Motor Unit Research Articles

Electrophysiological diagnostics in choosing treatment strategy for neuropathies in children with transcondylar fractures

A common complication of transcondylar fractures (TCF) in children is neuropathy requiring not only therapeutic but also surgical treatment. Despite numerous reports, clear criteria for selecting patients for surgical treatment have not been defined. To clarify the role of clinical and electrophysiological diagnostics in choosing treatment tactics for neuropathies in children with TCF. There were 20 patients with neuropathies after TCF between 2020 and 2022. Of these, 10 ones were selected for surgical treatment according to electrophysiological diagnostic data. Inclusion criteria: age 6-12 years, closed TCF within previous 3-12 months, symptoms of neuropathy confirmed by electroneuromyography (ENMG), no nerve disruption according to ultrasound data. Exclusion criteria: elbow joint contracture and post-traumatic ulnar nerve dislocation. All patients underwent needle myography with functional assessment of motor and sensory fibers, spontaneous activity in muscles, recruitment pattern and motor unit potentials. Intraoperative electrophysiological diagnostics included stimulation of motor fascicles with registration of M-responses from the target muscles. The follow-up period was 3-6 months. The study included 20 patients aged 6-12 years without peripheral nerve disruption. A group of 10 patients who required surgical treatment was identified. The control group consisted of 10 patients who did not require surgical treatment. To choose treatment tactics, we considered ENMG data. Surgical procedure was determined according to intraoperative neuromonitoring (IONM) data. When choosing treatment strategy, surgeons should consider objective ENMG and IONM criteria, as well as fascicular anatomy.

Evaluation of bone health in terms of osteoporosis in adult patients with neuromuscular disease.

There are no current guidelines to help clinicians decide whether patients with adult neuromuscular disease (NMD) should be screened or treated for osteoporosis (OP). This study was undertaken to investigate the presence of OP in patients with various types of NMD and to examine the relationship between OP evaluation parameters and functional status, daily living activities, balance, and ambulation levels. This cross-sectional study included 45 patients with NMDs. The patients were divided into 3 groups, depending on the affected component of the motor unit (neuronopathy group, neuropathy group, and myopathy group). The laboratory and demographic data were recorded from patient files. Functional level, pain, muscular strength, balance, and daily living activity scores were evaluated. The presence of OP was quantified using bone densitometry, fracture history, and biochemical parameters. Clinical findings were correlated with laboratory and dual-energy X-ray absorptiometry (DEXA) findings. The mean hip T-score was -1.20, and the mean lumbar spine (L1-L4) T-score was -0.95 in all groups. Six patients with T-score values of -2.5 or below were detected. Vitamin D level was found to be low in all patient groups, especially in the myopathy group, but there was no significant difference (p > 0.05). There was a negative correlation between hip T-score and the frequency of falling (r = -0.604, p = 0.022), while a positive correlation was found between hip T-score and the age at which independent walking was no longer possible (r = 0.900, p = 0.037). OP is often overlooked in NMD patients with neurological problems and a high risk of falling. These patients should be screened for bone health and fragility.

Neuromyotonia.

Neuromyotonia is continuous peripheral nerve hyper-excitability manifesting in muscle twitching at rest (myokymia), inducible cramps and impaired muscle relaxation, and characterized by EMG findings of spontaneous single motor unit discharges (with doublet, triplet, or multiplet morphology). The disorder may be genetic, acquired, and often in the acquired cases autoimmune. This chapter focuses on autoimmune acquired causes. Autoimmune associations include mainly contactin-associated protein-like 2 (CASPR2) antibody-associated disease (previously termed as VGKC or voltage-gated potassium channel antibody-associated neuromyotonia) (van Sonderen et al., 2016, p. 2), leucine-rich glioma-inactivated 1 (LGI1) antibody disease, the Guillain-Barré syndrome, NMDAR encephalitis (Varley et al., 2019), and IgLON5 (Gaig et al., 2021) disease. Nonimmune associations include radiation-induced plexopathy. An association with myasthenia gravis and other autoimmune disorders, response to plasma exchange (Newsom-Davis and Mills, 1993) and physiologically induced changes in mice injected with patient-derived immunoglobulins led to the discovery of autoantibodies to juxtaparanodal proteins complexed with potassium channels (Shillito et al., 1995). The target of the antibodies is most commonly the CASPR2 protein. The disorder may be paraneoplastic, and a search for and treatment of an underlying tumor is a necessary step. In cases in which there is evidence for an immune cause, then immune suppression, with an emerging role for B cell-depleting therapies, is associated with a good clinical outcome. In parallel, sodium channel blocking drugs remain effective symptomatic therapies.

