Motor Unit Potentials Research Articles

Neurophysiological Hallmarks of Axonal Degeneration in CIDP Patients: A Pilot Analysis.

In this work, we aim to identify sensitive neurophysiological biomarkers of axonal degeneration in CIDP patients. A total of 16 CIDP patients, fulfilling the clinical and neurophysiological criteria for typical CIDP, treated with subcutaneous immunoglobulin (ScIg) (0.4 g/kg/week) were evaluated at baseline (before ScIg treatment) and after long-term treatment with ScIg (24 months) by clinical assessment scales, nerve conduction studies (NCS) and electromyography (EMG). Conventional and non-conventional neurophysiological parameters: motor unit potential (MUP) analysis, MUP thickness and size index (SI)] and interference pattern (IP) features were evaluated after long-term treatment (24 months) and compared with a population of 16 healthy controls (HC). An increase of distal motor latency (DML) and reduced compound motor action potential (CMAP) amplitude and area in CIDP patients suggest axonal damage of motor fibers, together with a significant increase of MUP amplitude, duration and area. Analysis of non-conventional MUP parameters shows no difference for MUP thickness; however, in CIDP patients, SI is increased and IP area and amplitude values are lower than HC. Despite clinical and neurophysiological improvement after ScIg treatment, neurophysiological analysis revealed axonal degeneration of motor fibers and motor unit remodeling. Correlation analysis shows that the axonal degeneration process is related to the diagnostic and therapeutic delay. MUP area and SI parameters can detect early signs of axonal degeneration, and their introduction in clinical practice may help to identify patients with the worst outcome.

PSUN275 Autoimmune Dysglycemia Syndrome (ADS) Associated with Multiple Rheumatological Conditions

Abstract Background Autoimmune dysglycemia syndrome is rare entity that can be induced by drugs or associated with rheumatic diseases. This syndrome includes the insulin autoimmune syndrome caused by anti-insulin antibodies; and type B insulin resistance syndrome caused by anti-insulin receptor antibodies. Patients may present with hyperglycemia, hypoglycemia, or both. Clinical case A 41-year-old Peruvian woman; pulmonary tuberculosis at age 14. In 2008 she presented polyarthritis, elevated ESR and CRP, she received methotrexate and deflazacort for 3 months, presenting remission and suspending medication. In 2009, she was admitted to the emergency room with seizures that resolved after intravenous administration of 33% dextrose. She was hospitalized for study, during her stay she presented episodes of fasting hypoglycemia and postprandial hyperglycemia. She reported hyporexia, weight loss, alopecia, and joint pain. On examination: she presented malar and soft palate erythema, mild pretibial edema. Laboratory tests: fasting blood glucose: 52-69mg/dl, albumin 1,6g/L; fasting insulin: 69.3uIU/mL, C-peptide: 3ng/mL; Anti-insulin antibodies: 4,7 (NV < 0,5), proteinuria 4,2 g/24h, ANA 1/2560 mottled pattern. Anti-cardiolipin, Anti-Sm and Anti-DNA (-). Hemoglobin: 10.6, Leukocytes: 3,160, lymphocytes: 1,540, platelets: 166,000. Renal biopsy showed membranous glomerulonephritis. The determination of antibodies against the insulin receptor is not available in Peru. With the diagnosis of autoimmune dysglycemia associated with SLE, she received prednisone 30mg/d, azathioprine 125mg/d, hydroxychloroquine 400mg/d; fractionated normocaloric diet, NPH + crystalline insulin on a correction scale, she was discharged with a progressive decrease in NPH insulin and metformin 850mg bid. Her glucose levels stabilized, control of proteinuria and joint symptoms was achieved with azathioprine, hydroxychloroquine, prednisone 10mg. The patient remained asymptomatic with rheumatological treatment, she suspended metformin and endocrinological follow-up in 2011. In 2013 she presented recurrent episodes of Raynaud's phenomenon and symptoms of proximal muscle weakness, crusted ulcers on the pads of the fingers of both hands, malar rash and exanthema in heliotrope. Laboratory tests: CPK: 8347U/L. Electromyogram: Spontaneous activity with polyphasic short small motor unit potential and early recruitment. Muscle biopsy showed perifascicular atrophy, perivascular and perimysial inflammatory infiltrate with CD4+ T lymphocytes and B lymphocytes. Glucose, insulin, C3, and C4 levels were normal, and anti-insulin antibodies (-). The diagnosis of dermatomyositis was established. She received prednisone 60mg, hydroxychloroquine, methotrexate 10mg, and nifedipine. In August 2020, telemedicine care in endocrinology and rheumatology concluded that there were no episodes of hypoglycemia, glucose: 86 mg/dl, insulin: 12uIU/ml; anti-insulin antibodies (-); CPK levels 136IU/L, C3, C4 normal, no proteinuria and anti ds-DNA (-). Conclusion Autoimmune conditions could cause dysglycemia mainly through different autoantibodies which may cause hyperglycemia and in rare cases hypoglycemia. This case report emphasizes the importance of long-term follow-up in patients with autoimmune conditions including SLE and ADS. Many of these patients are prompt to develope a new autoimmune disease over time. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m.

