Quantitative Electromyography Research Articles

The Incidence of Residual Neuromuscular Block in Pediatrics: A Prospective, Pragmatic, Multi-institutional Cohort Study.

Introduction Residual neuromuscular block, defined as a quantitatively measured train-of-four ratio (TOFr) <0.9, is common postoperatively.Using a pragmatic trial design, we hypothesized that qualitative and/or clinical assessment of neuromuscular block would inadequately detect residual block following antagonism with neostigmine or sugammadex. Method After IRB approval and written informed consent, 74 children (aged 2-17 years), undergoing elective surgery and receiving rocuronium, were prospectively enrolled in the study at Children's Hospital Colorado and Children's Healthcare of Atlanta. Routine clinical practice at both institutions consisted of clinical signs and/or qualitative assessment with peripheral nerve stimulators. Children at the Colorado hospitalroutinely received sugammadex antagonism; whereas children at the Atlanta hospital received neostigmine. Residual neuromuscular block was assessed postoperatively using quantitative electromyography. If TOFr was <0.9, patients received sugammadex until TOFr ≥0.9. Result Qualitative and clinical assessment failed to detect residual block in 29.7% of patients in the neostigmine reversal cohort (adjusted odds ratio (aOR) 29.8, 95% confidence interval (CI): 2.7 to 5,559.5, p-value = 0.002). No residual block was detected in the sugammadex reversal cohort. A correlation between increasing patient weight and incidence of postoperative residual block was observed in the neostigmine cohort (aOR 1.05, 95% CI: 1.02 to 1.10, p-value = 0.002). Conclusion Qualitative and/or clinical assessment of neuromuscular block inadequately detects residual block following neostigmine antagonism.

Pathophysiological Mechanisms Underlying Unilateral Vocal Fold Paralysis in Female Patients: An Ultrasonographic Study.

Laryngeal ultrasonography (LUS) has been suggested as an alternative diagnostic tool for unilateral vocal fold paralysis (UVFP). The present study applied LUS and quantitative laryngeal electromyography (LEMG) in female UVFP patients to investigate the pathophysiologic mechanisms of UVFP. In this cross-sectional study, vocal fold (VF) length parameters included resting and phonating VF length measured using B-mode LUS, and color Doppler vibrating length (CDVL) measured using the color Doppler mode. Forty female patients with UVFP were enrolled, among whom 11 and 29 were assigned to the thyroarytenoid (TA) muscle+cricothyroid (CT) muscle group (with CT involvement) and the TA (without CT involvement) group, respectively. In the TA group, the turn frequency in thyroarytenoid-lateral cricoarytenoid (TA-LCA) on the paralyzed side, as observed through LEMG, correlated with the VF length during the resting phase (R=0.368, P=0.050) and CDVL values (R=0.627, P=0.000) on the paralyzed side. In the TA+CT group, the turn ratio in the CT muscle correlated with the normalized phonatory vocal length change (nPLC; R=0.621, P=0.041) on the paralyzed side. CDVL and nPLC are two parameters that can be utilized to predict the turn frequencies of TA-LCA in UVFP cases without CT involvement, and the turn ratio of CT in cases of UVFP with CT involvement, respectively. The findings suggest that LUS, as a noninvasive tool, can serve as an alternative method for assessing the severity of laryngeal nerve injury and offer valuable insights into the pathophysiology of UVFP.

N°377 – Are neuromuscular long-term COVID-19 complications chronic? A quantitative and single fiber electromyography follow-up study

N°377 – Are neuromuscular long-term COVID-19 complications chronic? A quantitative and single fiber electromyography follow-up study

Muscle velocity recovery cycles in myopathy

ObjectiveTo understand the pathophysiology of myopathies by using muscle velocity recovery cycles (MVRC) and frequency ramp (RAMP) methodologies. Methods42 patients with quantitative electromyography (qEMG) and biopsy or genetic verified myopathy and 42 healthy controls were examined with qEMG, MVRC and RAMP, all recorded from the anterior tibial muscle. ResultsThere were significant differences in the motor unit potential (MUP) duration, the early and late supernormalities of the MVRC and the RAMP latencies in myopathy patients compared to controls (p < 0.05 apart from muscle relatively refractory period (MRRP)). When dividing into subgroups, the above-mentioned changes in MVRC and RAMP parameters were increased for the patients with non-inflammatory myopathy, while there were no significant changes in the group of patients with inflammatory myopathy. ConclusionsThe MVRC and RAMP parameters can discriminate between healthy controls and myopathy patients, more significantly for non-inflammatory myopathy. MVRC differences with normal MRRP in myopathy differs from other conditions with membrane depolarisation. SignificanceMVCR and RAMP may have a potential in understanding disease pathophysiology in myopathies. The pathogenesis in non-inflammatory myopathy does not seem to be caused by a depolarisation of the resting membrane potential but rather by the change in sodium channels of the muscle membrane.

