Utility of the Clustering Index method for diagnosing neuromuscular disorders as compared with needle electromyography.

INTRODUCTION/AIMS: Concentric needle electromyography (CNEMG) is an essential examination for evaluating neuromuscular disorders, although pain is a drawback. Clustering Index (CI) method is a non-invasive quantitative analysis for surface electromyography (SEMG) that evaluates whether the signal area is clustered into the few large motor unit potentials (MUPs) or is evenly distributed. However, the diagnostic yield of the CI method in comparison with CNEMG is not known. In this study, we aimed to compare the sensitivity of the CI method with MUP parameters in CNEMG for diagnosing neurogenic or myogenic disorders. METHODS: We retrospectively identified patients for whom both SEMG and CNEMG were performed on the same tibialis anterior (TA) muscle. In CNEMG, seven MUP parameters were evaluated, including size index (SI) and revised size indices for neurogenic (rSIn) and myogenic (rSIm) disorders. RESULTS: Identified were 21 patients with neurogenic and 21 patients with myogenic disorders. Control data were constructed from 30 control subjects. The sensitivities of the CI method for the neurogenic and myogenic groups were 76% and 62%, respectively, which were not significantly different from MUP parameters, except for being significantly higher than those of amplitude and duration for myopathy (24%). Among MUP parameters, the sensitivities of rSIn (62%) and rSIm (57%) for myopathy were significantly higher than those of amplitude and duration. The CI method significantly correlated with the strength of the TA muscle in myopathy. DISCUSSION: The CI method, having comparable diagnostic yields to MUP parameters, is promising as a non-invasive diagnostic measure.

Needle electromyography does not meaningfully impact findings in MR-neurography/-myography.

INTRODUCTION: Magnetic resonance neurography (MRN) and myography (MRM) are emerging imaging methods for detecting diseases of the peripheral nerve system (PNS). Most patients with PNS diseases also undergo needle electromyography (EMG). This study examined whether EMG led to lesions that were detectable using MRN/MRM and whether these lesions could impair image interpretation. METHODS: Ten patients who underwent clinically indicated EMG were recruited. MRN/MRM was performed before and 2-6 h after EMG, and if achievable, 2-3 days later. T2 signal intensity (SI) of the tibialis anterior muscle (TA) was quantified, and sizes and SI of the new lesions were measured. Visual rating was performed independently by three neuroradiologists. RESULTS: T2 lesions at the site of needle insertion, defined as focal edema, were detectable in 9/10 patients. The mean edema size was 31.72 mm2 (SD = 14.42 mm2 ) at the first follow-up. Susceptibility-weighted imaging lesions, defined as (micro) hematomas were detected in 5/10 patients (mean size, 23.85 mm2 [SD = 12.59 mm2 ]). General muscle SI of the TA did not differ between pre- and post-EMG examinations. Lesions size was relatively small, and the readers described image interpretation as not impaired by these lesions. DISCUSSION: This study showed that focal edema and hematomas frequently occurred after needle EMG and could be observed using MRN/MRM. As general muscle SI was not affected and image interpretation was not impaired, we concluded that needle EMG did not interfere with MRN/MRM.

Electrodiagnostic and ultrasound evaluation of respiratory weakness.

Phrenic nerve conduction studies (NCSs) and needle electromyography (EMG) can provide important information on the underlying pathophysiology in patients presenting with unexplained shortness of breath, failure to wean from the ventilator, or consideration of phrenic nerve pacemaker implantation. However, these techniques are often technically challenging, require experience, can lack sensitivity and specificity, and, in the case of diaphragm EMG, involve some degree of risk. Diagnostic high-resolution ultrasound has been introduced in recent years as an adjuvant technique readily available at the bedside that can increase the overall sensitivity and specificity of the neurophysiologic evaluation of respiratory symptoms. Two-dimensional ultrasound in the zone of apposition can identify atrophy and evaluate contractility of the diaphragm, in addition to localizing a safe zone for needle EMG. M-mode ultrasound can identify decreased excursion or paradoxical motion of the diaphragm and can increase the reliability of phrenic NCSs. When used in combination, ultrasound, phrenic NCSs and EMG of the diaphragm can differentiate neuropathic, myopathic, and central disorders, and can offer aid in prognosis that is difficult to arrive at solely from clinical examination. This article will review techniques to successfully perform phrenic NCSs, needle EMG of the diaphragm, and ultrasound of the diaphragm. The discussion will include technical pitfalls and clinical pearls as well as future directions and clinical indications.

