Motor Unit Potentials Research Articles

Polymyoclonus aggravated by neck flexion as the isolated presenting symptom of Hirayama disease: case report

BackgroundWe report a rare case of an 18-year-old male with unilateral hand tremor who was finally diagnosed with Hirayama disease (HD).Case presentationAn 18-year-old male presented with unilateral polymyoclonus that aggravated with neck flexion. The patient did not complain of muscle weakness or muscle atrophy. The needle electromyography showed giant motor unit potentials in right cervical 7 and 8 innervated muscles. The cervical magnetic resonance imaging on supine and flexion state showed prominent forward effacement of posterior dural sac that was compatible with HD.ConclusionsHD usually presents with unilateral distal hand weakness, muscle atrophy and tremor. Although it is a benign and self-limiting disease, early diagnosis may lead to less clinical deterioration. Moreover, electromyography should be completed in the differentiation of young male patients who present with polymyoclonus without hand weakness or atrophy.

Differential value of external anal- and urethral-sphincter electromyography in multiple system atrophy cerebellar type and spinocerebellar ataxias

ObjectiveClinically differentiating multiple system atrophy cerebellar type (MSA-C) and spinocerebellar ataxias (SCAs) is challenging, especially at early disease stages, because of their similarities in clinical manifestation and imaging results. The purpose of this study was to explore the value of external anal-sphincter electromyography (EAS-EMG) and urethral-sphincter electromyography (US-EMG) for distinguishing between MSA-C and SCAs. MethodsA total of 51 subjects, including 33 MSA-C and 18 SCAs, were recruited. Average duration and amplitude of motor unit potentials (MUPs), percentage of polyphasic MUPs, amplitude during strong contraction and recruitment pattern during maximal voluntary contraction were recorded and analyzed to identify differential diagnostic results of EAS-EMG and US-EMG for MSA-C and SCAs. ResultsSignificant differences in average MUP duration, percentage of polyphasic MUPs, and ratio of simple phase and simple-mix phase using EAS-EMG were noted between patients with MSA-C and SCAs. These same parameters also differed significantly between MSA-C and SCAs male patients using US-EMG. ConclusionsEAS-EMG may serve as a potential method for early differential diagnosis between patients with MSA-C and SCAs. Furthermore, US-EMG could be a supplementary method for males when EAS-EMG is not available.

Jitter patterns in conventional concentric needle electromyography recordings of regenerating motor units.

The time interval between two potential components of the same motor unit potential (MUP) is measured for jitter analysis. Enhanced jitter is generally thought to result from impaired neuromuscular transmission as occurs in myasthenia gravis or during reinnervation. Within a database of conventional video-electromyography (EMG) recordings 4 MUP with peculiar jitter patterns were identified. In 1 spontaneously discharging MUP, massive and chaotic jitter was seen with a mean consecutive difference (MCD) of 9.3 ms. In 2 spontaneously discharging MUP a certain potential subgroup jittered relative to the other part(s) of the MUP (MCD 2.0 and 3.3 ms). A jittering satellite was detected in a fourth voluntarily recruited MUP (MCD 0.6 ms). These different jitter patterns recorded with conventional EMG technique may mainly result from dysmyelination. A new look at the contribution of dysmyelination to abnormal jitter is also warranted in single fiber EMG recordings.

Quantitative electromyography: Normative data in paraspinal muscles.

Quantitative electromyography of paraspinal muscle is a valuable diagnostic tool, but normative data are lacking. Needle electromyography (EMG) was obtained in 65 healthy subjects (49% men, 51% women) aged 21 to 82 years at C7, Th10, and L5 segments bilaterally. The incidence of spontaneous activity; motor unit potential (MUP) amplitudes, durations, and the incidence of polyphasic potentials; and the recruitment pattern at maximal voluntary contraction (MVC) were evaluated. The incidence of fibrillation potentials was similar to limb muscles. The mean MUP duration and amplitude, and the amplitude at MVC increased caudally, while the incidence of polyphasic potentials was similar at all levels. EMG parameters did not correlate with sex or age. In contrast to limb muscles, EMG parameters did not change with age, while polyphasic potentials were more frequent in paraspinal muscle than in limb muscles. The EMG gradient suggests larger motor units at more caudal segments.

Electrodiagnosis of Amyotrophic Lateral Sclerosis: A Review of Existing Guidelines.

