Motor Unit Potential Analysis Research Articles

Do Sacral/Peripheral Lesions Contribute to Detrusor-Sphincter Dyssynergia?

While detrusor-sphincter dyssynergia (DSD) occurs in conjunction with lesions between the brainstem and the sacral cord, it is not well known whether sacral/peripheral lesions contribute to DSD. We studied the relationship between DSD and sacral/peripheral lesions. One hundred and forty-four patients with diverse neurologic etiologies underwent urodynamic study and analysis of motor unit potentials in the external sphincter muscles, 117 of whom were able to void during a urodynamic test. Sacral/peripheral lesion (SPL) is defined as neurogenic change in motor unit potentials. Detrusor overactivity (DO) is defined as involuntary detrusor contractions during the filling phase, which commonly occurs in lesions above the sacral cord. We considered DO as a putative indicator of supra-sacral lesion. DSD was found in 44 (30.6%), SPL in 71 (49.3%), and DO in 83 (57.6%) of 144 patients, respectively. The incidence of DSD was the same in the SPL positive group (31%) and the SPL negative group (30.1%). By contrast, within the subgroup of patients without DO, the incidence of DSD was significantly more common in the SPL positive group (41.4%) than in the SPL negative group (25.0%) (P < 0.05). In 53 of the SPL positive group who were able to void, postvoid residual >100 mL was more common in patients with DSD (not statistically significant). The results of the present study suggest that not only suprasacral pathology, but also sacral/peripheral lesions can produce DSD. In light of the previous reports, DSD might also result from partial lesions in peripheral branches of the sphincter circuit.

Sacral neurophysiologic study in patients with chronic spinal cord injury

Neurophysiologic testing of the sacral reflex has demonstrated utility in the diagnosis of sacral lower motor neuron lesions. The aim of the present study was to also apply this test to patients with upper motor neuron lesions. A group of 16 male patients with chronic suprasacral spinal cord lesions was prospectively recruited. In addition to history and clinical neurologic examination (including anal sphincter tone, saddle sensation, and penilo-cavernosus reflex testing), sacral neurophysiologic studies were performed. Neurophysiologic testing included quantitative electromyography of the external anal sphincter (motor unit potential (MUP) count during relaxation and MUP analysis), and neurophysiologic measurement of the penilo-cavernosus reflex (elicitation threshold and latency) on electrical stimulation. The findings were compared to data obtained in the control group of 26 men. Clinical elicitability of the penilo-cavernosus reflex was increased, and the neurophysiologically measured reflex threshold reduced in patients (<0.02). No significant differences were found in clinical assessment of anal sphincter tone, MUP count, reflex latency, and quantitative MUP analysis. The diagnostic sensitivity of individual parameters was low (≤25%). In patients with chronic spinal cord injury, increased elicitability of the penilo-cavernosus reflex was found. However, none of the assessed neurophysiologic parameters was found to assist in the diagnosis of the sacral upper motor neuron lesion in individual patients. The shortened sacral reflex latency found in individual patients is therefore not a consequence of a suprasegmental lesion, but rather of the low position of the conus medullaris (e.g., in tethered cord syndrome).

JS2-1 Using motor unit potentials analysis to get an insight into the motor unit

JS2-1 Using motor unit potentials analysis to get an insight into the motor unit

Lower motor neuron involvement examined by quantitative electromyography in amyotrophic lateral sclerosis

