Motor Unit Potentials Research Articles

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.

Comprehensive approach to the diagnosis, treatment and rehabilitation of patients with facial nerve neuropathy at different periods of the disease

Diagnosis, treatment and rehabilitation of patients with facial neuropathy (FN) is a significant medical problem. The aim of the work was to create, implement and evaluate the effectiveness of an internal algorithm for working with patients suffering from FN.Material and methods. The study included 53 patients: group 1 (n = 27) — treatment in the first 2 weeks from the moment of development of symptoms, group 2 (n = 11) — for more than 2 weeks to 3 months, group 3 (n = 15) — for more than 1 year. The algorithm of diagnosis and treatment were created in the N.V. Sklifosovskii Research Institute of Emergency Medical Care. It includes a multidisciplinary approach, teamwork and continuity.Results. In patients with FN diff erent genesis, at the beginning of treatment in the acute period, complete restoration of the function of the facial nerve and facial muscles occurred in 74% of cases in the period from 2 weeks to 9 months, the period depended on the severity of clinical manifestations (House–Brackmann scale) (r = 0.539, p = 0.014), the degree of nerve damage according to electroneuromyography (ENMG) (r = 0.595, p = 0.006), the severity of complications (contractures and synkinesias) (r = 0.524, p = 0.018). In patients with idiopathic FN, at the beginning of treatment in the acute period, complete recovery was observed in 81.3% of cases. At the beginning of treatment of patients with a disease period of more than a year, conservative tactics led to an improvement in 67% of cases.There was an incomplete correspondence between the clinical (House–Brackmann scale) and degree of nerve damage according to ENMG (r = 0.620, p = 0.004). ENMG should be performed when the House–Brackmann is VI degree. In cases of a decrease in the amplitude of the M-response by 90% or more compared to the healthy side, needle myography (IMG) is indicated. In the absence of motor unit potentials (PDE), it is necessary to consider the issue of surgical treatment, which is indicated in the acute period of FN to every 10 patients, and after a year in cases of lack of recovery — to every second.FN should be considered a progressive disease due to the development of complications, such as the consequences of lagophthalmos, contracture, synkinesia. Lagophthalmos occurs in 73.5% of patients with various consequences — from dry eye syndrome to corneal ulcers, so it is important to use local protective and regenerating drugs early to prevent the development of keratopathies, even with a mild degree of lagophthalmos. Hypertonus of facial muscles is formed already on the 7th day of the disease on the healthy side of the face in an average of 67% of patients, and in the absence of timely treatment — in more than 90% of patients. Synkinesia develops in the period from 4 months to a year in every fifth patient. Timely detection and correction of complications prevents their further development and leads to a complete restoration of the facial nerve function.The success of recovery in FN depends more on identifying the risks of complications and carrying out their prevention. Risk factors for the development of contractures and synkinesias are: prosoplegia, facial nerve damage by more than 90% according to ENMG and gross exercises. FN, despite the different causes of its development, clinically has similar sanogenetic mechanisms, which should be used in rehabilitation.

Neuromuscular recruitment strategies of the vastus lateralis according to sex.

AimDespite males typically exhibiting greater muscle strength and fatigability than females, it remains unclear if there are sex‐based differences in neuromuscular recruitment strategies e.g. recruitment and modulation of motor unit firing rate (MU FR) at normalized forces and during progressive increases in force.MethodsThe study includes 29 healthy male and 31 healthy female participants (18‐35 years). Intramuscular electromyography (iEMG) was used to record individual motor unit potentials (MUPs) and near‐fibre MUPs from the vastus lateralis (VL) during 10% and 25% maximum isometric voluntary contractions (MVC), and spike‐triggered averaging was used to obtain motor unit number estimates (MUNE) of the VL.ResultsMales exhibited greater muscle strength (P < .001) and size (P < .001) than females, with no difference in force steadiness at 10% or 25% MVC. Females had 8.4% and 6.5% higher FR at 10% and 25% MVC, respectively (both P < .03), while the MUP area was 33% smaller in females at 10% MVC (P < .02) and 26% smaller at 25% MVC (P = .062). However, both sexes showed similar increases in MU size and FR when moving from low‐ to mid‐level contractions. There were no sex differences in any near‐fibre MUP parameters or in MUNE.ConclusionIn the vastus lateralis, females produce muscle force via different neuromuscular recruitment strategies to males which is characterized by smaller MUs discharging at higher rates. However, similar strategies are employed to increase force production from low‐ to mid‐level contractions. These findings of similar proportional increases between sexes support the use of mixed sex cohorts in studies of this nature.