Amyotrophic lateral sclerosis (ALS) is characterized by degeneration of upper motor neurons in the motor cortex and lower motor neurons (LMN) in the brainstem and spinal cord, resulting in a progressive functional impairment. Neurophysiology is a diagnostic tool to detect dysfunction of upper motor neurons and LMN, even when the changes are subclinical. Electromyography is the standard neurophysiological investigation to detect LMN changes, which is essential to exclude mimicking disorders and attain early diagnosis. Recently, Awaji criteria was proposed to support ALS diagnosis, in these criteria fasciculation potentials associated with neurogenic motor unit potentials represents a sufficient marker of LMN involvement, in each muscle. Many studies have confirmed that Awaji criteria are more sensitive, permitting earlier diagnosis without loss of specificity when compared with the revised El Escorial criteria. Fasciculations are easily detected by ultrasound; increasingly, this technique has been used to diagnose ALS, combined with electromyography. This combination can increase diagnostic accuracy. Many techniques for estimating the number of motor units have been proposed, they are useful to quantify LMN loss. Electrical impedance myography is an emerging technique with great potential to monitor ALS progression. Neurophysiological investigation of upper motor neuron dysfunction is difficult in ALS, detecting decreased cortical inhibition by threshold tracking cortical magnetic stimulation is a promising method, which needs to be validated in different centers.

Associations between magnetic resonance imaging and EMG findings in myopathies.

Magnetic resonance imaging (MRI) is a cornerstone in diagnosis of myopathies. The present study sought to elucidate possible associations between electromyography (EMG) findings and histogram parameters derived from clinical MRI in myositis and other myopathies. Twenty six patients with myopathies were included in this retrospective study. Clinical MRI was performed with a 1.5T MRI scanner including T2- and T1-weighted images. EMG analysis was performed during clinical diagnostic workup. The histogram parameters of the MRI sequences were obtained of the same muscle, which was investigated with EMG. Several correlations were identified between mean duration of the motor unit potentials (MUP) and histogram parameters derived from T1- and T2-weighted images. The highest for T1-weighted images was mode (r= -.73, P<.0001) and for T2-weighted images was p25 (r=-.57, P=.022). There were significant differences for several histogram parameters between muscles with pathological spontaneous activity and without. So, for T1-weighted images, the best discrimination was achieved with mean (P=.096), and for T2-weighted images for p10 (P=.05). Mean SI values derived from T1-weighted images achieved an AUC of 0.84 with a sensitivity of 0.81 and a specificity of 0.86 to discriminate patients with and without pathological spontaneous activity (PSA). The present study identified strong associations between histogram analysis derived from morphological MRI sequences and the duration of the MUP derived from EMG in myopathies strengthening the fact that both diagnostic modalities can reflect disease state in a similar fashion. Histogram parameters can predict muscles with PSA.

Causes of, and countermeasures to, increased ventilatory drive in tetraplegia.

Causes of, and countermeasures to, increased ventilatory drive in tetraplegia.

Electrophysiological Study in Acute Spinal Cord Injury Patients: Its Correlation to Neurological Deficit and Subsequent Recovery Assessment by ASIA Score.

To investigate the relationship between neurological deficit and subsequent recovery as assessed by ASIA score and findings of electrodiagnostic study in acute spinal cord injury (SCI) patients. Thirty-five patients with acute SCI presenting within 48h of injury were clinically evaluated for the level, extent, and severity of SCI according to the ASIA standards in a tertiary-level care center. Electrodiagnostic studies of bilateral two motor (tibial and peroneal), one sensory (sural) nerves, and five muscles [iliopsoas, vastus medialis, tibialis anterior, gastrocnemius, and extensor hallucis longus (EHL)] were conducted and repeated at 3months and 6months. The neurological recovery was highly significant (p < 0.001) at 6months. The difference in mean amplitude was statistically significant (p < 0.05) for all the nerves; mean conduction velocity significant for peroneal and sural nerves, and with no significant difference in mean latency. The differences in mean recruitment of motor unit potential (MUP) and mean peak-to-peak amplitude were highly significant (p < 0.001). Statistically significant kappa agreement between neurological recovery according to ASIA score and nerve conduction velocity was found for right tibial nerve (K = 0.324); electromyography finding of recruitment of MUP with right and left tibialis anterior (k = 0.400) and left EHL (k = 0.407); peak-to-peak amplitude with right tibialis anterior (k = 0.211), right gastrocnemius (k = 0.390), and right EHL (k = 0.211). There is a strong relationship between electrodiagnostic findings and ASIA scoring to predict neurological deficit and subsequent recovery after acute traumatic SCI. Serial neurologic evaluation by ASIA score and electrodiagnostic studies may help in designing customized rehabilitation programs for the patients according to the expected neurological recovery; and evaluating future research in the field of SCI with more scientific authenticity.