Objective The diagnosis of amyotrophic lateral sclerosis (ALS) includes demonstration of lower motor neuron (LMN) and upper motor neuron (UMN) involvement of bulbar and spinal muscles. Electromyography (EMG) is essential to confirm LMN affection in weak muscles, and to demonstrate changes in clinically non-involved muscles. The aim of the study was to determine the relative importance of ongoing (active) denervation, fasciculations, chronic partial denervation with reinnervation at weak effort and loss of motor units at maximal voluntary contraction (MVC) in ALS. Methods EMG was carried out in weak and non-weak muscles in 220 patients suspected of ALS using concentric needle electrodes. Denervation activity and fasciculations in 966 muscles was quantified, the mean durations and amplitudes of motor unit potentials (MUPs) were compared to controls in 745 muscles, and the amplitudes and recruitment patterns at maximal voluntary effort were measured in 939 muscles. Twenty-five percent of patients had clinical involvement of 1 region, 42% of 2 regions and 33% of 3 regions. Clinically 65% had UMN involvement. Eighty-six percent of the patients had died on follow-up. Results Denervation activity occurred in 72% of weak muscles but in only 45% of non-weak muscles. Fasciculations occurred in 56% of weak muscles and in 65% of non-weak muscles. MUPs showed reinnervation in 87–91% of weak and non-weak muscles and in 44% of muscles neurogenic MUPs occurred in the absence of denervation activity. In patients with clinical involvement of 1 region, combined EMG criteria increased the number of affected regions in 93%, and in 40% of patients with clinical involvement of 2 regions EMG increased the number of involved regions. Conclusions Quantitative EMG confirmed widespread LMN involvement in patients with early ALS including clinically non-involved regions. These findings suggest that the maintenance of force is due to compensatory reinnervation in early disease and that this capacity may decline at later stages of ALS. Significance These findings support a recent consensus report (the Awaji criteria) that EMG should have equivalent weight to clinical manifestations to indicate LMN involvement. The findings strongly indicate that spontaneous activity is insufficient to show LMN involvement in non-affected muscles at early stages of disease, and that analysis of MUPs are needed to document the distribution of LMN involvement.

Physician-writers in the age of blogging

Muscle atrophy, fiber-type shifting, reduced contractility, metabolic alterations, capillarization defect, and mitochondrial modifications are important adaptations in COPD. Skelatal muscle dysfunction is one of the most devastating systemic manifestations of COPD which eventually leads to increase in morbidity and mortality. In this study we aimed to demonstrate the effects of COPD on both muscles and nerves in neurologically normal patients with different degrees of airflow limitations, using current electrophysiological methods.Electrophysiological examinations were performed using a Keypoint EMG machine with subjects lying supine on a bed at a room temperature. Tests were nerve conduction studies, motor unit potential (MUP) analysis, interference pattern (IP) analysis and macro EMG (mEMG) analysis on the right side in the upper and lower extremities. Multi-motor unit potential (m-MUP) analysis and interference pattern (IP) analysis revealed some changes in biceps brachii (BB) and tibialis anterior (TA) muscles, but macro EMG (mEMG) analysis was similar except for increased fiber density at TA muscles in COPD patients. Increased ulnar and sural sensory latency, decreased ulnar sensory velocity, and increased ulnar motor latency values were found in COPD. There was increased motor unit potential (MUP) turn and phase values in BB muscles and increased MUP turn and decreased MUP duration, area, area/amplitude ratio and size index values in TA muscles in COPD patients. As a conclusion, in COPD more nerve conduction abnormalities and more MUP abnormalities which reflected muscle fiber diameter changes were observed by the use of electrophysiological methods including multi MUP - IP analysis and mEMG analysis.

Predictive values of motor unit potential analysis in limb muscles

In interpretation of diagnostic findings the probability that an abnormal test accurately indicates pathology (i.e., the positive predictive value), and a normal test accurately excludes pathology (i.e., the negative predictive value) is the most important. For motor unit potential (MUP) analysis no such data has been published; hence this was the aim of this study. In 31 patients with facioscapulohumeral muscular dystrophy (FSHD) and 34 controls the biceps brachii and vastus lateralis muscles were examined by concentric needle electromyography (EMG), using template operated MUP analysis. These results were compared to non-parametric reference data obtained in another group of 34 (biceps brachii) and 46 (vastus lateralis) control subjects. For the biceps brachii muscles sensitivity was 59%, specificity 91%, the positive predictive value 85%, and negative predictive value 72% with at least two criteria (mean values or outliers for MUP thickness, amplitude and duration) below the reference intervals. In addition, all subjects with three abnormal EMG criteria were FSHD patients, and 90% of subjects with normal EMG were controls. Template operated MUP analysis demonstrated reasonable predictive value for diagnosis and exclusion of myopathy. Quantitative MUP analysis seems to be useful for the preliminary diagnosis of FSHD in patients with appropriate clinical picture.