Evaluation and Utility of Submaximal Stimulation Intensity in Transcranial Magnetic Stimulation in the Standing Horse☆

Transcranial magnetic stimulation (TMS) has been successfully used in horses to evaluate function and integrity of descending motor pathways in patients affected by neurological gait abnormalities. In preceding studies, lengthening latency times (LT) of cranially evoked limb muscle potentials have been considered a reliable diagnostic parameter. Standardized settings use device output signal intensities of 100%. The aim of this study was to determine the effect of submaximal stimulation intensities (SI) and to determine the minimum coil output necessary to evoke motor unit potentials. As an additional effect, lower stimulation intensities are supposed to decrease sensory irritation of the equine patient. Altogether, 36 neurologically healthy horses underwent TMS under sedation with a dome coil at stimulation intensities varying from 40% to 100% of device output intensity. Motor potentials were recorded by surface electrodes from all four limbs and LT was calculated in milliseconds. To further refine the stimulation settings, cortical motor thresholds (CMT) were assessed in triplets, using IFCN recommendations. The electromyographic recordings were evaluated in 30 horses. Increasing stimulation intensities resulted in significant (P < .05) LT shortening until application of 80% of maximal output intensity. Further increase to maximal SI of 100%, brought up no significant differences (P > .05). Gating effects were excluded as there was no difference of LT upon ascending and descending SI changes (P > .05). CMT revealed a large inter-individual variability amongst horses independent of their body size. There was a strong linearity in between CMT and LT even within submaximal SI ranges (P < .001). The inverse impact of SI on LT may be explained by deeper penetration of the magnetic field, circumvention of interposed neurons and subsequent activation of fast acting motor pathways. However, in warmblood horses a stimulation intensity of 80% coil output already appeared sufficient for reproducible activation of lower motor neurons in all limbs. Furthermore, due to the strong linear correlation of CMT and LT, the tested CMT algorithms may be used to estimate the normal LT on submaximal stimulation for equine myelopathy patients in future.

HP42: EMG is a potential biomarker for myositis in patients with antisynthetase syndrome without muscle symptoms

Anti-aminoacyl-tRNA synthetase (ARS) antibodies positive patients sometimes present interstitial lung disease (ILD) without muscle symptoms. We investigated needle electromyography (nEMG) to explore whether there are some myogenic changes or not in patients with antisynthetase syndrome without muscle symptoms. Method: We enrolled three patients who fulfilled anti ARS antibodies positive and ILD of the Connor's criteria for antisynthetase syndrome, and not fulfill the PM/DM criteria. We investigated the nEMG, and magnetic resonance imaging (MRI) of muscles to explore whether there are some myogenic changes or not. Serum creatine kinase (CK), manual muscle testing of 8 muscle groups (MMT8), Inclusion Body Myositis-Functional Rating Scale (IBM-FRS) were measured. This study was approved by the ethics committee of the Nara Medical University School of Medicine. Results: All subjects were females and their ages at the examination were 54 years old (P1), 44(P2) and 69(P3). P1 and P2 had already initiated oral steroid therapy. Although all three patients had no high serum CK level nor decline in IBM-FRS, nEMG revealed that abnormally short durations of the motor unit potential (MUP) patterns in the deltoid and biceps. P3 presented the same MUP pattern in vastus lateralis. MRI revealed inflammatory changes in P2 at left triceps and P3 at anterolateral femurs and posterolateral lower legs. Conclusion: nEMG is usually performed when patients exhibit muscle weakness, but this examination tool can be applicated to detect muscle damage in patients with anti-ARS antibody-associated ILD, prior to muscle weakness, myalgia, and declines in ADLs.

