. The concentric macro EMG needle can be used to estimate motor unit size, to scan the unit, and to investigate its different concentric EMG signals.     

The standard concentric needle cannula cannot replace the Macro EMG electrode

ObjectiveTo establish the usefulness of the single use and affordable standard concentric EMG electrode as a substitute for the expensive standard macro electrode.MethodsMacro EMG performed with macro electrode is compared with recordings from the uninsulated cannula of a standard EMG electrode at two different recording depths in the tibialis anterior muscle. This was performed both in muscles with signs of collateral reinnervation and without.ResultsThe amplitude of the motor units recorded with the uninsulated concentric needle cannula were lower for the deeply recorded motor units compared to motor unit potential (MUP) amplitudes recorded with the standard macro electrode. The deeply recorded concentric needle (CN) cannula recorded MUPs amplitudes were also lower than superficially recorded CN cannula MUPs. The standard Macro EMG signals show no difference between deeply and superficially recorded motor units.ConclusionThe uninsulated cannula of the concentric needle electrode cannot replace the standard Macro EMG electrode due to technical reasons, probably from different effects of shunting of the bare cannula in deep vs. superficially recorded motor units.SignificanceThe standard CN electrode could not be used as substitute for the standard Macro EMG needle.     

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。     

Multi-motor unit action potential analysis (MMA)

We have developed an algorithm, called multi–motor unit action potential analysis (MMA), to aid quantification in routine needle EMG examination. In only 5–8 min, it was possible to extract, analyze, and validate 20 motor unit action potentials (MUAPs). In the biceps muscle of normal subjects, the MUAP measurements are compared with measurements using manual, triggered averaging, automatic decomposition, and other MMA algorithms described in the literature. The mean values of MUAP features by MMA fell between the extreme limits obtained from the amplitude-triggered method and the manual method described in the literature. In patients, the results are consistent with routine EMG and similar to those results described in the literature. Fast acquisition and analysis of MUAPs as well as interference pattern (IP) analysis make this technique useful to document EMG abnormalities in routine needle examination.© 1995 John Wiley & Sons, Inc.     

27例产瘫的神经肌电图分析

目的探讨神经电图、肌电图在分娩性臂丛神经损伤(产瘫)的特点及应用价值。方法对27例产瘫患儿进行神经电图(NCV)及肌电图(EMG)检查,测定臂丛五大神经的运动神经传导及其主要支配肌肉的肌电表现,并定期进行复查。结果27例中,上干损伤9例(33.3%),上中干损伤11例(40.7%),全干损伤7例(26%),初次检查小于3月小婴儿神经电图及肌电图异常率均为100%,3~6月后复查,肌电图异常率高于神经电图。结论产瘫患儿以上干、上中干损伤占多数(74%),神经电图及肌电图在产瘫患儿不同时期的表现特点及应用价值不同。     

Comparison between concentric needle EMG and macro EMG in patients with a history of polio.

OBJECTIVES: Acute poliomyelitis causes degeneration of anterior horn cells, followed by denervation. Reinnervation and muscle fibre hypertrophy are mechanisms that compensate this loss of neurones. Concentric needle EMG (CNEMG) and macro EMG are two methods to assess the magnitude of initial involvement and the compensatory reinnervation. The aim of this study is to explore the difference between CNEMG and macro EMG describing the status of the motor unit in patients previously affected by polio. METHODS: Macro and concentric needle EMG investigations were performed in 261 muscles in 121 patients with a remote history of polio. RESULTS: CNEMG was abnormal in 211 muscles, macro EMG was abnormal in 246 muscles. The macro amplitude was 3-4 times 'more abnormal' than CNEMG amplitude relative to the reference values. CNEMG duration was less abnormal and showed only weak correlation with macro amplitudes. The most likely explanation for the difference in magnitude of deviation from reference values for CNEMG and macro EMG, is a more pronounced 'phase cancellation' between single fibre action potentials in CNEMG. This is supported by simulation studies reported here. CONCLUSIONS: In conclusion macro EMG better reflects the size of the motor unit than the CNEMG. For detection of concomitant disorders, CNEMG is the method of choice.     