Chemotherapy induced juvenile dermatomyositis: a novel presentation- a case report

BackgroundIdiopathic connective tissue disease juvenile dermatomyositis (JDM) is characterised by inflammatory myositis and distinctive skin abnormalities. Only a few cases of Dermatomyositis (DM) owing to chemotherapy used to treat cancer have been reported, despite the fact that the link between DM and cancer in adults is widely known. We describe the case of a female, age 14, who experienced DM as a side effect of chemotherapy following enucleation for retinoblastoma. We also discussed our patient's likely pathophysiology of JDM after treatment.Case presentationA 14-year-old female came to our facility complaining of trouble walking and bluish-black discoloration on her neck, elbows, forehead, and knees that had been present for eight months. The patient had undergone enucleation of the left eye due to retinoblastoma, followed by 40 cycles of radiation therapy and 13 cycles of chemotherapy with Cyclophosphamide, Etoposide, Carboplatin, Vincristine, and Dactinomycin. Her serum LDH and CPK levels were high, and she tested positive for ANA. The muscle biopsy was consistent with the changes of DM. When electromyography was performed, it revealed tiny, fibrillating, polyphasic motor unit potentials and sharp, positive waves that were suggestive with DM. A diagnosis of JDM was made after taking into account the symptoms, biochemical data, muscle biopsy, and electromyography results. The patient's symptoms started to get better once methotrexate and oral corticosteroids were started.ConclusionThis case report emphasises the value of ongoing observation after cancer chemotherapy because specific cutaneous and muscle symptoms may lead paediatricians to consider the possibility of chemotherapy-induced JDM, which is uncommon in young patients.

UBC-Nepal Expedition: Motor Unit Characteristics in Lowlanders Acclimatized to High Altitude and Sherpa.

With acclimatization to high altitude (HA), adaptations occur throughout the nervous system and at the level of the muscle, which may affect motor unit (MU) characteristics. However, despite the importance of MUs as the final common pathway for the control of voluntary movement, little is known about their adaptations with acclimatization. Ten lowlanders and Sherpa participated in this study 7 to 14 d after arrival at HA (5050 m), with seven lowlanders repeating the experiment at sea level (SL), 6 months after the expedition. The maximal compound muscle action potential (M max ) was recorded from relaxed biceps brachii. During isometric elbow flexions at 10% of maximal torque, a needle electrode recorded the MU discharge rate (MUDR) and MU potential (MUP) characteristics of single biceps brachii MUs. Compared with SL, acclimatized lowlanders had ~10% greater MUDR, ~11% longer MUP duration, as well as ~18% lower amplitude and ~6% greater duration of the first phase of the M max (all P < 0.05). No differences were noted between SL and HA for variables related to MUP shape (e.g., jitter, jiggle; P > 0.08). Apart from lower near-fiber MUP area for Sherpa than acclimatized lowlanders ( P < 0.05), no M max or MU data were different between groups ( P > 0.10). Like other components of the body, MUs in lowlanders adapt with acclimatization to HA. The absence of differences between acclimatized lowlanders and Sherpa suggests that evolutionary adaptations to HA are smaller for MUs than components of the cardiovascular or respiratory systems.

