Turns-amplitude Analysis Research Articles

Permutation Entropy and Signal Energy Increase the Accuracy of Neuropathic Change Detection in Needle EMG.

Background and Objective. Needle electromyography can be used to detect the number of changes and morphological changes in motor unit potentials of patients with axonal neuropathy. General mathematical methods of pattern recognition and signal analysis were applied to recognize neuropathic changes. This study validates the possibility of extending and refining turns-amplitude analysis using permutation entropy and signal energy. Methods. In this study, we examined needle electromyography in 40 neuropathic individuals and 40 controls. The number of turns, amplitude between turns, signal energy, and “permutation entropy” were used as features for support vector machine classification. Results. The obtained results proved the superior classification performance of the combinations of all of the above-mentioned features compared to the combinations of fewer features. The lowest accuracy from the tested combinations of features had peak-ratio analysis. Conclusion. Using the combination of permutation entropy with signal energy, number of turns and mean amplitude in SVM classification can be used to refine the diagnosis of polyneuropathies examined by needle electromyography.

O21 Peak ratio and motor unit potential analyses in detection of chronic neurogenic changes in amyotrophic lateral sclerosis

Objectives Peak ratio analysis is a quantitative way of analyzing interference pattern by turns-amplitude analysis. We aimed in this study to compare the sensitivities of peak ratio analysis and quantitative motor unit potential (MUP) analysis in detecting chronic neurogenic changes in amyotrophic lateral sclerosis (ALS). Methods Twenty-two patients (1 definite, 7 probable, and 9 possible ALS according to Awaji criteria as reference standard, and 5 progressive muscular atrophy) were prospectively included. Quantitative MUP and peak ratio analyses were done in 22 biceps brachialis (BB), 22 tibialis anterior (TA) and 18 abductor pollicis brevis (APB) muscles on the least affected side. Results were compared to laboratory controls. The sensitivity of MUP duration and peak ratio was compared using the McNemar chi-square test. Results Peak ratio analysis was more frequently abnormal than MUP analysis in BB (59% vs. 23%), and TA (59% vs. 18%) muscles ( p Discussion Peak ratio analysis sampled at stronger effort detected more frequently chronic neurogenic changes than MUP analysis recruited at weak effort. Conclusions Peak ratio analysis may provide earlier detection of chronic neurogenic changes, thereby facilitating earlier diagnosis of ALS. Significance Peak ratio analysis which is available in commercial EMG machines should be considered in the electrodiagnostic investigation of ALS.

Quantitative MUP and peak ratio analysis in diagnosis of myopathy

Objective To determine the diagnostic value of quantitative motor unit potential (MUP) analysis and peak-ratio analysis of the turns amplitude analysis (Fuglsang-Frederiksen et al., 1992) in electrophysiological diagnosis of myopathy. Methods Electromyography (EMG) data of 163 patients consecutively referred for myopathy and in whom both MUP and peak-ratio analysis were done in biceps brachii (BB) muscle were analysed retrospectively. MUP and peak ratio analysis data from BB muscle were compared. Results Of 163 patients, the overall clinical and electrophysiological diagnosis estimated using the whole electrophysiological examination was myopathy in 97 patients, normal in 45 and other disorders in 21. In 97 myopathy patients, both MUP and peak-ratio analysis were myopathic in 33 BB muscles (34%), whereas 20 muscles (21%) showed normal peak-ratio but myopathic MUP and 26 muscles (27%) showed myopathic peak-ratio but normal MUP analysis. Overall, myopathic changes were seen in 79 muscles (82%). In 39 of 45 subjects without abnormality (87%) and in 18 of 21 subjects (86%) with other disorders, both MUP and peak-ratio analysis were normal without myopathic changes. Conclusion MUP and peak-ratio analysis supplement each other in electrophysiological diagnosis of myopathy.

Estimating the tendency of motor unit recruitment during steady-hold and rapid contractions using surface EMG and Turns-amplitude analysis.

The purpose of this study was to investigate changes in the interference pattern in surface electromyography (EMG), and its relationship with the tendency of motor unit (MU) recruitment during steady-hold and rapid muscle contractions. Fifteen healthy adults (eight females and seven males, 22.6±1.5 years old) performed steady-hold and rapid isometric contractions of the bicep brachii, adductor pollicis, and tibialis anterior muscles at various force levels. Surface EMG recordings were analyzed using Turns-Amplitude Analysis (TAA). During steady-hold contractions, the number of turns per second (T/s) increased exponentially with force during submaximal contractions, and plateaued after force levels of 66, 70 and 57% MVC for the tibialis anterior, bicep brachii and adductor pollicis muscles, respectively. These force levels were proximate to the maximal recruitment threshold (MaxRT) reported previously. The slopes of the T/s-force relationships before the MaxRT were significantly greater than the slopes after the MaxRT for all three muscles tested. During rapid contraction, the slopes of the T/s-force relationships were significantly lower than the slopes of the steady-hold contraction at 20-40% MVC in all three muscles, and for 40-60% MVC in TA muscles. Our results suggested that the changes in the number of turns in surface EMG with respect to muscle force can be used to estimate the force levels at which the majority of the MUs to be recruited, and completion of MU recruitment was observed at lower force levels during rapid muscle contraction.

Turn-amplitude analysis as a diagnostic test for myofascial syndrome in patients with chronic pelvic pain.