The neurological examination in the assessment of polyneuropathy in mechanically ventilated patients

Polyneuropathy has been implicated in critical illness as a cause of difficult weaning from artificial ventilation and of rehabilitation problems. We wanted to see which clinical parameters can be used to identify patients with polyneuropathy in the intensive care. In a prospective study during 18 months, mechanically ventilated patients underwent serial neurological and EMG investigations in the general intensive care unit of a large community hospital. Fifty patients under 75 years old were studied who were on the respirator for more than 7 days. Using simple criteria, both a provisional clinical and an EMG diagnosis were made with regard to polyneuropathy during the second and fourth week and the second month of mechanical ventilation. After the intensive care period, 34 surviving patients were also given a final clinical diagnosis which was compared to earlier EMG conclusions. Even with crude criteria, such as the presence of either paresis or areflexia, maximal sensitivity of the provisional clinical judgement was only 60% as compared to concurrent EMG diagnosed polyneuropathy. EMG investigations in the intensive care, however, did not identify two out of 10 patients with a final clinical diagnosis of polyneuropathy. Thus, neurological examination is an insufficient screening method for polyneuropathy in intensive care. EMG has a fair diagnostic yield but one should realize that it is not an infallible gold standard.     

Nerve-muscle involvement in a large family with mitochondrial cytopathy: electrophysiological studies.

Thirteen patients with mitochondrial cytopathy were investigated. They represent different generations, ages, stages, and severities of the disease. All were assumed to have the same metabolic defect. The disease is a multisystem disorder with a metabolic defect located at complex 1 in the respiratory chain. Clinically, the disorder gives symptoms such as hearing loss, retinal pigmental degeneration, ataxia, cardiomyopathy, muscular fatiguability and neuropathy. The patients were investigated with nerve conduction studies, concentric needle EMG, SFEMG, and macro EMG examinations. Neurophysiologic studies revealed signs of myopathy in both the younger members and in those with slight muscular symptoms. In the more advanced stages, neuropathic changes of the axonal type were seen as well. Macro EMG was interpreted as indicating muscle fiber membrane abnormalities in the early stages. Single fiber EMG studies indicate that this metabolic defect does not disturb neuromuscular transmission.     

Electroconvulsive therapy: A comparison of seizure duration as monitored with electroencephalograph and electromyograph

EEG and EMG were monitored simultaneously at 72 ECT sessions in 18 patients. When EMG was recorded from the leg the duration of EMG curve convulsions varied between 43 and 89 % of the EEG recorded seizure duration of the same fit. The EMG/EEG seizure ratio varied widely among different patients as well as within the single patient during a series of ECT sessions. EMG recording from the masseter muscles showed EMG seizure duration to be more in accordance with the EEG seizure duration than EMG recordings from the leg. The EMG/EEG seizure ratio (masseter) varied from 65 to 100 %, which was significantly higher than the EMG/EEG seizure ratio obtained with EMG recorded from the calf muscles. The use of EEG monitoring of ECT is advocated in order to obtain the most precise evaluation of the cerebral seizure activity. If EEG monitoring is not available EMG recorded from the masseter muscles provides a reasonably accurate and easily applicable method of monitoring the presence and duration of the ECT-induced seizure.     

Coactivation at the ankle joint is not sufficient to estimate agonist and antagonist mechanical contribution

The aim of this study was to assess, via an electromyographic (EMG) biofeedback method, the mechanical contribution of both agonist and antagonist muscles during maximal voluntary contraction (MVC). We compared this original method with the MVC–EMGmax ratio and the torque/EMG relationship method, both of which are commonly used to estimate antagonist torque. The plantarflexion (PF) and dorsiflexion (DF) MVCs were measured simultaneously with EMG activity of triceps surae (TS) and tibialis anterior in 15 young adults (mean age 23 years). Antagonist torques obtained from the torque/EMG relationship and EMG biofeedback methods appeared to be similar. TS antagonist torque had a major mechanical impact on DF MVC (～42%). EMG coactivation is significantly different than normalized antagonist torque. TS antagonist torque is not negligible when maximal DF is assessed, and the EMG biofeedback method is a simple method to estimate antagonist torque. Muscle Nerve, 2010     

fMRI analysis for motor paradigms using EMG-based designs: a validation study

The goal of the present validation study is to show that continuous surface EMG recorded simultaneously with 3T fMRI can be used to identify local brain activity related to (1) motor tasks, and to (2) muscle activity independently of a specific motor task, i.e. spontaneous (abnormal) movements. Five healthy participants performed a motor task, consisting of posture (low EMG power), and slow (medium EMG power) and fast (high EMG power) wrist flexion-extension movements. Brain activation maps derived from a conventional block design analysis (block-only design) were compared with brain activation maps derived using EMG-based regressors: (1) using the continuous EMG power as a single regressor of interest (EMG-only design) to relate motor performance and brain activity, and (2) using EMG power variability as an additional regressor in the fMRI block design analysis to relate movement variability and brain activity (mathematically) independent of the motor task. The agreement between the identified brain areas for the block-only design and the EMG-only design was excellent for all participants. Additionally, we showed that EMG power variability correlated well with activity in brain areas known to be involved in movement modulation. These innovative EMG-fMRI analysis techniques will allow the application of novel motor paradigms. This is an important step forward in the study of both the normally functioning motor system and the pathophysiological mechanisms in movement disorders.     