Adaptive Real-Time Decomposition of Electromyogram During Sustained Muscle Activation: A Simulation Study.

Real-time decomposition of electromyogram (EMG) into constituent motor unit (MU) activity has shown promising applications in neurophysiology and human-machine interactions. Existing decomposition methods could not accommodate stochastic variations in EMG signals such as drifts of action potential amplitudes and MU recruitment-derecruitment (rotation) patterns during long-term recordings. The objective of this study was to develop an adaptive real-time decomposition approach suitable for prolonged muscle activation. We developed a parallel-double-thread computation algorithm. The backend thread initiated and periodically refined and updated the MU information (separation matrix) using independent component analysis and convolution kernel compensation. The frontend thread performed the real-time decomposition. We evaluated our algorithm on synthesized high-density EMG signals, in which MUs were recruited-derecruited sporadically and MU action potentials amplitude drifted over time. Different signal-to-noise levels were also simulated. Compared with the decomposition without the adaptive processes, periodically fine-tuned and updated separation matrix increased identifiable MU number by 3-4 fold over 30-minute of signals. The increased MU number was more prominent at higher signal-to-noise ratios. The decomposition accuracy also increased by up to 10% with greater improvement observed at higher muscle contraction levels. The adaptive algorithm can maintain the decomposition performance over time, allows us to continuously track the same MUs during sustained activation, and, at the same time, can add newly recruited MU information to existing separation matrix. Our approach showed robust performance over time, which has the potential to longitudinally evaluate MU firing and recruitment properties and improve neural decoding performance for neural-machine interactions.

Virtual Rehabilitation of Elbow Flexion Following Nerve Transfer Reconstruction for Brachial Plexus Injuries Using the Single-Joint Hybrid Assisted Limb

PurposeThe upper limb single-joint hybrid assistive limb (HAL), a wearable robot that can support elbow flexion and extension motions, was originally used to rehabilitate patients with stroke. We report the preliminary outcomes of serial HAL use for rehabilitation following nerve transfer (NT) for elbow flexion reconstruction in brachial plexus injuries.MethodsHybrid assistive limb training consisted of virtual and power training courses. Virtual training was started before HAL picked up motor unit potentials (MUPs) from the target muscle through electrodes attached to the skin overlying the original donor muscles. Power training was started after the maturation of MUPs, the stage where the MUPs were strong to be recognized to arise from the target muscles. Hybrid assistive limb assist at this stage was carried out by decreasing the settings in an inversely proportionate manner to the increase in target muscle strength. Fourteen patients underwent HAL training following NT. Eight patients had the intercostal nerve to musculocutaneous nerve (ICN-MCN) transfer, and their postoperative functional outcomes and rehabilitation performance were compared to 50 patients with ICN-MCN transfer who underwent conventional postoperative rehabilitation with electromyographic biofeedback (EMG-BF) techniques.ResultsComparison of the long-term results following ICN-MCN transfer between EMG-BF and HAL groups showed similar follow-up times, elbow flexion range of motion, or power of elbow flexion assessed using the British Medical Council grade, and quantitative measurement using Kin-Com dynamometer. However, the number of rehabilitation sessions was significantly fewer in the HAL than EMG-BF group.ConclusionHAL training accelerated patients’ learning to convert the original muscle function into elbow flexion following NT by replicating elbow flexion during the pre-MUP detection stage and shortening the rehabilitation time.Type of study/level of evidenceTherapeutic IV.

Motor Nerve Conduction Block Estimation in Demyelinating Neuropathies by Deconvolution.