Electromyogram Similarity of The Morphologically Similar Muscles

Introduction: Muscles are the largest tissue group in the body and can be classified into various classifications, one of which is based on their morphological shape. Examination of muscles, especially skeletal muscles, can use electromyography. The purpose of this study was to determine whether muscles that have similar morphology have no different electromyogram.Method: This is a descriptive observational study using needle electromyography. The sample amounted to 5 with five times MUP (Motor Unit Potential) in each musculus deltoideus and musculusResult: The mean amplitude, duration, number of voltage phases and the number of voltage turns off the musculus deltoideus and musculus gluteus medius in the study subjects were similar (p-value &gt; 0.05).Conclusion: Muscles that have similar morphology in each parameter of amplitude, duration, number of voltage phases, and number of voltage turns do not have a significant difference in electromyogram.&#x0D;

Ultrasound-guided-electromyography in plegic muscle: Usefulness of nerve stimulation.

In traumatic nerve lesions (TNLs), motor unit potentials (MUPs) may be difficult to detect in early injury. Ultrasound-guided electromyography (US-EMG) can aid in identifying areas of muscle activation, but its sensitivity can be improved. In this study we compare the sensitivity of US-EMG alone with US-EMG after peripheral nerve stimulation (NC-US-EMG) to better identify active muscle regions. In this prospective study, 32 patients with severe TNLs were evaluated with standard EMG (ST-EMG), US-EMG, and NC-US-EMG at baseline (T0), after 2 to 3months (T1), and after 5 to 6months (T2). NC-US-EMG was more sensitive in detecting MUPs compared with US-EMG and ST-EMG at T0 (19 patients vs 14 and 5 patients, respectively). In addition, both US-guided techniques were more sensitive than ST-EMG in detecting MUPs (ST-EMG vs US-EMG: P=.014; ST-EMG vs NC-US-EMG: P=.003). At T1, ST-EMG remained less sensitive NC-US-EMG (P=.019). No significant differences were observed among the three techniques at T2. In the evaluation of severe TNLs, the combination of peripheral nerve stimulation and US increases the sensitivity of EMG for MUP detection at baseline and 2 to 3months postinjury.

Motor unit dysregulation following 15days of unilateral lower limb immobilisation.

Disuse atrophy, caused by situations of unloading such as limb immobilisation, causes a rapid yet diverging reduction in skeletal muscle function when compared to muscle mass. While mechanistic insight into the loss of mass is well studied, deterioration of muscle function with a focus towards the neural input to muscle remains underexplored. This study aimed to determine the role of motor unit adaptation in disuse-induced neuromuscular deficits. Ten young, healthy male volunteers underwent 15days of unilateral lower limb immobilisation with intramuscular electromyography (iEMG) bilaterally recorded from the vastus lateralis (VL) during knee extensor contractions normalised to maximal voluntary contraction (MVC), pre and post disuse. Muscle cross-sectional area was determined by ultrasound. Individual MUs were sampled and analysed for changes in motor unit (MU) discharge and MU potential (MUP) characteristics. VL CSA was reduced by approximately 15% which was exceeded by a two-fold decrease of 31% in muscle strength in the immobilised limb, with no change in either parameter in the non-immobilised limb. Parameters of MUP size were reduced by 11% to 24% with immobilisation, while neuromuscular junction (NMJ) transmission instability remained unchanged, and MU firing rate decreased by 8% to 11% at several contraction levels. All adaptations were observed in the immobilised limb only. These findings highlight impaired neural input following immobilisation reflected by suppressed MU firing rate which may underpin the disproportionate reductions of strength relative to muscle size. KEY POINTS: Muscle mass and function decline rapidly in situations of disuse such as bed rest and limb immobilisation. The reduction in muscle function commonly exceeds that of muscle mass, which may be associated with the dysregulation of neural input to muscle. We have used intramuscular electromyography to sample individual motor unit and near fibre potentials from the vastus lateralisfollowing 15days of unilateral limb immobilisation. Following disuse, the disproportionate loss of muscle strength when compared to size coincided with suppressed motor unit firing rate. These motor unit adaptations were observed at multiple contraction levels and in the immobilised limb only. Our findings demonstrate neural dysregulation as a key component of functional loss following muscle disuse in humans.

Effects of short-term unloading and active recovery on human motor unit properties, neuromuscular junction transmission and transcriptomic profile.