Artificial intelligence-based classification of motor unit action potentials in real-world needle EMG recordings.

OBJECTIVE: To develop an artificial neural network (ANN) for classification of motor unit action potential (MUAP) duration in real-word, unselected and uncleaned needle electromyography (n-EMG) recordings. METHODS: Two nested ANN models were trained, the first discerning muscle rest, contraction and artifacts in n-EMG recordings from 2674 individual muscles from 326 patients obtained as part of daily care. The second ANN model subsequently used segments labeled as contraction for prediction of prolonged, normal and shortened MUAPs. Model performance was assessed in one internal and two external validation datasets of 184, 30 and 50 muscles, respectively. RESULTS: The first model discerned rest, contraction and artifacts with an accuracy of 96%. The second model predicted prolonged, normal and shortened MUAPs with an accuracy of 67%, 83% and 68% in the different validation sets. CONCLUSIONS: We developed a two-step ANN that classifies rest, muscle contraction and artifacts from real-world n-EMG recordings with very high accuracy. MUAP duration classification had moderate accuracy. SIGNIFICANCE: This is the first study to show that an ANN can classify MUAPs in real-world n-EMG recordings highlighting the potential for AI assisted MUAP classification as a clinical tool.

Neuromuscular electrodiagnosis.

The electrodiagnostic (EDX) study is an extension of the clinical examination, which means that the clinical features dictate the initial nerve conduction studies (NCS) performed. However, once the EDX study is started, it continues in an independent manner, meaning that the initial NCS findings dictate the subsequent studies performed. Because competent EDX study performance requires considerable knowledge (and special training), it is not possible to convey all of the basic and advanced concepts in a single chapter. Nonetheless, the most important concepts are easily conveyed by a discussion limited to EDX-pertinent anatomical, physiological, pathological, pathophysiological, and basic electrical concepts. The focus of this chapter will be on the standard NCS and needle EMG measurements made during EDX studies and their significance with regard to lesion localization and characterization. Because the most challenging portion of EDX study is motor unit action potential analysis, this topic is more extensively reviewed. The utility of the sensory NCS for identifying focal axon loss, the utility of the motor NCS for screening long nerve segments for focal demyelination and for determining lesion severity, and the utility of the needle EMG for confirming the NCS findings, better defining lesion localization, and identifying the temporal features (e.g., chronicity) and rate of progression of the lesion are also reviewed.

Assessment of neuromuscular electrical stimulation effect on contralateral quadriceps muscle.

BACKGROUND: In the field of rehabilitation, the acute application of neuromuscular electrical stimulation (NMES) causes not only peripheral muscle contraction but also involve the central nervous system by the transient increase in spinal motor neuron and cortical activity. Therefore it has been used in several fields of rehabilitation. Previous studies used surface electromyography to assess this effect. But we conducted our study to assess the effect of NMES on contralateral quadriceps muscle in normal individuals using another method needle electromyography. METHODS: A study carried out on 20 normal males, who were subjected to (i) NMES Training Program for 60 min for the right quadriceps muscle. (ii) Assessment of EMG activity for rectus femoris muscle (RF) on the contralateral side. An assessment was done for minimal volition and maximal volition or interference pattern analysis, this assessment was done twice: before the start of NMES and during the session. RESULTS: EMG of voluntary activity (Minimal volition) and Maximum voluntary activity analysis for RF muscles showed increased duration (in millisecond), amplitude (in millivolt) (P < 0.01), increased activity in turn per second, amplitude/turn (M) (uV) compared to the result before NMES application. CONCLUSION: Our study provides a new evident date that the acute NMES application to the contralateral quadriceps muscles, leads to significant facilitation of the maximal voluntary power in the ipsilateral muscles through activation of efferent neural control. This facilitating effect of motor neurons in the contralateral muscles is likely due to the complex combination interaction between spinal and supraspinal control. TRIAL REGISTRATION: Trial registration: PACTR202010887172053.

Electrodiagnostic Abnormalities Associated with Fibromyalgia.