A deconvolution method is proposed for conduction block (CB) estimation based on two compound muscle action potentials (CMAPs) elicited by stimulating a nerve proximal and distal to the region in which the block is suspected. It estimates the time delay distributions by CMAPs deconvolution, from which CB is computed. The slow afterwave (SAW) is included to describe the motor unit potential, as it gives an important contribution in case of the large temporal dispersion (TD) often found in patients. The method is tested on experimental signals obtained from both healthy subjects and pathological patients, with either Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) or Multifocal Motor Neuropathy (MMN). The new technique outperforms the clinical methods (based on amplitude and area of CMAPs) and a previous state-of-the-art deconvolution approach. It compensates phase cancellations, allowing to discriminate among CB and TD: estimated by the methods of amplitude, area and deconvolution, CB showed a correlation with TD equal to 39.3%, 29.5% and 8.2%, respectively. Moreover, a significant decrease of percentage reconstruction errors of the CMAPs with respect to the previous deconvolution approach is obtained (from a mean/median of 19.1%/16.7% to 11.7%/11.2%). Therefore, the new method is able to discriminate between CB and TD (overcoming the important limitation of clinical approaches) and can approximate patients’ CMAPs better than the previous deconvolution algorithm. Then, it appears to be promising for the diagnosis of demyelinating polyneuropathies, to be further tested in the future in a prospective clinical trial.

The neuropathy of marginal mandibular branch of the facial nerve

To analyze the diagnosis, treatment and rehabiltation of patients with marginal mandibular branch of the facial nerve (MMB). We have collected 6 patients (mean age 40 [33.8; 44] years) with isolated lesion of MMB that innervates the depressor labii inferioris and chin muscle. The illness duration without any improvement was 35 [13; 44] days. Diagnosis and treatment were carried out according to the special algorithm developed and implemented at the N.V. Sklifosovsky Research Institute of Emergency Medicine. With needle myography of the muscle that lowers the lower lip, the change in the ratio of the maximum amplitudes of the interference pattern (MAIP) in all patients exceeded 15%, and in 2 cases it was more than 90%. Comparing with the healthy face side, a change of the MAIP ratio less than 90% was considered as the biomarker of favorable prognosis, with conservative treatment recommendations, e.g. the set of exercises with targeted effects on depressor labii inferioris. With regular exercises, patients noted positive dynamics of restoring the symmetry of the smile in 1-2 months of the disease, full recovery - in 4-5 months. In case of exercises rejection, there was no positive dynamics. A change in the MAIP ratio more than 90% or the absence of motor unit potentials was considered as the biomarker of an unfavorable outcome and an indication for surgical treatment. After surgical treatment, the improvement occurred within 4-5 months. In conservative treatment group, there were no positive changes even with regular exercises. The diagnosis of an isolated lesion of MMB is established clinically using a protocol of step-by-step assessment of facial muscle function, and tactics is determined by needle myography with depressor labii inferioris. Even with favorable myographic predictors, spontaneous recovery may not occur, exercises with a targeted effect on the depressor labii inferioris are required, and in the presence of unfavorable predictors, surgical treatment is reccomended.

Large- and Small-Fiber Neuropathy in Patients with Tarlov Cysts.

PurposeTarlov cysts (TCs) are dilated nerve root sheaths originating from increased cerebrospinal pressure. Patients with TCs often complain of neuropathic pain and paresthesia. The aim of this study was to retrospectively review intraepidermal nerve fiber density (IENFD) and electrodiagnostic (EDX) data from TC patients.Patients and MethodsLower leg skin biopsy results and EDX data from the L2–S4 myotomes of patients with lumbar or sacral TCs ≥8 mm were retrieved from a database of a physical medicine clinic. Patients with compressive pathology, diabetes mellitus and chemotherapy were excluded.ResultsIENFD data from 17 patients and EDX data from 24 patients with TCs ≥8 mm were available. The mean age was 47 ± 10y, and 83% were women. In 82% of patients, the IENFD was below the 5th percentile by age and sex. EDX showed increased Hoffmann reflex latencies in 25%, increased anal reflex latencies in 95%, and a patchy distribution of neurogenic motor unit potentials in 100%. More than 50% of needle EMG abnormalities appeared in myotomes unrelated to the location of the TCs.ConclusionSmall- and/or large-fiber neuropathy was documented in a significant proportion of patients with TCs. The novel findings may add to the understanding of the mechanisms involved in symptomatic TCs. We propose that pathologically elevated cerebrospinal fluid pressure not only dilates some of the nerve root sheaths to form TCs but also potentially damages axons in nondilated nerve root sheaths and neurons in the dorsal root ganglia.