Not myopathic, but autonomic changes in patients with long-COVID syndrome: a case series

IntroductionNeurological sequelae following SARS-CoV-2 infection still represent a serious concern both for neurologists and neuroscientists. In our paper, we investigated pain, myalgia, and fatigue as symptoms in long-COVID patients with an electrophysiological approach, comprising the evaluation of sympathetic skin responses (SSRs) and quantitative electromyography (qEMG).Materials and methodsTwelve patients were enrolled (mean age, 47.7 ± 11.6 years), referred to our attention because of myalgia, pain, or muscle cramps, which persisted about 6 months after the diagnosis of SARS-CoV-2 infection. They underwent conventional electroneurography (ENG), needle electromyography (EMG), and SSRs; moreover, qEMG was performed by sampling at least 20 motor unit potentials (20–30 MUPs) during weak voluntary contraction in deltoid and tibialis anterior muscles. The mean duration, amplitude, and percentage of polyphasic potentials were assessed and compared with healthy and age-matched volunteers.ResultsENG did not disclose significant changes compared to healthy subjects; needle EMG did not reveal denervation activity. In addition, qEMG showed MUPs similar to those recorded in healthy volunteers in terms of polyphasia (deltoid: p = 0.24; TA: p = 0.35), MUP area (deltoid: p = 0.45; TA: p = 0.44), mean duration (deltoid: p = 0.06; TA: p = 0.45), and amplitude (deltoid: p = 0.27; TA: p = 0.63). SSRs were not recordable from lower limbs in seven patients (58%) and from the upper ones in three of them (25%).ConclusionOur data suggest an involvement of the autonomic system, with a focus on cholinergic efferent sympathetic activity, without any evidence of myopathic changes.

Myopathy as a cause of Long COVID fatigue: Evidence from quantitative and single fiber EMG and muscle histopathology

ObjectiveTo describe neurophysiological abnormalities in Long COVID and correlate quantitative electromyography (qEMG) and single fiber EMG (sfEMG) results to clinical scores and histopathology. Methods84 patients with non-improving musculoskeletal Long COVID symptoms were examined with qEMG and sfEMG. Muscle biopsies were taken in a subgroup. ResultsMean motor unit potential (MUP) duration was decreased in ≥ 1 muscles in 52 % of the patients. Mean jitter was increased in 17 % of the patients in tibialis anterior and 25 % in extensor digitorum communis. Increased jitter was seen with or without myopathic qEMG. Low quality of life score correlated with higher jitter values but not with qEMG measures. In addition to our previously published mitochondrial changes, inflammation, and capillary injury, we show now in muscle biopsies damage of terminal nerves and motor endplate with abundant basal lamina material. At the endplate, axons were present but no vesicle containing terminals. The post-synaptic cleft in areas appeared atrophic with short clefts and coarse crests. ConclusionsMyopathic changes are common in Long COVID. sfEMG abnormality is less common but may correlate with clinical scores. sfEMG changes may be due to motor endplate pathology. SignificanceThese findings may indicate a muscle pathophysiology behind fatigue in Long COVID.