Electrophysiological alterations of the neuromuscular junction (NMJ) and motor unit potential (MUP) with unloading are poorly studied. We aimed to investigate these aspects and the underlying molecular mechanisms with short-term unloading and active recovery (AR). Eleven healthy males underwent a 10-day unilateral lower limb suspension (ULLS) period, followed by 21-day AR based on resistance exercise. Quadriceps femoris (QF) cross-sectional area (CSA) and isometric maximum voluntary contraction (MVC) were evaluated. Intramuscular electromyographic recordings were obtained during 10% and 25% MVC isometric contractions from the vastus lateralis (VL). Biomarkers of NMJ molecular instability (serum c-terminal agrin fragment, CAF), axonal damage (neurofilament light chain) and denervation status were assessed from blood samples and VL biopsies. NMJ and ion channel transcriptomic profiles were investigated by RNA-sequencing. QF CSA and MVC decreased with ULLS. Increased CAF and altered NMJ transcriptome with unloading suggested the emergence of NMJ molecular instability, which was not associated with impaired NMJ transmission stability. Instead, increased MUP complexity and decreased motor unit firing rates were found after ULLS. Downregulation of ion channel gene expression was found together with increased neurofilament light chain concentration and partial denervation. The AR period restored most of these neuromuscular alterations. In conclusion, the human NMJ is destabilized at the molecular level but shows functional resilience to a 10-day unloading period at least at relatively low contraction intensities. However, MUP properties are altered by ULLS, possibly due to alterations in ion channel dynamics and initial axonal damage and denervation. These changes are fully reversed by 21days of AR. KEY POINTS: We used integrative electrophysiological and molecular approaches to comprehensively investigate changes in neuromuscular integrity and function after a 10-day unilateral lower limb suspension (ULLS), followed by 21days of active recovery in young healthy men, with a particular focus on neuromuscular junction (NMJ) and motor unit potential (MUP) properties alterations. After 10-day ULLS, we found significant NMJ molecular alterations in the absence of NMJ transmission stability impairment. These findings suggest that the human NMJ is functionally resilient against insults and stresses induced by short-term disuse at least at relatively low contraction intensities, at which low-threshold, slow-type motor units are recruited. Intramuscular electromyography analysis revealed that unloading caused increased MUP complexity and decreased motor unit firing rates, and these alterations could be related to the observed changes in skeletal muscle ion channel pool and initial and partial signs of fibre denervation and axonal damage. The active recovery period restored these neuromuscular changes.

On the establishment of reference values of clouds of electromyography interference pattern by linear regression method and percentile method and comparison of sensitivity and specificity of both methods.

ObjectiveTurn-amplitude clouds were widely used in automatic electromyography (EMG) interference pattern analysis. Earlier works employed the intercept ± 2SD (standard deviation) of the linear regression equation as the upper and lower boundaries of the clouds. The goal of this study was to employ the linear regression method and percentile method to calculate the reference value of turn-amplitude clouds, identify the determining criteria in accordance with the receiver operator characteristic curve (ROC), and analyze the sensitivity and specificity of the linear regression cloud, percentile cloud, and quantitative assessment of the motor unit potential (QMUP).MethodsFirst, we explore what factors affect the number of turns per second and the mean amplitude. Then, their logarithms were taken for the normal test. All muscle data were used to calculate the reference values of percentile clouds. However, the reference values of the linear regression clouds were obtained for the muscles with a bivariate normal distribution, homogeneous variances and a linear correlation. We calculated the prediction interval with the standard errors of the intercept and slope of the linear regression equation, which can determine the upper and lower boundaries of the linear regression clouds. Furthermore, we obtained ROCs of these clouds, which were used as the determining criteria to determine the optimum cut-off values. Finally, our study analyzed the sensitivity and specificity of the linear regression cloud, percentile cloud, and QMUP.ResultsWe here presented the reference values and ROCs of the linear regression clouds and percentile clouds. We suggest the determining criteria be based on ROCs. The areas under the curve (AUC) of both clouds are larger than 0.8, revealing that they have significant diagnostic value. Our results display that the specificities of the linear regression clouds, percentile clouds, and QMUP are almost identical to each other, whereas the sensitivity of percentile cloud is higher than those of QMUP and linear regression clouds.ConclusionAccording to ROCs, the researchers determine the determining criteria of the linear regression clouds and percentile clouds. Our findings suggest that the percentile clouds possess a wide application range and significant diagnostic value, therefore it may be the optimum for automatic EMG interference pattern analysis.