Anesthetic management in a patient with steinert syndrome undergoing laparoscopic cholecystectomy: A case report

A male patient, 47 years old, 67 kg, 1.70 m, with SS for 30 years, on preanesthetic evaluation to perform LC. He had muscular atrophy, myotonia, history of asthma and cataract, and had been submitted to tracheostomy and gastrostomy three years ago.Domperidone (20 mg), amitriptyline (25 mg), lactulone (13 g), muvinlax (14 g), dipyrone (500 mg), montelukast (10 mg), and loratadine (10 mg) were used. He had a brother and mother with SS.In electroneuromyography of the limbs, during mild exertion, he presented motor unit potentials of decreased durations and amplitudes in all muscles. During rest, fibrillation potentials and positive spikes wore observed.

Effects of muscle shortening on single-fiber, motor unit, and compound muscle action potentials

Even under isometric conditions, muscle contractions are associated with some degree of fiber shortening. The effects of muscle shortening on extracellular electromyographic potentials have not been characterized in detail. Moreover, the anatomical, biophysical, and detection factors influencing the muscle-shortening effects have been neither identified nor understood completely. Herein, we investigated the effects of muscle shortening on the amplitude and duration characteristics of single-fiber, motor unit, and compound muscle action potentials. We found that, at the single-fiber level, two main factors influenced the muscle-shortening effects: (1) the electrode position and distance relative to the myotendinous zone and (2) the electrode distance to the maxima of the dipole field arising from the stationary dipole created at the fiber-tendon junction. Besides, at the motor unit and muscle level, two additional factors were involved: (3) the overlapping between the propagating component of some fibers with the non-propagating component of other fibers and (4) the spatial spreading of the fiber-tendon junctions. The muscle-shortening effects depend critically on the electrode longitudinal distance to the myotendinous zone. When the electrode was placed far from the myotendinous zone, muscle shortening resulted in an enlargement and narrowing of the final (negative) phase of the potential, and this enlargement became less pronounced as the electrode approached the fiber endings. For electrode locations close to the myotendinous zone, muscle shortening caused a depression of both the main (positive) and final (negative) phases of the potential. Beyond the myotendinous zone, muscle shortening led to a decrease of the final (positive) phase. The present results provide reference information that will help to identify changes in MUPs and M waves due to muscle shortening, and thus to differentiate these changes from those caused by muscle fatigue.Graphical abstract

Circulating testosterone and dehydroepiandrosterone are associated with individual motor unit features in untrained and highly active older men

Long-term exercise training has been considered as an effective strategy to counteract age-related hormonal declines and minimise muscle atrophy. However, human data relating circulating hormone levels with motor nerve function are scant. The aims of the study were to explore associations between circulating sex hormone levels and motor unit (MU) characteristics in older men, including masters athletes competing in endurance and power events. Forty-three older men (mean ± SD age: 69.9 ± 4.6 years) were studied based on competitive status. The serum concentrations of dehydroepiandrosterone (DHEA), total testosterone (T) and estradiol were quantified using liquid chromatography mass spectrometry. Intramuscular electromyographic signals were recorded from vastus lateralis (VL) during 25% of maximum voluntary isometric contractions and processed to extract MU firing rate (FR), and motor unit potential (MUP) features. After adjusting for athletic status, MU FR was positively associated with DHEA levels (p = 0.019). Higher testosterone and estradiol were associated with lower MUP complexity; these relationships remained significant after adjusting for athletic status (p = 0.006 and p = 0.019, respectively). Circulating DHEA was positively associated with MU firing rate in these older men. Higher testosterone levels were associated with reduced MUP complexity, indicating reduced electrophysiological temporal dispersion, which is related to decreased differences in conduction times along axonal branches and/or MU fibres. Although evident in males only, this work highlights the potential of hormone administration as a therapeutic interventional strategy specifically targeting human motor units in older age.