Motor unit changes in thoracic paraspinal muscles in amyotrophic lateral sclerosis

In 38 amyotrophic lateral sclerosis (ALS) patients and 28 controls, we performed motor unit potential (MUP) analysis in the C-6 and T-5 paraspinal and biceps muscles. In ALS cases, we found similar abnormalities in MUPs in paraspinal and limb muscles. Fasciculation potentials (FPs) were more frequent in biceps than in paraspinal muscles, but fibrillation potentials and positive sharp waves (fibs-sw) were equally frequent in all three muscles. These results confirm the value of paraspinal MUP analysis in the diagnosis of ALS.

Approximation of motor unit structure from the analysis of motor unit potential

Objectives: The aim of this simulation study was to approximate certain features of motor unit structure on the basis of motor unit potential (MUP) analysis. Methods: The principle of the approximation method has been to invert the procedure used in the simulation of the MUP. An algorithm has been developed that analyses the recorded potential and estimates the number of fibers that contribute to the MUP, their diameters and localization relative to the electrode. These parameters have been determined by minimizing the differences between the recorded and modeled potentials. Results: The method has been tested on MUPs recorded in the muscles of healthy and diseased subjects. The evaluated range of fiber diameters and densities in a healthy muscle was consistent with its morphological characteristics. In pathological cases, the results of the analysis indicated changes of fiber diameters and densities typical of a given pathological process. Conclusion: Preliminary results of simulations suggest that the proposed method is a potentially useful tool for the approximation of morphological features of muscle fibers contributing to the MUP. Significance: The analysis of MUPs, in addition to the evaluation of the electrical activity of the muscle with the use of the proposed approximation method, may also permit characterization of muscle morphology, and therefore it may improve the diagnostic value of electromyography.

Paraspinal and limb motor neuron involvement within homologous spinal segments in ALS

Objective We studied the involvement of motor neuron groups innervating paraspinal muscles in amyotrophic lateral sclerosis (ALS) and evaluated the value of paraspinal muscle EMG in the diagnosis of the disease. Methods We used quantitative concentric needle EMG to study denervation and reinnervation in a paraspinal muscle and a limb muscle innervated by the C6 and L5 segments in 32 patients with ALS. As control subjects we studied 11 patients with peripheral neuropathy, and 46 non-neurogenic control subjects. Results We found similar abnormalities in motor-unit potentials (MUPs) in paraspinal and limb muscles in these two segments in ALS. Fasciculation potentials (FPs) were more frequent in limb muscles than in paraspinal muscles and fibrillations and sharp waves (fibs-sw) were most frequent in tibialis anterior. In peripheral neuropathy paraspinal muscles were normal but tibialis anterior showed very abnormal motor unit potentials. Conclusions These results are consistent with generalised involvement of motor neurons in motor neuron pools in spinal segments in early stages of ALS progression. However, distally predominant fibrillations indicate susceptibility to ongoing denervation in reinnervated distal axons. Complex FPs of similar morphology to MUP analysis in the same early affected muscle suggests a proximal origin for these FPs at this phase. Significance Our observations emphasize the value of paraspinal muscle EMG in the electrophysiological diagnosis of ALS.

Quantitative motor unit potential analysis in the diaphragm: A normative study

Although quantitative motor unit potential (MUP) analysis has an established role in other skeletal muscles, it has not been performed in the diaphragm. The aim of the present study was to test whether such studies are possible and to establish normative data. Twenty-nine healthy volunteers (15 men), aged 21-65 years (median, 33 years), were studied using standard concentric needle electrodes, and equipment with the facility for template-operated multi-MUP analysis. Needle electrodes were inserted into the right medial recess of the seventh to ninth intercostal spaces. During MUP sampling, subjects were asked to hold their breath in partial inspiration for 5 s. At least 20 MUPs were obtained in 28 subjects. Diaphragmatic MUPs were confirmed to be much smaller than those of limb muscles. We found diaphragmatic quantitative MUP analysis to be possible in healthy volunteers. However, further studies in patient groups are needed to establish the feasibility and clinical value of such studies.