Neuro-Muscular Responses Adaptation to Dynamic Changes in Grip Strength.

Precise control of strength is of significant importance in upper limb functional rehabilitation. Understanding the neuro-muscular response in strength regulation can help optimize the rehabilitation prescriptions and facilitate the relative training process for recovery control. This study aimed to investigate the inherent characteristics of neural-muscular activity during dynamic hand strength adjustment. Four dynamic grip force tracking modes were set by manipulating different magnitude and speed of force variations, and thirteen healthy young individuals took participation in the experiment. Electroencephalography were recorded in the contralateral sensorimotor cortex area, as well as the electromyography from the first dorsal interosseous muscle were collected synchronously. The metrics of the Event-related desynchronization, the electromyography stability index, and the force variation, were used to represent the corresponding cortical neural responses, muscle contraction activities, and the level of strength regulation, respectively; and further neuro-muscular coupling between the sensorimotor cortex and the first dorsal interosseous muscle was investigated by transfer entropy analysis. The results indicated a strong relationship that the increase of force regulation demand would result in a force variation increase as well as a stability reduction in muscle motor unit output. Meanwhile, the intensity of neural response increased in both the α and β frequency bands. As the force regulation demand increased, the strength of bidirectional transfer entropy showed a clear shift from β to the γ frequency band, which facilitate rapid integration of dynamic strength compensation to adapt to motor task changes.

The relationship between the functional status of upper extremity motor neurons and motor function and prognosis in stroke patients.

This study investigates the correlation between neuroelectrop-hysiological assessments such as motor unit number estimation (MUNE) and F-waves with upper extremity motor function and one-year prognosis in stroke patients. Neuroelectrophysiological assessments of the abductor pollicis brevis muscle, including MUNE and F-waves, were conducted. Upper extremity motor function was evaluated using the Fugl-Meyer Assessment of Upper Extremity (FMA-UE) and the Modified Ashworth Scale (MAS). Pearson correlation and multiple linear regression analyses were performed to explore the relationship between upper extremity motor function and variables such as MUNE and F-waves. ROC curve analysis assessed the predictive ability of MUNE and F-waves for upper extremity motor function, and binary logistic regression analysis examined factors related to motor function improvement 1 year post-discharge. A total of 130 patients were ultimately included. Significant differences in MUNE and occupancy rate of non-repeater F-waves (non-ORF) were found between hemiplegic and unaffected sides (p < 0.001), with a significant difference in F-wave mean latency (p < 0.05). Pearson correlation analysis showed a positive correlation between FMA-UE at admission and hemiplegic side's MUNE and non-ORF (p < 0.001). Multiple linear regression indicated that hemiplegic side's MUNE (β = 0.88, p < 0.001) and non-ORF (β = 0.275, p = 0.005) influenced FMA-UE. ROC analysis demonstrated higher predictive ability for hemiplegic side's MUNE (AUC = 0.696, p < 0.001) than non-ORF (AUC = 0.622, p = 0.018). Binary logistic regression showed that hemiplegic side's MUNE was associated with FMA-UE improvement 1 year post-discharge. MUNE and F-waves are correlated with upper extremity motor function in patients, reflecting their motor function status. These indicators have good predictive value for motor function and are associated with the prognosis of upper extremity motor function to a certain extent.

Effects of Alaska Pollack Protein Ingestion on Neuromuscular Adaptation in Young Healthy Adults: A Randomized, Placebo-Controlled Trial.