KANDID–an EMG decision support system–evaluated in a European multicenter trial

KANDID is an advanced EMG decision support system dedicated to the support of the clinical neurophysiologist during EMG examinations. It has facilities for test planning, automatized and structured data interpretation, EMG diagnosis, explanation, and reporting. In a prospective European multicenter field trial, the agreement levels between clinical neurophysiologists and KANDID's diagnostic statements were measured under ordinary clinical EMG practice. KANDID was assessed in 159 individual patient EMG examinations by nine clinical neurophysiologists at seven different EMG laboratories. The reasoning of KANDID was considered understandable for the examiners in 80–90% of cases. The agreement level for the electrophysiological states of muscles and nerves between KANDID and the individual examiners was, on average, 81%. The corresponding diagnostic agreement with KANDID was, on average, 61%. A pronounced interexaminer variation in the agreement level related to the different EMG centers was observed. All Danish and Belgian examiners agreed with KANDID in more than 50% of their cases with regard to the EMG diagnosis, while the English examiners were in agreement with KANDID in 50% or less of their cases. These differences were possibly due to differences in epidemiology, examination techniques, control material, and examination planning strategies. It is concluded that it is possible to transfer systems like KANDID out of their development sites and apply them successfully if they can be locally customized by the clinical end users via editors. © 1993 John Wiley & Soncs, Inc.     

肌电生物反馈治疗脑卒中患者运动功能障碍的疗效观察

目的观察在进行常规药物治疗的同时,早期使用肌电生物反馈疗法辅助治疗脑卒中患者运动功能障碍的疗效。方法对我科2008年5月至2010年1月收治的105例脑梗死及脑出血住院患者进行回顾性分析。其中治疗组55例住院期间使用肌电生物反馈疗法辅助治疗14d。对照组50例未做辅助治疗。两组患者于治疗前后进行简式Fugl—Meyer运动功能评定（FMA）并进行统计分析。结果两组运动功能恢复比较显示治疗组改善较对照组明显,统计学分析差异有显著性（P〈0．01）。结论本研究结果表明在进行常规药物治疗的同时,早期使用肌电生物反馈疗法辅助治疗脑卒中偏瘫患者有明显疗效,有利于患者运动功能的康复。     

Effects of changes in intracellular action potential on potentials recorded by single-fiber, macro, and belly-tendon electrodes

Some myopathies are accompanied by abnormal calcium homeostasis. Electromyography (EMG) in such patients shows signs of normal or myopathic EMG when detected by a single-fiber electrode and abnormally increased values in macro EMG. As calcium accumulation might be accompanied by changes in intracellular action potential (IAP) and muscle-fiber propagation velocity, we simulated the effects of such changes on motor unit potentials (MUPs) recorded by different kinds of electrodes. We found that: (1) the requirements for what potential can be accepted as a single-fiber action potential (SFAP) are too rigorous; (2) macro MUP amplitude can increase while SFAP amplitude can decrease when there is an increase in the spatial length of IAP spike; and (3) changes in the second phase of a belly-tendon-detected MUP or M wave could be used for noninvasive detection of increased IAP depolarizing (negative) after-potential.     

Variability of frequency and phase between antagonistic muscle pairs in pathological human tremors

We investigated the electromyographic activity (EMG) of flexor and extensor muscles with different hand positions in patients with essential (ET) and parkinsonian (PD) tremor. Using a previously developed bootstrap method and standard cross-spectral analysis, we performed statistical tests to assess the effect of hand position on: (1) the frequency of the EMG; and (2) the phase between the EMGs recorded from antagonistic muscle pairs. Frequency as well as phases changed significantly with different positions of the hands but not during the recordings when the position was left unchanged. Besides confirmation that frequency and phase are stationary and reliable parameters during short-term recordings under controlled laboratory conditions, these results are of particular interest for ambulatory long-term tremor measurements. A higher variability of the estimated parameters reported in long-term recordings may perhaps reflect a patient's mobility only. Our study shows that long-term recording systems should have the means to monitor the patient's movements to provide reliable results.     