Hip abductor dysfunction following total hip arthroplasty by modified direct lateral approach: Assessment by quantitative electromyography

Abstract Background The use of the direct lateral approach and its modifications for total hip arthroplasty (THA) may lead to postoperative abductor weakness. Assessment of abductor muscle function by the use of quantitative electromyography (EMG) aims to investigate the nature of abductor muscle dysfunction. Methods We conducted a study on 40 patients who had hip replacement through the modified direct lateral approach. EMG was performed before surgery on the affected and normal sides and repeated on the operated side after surgery by 6 and 12 weeks. Analysis of EMG of the three abductor muscles was done in all patients. Results EMG evidence of acute denervation of hip abductors was present in 15 hips (37.5%) after 6 weeks. Improvement of EMG findings occurred in 8 out of 15 patients. Quantitative electromyography (QEMG) showed early significant increase in amplitude in all muscles and decrease in duration in gluteus medius (G. Med) with a pattern of acute nerve injury. At 12 weeks, the values of duration, amplitude, and phase were insignificantly different from the preoperative values signifying the return of near normal muscle activity. Conclusion The use of modified direct lateral approach can cause denervation of hip abductors. It is common in the early postoperative weeks. However, it tends to improve and the residual weakness in some patients is not marked. Quantitative electromyography showed that partial denervation is related to superior gluteal nerve stretching and not to direct injury of the terminal branches of the nerve through the incision.

Aerodynamic Performance and Neuromuscular Control in Patients with Unilateral Vocal Fold Paralysis.

Unilateral vocal fold paralysis (UVFP) causes glottal incompetence and poor vocal efficiency. The influence of laryngeal neuromuscular control on aerodynamics in UVFP remains unclear. This study investigated the relationship between laryngeal muscle activities using quantitative laryngeal electromyography (LEMG) and aerodynamics in UVFP. This prospective study recruited patients with UVFP, and the diagnosis was confirmed with videolaryngostroboscopy and LEMG. The patient received aerodynamic assessment and LEMG of the thyroarytenoid-lateral cricoarytenoid (TA-LCA) muscle complex and the cricothyroid (CT) muscle. The relationship between quantitative LEMG and aerodynamic parameters was analyzed. A total of 134 UVFP patients without concurrent CT muscle involvement were enrolled. Compared with the normal side, the peak turn frequency of the lesioned side was lower in the TA-LCA (p &lt; 0.001) and CT (p = 0.048) muscles. Stepwise linear regression revealed that the turn ratio of TA-LCA muscles was a robust factor in the decrease in peak expiratory airflow (β = -0.34, p = 0.036), mean airflow during voicing (β = -0.28, p = 0.014), and aerodynamic power (β = -0.42, p = 0.019), and an increase in aerodynamic efficiency (β = 27.91, p = 0.012). In addition, the turn ratio of CT muscles was a potent factor in inducing an increase in aerodynamic resistance (β = 14.93, p = 0.029). UVFP without CT involvement still showed suppression of CT muscles on the lesioned side, suggesting that neurological impairment of the TA-LCA complex could cause asymmetrical compensation of CT muscles, further impeding aerodynamics. The residual function of TA-LCA muscle complexes facilitates less air leakage and power dissipation, enhancing aerodynamic efficiency. On the other hand, the symmetrical compensation of the CT muscles improves aerodynamic resistance.

WE-206. Quantitative electromyography in the prognosis of recovery in traumatic nerve injury

WE-206. Quantitative electromyography in the prognosis of recovery in traumatic nerve injury

TH-253. The relationship between quantitative EMG findings and fatigue in patients with myasthenia gravis

TH-253. The relationship between quantitative EMG findings and fatigue in patients with myasthenia gravis

Quantitative Electroencephalography and Surface Electromyography Correlations upon Predictable and Unpredictable Perturbation in Older Adults.

Background: Quantitative Electroencephalography (qEEG) is a non-invasive method used to quantify electrical activity over the cortex. QEEG provides an accurate temporal resolution of the brain activity, making it a useful tool for assessing cortical function during challenging tasks.Objective: This study aimed to investigate postural adjustments in older adults in response to an external perturbation.Material and Methods: In this observational study, nineteen healthy older adults were involved. A 32-channel qEEG was employed to track alterations in beta power on the electrodes over the two sensory-motor areas. Integrated electromyographic activity (IntEMG) of the leg muscles was evaluated in response to perturbations under predictable and unpredictable conditions.Results: The results indicated higher beta power during late-phase in the Cz electrode in both conditions. IntEMG was significantly greater in the tibialis anterior muscle during both conditions in the CPA epoch. In predictable condition, a positive correlation was found between the beta power over C4 (r = 0.560, p = 0.013) and C3 (r = 0.458, p = 0.048) electrodes and tibialis anterior muscle amplitude, and between beta power in C4 and gastrocnemius amplitude (r = 0.525, p = 0.021). In unpredictable condition, there was a positive correlation between beta power over the C4 and the tibialis anterior amplitude (r = 0.580, p = 0.009) and also it over the C3 and the tibialis anterior amplitude (r = 0.452, p = 0.049).Conclusion: Our findings demonstrate that sensorimotor processing occurs in the brain during response to perturbation. Furthermore, cortical activity appeared to be greatest during the recruitment of the muscles upon late-phase in older adults.