Alaska pollack protein (APP), has been reported as a protein source that can enhance muscle hypertrophy more than other protein sources in animal studies. This study aimed to examine the effects of APP ingestion on muscle quantity and quality in young adults. Fifty-five young college students were assigned to two groups: APP and placebo (whey protein: WP) groups, and instructed to ingest 4.5 g of each protein in addition to daily meals, and to maintain their usual daily physical activities for 3 mo. Twenty-one and 23 students completed the intervention and were analyzed in APP and WP groups, respectively. The maximum knee extension torque significantly increased in both groups during the intervention. The motor unit discharge rate, which is an indicator of activation, for a given force level significantly decreased in both groups during the intervention, but its decrease in the APP group was significantly greater than in the WP group. Echo intensity of the vastus lateralis evaluated by ultrasound images significantly decreased in both groups. The muscle thickness and skeletal muscle mass did not change. Small amount of additional APP intake induces greater effects on neural activation than WP, suggesting the greater neural economy of generation of force.

Post-activation potentiation and potentiated motor unit firing patterns in boys and men.

Post-activation potentiation (PAP) describes the enhancement of twitch torque following a conditioning contraction (CC) in skeletal muscle. In adults, PAP may be related to muscle fibre composition and is accompanied by a decrease in motor unit (MU) firing rates (MUFRs). Muscle fibre composition and/or activation is different between children and adults. This study examined PAP and MU firing patterns of the potentiated knee extensors in boys and men. Twenty-three boys (10.5 ± 1.3years) and 20 men (23.1 ± 3.3years) completed familiarization and experimental sessions. Maximal isometric evoked-twitch torque and MU firing patterns during submaximal contractions (20% and 70% maximal voluntary isometric contraction, MVIC) were recorded before and after a CC (5s MVIC). PAP was calculated as the percent-increase in evoked-twitch torque after the CC. MU firing patterns were examined during submaximal contractions before and after the CC using Trigno Galileo surface electrodes (Delsys Inc) and decomposition algorithms (NeuroMap, Delsys Inc). MU action potential amplitudes (MUAPamp) and MUFRs were calculated for each MU and exponential MUFR-MUAPamp relationships were calculated for each participant and trial. PAP was higher in men than in boys (98.3 ± 37.1% vs. 68.8 ± 18.3%, respectively; p = 0.002). Following potentiation, the rate of decay of the MUFR-MUAPamps relationship decreased in both contractions, with a greater decrease among boys during the high-intensity contractions. Lower PAP in the boys did not coincide with smaller changes in potentiated MU firing patterns, as boys had greater reductions in MUFRs with potentiation compared with men in high-intensity contractions.

Intramuscular and intermuscular coherence analysis while obstacle crossing during treadmill gait

Purpose This study aimed to identify the contribution of the common synaptic drives to motor units during obstacle avoidance, using coherence analysis between a-pair electromyography (EMG) signals (EMG-EMG coherence). Materials and Methods Fourteen healthy volunteers walked on a treadmill with and without obstacle avoidance. During obstacle gait, subjects were instructed to step over an obstacle with their right leg while walking that would randomly and unpredictably appear. Surface EMG signals were recorded from the following muscles of the right leg: the proximal and distal ends of tibialis anterior (TAp and TAd), biceps femoris (BF), semitendinosus (ST), lateral gastrocnemius (LG), and medial gastrocnemius (MG). Beta-band (13–30 Hz) EMG-EMG coherence was analysed. Results Beta-band EMG-EMG coherence of TAp-TAd during swing phase and BF-ST during pre and initial swing phase when stepping over an obstacle were significantly higher compared to normal gait (both p < 0.05). Beta-band EMG-EMG coherence of TAp-TAd, BF-ST, and LG-MG during stance phase were not significantly different between the two gait conditions (all p > 0.05). Conclusions The present findings suggest increased common synaptic drives to motor units in ankle dorsiflexor and knee flexor muscles during obstacle avoidance. It also may reflect an increased cortical contribution to modify the gait patterns to avoid an obstacle.