Increased diaphragm motor unit discharge frequencies during quiet breathing in people with chronic tetraplegia.

Respiratory muscle strength is compromised in people with tetraplegia, which may be compensated for by an increase in neural drive to the diaphragm. We found that the discharge frequencies of diaphragm motor units are higher in people with chronic tetraplegia compared with able-bodied people during quiet breathing. Furthermore, we found that the area of single motor unit potentials was increased in people with tetraplegia. These results suggest an increased motoneurone output to the diaphragm and remodelling of diaphragm motor units to maintain ventilation in tetraplegia. People with tetraplegia have reduced inspiratory muscle strength, ∼40% of able-bodied individuals. Paralysed or partially paralysed respiratory muscles as a result of tetraplegia compromise lung function, increase the incidence of respiratory infections and can cause dyspnoea. We hypothesised that reduced inspiratory muscle strength in tetraplegia may increase neural drive to the inspiratory muscles to maintain ventilation. We recorded the discharge properties of single motor units from the diaphragm in participants with chronic tetraplegia (8 males, 42-78 years, C3-C6 injury, AIS A-C) and able-bodied control participants (6 males matched for age and body mass index). In each group, 117 and 166 single motor units, respectively, were discriminated from recordings in the costal diaphragm using a monopolar electrode. A linear mixed-effects model analysis showed higher peak discharge frequencies of motor units during quiet breathing in tetraplegia (17.8 ± 4.9Hz; mean ± SD) compared with controls (12.4 ± 2.2Hz) (P < 0.001). There were no differences in tidal volume, inspiratory time or mean air flow between groups. Motor unit potentials in tetraplegia, compared with controls, were larger in amplitude (1.1 ± 0.7mV and 0.5 ± 0.3mV, respectively, P = 0.007) and area (1.83 ± 1.49µV ms and 0.69 ± 0.52µV ms, respectively, P = 0.003). The findings indicate that diaphragm motor unit remodelling is likely to have occurred in people with chronic tetraplegia and that there is an increase in diaphragm motor unit discharge rates during quiet breathing. These neural changes ensure that ventilation is maintained in people with chronic tetraplegia.

Can Wavelet Denoising Improve Motor Unit Potential Template Estimation?

Background: Electromyographic (EMG) signals obtained from a contracted muscle contain valuable information on its activity and health status. Much of this information lies in motor unit potentials (MUPs) of its motor units (MUs), collected during the muscle contraction. Hence, accurate estimation of a MUP template for each MU is crucial.Objective: To investigate the possibility of improving MUP template estimation using the wavelet denoising technique.Material and Methods: In this analytical study, several MUP template estimators were developed by combining conventional estimation methods and wavelet denoising techniques. A MUP template was initially estimated using conventional methods such as mean, median, median-trimmed mean, or mode. Thereafter, it was post-processed using the wavelet denoising technique. Results: Evaluation results of the studied estimators using 40 simulated EMG signals with a true template for each constituent MUP train showed that augmented wavelet- based template estimation methods are more reliable than conventional methods. However, on average, wavelet denoising was not much effective. Around 40 MUPs of a MU is sufficient to estimate its MUP template.Conclusions: Although wavelet techniques are effective in EMG signal analysis, here wavelet denoising did not practically improve MUP template estimation. Considering computational simplicity and estimation error, the two methods median and median-trimmed mean are practical estimators that can provide a good estimation of a MUP template for a MU when approximately 40 MUPs are available. Nevertheless, the baseline noise level in the MUP templates estimated using the median-trimmed mean method is slightly lower than that in the templates estimated using the median method.

Electrodiagnostic Abnormalities Associated with Fibromyalgia.

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

Transparent Electrophysiological Muscle Classification From EMG Signals Using Fuzzy-Based Multiple Instance Learning.

Although a well-established body of literature has examined electrophysiological muscle classification methods and systems, ways to enhance their transparency is still an important challenge and requires further study. In this work, a transparent semi-supervised electrophysiological muscle classification system which uses needle-detected EMG signals to classify muscles as normal, myopathic, or neurogenic is proposed. The electrophysiological muscle classification (EMC) problem is naturally formulated using multiple instance learning (MIL) and needs an adaptation of standard supervised classifiers for the purpose of training and evaluating bags of instances. Here, a novel MIL-based EMC system in which the muscle classifier uses predictions based on motor unit potentials (MUPs) to infer muscle labels is described. This system uses morphological, stability, near fiber and spectral MUP features. Quantitative results obtained from applying the proposed transparent system to four electrophysiologically different groups of muscles, composed of proximal and distal hand and leg muscles, resulted in an average classification accuracy of 95.85%. The findings show the superior and stable performance of the proposed EMC system compared to previous works using other supervised, semi-supervised and unsupervised methods.