Automatic jitter measurement in needle-detected motor unit potential trains

In an active motor unit (MU), the time intervals between the firings of its muscle fibers vary across successive MU activations. This variability is called jitter and is increased in pathological processes that affect the neuromuscular junctions or terminal axonal segments of MUs. Traditionally, jitter has been measured using single fiber electrodes (SFEs) and a difficult and subjective manual technique. SFEs are expensive and reused, implying a potential risk of patient infection; so, they are being gradually substituted by safer, disposable, concentric needle electrodes (CNEs). As CNEs are larger, voltage contributions from individual fibers of a MU are more difficult to detect, making jitter measurement more difficult. This paper presents an automatic method to estimate jitter from trains of motor unit potentials (MUPs), for both SFE and CNE records. For a MUP train, segments of MUPs generated by single muscle fibers (SF MUP segments) are found and jitter is measured between pairs of these segments. Segments whose estimated jitter values are not reliable, according to several SF MUP segment characteristics, are excluded. The method has been tested in several simulation studies that use mathematical models of muscle fiber potentials. The results are very satisfactory in terms of jitter estimation error (less than 10% in most of the cases studied) and mean number of valid jitter estimates obtained per simulated train (greater than 1.0 in many of the cases and less than 0.5 only in the most complicated). A preliminary study with real signals was also performed, using 19 MUP trains from 3 neuropathic patients. Jitter measurements obtained by the automatic method were compared with those extracted from a commercial system (Keypoint) and the edition and supervision of an expert electromyographer. From these measurements 63% were taken from equivalent interval pair sites within the time span of the MUP trains and, as such, were considered as compatible measurements. Differences in jitter of these compatible measurements were very low (mean value of 1.3 μs, mean of absolute differences of 2.97 μs, 25% and 75% percentile intervals of −0.85 and 3.82 μs, respectively). Although new tests with larger number of real recordings are still required, the method seems promising for clinical practice.

Glycogen accumulation in GNE myopathy

Patient 1, a 23-year-old male, and patient 2, a 28-year-old female, developed progressive painless footdrop at age 18 and 20 years, respectively. The weakness progressed to involve distal upper limb and proximal muscles. Neurologic examination showed generalized limb weakness, most severely affecting tibialis anterior. Creatine kinase levels were mildly elevated. Needle electromyography detected myopathic motor unit potentials and frequent fibrillation potentials. Muscle biopsy revealed several fibers harboring rimmed vacuoles and a few fibers containing non-rimmed vacuoles filled with periodic acid-Schiff-positive, diastase-labile material, consistent with glycogen (Fig. 1).

Modulation of spontaneous motor unit potentials by a new motor cortical magnetic stimulation method in amyotrophic lateral sclerosis

Patients with amyotrophic lateral sclerosis (ALS) show altered cortical excitability. In this study, we measure modulation of spontaneous motor unit potentials (sMUPs) in hand muscles by multifocal cortical stimulation with a newly developed wearable transcranial rotating permanent magnet stimulator (TRPMS). We conducted cross-sectional and longitudinal electromyographic assessments in 40 and 20 ALS patients, respectively, of the stimulation-induced peak increase in the count of sMUPs in two hand muscles modulated by unilateral TRPMS stimulation of the primary motor cortex. We measured peak sMUP counts during several short sessions consisting of 10 stimuli over 60s and 30s post-stimulation periods. The longitudinal component involved an initial assessment at an early stage of the disease and up to five follow-up assessments at least 3months apart. TRPMS stimulation produced no device-related adverse effects. It showed an inverted V-shaped modulation of the peak sMUP counts as a function of ALS functional rating scale revised scores. The ratios of ALS subjects showing peak sMUP count increases between early and intermediate stages (χ2 = 4.086, df = 1, p = 0.043) and intermediate and late stages (χ2 = 4.29, df = 1, p = 0.038) in cross-sectional data were significantly different. Longitudinal assessment also produced a significant (z = 2.31, p = 0.021) result, with all subjects showing a post-initial visit increase in peak sMUP counts. These results are consistent with delayed onset of upper motor neuronal dysfunction with respect to onset of clinical features. However, the above results need to be confirmed in a larger sample of patients and with multiple lines of evidence.

The electromyographic analysis of orbicularis oculi muscle in epiphora.