Current trends in pedicle screw stimulation techniques: lumbosacral, thoracic, and cervical levels

Unequivocally, pedicle screw instrumentation has evolved as a primary construct for the treatment of both common and complex spinal disorders. However an inevitable and potentially major complication associated with this type of surgery is misplacement of a pedicle screw(s) which may result in neural and vascular complications, as well as impair the biomechanical stability of the spinal instrumentation resulting in loss of fixation. In light of these potential surgical complications, critical reviews of outcome data for treatment of chronic, low-back pain using pedicle screw instrumentation concluded that "pedicle screw fixation improves radiographically demonstrated fusion rates;" however the expense and complication rates for such constructs are considerable in light of the clinical benefit (Resnick et al. 2005a). Currently, neuromonitoring using free-run and evoked (triggered) electromyography (EMG) is widely used and advocated for safer and more accurate placement of pedicle screws during open instrumentation procedures, and more recently, guiding percutaneous placement (minimally invasive) where the pedicle cannot be easily inspected visually. The latter technique, evoked or triggered EMG when applied to pedicle screw instrumentation surgeries, has been referred to as the pedicle screw stimulation technique. As concluded in the Position Statement by the American Society of Neurophysiological Monitoring (ASNM), multimodality neuromonitoring using free-run EMG and the pedicle screw stimulation technique was considered a practice option and not yet a standard of care (Leppanen 2005). Subsequently, the American Association of Neurological Surgeons/Congress of Neurological Surgeons (AANS/CNS) Joint Section on Disorders of the Spine and Peripheral Nerves published their "Guidelines for the Performance of Fusion Procedures for Degenerative Disease of the Lumbar Spine" (Heary 2005, Resnick et al. 2005a, Resnick et al. 2005b). It was concluded that the "primary justification" of intraoperative neuromonitoring"... is the perception that the safety and efficacy of pedicle screw fixation are enhanced..." (Resnick et al. 2005b). However in summarizing a massive (over 1000 papers taken from the National Library of Medicine), contemporary, literature review spanning nearly a decade (1996 to 2003), this invited panel (Resnick et al. 2005b) recognized that the evidence-based documents contributing to the parts related to pedicle screw fixation and neuromonitoring were "... full of potential sources of error ..." and lacked appropriate, randomized, prospective studies for formulating rigid standards and guidelines. Nevertheless, current trends support the routine use and clinical utility of these neuromonitoring techniques. In particular free-run and triggered EMG have been well recognized in numerous publications for improving both the accuracy and safety of pedicle screw implantation. Currently, treatment with pedicle screw instrumentation routinely involves all levels of the spine - lumbosacral, thoracic, and cervical. Significant historical events, various neuromonitoring modalities, intraoperative alarm criteria, clinical efficacy, current trends, and caveats related to pedicle screw stimulation along the entire vertebral column will be reviewed.     

Minimum standards for electromyography in Canada: a statement of the Canadian Society of Clinical Neurophysiologists

BACKGROUND: Electromyography (EMG) is a widely used diagnostic technique for disorders of the nervous system. The Canadian Society of Clinical Neurophysiologists (CSCN) promotes the education, evaluation and standards of EMG in Canada. A statement of practice standards was needed to clarify the position of the CSCN on several issues relevant to the practice of EMG. METHODS AND RESULTS: A subcommittee of the CSCN reviewed current patterns of practice and established guidelines for review by the CSCN. The guidelines developed by the subcommittee were reviewed by the CSCN and adopted as recommendations for EMG practice. The subcommittee was charged with formulation of a document for publication. CONCLUSIONS: This document deals with minimum standards for electromyographer education, laboratory operation, equipment and a variety of special circumstances relevant to the practice of EMG. The standards can be adopted by EMG laboratories to guide quality assurance.     

Sources of error in the spike-triggered averaging method of motor unit number estimation (MUNE)

Motor unit number estimation (MUNE) is an electrophysical technique to estimate the number of motor units innervating a muscle or muscle group. MUNE may be useful as a measure of progression of lower motor neuron loss in amyotrophic lateral sclerosis (ALS). Several methods of MUNE have been developed. The spike-triggered averaging method can be readily performed on EMG machines with signal averaging capabilities and is suitable for estimating the number of motor neurons innervating proximal muscles. We have used MUNE as a measure of disease state in a drug efficacy trial for ALS. From our experience with this method we have identified sources of error which can affect MUNE accuracy. We have investigated these sources and report their effect on MUNE.© 1995 John Wiley & Sons, Inc.