Recording of Motor Unit Potentials Count of Middle Trapezius in Children with Rounded Back

Background: Poor posture is unfortunately wide spreading not only among adults but also among children. Aim of Study: To detect the effect of rounded back posture on the Motor Unit Potentials (MUPs) count of middle trapezius. Patients and Methods: The right and left trapezius motor unit potentials countof 15 normal children (8.64±0.77 years) were compared with 15 children with rounded back (8.92±0.73 years) using electromyography apparatus (EMG). Results: There was a significant increase in the right trapezius motor unit count of the rounded back group compared with that of the normal group (p=0.02). There was no signif-icant difference in the left trapezius motor unit count between the normal and the rounded back groups (p=0.25). Conclusion: Rounded back posture affects the middle trapezius motor unit potential count.

Dynamic Brow Restoration Using a Soft Tissue Expander in Adult Patients With Arteriovenous Malformation.

Impaired brow function in adult patients with arteriovenous malformation is a serious disability that can even influence the field of vision. Brow reanimation techniques are used to recover a more natural appearance and brow function. Many static procedures have been set to augment brow elevation, but only dynamic procedures can lead to better functional results. In this study, the experience of a single surgeon addressing the challenge of brow restoration with dynamic procedures is presented. A retrospective review was performed using the records of 4 adult patients who underwent dynamic procedures using a soft tissue expander for brow restoration after arteriovenous malformation excision in the unilateral site of the forehead with the expander on the contralateral side. Movement and electrodiagnostic examinations were performed postoperatively at 2 months. The patients included 3 males and 1 female (mean age, 20.5 ± 4.04 years). Brow improvement was noted in all patients. The results of the electrodiagnostic examination showed synchronous and spontaneous motor unit potentials and compound muscle action potentials with the contralateral forehead. Dynamic procedures using a soft tissue expander can provide both static and dynamic functional brow elevation of the contralateral frontalis and skin.

The effects of local forearm heating and cooling on motor unit properties during submaximal contractions.

What is the central question of this study? How do temperature manipulations affect motor unit (MU) properties during submaximal contractions to the same relative percentage of maximal force? What is the main finding and its importance? MU recruitment patterns are affected by temperature manipulations at the forearm. However, the relationship between MU potential amplitude and recruitment threshold indicates no change to the order or recruitment. Additionally, the MU potential amplitude and firing rate relationship was affected by temperature, suggesting that smaller MUs are more affected by temperature changes than larger MUs. Temperature impacts muscle contractile properties, such that experiments with workloads based on thermoneutral values will produce different relative intensities if maximal force changes due to muscle temperature. We investigated how temperature affected motor unit (MU) properties with contractions performed at the same normalized percentage of maximal force. Twenty participants (10 females) completed evoked, maximal, and trapezoidal voluntary contractions during thermoneutral-, hot-, and cold-temperature conditions. Forearm temperature was established using 25min of neutral (∼32°C), hot (∼44°C) or cold (∼13°C) water circulated through a tube-lined sleeve. Flexor carpi radialis MU properties were assessed with contractions at 30% and 60% MVC relative to each temperature using surface electromyography decomposition. Changes to contractile properties and electromechanical delay from the evoked twitch suggest that muscle contractility was changed from the thermal manipulations (effect size (d)≥0.42, P<0.05). Maximal force was not different between neutral and hot conditions (d=0.16, P>0.05) but decreased in the cold (d≥0.34, P<0.05). For both contraction intensities, MU potential (MUP) amplitude was larger and duration was longer in the cold compared to neutral and hot conditions (d≥1.24, P<0.05). Cumulative probability density for the number of MUs recruited revealed differences in MU recruitment patterns among temperature conditions. The relationship between MU recruitment threshold and firing rate or MUP amplitude was not different among temperature conditions (P>0.05); however, the relationship between MUP amplitude and firing rate was (P<0.05). Local temperature manipulations appear to affect MU recruitment patterns, which may act as compensatory mechanisms to the changes in muscle viscosity and contractile properties due to local temperature changes.