PURPOSE: Increasing evidence suggests that fibromyalgia most likely represents a neurological dysfunction. We previously hypothesized that at least some fibromyalgia cases may be caused by irritation of nerve root fibers and sensory neurons due to moderately increased cerebrospinal pressure. Because of the rostro-caudal hydrostatic pressure gradient, neurogenic abnormalities are expected to be most pronounced in sacral nerve roots. The purpose was to review electrodiagnostic tests of patients with fibromyalgia. METHODS: A retrospective review of electrodiagnostic test results, including the lumbar and sacral nerve root myotomes of patients diagnosed with fibromyalgia according to the 1990 criteria of the American College of Rheumatology was done. RESULTS: All 17 patients were female. Sural nerve responses could not be elicited in 12% and S1-Hoffmann reflex latencies were increased in 41%. In 12% of the patients, fibular motor nerve distal latency and conduction velocity were outside normal limits. Needle-EMG revealed neurogenic motor unit potentials in 0% of L2, 6% of L3, 29% of L4, 71% of L5, 47% of S1, 94% of S2, and 76% of S3-S4 myotomes. S3-S4 nerve-supplied anal reflexes were delayed in 94%. CONCLUSION: This is the first time that electrodiagnostic data of both lumbar and sacral nerve root myotomes in fibromyalgia patients are presented. All patients showed neurogenic abnormalities that were more pronounced in the sacral than in the lumbar myotomes with a rather patchy distribution pattern. We propose that, in addition to skin punch biopsies to assess small fiber neuropathy, assessment of the anal reflex may be a useful part of the diagnostic pathway in patients with fibromyalgia.

Ultrasound analysis of cervical paraspinal muscles for needle EMG examination.

BACKGROUND: Ultrasound was used to determine optimal needle insertion parameters and assess the vasculature of paraspinal muscles at C5-T1 spinal levels across patients with different body mass indices (BMIs). METHODS: Thirty patients underwent ultrasound examination of the cervical paraspinal muscles at the C5-T1 levels. Images were analyzed to determine the optimal distance and angle of needle insertion to reach the base of the right lamina. Color and spectral Doppler analysis were used to identify and map paraspinal blood vessels. RESULTS: Mean distances and angles varied from 35.1 mm and 17.27 degrees for the low BMI group at C5 to 65.1 mm and 9.85 degrees for the high BMI group at T1. Paraspinal blood vessel mapping revealed a random distribution of vasculature. CONCLUSIONS: Longer distances and steeper angles of needle insertion are required for patients with higher BMIs. Cervical paraspinal arteries vary in distribution and can be visualized with ultrasound.

Upper extremity neuropathies.

This chapter covers the electrodiagnostic (EDX) evaluation of upper extremity nerves and the brachial plexus. Carpal tunnel syndrome is the most common peripheral nerve disorder of the upper extremity. A number of techniques are used but there is no gold standard approach for its diagnosis. Needle EMG aids in the differentiation of proximal and distal median neuropathies. Ulnar neuropathy at the elbow and ulnar neuropathy at or distal to the wrist can be distinguished by EDX techniques. Radial neuropathy at the spiral groove has a specific EDX pattern. EDX assessment of proximal upper extremity nerve lesions such as brachial plexopathy is a valuable tool for exploring the diagnosis and differential diagnosis of this complex disorder.

The Diagnostic Sensitivity for Ulnar Neuropathy at the Elbow Is Not Increased by Addition of Needle EMG of ADM and FDI When Nerve Conduction Studies Are Normal.

Introduction: The main objective of this study was to investigate whether electromyography (EMG) has additional value in the confirmation of the clinical diagnosis of ulnar nerve entrapment at the elbow (UNE) if nerve conduction studies (NCS) are normal. Methods: A prospective cross-sectional cohort observational study was conducted among patients with the clinical suspicion of UNE. A total of 199 arms were included, who were examined according to a standard neurophysiological protocol, i.e., NCS and EMG relevant to the ulnar nerve. Results: NCS were normal in 76 (38.2%) arms. No abnormal spontaneous muscle fiber activity was found with EMG in any of these cases. In 9 arms with normal NCS (11.8%), isolated abnormal MUAP configurations were found with EMG. Of these nine arms one UNE was diagnosed clinically, in which additional ultrasound and repeated NCS/EMG were negative. One had already been diagnosed with neuralgic amyotrophy and one with CTS. The other 6 arms had additional diagnostics which did not reveal an UNE. Conclusion: EMG as part of the standard neurophysiological protocol exclusively in the confirmation of the clinical diagnosis of UNE has limited added value if NCS are normal in a high prior-odds setting. However, removing EMG may prevent detecting concomitant and/or additional differential diagnoses.

Nerve conduction studies and EMG in carpal tunnel syndrome: Do they add value?