Myopathy as a cause of fatigue in long-term post-COVID-19 symptoms: Evidence of skeletal muscle histopathology.

Background and purposeAmong post‐COVID‐19 symptoms, fatigue is reported as one of the most common, even after mild acute infection, and as the cause of fatigue, myopathy diagnosed by electromyography has been proposed in previous reports. This study aimed to explore the histopathological changes in patients with post‐COVID‐19 fatigue.MethodsSixteen patients (mean age = 46 years) with post‐COVID‐19 complaints of fatigue, myalgia, or weakness persisting for up to 14 months were included. In all patients, quantitative electromyography and muscle biopsies analyzed with light and electron microscopy were taken.ResultsMuscle weakness was present in 50% and myopathic electromyography in 75%, and in all patients there were histological changes. Muscle fiber atrophy was found in 38%, and 56% showed indications of fiber regeneration. Mitochondrial changes, comprising loss of cytochrome c oxidase activity, subsarcollemmal accumulation, and/or abnormal cristae, were present in 62%. Inflammation was found in 62%, seen as T lymphocytes and/or muscle fiber human leukocyte antigen ABC expression. In 75%, capillaries were affected, involving basal lamina and cells. In two patients, uncommon amounts of basal lamina were found, not only surrounding muscle fibers but also around nerves and capillaries.ConclusionsThe wide variety of histological changes in this study suggests that skeletal muscles may be a major target of SARS‐CoV‐2, causing muscular post‐COVID‐19 symptoms. The mitochondrial changes, inflammation, and capillary injury in muscle biopsies can cause fatigue in part due to reduced energy supply. Because most patients had mild–moderate acute affection, the new variants that might cause less severe acute disease could still have the ability to cause long‐term myopathy.

Effects of H-Reflex Onset Latency on Gait in Elderly and Hemiplegic Individuals.

Background and Objectives: The Hoffmann’s reflex (H-reflex) is important in electrodiagnostic testing because it improves sensitivity and specificity in diagnosing radiculopathies. Although quantitative electromyography (EMG) measurements for H-reflex amplitudes during the gait cycle have been performed in both hemiplegic and healthy individuals, research on the H-wave latency in these individuals during the gait cycle is lacking. Materials and Methods: The H-reflex latency of the soleus muscle was investigated in hemiplegic stroke patients and healthy elderly persons in this observational analytical study. Two groups of individuals participated in this study: healthy adults (n = 25) and stroke patients with hemiplegia (n = 25) were compared. An MP150 with Ag-Ag/Cl electrodes was utilized to record and analyse electromyography measurements. All individuals could walk independently indoors. Stimuli were administered to elicit the H-reflex in the four gait phases as the participant walked. Results: Stroke patients had a significantly shorter latency than did healthy patients in the mid-swing, mid-stance, and toe-off phases of the gait cycle; heel-strike latency did not significantly differ. Conclusions: These results can be used as diagnostic data to help account for patient characteristics or measure the recovery extent for treatment planning and gait training in hemiplegic individuals.

Developing and exploring a methodology for multi-modal indoor and outdoor gait assessment.

Gait assessment is emerging as a prominent way to understand impaired mobility and underlying neurological deficits. Various technologies have been used to assess gait inside and outside of laboratory settings, but wearables are the preferred option due to their cost-effective and practical use in both. There are robust conceptual gait models developed to ease the interpretation of gait parameters during indoor and outdoor environments. However, these models examine uni-modal gait characteristics (e.g., spatio-temporal parameters) only. Previous studies reported that understanding the underlying reason for impaired gait requires multi-modal gait assessment. Therefore, this study aims to develop a multi-modal approach using a synchronized inertial and electromyography (EMG) signals. Firstly, initial contact (IC), final contact (FC) moments and corresponding time stamps were identified from inertial data, producing temporal outcomes e.g., step time. Secondly, IC/FC time stamps were used to segment EMG data and define onset and offset times of muscle activities within the gait cycle and its subphases. For investigation purposes, we observed notable differences in temporal characteristics as well as muscle onset/offset timings and amplitudes between indoor and outdoor walking of three stroke survivors. Our preliminary analysis suggests a multi-modal approach may be important to augment and improve current inertial conceptual gait models by providing additional quantitative EMG data.