All 3D‐Printed Soft High‐Density Surface Electromyography Electrode Arrays for Accurate Muscle Activation Mapping and Decomposition

AbstractHigh‐density surface electromyography (sEMG) electrode arrays enable the recording of tens to hundreds of channels of electromyographic signals, which have found wide applications in clinics and human‐machine interfaces. However, current manufacturing technologies of high‐density sEMG electrode arrays generally involve high‐cost equipments, complicated procedures, and insufficient programmability, severely hampering the rational design and practical applications of customized yet cost‐effective high‐density electrode arrays. Herein, the facile and efficient fabrication of novel 32‐channel soft high‐density sEMG electrode arrays by an all‐printed technique based on multimaterial direct ink writing 3D printing is presented. By employing rational four‐layer stacked structure designs with systematic ink printability evaluation, it can successfully realize seamless interfacial integration during the multimaterial printing, achieving reproducible, programmable, continuous fabrication of soft high‐density sEMG electrode arrays. The all 3D‐printed soft electrode arrays exhibit excellent stability, low impedance, and high signal‐to‐noise ratio superior to commercial products with an increase of 32.2%. Such intriguing properties enable this all 3D‐printed electrode arrays the unique capability of mapping muscle activation of the forearm, and the motor unit action potential trains can be precisely identified for varying hand gestures to effectively explore the innovative human‐machine interface toward diverse applications such as teleoperation and prosthetic control.

Mini-review: Biological Movements as Objects of Natural Science

BACKGROUND: Two approaches to biological movement have dominated the field, the computational approach (internal models) and the approach based on laws of nature pioneered by several researchers including Michael Turvey. AIM AND METHOD: We review a body of literature exploring and expanding the approach based on laws of nature. We show, in particular, how this approach fits the philosophical traditions of Merleau-Ponty, the theory of control with spatial referent coordinates, the principle of abundance, and the concept of performance-stabilizing synergies using the uncontrolled manifold hypothesis. RESULTS: Currently, this scheme of motor control has been applied successfully in studies of a variety of effectors, from single motor units to the whole body, a variety of tasks, and various populations. It led to the discovery of new phenomena and new interpretations of known phenomena. It has been productive in studies of neurological patients offering new understanding of some of the common pathologies (e.g., spasticity) and new tools for early diagnosis of various subcortical disorders and monitoring treatment effects. CONCLUSION: Currently, this field faces a number of challenges including the following: Mapping steps in the hierarchical control scheme on neurophysiological structures and circuits, understanding the relative role of intra-muscle (spinal) and multi-effector (supraspinal) synergies, expanding studies of movements in intact animals and animal preparation, and moving beyond the current scheme to fields traditionally associated with psychology. Just like the current scheme represents moving “outside the box” of classical mechanics, a step outside the current thinking is needed.

Neuromuscular behaviour in the first dorsal interosseus following mental fatigue.

We examined sex-specific changes to neuromuscular function in response to mental fatigue. Twenty-five young, healthy adults (13 F, 12M) performed a mentally fatiguing task and control condition for 30min on two separate days. Neuromuscular function was assessed in the first dorsal interosseous before and after each condition. Reaction time decreased after the mentally fatiguing task (P<0.001, η2 =0.47). Males and females reported higher levels of subjective fatigue after the mentally fatiguing task (P<0.02, η2 =0.07). Motor unit firing rate increased over time at 10% maximal voluntary contraction (MVC; P<0.04, η2 =0.16), and decreased over time at 50% MVC (P<0.01, η2 =0.14); however, this was not unique to either sex. During a variable force contraction, error decreased in females over time and increased in males (P<0.05, η2 =0.13), although changes were not unique to mental fatigue. Physiological function of the neuromuscular system was not specifically affected by mental fatigue in males or females.

Motor unit activity and synaptic inputs to motoneurons in the caudal part of the injured spinal cord.