Neurophysiological markers in familial amyloid polyneuropathy patients: Early changes

Objective Familial amyloid polyneuropathy-type I (FAP-I) is a hereditary, axonal, sensory-motor and autonomic polyneuropathy, with early involvement of small fibres. Liver transplantation is the only effective therapy in FAP, but should be performed early in the course of the disease. Reliable quantitative methods that could allow the determination of early changes in the peripheral nerve function are essential. Our aim was to find sensitive neurophysiological markers in FAP-I. Methods Eighty-one FAP-I patients were included in this study. They were divided into two groups (G1, asymptomatic FAP-I mutation carriers; G2, early symptomatic). Seventy-six healthy controls formed a control group (G3). Nerve conduction studies, needle electromyography with motor unit potential analysis of the extensor digitorum brevis, RR interval and sympathetic skin response (SSR) were analyzed. Results The amplitudes of the motor response of the peroneus nerve and of the plantar SSR were significantly lower in G1 compared to G3. No other differences were found between those two groups. With a cut-off point of 0.2 mV for plantar SSR, its sensitivity and specificity are 0.53 and 0.95, respectively. The positive predictive value and the negative predictive value are 0.82. Conclusions SSR response at foot is a useful measurement to detect early dysfunction of peripheral nerve fibres in FAP-I. Its abnormality should be considered a warning sign and lead to a careful clinical assessment. Significance SSR is a useful neurophysiological marker in FAP-I.

6. Specificity of motor unit potential analysis in limb muscles

6. Specificity of motor unit potential analysis in limb muscles

Effect of paralysis of the abdominal wall muscles by botulinum A toxin to intraabdominal pressure: an experimental study

Purpose To show the effect of botulinum A toxin–induced paralysis of abdominal muscles on intraabdominal pressure. Material and Methods Fifteen Sprague-Dawley rats were divided into 2 groups. An abdominal skin incision was done, and 2 catheters were placed for the pressure monitoring and saline infusion. Saline solution was given to the abdomen until reaching to a pressure level of 9 cm H 2O and 6 mm Hg in pressure device, and the amounts of injected saline were recorded. Then intraabdominal saline was drained. Two milliliters (5 U/mL) botulinum A toxin was applied to the abdominal muscles in group 2. Saline was injected at the same points in same amounts in group 1. After 3 days, catheters were placed, and the saline volumes needed to obtain the same pressure levels were recorded for each rat. Spontaneous motor unit potential (MUP), single MUP analysis and interference patterns of the muscles, respiratory rates, and vascular pressure measurements were recorded before and after botulinum toxin (Botox) injections. Results Mean intraabdominal saline volumes in the first and third days were 63.8 and 64.4 mL in group 1 and 67.6 and 80.6 mL in group 2, respectively. Mean MUP amplitude and duration of the rectus muscles in group 2 (17.1 μV and 1.47 milliseconds) were significantly lower than those of group 1 (187 μV and 4.9 milliseconds) in the third day. There were no pathological changes in respiratory rates and pressure measurements before and after Botox injections. Conclusion This pilot experimental study showed that local injection of botulinum A toxin causes paralysis in abdominal wall muscles, increases the intraabdominal volume, and decreases the pressure, and this application may be used as an adjunct in abdominal wall closure in selective cases.