The role of potassium in muscle membrane dysfunction in end-stage renal disease

ObjectiveUremic myopathy is a condition seen in end-stage renal disease (ESRD), characterized by muscle weakness and muscle fatigue, in which the pathophysiology is uncertain. The aim of this study was to assess the role of abnormal serum constituents in ESRD patients by relating them to the excitability properties of the tibialis anterior muscle, at rest and during electrically induced muscle activation, by recording muscle velocity recovery cycles (MVRC) and frequency ramp responses. MethodsEighteen ESRD patients undergoing hemodialysis were evaluated by blood sample, MVRC, and frequency ramp (before and near the end of dialysis treatment), quantitative electromyography, and nerve conduction studies. Patients were compared to 24 control subjects. ResultsIn patients, muscle relative refractory period, early supernormality, late supernormality after 5 conditioning stimuli, and latency of the last of 15 and 30 frequency ramp pulses were strongly associated with potassium levels (p < 0.01), showing depolarization before and normalization in the end of hemodialysis. ConclusionsIn ESRD patients, the muscle membrane is depolarized, mainly due to hyperkalemia. SignificanceSince normal muscle fatigue has been attributed to potassium-induced depolarization, it seems likely that this mechanism is also a major cause of the exaggerated muscle fatigue and weakness in ESRD patients.

Global Brain Consortium Open Science Platform

Rapid eye movement (REM) sleep without atonia (RWA) is observed in some patients without a clinical history of REM sleep behavior disorder (RBD). It remains unknown whether these patients meet the refined quantitative electromyographic (EMG) criteria supporting a clinical RBD diagnosis. We quantitatively evaluated EMG activity and investigated its overnight distribution in patients with isolated qualitative RWA.Fifty participants with an incidental polysomnographic finding of RWA (isolated qualitative RWA) were included. Tonic, phasic, and ‘any’ EMG activity during REM sleep on PSG were quantified retrospectively.Referring to the quantitative cut-off values for a polysomnographic diagnosis of RBD, 7/50 (14%) and 6/50 (12%) of the patients showed phasic and ‘any’ EMG activity in the mentalis muscle above the respective cut-off values. No patient was above the cut-off value for tonic EMG activity or phasic EMG activity in the anterior tibialis muscles. Patients with RWA above the cut-off value showed higher amounts of RWA during later REM sleep periods.This is the first study showing that some subjects with incidental RWA meet the refined quantitative EMG criteria for a diagnosis of RBD. Future longitudinal studies must investigate whether this subgroup with isolated qualitative RWA is at an increased risk of developing fully expressed RBD and/or neurodegenerative disease.

WS4.2. My Approach to Quantitative EMG (with Demonstration)

The routine needle EMG examination is usually performed by observing the waveforms on the display screen and listening to their sound. It is subjective. Quantitative analysis (QA) is considered time consuming and not used. In this workshop, I will describe the “objective and interactive” approach. It adds elements of QA to record and measure EMG signals. It does not add time for analysis, and provides quantitative data to document abnormalities. The techniques of recording and measurements will be demonstrated. This includes use of dual time base, amplitude trigger, cascaded traces, etc. The “quality” control of the recording will be emphasized. The various signal displays help better assessment of amplitude, duration, phases, turns, stability, and firing rate of motor unit potentials (MUPs). It is also useful to assess the fullness of the interference pattern and its amplitude. The additional information captured by this approach will improve the quality of the needle EMG examination. Finally, I will demonstrate the fully automated methods for MUP analysis (Multi-motor unit analysis) and IP (Turns & amplitude). This requires just a few minutes per muscles. Using modern algorithms, QA is not time consuming. It should be included in the laboratory routine.

Can tendon reflexes be elicited by both stretch and vibration in man?