Spinal cord injury (SCI) disrupts neuronal function below the lesion epicenter, causing disuse muscle atrophy. We investigated motor unit (MU) activity and synaptic inputs to motoneurons in the caudal region of the injured spinal cord. Participants with C4-C7 cervical injuries were studied. The extensor digitorum communis (EDC) muscle, which is mainly innervated by C8, was assessed for disuse muscle atrophy. Using advanced electromyography and signal-processing techniques, we examined the concurrent activation of a substantial population of MUs during force-tracking tasks. We found that in participants with SCI (n = 9), both MU discharge rates and the amplitudes of MU action potentials were significantly lower than in controls (n = 9). After SCI, MUs were recruited in a limited force range as the strength of muscle contractions increased, implying a disruption in the orderly MU recruitment pattern. Coherence analysis revealed reduced synaptic inputs to motoneurons in the delta band (0.5-5 Hz) for participants with SCI, suggesting diminished common synaptic inputs to the EDC muscle. In addition, participants with SCI exhibited greater muscle force variability. Using principal component analysis on low-frequency MU discharge rates, we found that the first common component (FCC) captured the most discharge variability in participants with SCI. The coefficients of variation (CV) of the FCC correlated with force signal CVs, suggesting force variability mainly results from common synaptic inputs to the EDC muscle after SCI. These results advance our understanding of the neurophysiology of disuse muscle atrophy in human SCI, paving the way for therapeutic interventions to restore muscle function.NEW & NOTEWORTHY This study analyzed motor unit (MU) function below the lesion epicenter in patients with spinal cord injury (SCI). We found reduced MU discharge rates and action potential amplitudes in participants with SCI compared with controls. The strength of common synaptic inputs to motoneurons was reduced in patients with SCI, with increased force variability primarily due to low-frequency oscillations of common inputs. This study enhances understanding of neurophysiological and behavioral changes in disuse muscle atrophy post-SCI.

Two classes of action-stabilizing synergies reflecting spinal and supraspinal circuitry.

We explored force-stabilizing synergies during accurate four-finger constant force production tasks in spaces of finger modes (commands to fingers computed to account for the finger interdependence) and of motor unit (MU) firing frequencies. The main specific hypothesis was that the multifinger synergies would disappear during unintentional force drifts without visual feedback on the force magnitude, whereas MU-based synergies would be robust to such drifts. Healthy participants performed four-finger accurate cyclical force production trials followed by trials of constant force production. Individual MUs were identified in the flexor digitorum superficialis (FDS) and extensor digitorum communis (EDC). Principal component analysis was applied to motor unit frequencies to identify robust MU groups (MU-modes) with parallel scaling of the firing frequencies in FDS, in EDC, and the combined MUs of FDS + EDC. The framework of the uncontrolled manifold hypothesis was used to quantify force-stabilizing synergies when visual feedback on the force magnitude was available and 15 s after turning the visual feedback off. Removing visual feedback led to a force drift toward lower magnitudes, accompanied by the disappearance of multifinger synergies. In contrast, MU-mode synergies were minimally affected by removing visual feedback off and continued to be robust for the FDS and for the EDC, while being absent for the (FDS + EDC) analysis. We interpret the findings within the theory of hierarchical control of action with spatial referent coordinates. The qualitatively different behavior of the multifinger and MU-mode-based synergies likely reflects the difference in the involved neural circuitry, supraspinal for the former and spinal for the latter.NEW & NOTEWORTHY Two types of synergies, in the space of commands to individual fingers and in the space of motor unit groups, show qualitatively different behaviors during accurate multifinger force-production tasks. After removing visual feedback, finger force synergies disappear, whereas motor unit-based synergies persist. These results point at different neural circuitry involved in these two basic classes of synergies: supraspinal for multieffector synergies, and spinal for motor unit-based synergies.

Estimates of persistent inward currents in lower limb muscles are not different between inactive, resistance-trained, and endurance-trained young males.