Purpose:Functional epiphora is a clinical condition that presents with the complaint of watery eyes, but without anatomical stenosis in the lacrimal drainage system. Although the mechanism is not clear, there are various possibilities involving the movement of the orbicularis oculi muscle, especially its deeper segment (Horner’s muscle). We aimed to evaluate the function of the orbicularis oculi muscle in patients with patent, but dysfunctional lacrimal drainage system using a quantitative motor unit potential (MUP) analysis.Methods:Twenty-eight patients with functional epiphora (mean age = 59 years) and a control group of 28 volunteers were included in the study. Inclusion criteria were persistent and symptomatic epiphora or wiping >10 times per day and diagnosis confirmation by lacrimal irrigation test. Electromyography (EMG) was performed on the deeper segment of the orbicularis oculi muscle (medial and lateral parts). MUP parameters (duration time, amplitude, number of phases, number of turns, area, rise time, and thickness) were evaluated in both groups. Any increase in amplitude, prolongation time (>14 ms), number of turns, and satellite potential was taken as characteristic of the neurogenic type of epiphora, whereas shortened motor unit duration time, increased phase number, and low amplitude are the features of myopathic type.Results:Upon MUP analysis of the medial and lateral orbicularis oculi muscle, the increase in duration and thickness values in the medial part and the increase in duration, amplitude, area, and thickness values of the lateral part were found to be statistically significant in the patient group compared to the control group (P < 0.001). In the evaluation of the patients’ medial and lateral orbicularis oculi muscle, the increase in phase values and decrease in amplitude, area, and rise time values were found to be statistically significant (P = 0.024, P < 0.001, P < 0.001, and P = 0.010, respectively).Conclusion:These data show that functional epiphora is due to neurogenic damage of the orbicularis oculi muscle and should be investigated in more detail.

Commentary: The electromyographic analysis of orbicularis oculi muscle in epiphora.

The simplest description of functional epiphora is “epiphora in the presence of a patent lacrimal drainage system, absence of any demonstrable anatomical abnormality, and absence of alternative etiology.”[1] It is a complex and underdiagnosed entity. Jones, in 1957, suggested dysfunctions of the lacrimal pump as the major aberration in functional epiphora.[2] Ali et al.,[3] in 2020, presented a new theory of lacrimal pump functions based on their anatomical, ultrastructural, and immunohistochemical studies of the Horner–Duverney (HD) muscle. The diagnosis of functional epiphora is by a series of examinations and imaging to exclude other causes. In essence, it is a diagnosis of exclusion. Hence, a careful clinical examination along with magnetic resonance dacryocystography or dacryoscintigraphy are helpful.[4] The data on the use of electromyography (EMG) and its characteristics in such cases is evolving. The present study succinctly described the electromyographic response of the deeper heads of the orbicularis oculi muscle using the motor unit potential (MUP) analysis.[5] A statistically significant change in the amplitude, duration, number of phases, turns, and rise time were noted between the functional epiphora cohort and normal volunteers. The EMG was suggestive of a neurogenic origin of lacrimal pump weakness in patients with functional epiphora. Apart from the earlier known motor innervation by the branches of the facial nerve, recent other explorations have pointed to the presence of an extensive network of additional sensory, sympathomimetic, and parasympathetic innervation of the HD muscle.[3] Hence, the EMG needs to be further explored. Although the present study had several limitations, including difficulties with the not very conclusive results, it is nevertheless an excellent strategy to begin answering the proposed research query. To what extent can an EMG help appreciate the complex physiology of the HD muscle is yet to be deciphered. Although EMG partly enhances our understanding of the orbicularis oculi behavior in different clinical settings, it does not directly assess the lacrimal pump mechanisms of tear flow. Besides, it is unhelpful to assess other mechanisms in tear flow dynamics such as capillary action, gravity, and pressure gradient. At present, EMG of the HD muscle has limited clinical worth and, at best, can be of adjunctive value. However, its utility as a research tool has the potential to further our understanding of the lacrimal pump. Financial disclosure Mohammad Javed Ali receives royalties from Springer for the textbook “Principles and Practice of Lacrimal Surgery,” “Atlas of Lacrimal Drainage Disorders,” and “Video Atlas of Lacrimal Surgery.”

Outcomes of Nerve Transfers in Peroneal Nerve Palsy.