Sensitivity of motor unit potential analysis in facioscapulohumeral muscular dystrophy

Template-operated motor unit potential (MUP) analysis has made quantitative electromyography (EMG) feasible, even in busy laboratories, but validation of this approach is still necessary. In the present study, the utility of multi-MUP analysis was assessed in patients with a molecular genetic diagnosis of facioscapulohumeral muscular dystrophy (FSHD). Manual assessment of muscle strength and concentric-needle EMG of the biceps brachii and vastus lateralis muscles were performed. The sensitivity for diagnosing myopathy (mean values and outliers) was tested for eight MUP parameters and four of their combinations. The group comprised 31 patients. Elbow flexion and knee extension strength was normal in 45% and 52% of patients, respectively. The most sensitive MUP parameter was thickness, followed by duration. A combination of three MUP parameters (thickness, amplitude, and duration/area) was needed for maximal sensitivity. The study demonstrated a high sensitivity of multi-MUP analysis in FSHD. Myopathic abnormalities were demonstrated in all weak biceps brachii muscles, and in 77% of biceps brachii muscles with normal strength.

When is Onuf’s nucleus involved in multiple system atrophy? A sphincter electromyography study

Background: External anal sphincter (EAS) electromyography (EMG) abnormalities can distinguish multiple system atrophy (MSA) from Parkinson’s disease in the first five years after disease onset. However, the prevalence of the...

Comparison of different outlier criteria in quantitative anal sphincter electromyography

Objective Analysis based on ‘outliers’ has been demonstrated to be a useful adjunct to mean value analysis in quantitative needle electromyography (EMG). However, the outlier criteria applied have been arbitrarily chosen. The aim of the present study was to determine the most useful outlier criteria in motor unit potential (MUP) analysis. Methods The external anal sphincter (EAS) muscles were examined by multi-MUP analysis. From 115 muscles of 64 normative subjects, the 0/100, 5/95, 10/90, 15/85, 20/80, and 25/75 percentile MUP parameter values were grouped individually. From these, the 5/95, 2.5/97.5, 1/99 and 0/100% confidence limits were determined. Thus, 24 sets of outlier limits were formed. To calculate sensitivity and specificity, data from 79 patients with cauda equina lesions (189 muscles), and from 77 controls (119 muscles) were compared to normative outlier limits. Results Sensitivities were highest with outlier limits formed from the 10–90 percentile ranges, followed by the 5–95 and 15–85 percentile ranges, while specificity was highest using the 15–85, followed by the 20–80, and 25–75 percentile ranges. On direct head-to-head comparison the 10–90 percentile ranges were more sensitive and 5–95 were more specific. Conclusions The study demonstrated considerable differences in the sensitivity and specificity of outlier limits calculated from different percentile ranges, with outlier criteria calculated from the 10–90 and from the 5–95 percentile ranges appearing to be the most useful for detection of neuropathy in the EAS muscle. Significance In future EAS muscle EMG I propose that outlier criteria calculated from the 10–90 percentile ranges be used.

Usefulness of an increase in size of motor unit potential sample

Objective It is known that the sensitivity of quantitative electromyographic (EMG) analysis of motor unit potentials (MUPs) improves with an increase in MUP sample size to more than 20. However, no normative data and estimate of sensitivity have been published. Methods In the present study sample sizes of 5, 10, 15, 20, 30 and 40 MUPs were obtained from the external anal sphincter (EAS) muscles of 81 controls and 70 patients with cauda equina lesions. For each sample size normative limits and sensitivities for mean values and ‘outliers’ were calculated for 8 MUP parameters. Results As the size of the MUP samples increased, normative limits narrowed and sensitivities increased for both statistics of all MUP parameters (sensitivities were 26% at 10, 44% at 20, and 67% at 40 MUPs with mean values and outliers of MUP area, duration and number of turns). Conclusions Our results confirmed a substantial increase in the sensitivity of MUP analysis by enlargement of the MUP sample size to more than 20 MUPs. The gain in sensitivity seem to be greater than the increase obtained by examination of contralateral EAS muscle. Significance Findings might be useful to clinical neurophysiologists planning strategies for electrodiagnostic evaluation of lower sacral segments.