Persistent inward currents (PICs) increase the intrinsic excitability of α-motoneurons. The main objective of this study was to compare estimates of α-motoneuronal PICs between inactive, chronic resistance-trained, and chronic endurance-trained young individuals. We also aimed to investigate whether there is a relationship in the estimates of α-motoneuronal PIC magnitude between muscles. Estimates of PIC magnitude were obtained in three groups of young individuals: resistance-trained (n = 12), endurance-trained (n = 12), and inactive (n = 13). We recorded high-density surface electromyography (HDsEMG) signals from tibialis anterior (TA), gastrocnemius medialis (GM), soleus (SOL), vastus medialis (VM), and vastus lateralis (VL). Then, signals were decomposed with convolutive blind source separation to identify motor unit (MU) spike trains. Participants performed triangular isometric contractions to a peak of 20% of their maximum voluntary contraction. A paired-motor-unit analysis was used to calculate ΔF, which is assumed to be proportional to PIC magnitude. Despite the substantial differences in physical training experience between groups, we found no differences in ΔF, regardless of the muscle. Significant correlations of estimates of PIC magnitude were found between muscles of the same group (VL-VM, SOL-GM). Only two correlations (out of 8) between muscles of different groups were found (TA-GM and VL-GM). Overall, our findings suggest that estimates of PIC magnitude from lower-threshold MUs at low contraction intensities in the lower limb muscles are not influenced by physical training experience in healthy young individuals. They also suggest muscle-specific and muscle group-specific regulations of the estimates of PIC magnitude.NEW & NOTEWORTHY Chronic resistance and endurance training can lead to specific adaptations in motor unit activity. The contribution of α-motoneuronal persistent inward currents (PICs) to these adaptations is currently unknown in healthy young individuals. Therefore, we studied whether estimates of α-motoneuronal PIC magnitude are higher in chronically trained endurance- and resistance-trained individuals. We also studied whether there is a relationship between the estimates of α-motoneuronal PIC magnitude of different lower limb muscles.

Myomatrix arrays for high-definition muscle recording.

Neurons coordinate their activity to produce an astonishing variety of motor behaviors. Our present understanding of motor control has grown rapidly thanks to new methods for recording and analyzing populations of many individual neurons over time. In contrast, current methods for recording the nervous system's actual motor output - the activation of muscle fibers by motor neurons - typically cannot detect the individual electrical events produced by muscle fibers during natural behaviors and scale poorly across species and muscle groups. Here we present a novel class of electrode devices ('Myomatrix arrays') that record muscle activity at unprecedented resolution across muscles and behaviors. High-density, flexible electrode arrays allow for stable recordings from the muscle fibers activated by a single motor neuron, called a 'motor unit,' during natural behaviors in many species, including mice, rats, primates, songbirds, frogs, and insects. This technology therefore allows the nervous system's motor output to be monitored in unprecedented detail during complex behaviors across species and muscle morphologies. We anticipate that this technology will allow rapid advances in understanding the neural control of behavior and identifying pathologies of the motor system.

Myomatrix arrays for high-definition muscle recording

Neurons coordinate their activity to produce an astonishing variety of motor behaviors. Our present understanding of motor control has grown rapidly thanks to new methods for recording and analyzing populations of many individual neurons over time. In contrast, current methods for recording the nervous system’s actual motor output – the activation of muscle fibers by motor neurons – typically cannot detect the individual electrical events produced by muscle fibers during natural behaviors and scale poorly across species and muscle groups. Here we present a novel class of electrode devices (‘Myomatrix arrays’) that record muscle activity at unprecedented resolution across muscles and behaviors. High-density, flexible electrode arrays allow for stable recordings from the muscle fibers activated by a single motor neuron, called a ‘motor unit,’ during natural behaviors in many species, including mice, rats, primates, songbirds, frogs, and insects. This technology therefore allows the nervous system’s motor output to be monitored in unprecedented detail during complex behaviors across species and muscle morphologies. We anticipate that this technology will allow rapid advances in understanding the neural control of behavior and identifying pathologies of the motor system.