Upper camptocormia in Parkinson's disease: Neurophysiological and imaging findings of both central and peripheral pathophysiological mechanisms

BackgroundCamptocormia is a disabling complication of Parkinson's disease (PD), but its pathophysiology is poorly elucidated. Depending on the fulcrum of forward trunk flexion, two subtypes have been defined, upper (UCC) and lower camptocormia, the former being much more frequent. The aim of the study was to explore possible pathophysiological mechanisms of PD-related UCC. MethodsTen PD patients with UCC (UCC-PD) and ten PD patients without camptocormia (NoUCC-PD) underwent simultaneous electromyography (EMG) of thoracic paraspinal (TPS), obliquus externus abdominis (OEA), rectus abdominis (RA), and iliopsoas (IP) muscles during relaxed standing (both groups) and trunk realignment (UCC-PD group). Quantitative EMG and magnetic resonance imaging (MRI) of TPS muscles were also performed. ResultsUCC-PD patients showed hyperactivity of TPS and OEA muscles in quiet stance. During voluntary trunk extension, hyperactivity of OEA muscles persisted, thus revealing a co-contraction of flexor and extensor trunk muscles. Motor unit potentials (MUP) of TPS muscles showed shorter duration (p = 0.005) and lower amplitude (p = 0.004) in UCC-PD than in NoUCC-PD patients. MRI did not detect significant between-group differences in the cross-sectional area and fat fraction of TPS muscles, although the latter was higher in the UCC-PD than in the NoUCC-PD group at all thoracic levels. ConclusionOur findings suggest that hyperactivity of OEA might sustain UCC in PD. Concurrent mild myopathic changes in TPS muscles in PD with UCC may be secondary to muscle disuse but nevertheless may contribute to abnormal trunk posture.

Spinal and bulbar muscular atrophy with pseudomyotonia phenomena: a clinical case report

A clinical description of a 28-year-old man with spinal and bulbar muscular atrophy diagnosed on the basis of the CAG-trinucleotide expansion in the gene coding androgen receptor is presented. He exhibited skeletal muscles and tongue fasciculations, gynecomastia, increased serum testosterone and creatine kinase levels. The peculiarities of the case were the gynecomastia under the age of 7, development of fasciculations at the age of 11 and appearance of hard muscle stiffness with delayed muscle relaxation after voluntary contraction at the age of 15, which resembled typical myotonia. Electromyography showed few signs of mild without myotonic discharge, contrasting with giant motor unit potentials and reduced recruitment. The cause of myotonia-like symptom without myotonic discharge as a feature of skeletal muscles disorder is discussed with the modern view of spinal and bulbar muscular atrophy as a multisystem genetic pathology.

Motor Unit Potential Analysis of the Palatal Muscles in Obstructive Sleep Apnea Syndrome

Objectives: Among different theories about pathogenesis of obstructive sleep apnea syndrome (OSAS), dysfunction of upper airway muscles still awaits to be delineated. The aim of this study is to examine differences in motor unit potential (MUP) parameters of upper airway muscles between OSAS patients and healthy controls. Methods: Ten male patients diagnosed as OSAS by whole-night polysomnography were analyzed for MUP parameters of genioglossus (GG) muscle, palatoglossus muscle (PG), palatopharyngeus muscle, and uvular (U) muscle. Eight healthy volunteer men matched by age were enrolled as a control group. Results: In PG muscle parameters, the mean MUP area was significantly smaller (P = 0.040) in OSAS patients than those in controls. On the other hand, U muscle parameters showed a significantly larger mean MUP area (P = 0.022) in OUAS patients compared to those in the control group. In OSAS patients, the percentages of polyphasic MUPs of GG and PG muscles were significantly high (P &lt; 0.001 and P = 0.05, respectively). Body mass index was positively correlated with number of phases of GG muscle (r s = 0.63, P &lt; 0.05) and duration of U muscle (r s = 0.71, P &lt; 0.05) in OSAS patients. Other MUP parameters of palatal muscles were similar between the two groups. Conclusion: Our results showed that, although mild in severity, structural neurogenic and myogenic changes characterized as mild and nonuniform MUP changes may co-exist in OSAS patients. These changes in palatal muscles may be attributed to compensatory adaptation of muscle fibers to other precipitating factors in OSAS.

Influence of Pathological Processes on Motor Unit Potential

Influence of Pathological Processes on Motor Unit Potential

76-Year-Old Woman With Generalized Weakness

76-Year-Old Woman With Generalized Weakness