Acute carpal tunnel syndrome: Clinical, electromyographic, and ultrasound features in 25 patients

BackgroundThe acute presentation of carpal tunnel syndrome (CTS) is rare. When symptoms start acutely with no obvious causes, ultrasound (US) imaging may provide clues to the etiology. ObjectiveThis study describes the clinical, electromyographic, and US findings in 25 patients presenting with acute CTS (ACTS). MethodsIn this analysis, of the patients referred for electrodiagnostic confirmation of CTS over the past decade, 25 had an acute onset of symptoms. All patients underwent EMG/NCV and US of the median nerve at the carpal tunnel and forearm. ResultsOf the 25 cases with ACTS, 5 (20%) had bilateral involvement leading to the total hands studied to 30. In 14 (56%) patients, an inciting event was identified as a possible cause of ACTS. In 11 (44%) patients without an antecedent event, 7 (64%) had a persistent median artery (PMA) detected by US. Electrodiagnostic studies showed prolonged distal motor latency with normal motor conduction velocity proximal to the carpal tunnel in 24 (80%) of 30 hands, 6 (20%) hands showed absent compound muscle action potentials over the abductor pollicis brevis (APB), and 22 (73%) hands had absent sensory potentials. Denervation changes were seen in the APB in 13 (43%) hands, and motor unit potentials were absent in 6 (20%) hands. Sixteen (64%) patients underwent a carpal tunnel release for severe symptoms. ConclusionCTS may present acutely without a clinically identifiable cause. US complements electrodiagnostic studies and is particularly useful when electrodiagnostic tests are non-diagnostic (due to absent compound muscle and sensory action potentials). US may also provide clues to the underlying cause.

Inclusion body myositis: correlation of clinical outcomes with histopathology, electromyography and laboratory findings.

To determine whether histopathological, electromyographic and laboratory markers correlate with clinical measures in inclusion body myositis (IBM). We reviewed our electronic medical records to identify patients with IBM according to European Neuromuscular Center (ENMC) 2011 criteria, seen between 2015 and 2020. We only included patients who had a muscle biopsy and needle electromyography (EMG) performed on the same muscle (opposite or same side). We used a detailed grading system [0 (normal) to 4 (severe)] to score histopathological and EMG findings. Clinical severity was assessed by the modified Rankin scale (mRS), muscle strength sum score (SSS), quadriceps strength and severity of dysphagia on swallow evaluation. Serum markers of interest were creatine kinase level and cN-1A antibodies. We included 50 IBM patients, with a median age of 69 years; 64% were males. Median disease duration at diagnosis was 51 months. On muscle biopsy, endomysial inflammation mainly correlated with dysphagia, and inversely correlated with mRS. Vacuoles and congophilic inclusions did not correlate with any of the clinical measures. On EMG, the shortness of motor un it potential (MUP) duration correlated with all clinical measures. Myotonic discharges, and not fibrillation potentials, correlated with the severity of inflammation. Serum markers did not have a statistically significant correlation with any of the clinical measures. Dysphagia was the main clinical feature of IBM correlating with endomysial inflammation. Otherwise, inclusion body myositis clinical measures had limited correlation with histopathological features in this study. The shortness of MUP duration correlated with all clinical measures.

Rate-dependent depression is impaired in amyotrophic lateral sclerosis.

We investigated rate-dependent depression (RDD) of the Hoffman reflex (H-reflex) in patients with amyotrophic lateral sclerosis (ALS), a degenerative disease with ventral horn involvement. In this case-control study, we enrolled 27 patients with ALS and 30 matched healthy control subjects. Clinical and electrophysiological assessments, as well as RDD in response to various stimulation frequencies (0.5Hz, 1Hz, 3Hz and 5Hz), were compared between groups. Multiple clinical and electrophysiological factors were also explored to determine any underlying associations with RDD. The ALS group showed a significant loss of RDD across all frequencies compared to the control group, most notably following 1Hz stimulation (19.1 ± 20.3 vs. 34.0 ± 13.7%, p = 0.003). Among factors that might influence RDD, the enlargement of the motor unit potential (MUP) showed a significant relationship with RDD following multifactor analysis of variance (p = 0.007) and Pearson correlation analysis (ρ = - 0.70, p < 0.001), while various upper motor neuron manifestations were not correlated with RDD values (p > 0.05). We report a loss of RDD in patients with ALS. The strong correlation detected between the RDD deficit and increased MUP suggests that RDD is a sensitive indicator of underlying spinal disinhibition in ALS. ChiCTR2000038848, 10/7/2020 (retrospectively registered), http://www.chictr.org.cn/ .