Background: The objective of this work is to: (i) evaluate the postoperative outcomes after lower extremity nerve transfer (LENT) in patients with peroneal nerve palsy, and (ii) evaluate the patient and surgical factors that best predict successful restoration of ankle dorsiflexion following nerve transfer. Methods: A retrospective cohort of prospectively collected data included all patients who underwent LENT (2010-2018). Two independent reviewers performed data collection. Primary outcome measures were: (i) clinically with British Medical Research Council (MRC) strength assessments, and (ii) electrodiagnostically with nascent motor unit potentials. Statistical analysis was performed using descriptive and nonparametric statistics. Results: Nine patients (56% male, mean age 38.3, range 18-57 years) underwent LENT surgery a mean of 4.3 months following injury (range 2.2-6.4 months). Mean follow-up was 15.6 months (range 9.1-28.2 months). Postoperatively, ankle dorsiflexion (P = .015) and ankle eversion (P = .041) increased significantly. After surgery, 44% achieved MRC 4, 33% obtained MRC 1 motor recovery, and 22% sustained MRC 0. A shorter time to surgery was associated with significantly better outcomes (P = .049). Conclusions: It appears that there is a bimodal distribution between responders and nonresponders to LENT for foot drop. Further research is required to elucidate patient and surgical factors that prognosticate success.

Needle Electromyography in the Acute Phase of Stroke: Correlation With Severity and Muscle Strength: Preliminary Findings.

After the stroke, the development of the second motor neuron degeneration can reduce muscle strength and functional capacity. The aim of this study was to describe the electro-myographic findings in the acute phase of stroke and to correlate them with the severity and muscle strength. Twenty patients were studied in the first 72 hours after stroke. The severity of the lesion was assessed using the National Institutes of Health Stroke Scale (NIHSS), and muscle strength was assessed using the Medical Research Council Scale (MRC). Sensory conduction and motor conduction were studied to exclude peripheral polyneuropathy, radiculopathies, or other neuro-muscular diseases, and electro-myography (EMG) was performed with co-axial needle electrodes in the deltoid, carpal radial extensor, vastus lateralis, and anterior tibialis at rest, slight effort and maximum effort. The associations between qualitative and quantitative variables were studied using the Chi-square test and Fisher's exact test. Among the patients, 40% had abnormal EMG [positive sharp waves (PSWs), fibrillation, fasciculations, and abnormal patterns in maximum effort]. Positive correlations were found between NIHSS and PSW (p = 0.005; r = 0.65) and abnormal EMG (p = 0.017; r = 0.72), and negative correlations were found between MRC and PSW (p = 0.041; r = -0.83) and abnormal EMG (p = 0.027; r = -0.81). It was concluded that the main EMG findings in the acute phase of stroke were the presence of the denervation process and polyphasic motor unit potentials. These changes in EMG were correlated with stroke severity and lower muscle strength.

Effect of nitrate supplementation on skeletal muscle motor unit activity during isometric blood flow restriction exercise

BackgroundNitrate (NO3−) supplementation has been reported to lower motor unit (MU) firing rate (MUFR) during dynamic resistance exercise; however, its impact on MU activity during isometric and ischemic exercise is unknown.PurposeTo assess the effect of NO3− supplementation on knee extensor MU activities during brief isometric contractions and a 3 min sustained contraction with blood flow restriction (BFR).MethodsSixteen healthy active young adults (six females) completed two trials in a randomized, double-blind, crossover design. Trials were preceded by 5 days of either NO3− (NIT) or placebo (PLA) supplementation. Intramuscular electromyography was used to determine the M. vastus lateralis MU potential (MUP) size, MUFR and near fibre (NF) jiggle (a measure of neuromuscular stability) during brief (20 s) isometric contractions at 25% maximal strength and throughout a 3 min sustained BFR isometric contraction.ResultsPlasma nitrite (NO2−) concentration was elevated after NIT compared to PLA (475 ± 93 vs. 198 ± 46 nmol L−1, p < 0.001). While changes in MUP area, NF jiggle and MUFR were similar between NIT and PLA trials (all p > 0.05), MUP duration was shorter with NIT compared to PLA during brief isometric contractions and the sustained ischemic contraction (p < 0.01). In addition, mean MUP duration, MUP area and NF jiggle increased, and MUFR decreased over the 3 min sustained BFR isometric contraction for both conditions (all p < 0.05).ConclusionsThese findings provide insight into the effect of NO3− supplementation on MUP properties and reveal faster MUP duration after short-term NO3− supplementation which may have positive implications for skeletal muscle contractile performance.

Design and pilot testing of a 26-gauge impedance-electromyography needle in wild-type and ALS mice.