Aim of studyWhen the biceps tendon is tapped, a contraction is elicited in the biceps muscle. This also occurs with tapping of the radial bone, and it has been suggested that vibration is a stimulus for deep tendon reflexes. We investigated whether the normal stimulus for the deep tendon reflex is a sudden stretch, a phasic vibration, or both. Furthermore, we investigated the importance of forearm position for the reflex response in controls and stroke patients.MethodsWe investigated 50 neurological outpatients without clinical signs of neurological disorders in the arms. The biceps tendon and distal radius were tapped with the forearm in the midway (90°), supinated, and pronated positions. In 10 of these patients, the two reflexes were also investigated with quantitative electromyography (EMG) measurements in the 3 positions. Another 10 patients were investigated clinically when stretch of elbow was eliminated and 17 patients were examined when prestretching of the biceps tendon was avoided. Finally, we examined 32 patients that had experienced stroke.ResultsIn 94% (47/50) of patients, after a radial tap, the biceps contraction disappeared in the supinated forearm, and the median peak‐to‐peak amplitude of the surface EMG response (n = 10) decreased from 1.1 to 0.2 mV (p < .01). Elimination of elbow stretch as well as pressure on the biceps tendon did not change the reflex response. In 84% (27/32) of stroke patients, after a radial tap, the biceps contraction persisted in supination in the arm with hyperreflexia.ConclusionThe combined clinical and EMG results are consistent with the concept that the deep tendon reflexes in man can be elicited by both stretch and phasic vibration. Clinicians should be aware that the brachioradial reflex depends on the forearm position.

Myopathic changes in patients with long-term fatigue after COVID-19

ObjectiveTo investigate the peripheral nerve and muscle function electrophysiologically in patients with persistent neuromuscular symptoms following Coronavirus disease 2019 (COVID-19). MethodsTwenty consecutive patients from a Long-term COVID-19 Clinic referred to electrophysiological examination with the suspicion of mono- or polyneuropathy were included. Examinations were performed from 77 to 255 (median: 216) days after acute COVID-19. None of the patients had received treatment at the intensive care unit. Of these, 10 patients were not even hospitalized. Conventional nerve conduction studies (NCS) and quantitative electromyography (qEMG) findings from three muscles were compared with 20 age- and sex-matched healthy controls. ResultsqEMG showed myopathic changes in one or more muscles in 11 patients (55%). Motor unit potential duration was shorter in patients compared to healthy controls in biceps brachii (10.02 ± 0.28 vs 11.75 ± 0.21), vastus medialis (10.86 ± 0.37 vs 12.52 ± 0.19) and anterior tibial (11.76 ± 0.31 vs 13.26 ± 0.21) muscles. All patients with myopathic qEMG reported about physical fatigue and 8 patients about myalgia while 3 patients without myopathic changes complained about physical fatigue. ConclusionsLong-term COVID-19 does not cause large fibre neuropathy, but myopathic changes are seen. SignificanceMyopathy may be an important cause of physical fatigue in long-term COVID-19 even in non-hospitalized patients.

Early detection of evolving critical illness myopathy with muscle velocity recovery cycles

ObjectiveTo investigate the sensitivity of muscle velocity recovery cycles (MVRCs) for detecting altered membrane properties in critically ill patients, and to compare this to conventional nerve conduction studies (NCS) and quantitative electromyography (qEMG). MethodsTwenty-four patients with intensive care unit acquired weakness (ICUAW) and 34 healthy subjects were prospectively recruited. In addition to NCS (median, ulnar, peroneal, tibial and sural nerves) and qEMG (biceps brachii, vastus medialis and anterior tibial muscles), MVRCs with frequency ramp were recorded from anterior tibial muscle. ResultsMVRC and frequency ramp parameters showed abnormal muscle fiber membrane properties with up to 100% sensitivity and specificity. qEMG showed myopathy in 15 patients (63%) while polyneuropathy was seen in 3 (13%). Decreased compound muscle action potential (CMAP) amplitude (up to 58%) and absent F-waves (up to 75%) were frequent, but long duration CMAPs were only seen in one patient with severe myopathy. ConclusionsAltered muscle fiber membrane properties can be detected in patients with ICUAW not yet fulfilling diagnostic criteria for critical illness myopathy (CIM). MVRCs may therefore serve as a tool for early detection of evolving CIM. SignificanceCIM is often under-recognized by intensivists, and large-scale longitudinal studies are needed to determine its incidence and pathogenesis.