This paper summarises the views of four experts on the place of neurophysiological testing (EDX) in patients presenting with possible carpal tunnel syndrome, in guiding their treatment, and in reevaluations. This is not meant to be a position paper or a literature review, and heterogeneous viewpoints are presented. Nerve conduction studies should be performed in patients presenting with possible carpal tunnel syndrome to assist diagnosis, and may need to be repeated at intervals in those managed conservatively. There is evidence that local corticosteroid injection is safe and effective for many patients, thereby avoiding or deferring surgical decompression. All patients should undergo EDX studies before any invasive procedure for CTS (injection or surgery). Needle EMG studies are not obligatory, but may be needed in those with severe disease and those in whom an alternate or concomitant diagnosis is suspected.

Three-dimensional needle-tip localization by electric field potential and camera hybridization for needle electromyography exam robotic simulator.

As one of neurological tests, needle electromygraphy exam (NEE) plays an important role to evaluate the conditions of nerves and muscles. Neurology interns and novice medical staff need repetitive training to improve their skills in performing the exam. However, no training systems are able to reproduce multiple pathological conditions to simulate real needle electromyogram exam. For the development of a robotic simulator, three components need to be realized: physical modeling of upper limb morphological features, position-dependent electromyogram generation, and needle localization; the latter is the focus of this study. Our idea is to couple two types of sensing mechanism in order to acquire the needle-tip position with high accuracy. One is to segment the needle from camera images and calculate its insertion point on the skin surface by a top-hat transform algorithm. The other is voltage-based depth measurement, in which a conductive tissue-like phantom was used to realize both needle-tip localization and physical sense of needle insertion. For that, a pair of electrodes was designed to generate a near-linear voltage distribution along the depth direction of the tissue-like phantom. The accuracy of the needle-tip position was investigated by the electric field potential and camera hybridization. The results showed that the needle tip could be detected with an accuracy of 1.05±0.57 mm.

Perception of pain during electromyography in children: A prospective study.

INTRODUCTION: Electrodiagnostic examination is perceived as a painful examination. An accurate assessment of its discomfort would be valuable to children, their parents, and clinicians. METHODS: We performed a prospective study of pediatric patients seen over 3 months at 1 center. Pain was scored for both nerve conduction studies and needle electromyography (EMG) on validated scales, depending on the child's age and in comparison with venipuncture. RESULTS: In 100 cases the pain recorded fell within the moderate range on the scoring systems used. Sixty-six percent of patients described the pain to be equivalent or less than that with venipuncture. EMG of > 1 muscle or a proximal muscle produced more pain in patients <4 years of age. CONCLUSIONS: When discussing the test with patients, the physician should reassure the patient and parents regarding the degree of pain that may be encountered, which is not materially different from venipuncture. Muscle Nerve 54: 422-426, 2016.

Expected and Experienced Pain Levels in Electromyography.

INTRODUCTION: The aim of the present study was to assess pain using a visual analogue scale (VAS) in patients awaiting an EMG procedure (i.e., expected VAS) and after an EMG procedure (i.e., experienced VAS). METHODS: Expected and experienced pain in response to nerve conduction studies (NCS) and needle EMG were assessed in 108 patients (61 females, 47 males; mean age 43.2±11.6) using a VAS. RESULTS: No significant correlations were noted between the expected or the experienced VAS in response to EMG and demographic features of the patients. The expected VAS was significantly higher than the experienced VAS in response to needle EMG (p=0.005). The highest VAS level was noted in the expected VAS in response to needle EMG (4.7±2.2). The lowest VAS level was noted in the experienced VAS in response to NCS (3.6±2.5). CONCLUSION: The present study demonstrated that neither the expected nor the experienced pain associated with EMG exceeded a moderate level. Interestingly, we found that expected pain levels in response to needle EMG were significantly higher than experienced pain levels. Therefore, it may be possible to increase compliance if patients are provided with this information before undergoing electrophysiological procedures.

Needle EMG Response of Lumbar Multifidus to Manipulation in the Presence of Clinical Instability.

A proposed mechanism for the persistence of low back pain due to clinical instability is a decrease in control of local spinal musculature, more specifically decreased recruitment of multifidus. Altered segmental mechanoreceptor input has been proposed as a contributing factor responsible for a decrease in local muscle recruitment. In this case report, immediate changes in the recruitment of the deep multifidus following manipulation were examined using needle EMG and isometric testing of trunk rotational force. Trunk rotational force appeared to improve while the multifidus demonstrated a decrease in activity as measured by needle EMG. No specific conclusions can be drawn from this report; however, the results do suggest that immediate multifidus function may be influenced with manipulation, resulting in improved muscular control of the trunk.