Lower urinary tract dysfunction in Machado–Joseph disease: a study of 11 clinical-urodynamic observations

Objectives: Machado–Joseph disease (MJD), or hereditary spinocerebellar ataxia type 3, is the most common dominantly inherited ataxia. However, lower urinary tract (LUT) dysfunction in MJD has not been fully delineated. We investigated LUT dysfunction in MJD by clinical-urodynamic observations. Methods: In 24 genetically diagnosed MJD, we recruited all 11 patients with LUT symptoms (six men, five women; age, 18–61 [mean 48] years; disease duration, 2–24 [mean 9] years; voiding difficulty, 7, urinary incontinence, 4). Urodynamic studies consisted of uroflowmetry, measurement of post-void residuals and electromyography (EMG)-cystometry. Neurophysiology tests consisted of motor unit potential (MUP) analysis of the sphincter and extremity muscles, tibial nerve somatosensory evoked potentials (SEP) and nerve conduction studies (NCS) of the extremities. Results: Urodynamic abnormalities were seen in all 11 patients studied. Maximum or average flow rate was decreased in five. Post-void residual was noted in three but residual urine volume >100 ml was noted in only one patient. Maximum urethral closure pressure was low in one and high in one of five patients studied. EMG-cystometry during filling showed detrusor overactivity in five, impaired bladder sensation in four, low compliance detrusor in one, uninhibited sphincter relaxation in one and incompetent urethra in one. Voiding phase abnormalities included detrusor areflexia in three and detrusor-sphincter dyssynergia in two. Bethanechol supersensitivity of the bladder was noted in one of three patients studied. Bulbocavernosus reflex was absent in two of five patients studied. MUP analysis showed neurogenic changes in six of nine sphincter muscles and in all six extremity muscles studied. Five patients had prolonged or absent cortical response in SEP and four had sensory axonal neuropathy in NCS, which were relevant to the impaired bladder sensation. Conclusion: In the present study, a half of MJD patients had LUT symptoms and they showed various urodynamic abnormalities. Detrusor overactivity, impaired bladder sensation, and neurogenic sphincter EMG were common findings, and large post-void residuals were rare. These findings are relevant to central and peripheral nervous system pathology of MJD.

Needle EMG of abductor hallucis and peroneus tertius in normal subjects.

Normal values for standard concentric-needle electromyography (EMG) of the abductor hallucis (AH) and peroneus tertius (PT) muscles have not been established to date, yet both are potentially useful muscles in the diagnosis of length-dependent peripheral nerve disorders. Forty-three normal asymptomatic subjects stratified by age underwent a standard set of nerve conduction studies and concentric-needle examination to exclude asymptomatic disease and develop normal values for the AH and the PT for various EMG parameters. Fibrillation potentials were observed in the AH in 21% of normal subjects (10% < 60 years old, 30% > 60 years old); 19% of subjects were unable to voluntarily activate the AH. All subjects could activate the PT regardless of age. No fibrillation potentials were observed in subjects < 60 years of age, whereas 9% of those older than 60 years had mild fibrillation potentials in the PT. The PT is a useful muscle in the evaluation of length-dependent peripheral neuropathy and other peripheral nerve disorders of the lower extremities, on the basis of ease of motor unit potential activation and analysis, and relative infrequency of fibrillation potentials in normal subjects.

Size of motor unit potential sample.

In quantitative electromyography (EMG), a sample size of 20 motor unit potentials (MUPs) is standard. The effect of increase in the number of MUPs above 20 is not known, although advanced MUP analysis techniques make such samples practical. In the present study, using multi-MUP analysis, pools of 3,720 neuropathic and 2,526 control MUPs were obtained from external anal sphincter muscles. From each pool, 10,000 random samples of 5, 10, 15, 20, 30, 40, 50, and 100 MUPs were obtained by a computer. For each sample size, 95% normative limits for mean values, SDs, and "outliers," and sensitivities were calculated for eight MUP parameters. As the magnitude of MUP samples increased, normative limits narrowed and sensitivities increased (at 5: 20-30%; at 20: 30-55%; at 100: 80-100%) for all statistics of all MUP parameters. Our results demonstrated a substantial increase in sensitivity by increasing the MUP sample to more than 20. This option deserves consideration in an attempt to improve the usefulness of quantitative EMG.