Needle impedance-electromyography (iEMG) is a diagnostic modality currently under development that combines intramuscular electrical impedance with concentric electromyography (EMG) in a single needle. We designed, manufactured, and tested a prototype iEMG needle in a cohort of wild-type (WT) and SOD1G93A amyotrophic lateral sclerosis (ALS) mice to assess its ability to record impedance and EMG data. A new six-electrode, 26-gauge, iEMG needle was designed, manufactured and tested. Quantitative impedance and qualitative "gestalt" EMG were performed sequentially on bilateral quadriceps of 16-wk-old SOD1G93A ALS (N= 6) and WT (N= 6) mice by connecting the needle first to an impedance analyzer (with the animal at rest) and then to a standard EMG system (with the animal fully under anesthesia to measure spontaneous activity and briefly during awakening to measure voluntary activity). The needle remained in the muscle throughout the measurement period. EMG data were qualitatively similar to that observed with a commercially available concentric EMG needle; fibrillation potentials were observed in 84% of the ALS mice and none of the WT mice; motor unit potentials were also readily identified. Impedance data revealed significant differences in resistance, reactance, and phase values between the two groups, with ALS animals having reduced reactance and resistance values. This work demonstrates the feasibility of a single iEMG needle conforming to standard dimensions of size and function. Further progress of iEMG technology for enhanced neuromuscular diagnosis and quantification of disease status is currently in development.

Electrodiagnostic Characteristics Suggestive of Muscle-Specific Kinase Myasthenia Gravis.

Muscle-specific kinase (MuSK) antibody-positive myasthenia gravis (MuSK + MG) is a form of MG with bulbar-predominant symptoms often resistant to conventional treatments. Patients with MuSK + MG may have an electrodiagnostic (EDX) profile distinct from other MG. This study compares EDX features of MuSK + MG with acetylcholine receptor (AChR) antibody-positive MG (AChR + MG) to discern whether any unique EDX pattern exists that can aid in clinical diagnosis. From January 1, 2010, through December 31, 2020, all patients with MuSK + MG at our institution were identified and randomly matched to an AChR + MG cohort in a 1:2 ratio based on sex, age at onset, and subsequently Myasthenia Gravis Foundation of America (MGFA) clinical severity for a case-control study. Each patient's clinical profile, treatment, and EDX testing were summarized and analyzed. Twenty-two patients with MuSK + MG (18 female) and 44 patients with AChR + MG were studied. The average symptom duration at presentation was shorter in the MuSK + MG group (4.7 years) compared with AChR + MG (10.9 years). Myotonic discharges were rare in both groups but more frequently observed in patients with MuSK + MG (10%) identified in 5 muscles in 2 patients compared with AChR + MG (2%) noted in only 1 muscle in 1 patient. Patients with MuSK + MG more often had myopathic appearing motor unit potentials (MUPs) (41% vs 30%) compared with AChR + MG. Myopathic appearing MUPs were found in milder cases of MuSK + MG (MGFA class I-IIB) compared with AChR + MG (MGFA Class IIB-V). Patients with MuSK + MG may have a recognizable EDX profile from AchR + MG that includes (1) myotonic discharges, (2) greater occurrence of myopathic appearing MUPs in clinically mild disease, and (3) symptoms leading to earlier testing.

Laryngeal Electromyography in the Therapeutic Process of Patients with Vocal Fold Immobility or Dysmobility

(1) Background: Laryngeal electromyography (LEMG) plays a key role in classifying the severity of nerve damage and determining the prognosis of the nerve recovery. LEMG is primarily a qualitative study, without a standardized approach to interpretation. The development of qualitative and quantitative analysis would situate LEMG in the gold standard of modern neurolaryngologic diagnostics. The aim of this study was to quantitatively evaluate laryngeal electromyography recorded in patients with vocal fold immobility or dysmobility. (2) Methods: The electromyographic material comprised 84 thyroarytenoid muscles recordings of 42 patients. (3) Results: In our study, we observed significant differences between EMG characteristics of healthy and paralyzed VF. Our study showed that recording laryngeal muscle activity during successive phases of breathing provides additional valuable information. We noticed that the frequency and amplitude of motor unit potentials correlates with the return of vocal fold functionality. (4) Conclusions: Laryngeal EMG guides the clinician on the best course of treatment for the patient. It is therefore important to develop an effective methodology and consensus on the quantitative interpretation of the record. Amplitude and frequency parameters are valuable in predicting neural recovery and in the return of vocal fold mobility.