Alcohol-induced damage to skeletal muscles in women with chronic alcohol intoxication

In Russia, there is a high level of alcohol consumption among women in doses that represent a high risk of developing alcoholic diseases, manifested, in particular, by damage to skeletal muscles.The purpose of the study. Analysis of clinical, biochemical, neurophysiological, as well as morphometric and immunohistochemical features of alcoholic skeletal muscle damage in women with chronic alcohol intoxication.Material and methods. A clinical and laboratory examination of 30 women aged 20 to 60 years with chronic alcohol intoxication was performed, which included the determination of creatine phosphokinase (CPK) and insulin-like growth factor I (IGF-I) in blood plasma, stimulation and needle electromyography (EMG), as well as morphological and immunohistochemical examination of biopsies of the quadriceps femoris.Results. Myopathic syndrome in the form of proximal para-or tetraparesis was observed in 73.3% of the examined women in combination with a decrease in IGF-1 at normal values of CPK in blood plasma. The EMG results indicated the absence of changes in the parameters of the potentials of motor units, characteristic of primary muscular lesions, and of conduction disturbances along the femoral nerve. Morphometric and immunohistochemical studies of skeletal muscle biopsies showed a decrease in the cross-sectional area of muscle fibers of types I and II without signs of muscle tissue necrosis.Conclusion. Chronic alcoholic myopathy is a common manifestation of alcoholic disease in women with long-term alcohol intoxication. The severity of the atrophic process in the skeletal muscle is comparable to the degree of proximal paresis. Violations of systemic protein synthesis and acceleration of apoptosis are considered as pathogenetic mechanisms of the atrophic process in the muscles in chronic alcoholic myopathy in women.

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.

Workshop 4: Advanced Neurophysiology Techniques WS4.1. My Approach to Motor Unit Number Estimation (with Demonstration)

In motor neuron disease such as amyotrophic lateral sclerosis, the motor neurons die from the disease process. They cannot be replaced. The loss of motor units (MUs) is partially compensated by reinnervation. As a result, the number of MUs is reduced and their size is increased. Reinnervation cannot sustain and may not be sufficient as the MU loss continues. This leads to progressive weakness. As we look for treatments, we need a biomarker to track the disease progression. This had led to the methods of “motor unit number estimation (MUNE)” over the last 5 decades. If a treatment is effective, the rate of MU loss should decrease. In this workshop I will review MUNE methods that were based on recording and measuring individual surface recorded motor unit potentials (SMUPs). They are called “incremental stimulation”, “multiple point stimulation”, etc. The methods are time consuming due to low amplitude signals and have been used to study small distal muscles. Furthermore, they are not automated. In the last 15 years we have seen new methods based on mathematical models. Hence the calculation is described as “motor unit number index (MUNIX)”. In MUNIX the compound muscle action potential (CMAP) and surface EMG interference pattern are analyzed. The procedure is automated, requires less than 5 minutes per muscle, and can be used for large muscles such as tibialis anterior. By adding results from several muscles, one can better track the disease progression. The methods also provide a measure for the amplitude of SMUP. The motor unit size index (MUSIX) increases with reinnervation. Another set of methods is based on ‘CMAP scan’. The stimulus intensity is reduced in fine steps from supramaximal level to low intensity where no response is recorded. The amplitude of 500 responses is analyzed using different algorithms. This method is also automated for recording the data. All methods have their advantages and disadvantages. They provide different numerical results. However, each method shows disease progression when serial investigations are performed. Such assessment requires careful measurements of the CMAP regardless of the method.