Adding the latency period to a muscle contraction model coupled to a membrane action potential model

Introduction: Skeletal muscle is responsible for multiple functions for maintaining energy homeostasis and daily activities. Muscle contraction is activated by nerve signals, causing calcium release and interaction with myofibrils. It is important to understand muscle behavior and its impact on medical conditions, like in the presence of some diseases and their treatment, such as cancer, which can affect muscle architecture, leading to deficits in its function. For instance, it is known that radiotherapy and chemotherapy also have effects on healthy tissues, leading to a reduction in the rate of force development and the atrophy of muscle fibers. The main aim is to reproduce the behavior of muscle contraction using a coupled model of force generation and the action potential of the cell membrane, inserting the latency period observed between action potential and force generation in the motor unit.Methods: Mathematical models for calcium dynamics and muscle contraction are described, incorporating the role of calcium ions and rates of reaction. An action potential initiates muscle contraction, as described by the Hodgkin–Huxley model. The numerical method used to solve the equations is the forward Euler method.Results and Discussion: The results show dynamic calcium release and force generation, aligning with previous research results, and the time interval between membrane excitation and force generation was accomplished. Future work should suggest simulating more motor units at the actual scale for the possibility of a comparison with real data collected from both healthy individuals and those who have undergone cancer treatment.

Investigation of motor unit behavior in exercise and sports physiology: challenges and perspectives.

Several methods are in use to record and analyze neuronal activation, each with specific advantages and challenges. New developments like the decomposition of high-density surface electromyography (HDsEMG) have enabled novel insights into discharge characteristics noninvasively in laboratory settings but face certain challenges to be applied in sports physiology in a broader scope. Several challenges can be accounted for by methodological considerations, others require further technological developments to allow this technology to be used in more applied settings. This paper aims to describe the developments of surface electromyography and identify the challenges and perspectives of HDsEMG in the context of an application in sports physiology. We further discuss methodological possibilities to overcome some of the challenges to investigate specific research questions and identify areas that require further advancements.

Огляд досліджень в напрямку міоелектричного методу керування біонічним протезом

Myoelectric control of bionic prostheses is an important field of research in the field of rehabilitation. Intuitive and intelligent myoelectric control can restore upper limb function. However, much research now focuses on the development of various myoelectrical and biotechnical control methods, limiting research to the complex daily tasks of prosthetic manipulation, such as grasping and releasing. The article examines the latest advances in the research areas of bionic prosthesis management. In particular, attention is paid to the methods of determining movement intentions, classification of discrete movements, estimation of continuous movements, single-channel control, feedback control and combined control. Motor neurons group input signals from the central nervous system that affect muscles and form motor units. The electromyography (EMG) signal, which is obtained by recording motor neuron action potentials, reflects muscle activity. This signal, oscillating within ±5000 μV with a frequency of 6 to 500 Hz, reflects the characteristics of muscle contraction. Depending on the location of the sensors, EMG signals are divided into intramuscular and surface electromyography. Intramuscular electromyography provides an accurate study of muscle activation, but requires the implantation of sensors, which can lead to physical problems. EMG, which captures a signal from the surface of the skin, is easier to use and is widely used in experiments with myoelectric prostheses.

“Winged” Eagle’s syndrome: neurophysiological findings in a rare cause of spinal accessory nerve palsy. Illustrative cases

BACKGROUND Eagle’s syndrome (ES) classically describes dysphagia, globus sensation, and otalgia from an elongated and calcified styloid process or stylohyoid ligament. Compression of the spinal accessory nerve (SAN) has not been reported as an associated feature of ES or related variants. OBSERVATIONS The authors describe two cases of an atypical “winged” variant with SAN palsy resulting from compression by a posteriorly angulated or calcified styloid process. Both patients exhibited lateral scapular winging and atrophy of the trapezius and sternocleidomastoid muscles. Electrophysiological studies demonstrated motor unit preservation; therefore, surgical exploration, styloidectomy, and SAN decompression were performed through a transcervical approach. Postoperatively, both patients had improvements in pain and shoulder mobility, the return of muscle strength, and electrophysiological evidence of trapezius reinnervation. LESSONS Compression of the SAN, which can be identified both clinically and on electrodiagnostic testing, is an atypical finding that can result from a posteriorly angulated or calcified styloid process. This winged variant of ES should be included in the differential for SAN palsy, and a multidisciplinary approach is recommended for assessment and management.