Myofascial pain syndrome of the pelvic floor (MPSPF) is a common disease in the context of chronic pelvic pain (CPP); however, there is currently no gold-standard test to diagnose it. To validate the turns-amplitude analysis (TAA) as a diagnostic test for MPSPF in patients with CPP. A case-control study was performed, and patients were consecutively sampled within a specified period of time. A total of 128 patients were included: 64 patients with CPP (32 men and 32 women) and 64 control patients (32 men and 32 women). The same operator conducted all tests. Electromyography of the TAA is based on the collection of motor unit potentials that measure the number of changes in the signal and the mean amplitude of the changes. The electromyogram transfers the data to a graphical point cloud, which enables the patient's results to be compared with the results of the healthy subjects. In patients and control subjects, the sensitivity and specificity of the proposed diagnostic test showed a marked clinical significance: the sensitivity was 83%, and the specificity was 100%. A positive predictive value of 1 (95% CI 1 to 1) and a negative predictive value of 0.85 (95% CI 0.77 to 0.93) were observed. TAA is a reliable diagnostic test to detect MPSPF. Further studies are needed to reproduce these results.

Diagnostic yield of muscle fibre conduction velocity in myopathies

We prospectively assessed diagnostic yield of muscle fiber conduction velocity (MFCV) studies in patients with signs and symptoms suggestive of a myopathy. Results were analysed with respect to the final diagnosis, and compared to the reference standard, which was qualitative electromyography (EMG), turns-amplitude analysis (TAA), and muscle biopsy. We included 125 patients, in whom a myopathy was diagnosed in 71, and a neuromuscular disorder was excluded in 54. Sensitivity of MFCV for the presence of a myopathy was 84%, and specificity 83%. Diagnostic yield of MFCV was superior to EMG, TAA, and muscle biopsy in patients with metabolic myopathies, non-dystrophic myopathies, and channelopathies. We concluded that measurement of MFCV is a quantitative EMG technique with a high diagnostic yield. In certain myopathies, MFCV may be more informative than conventional EMG examination.

Correlation of Electromyogram and Muscle Biopsy in Myopathy of Young Age

Chang JH, Park YG, Choi YC, Choi JH, Moon JH. Correlation of electromyogram and muscle biopsy in myopathy of young age. Objective To investigate the accuracy of electromyogram (EMG) compared to muscle biopsy in young myopathic patients. Design Observational study. Setting A university rehabilitation hospital. Participants Cases (N=62) were included if the patient was 18 years or younger, and if data were available from muscle biopsy, EMG, and final clinical diagnosis. Intervention No intervention. Main Outcome Measure Sensitivity of EMG. Results EMG showed myopathic findings in 55 patients, and microscopy revealed myopathy in 50 patients and nonspecific findings in 5 patients. Twenty-eight out of 33 patients showed myogenic EMG findings with a conventional EMG, and histology revealed myopathy in 24 patients. In comparison, turns/amplitude analysis (TAA) with a conventional EMG detected myogenic findings in 27 of 29 patients. Twenty-six of these 27 patients showed myogenic findings in the biopsy. Conclusions We concluded that EMG is useful for the detection of myopathy in young patients. In addition, TAA may be helpful in cases of no definite conventional EMG findings and less cooperative patients.

Turns–amplitude analysis in normal and myopathic facial muscles

The purpose of this study was to assess turns/amplitude analysis (TAA) as an objective alternative to conventional qualitative electromyography (EMG) for detection of myopathy in facial muscles. Normal values of TAA parameters were calculated in the frontalis and mentalis muscles of 26 control subjects. We estimated the slope of the regression line of mean amplitude/turn values (MA) plotted against the number of turns/second (NT) and the resulting clouds. The 95% confidence limits of the cloud data were drawn as an ellipse. The sensitivity of TAA was determined from a group of 35 myopathic patients and specificity from a second group of 25 control subjects. Significant differences for every TAA parameter were found between frontalis and mentalis. Cumulative sensitivity and specificity of TAA for frontalis and mentalis were 74.6%, 56.5%, and 73.3%, 70.8%, respectively. With at least two of the aforementioned criteria abnormal, the sensitivity and specificity for frontalis and mentalis were 61.3%, 82.6%, and 56.7%, 100.0%, respectively.

P13-16 Turns amplitude analysis of facial muscles in normal subjects and myopathic patients

P13-16 Turns amplitude analysis of facial muscles in normal subjects and myopathic patients

Quantitative EMG of facial muscles in myasthenia patients with MuSK antibodies

ObjectiveOur aim was to study the pathophysiological process leading to facial muscle atrophy in 13 patients with MuSK antibody positive myasthenia gravis (MuSK-MG), and to compare with findings from 12 acetylcholine receptor antibody positive myasthenia patients (AChR-MG), selected because they suffered from the same degree of disease severity and required similar treatment. MethodsMotor unit action potential (MUAP) and interference pattern analysis from orbicularis oculi (O oculi) and orbicularis oris (O oris) muscles were studied using a concentric needle electrode, and compared with findings in 20 normal subjects, 6 patients receiving botulinum toxin injections (representing a neurogenic model) and 6 patients with a muscle dystrophy (representing a myopathic model). The techniques and control data have been reported previously. ResultsThe mean MUAP durations for O oculi and O oris were significantly reduced (p<0.001) in both MG cohorts when compared with healthy subjects, and were similar to those in the myopathic control group. They were significantly different from those obtained from the neurogenic control group (p<0.001 for both O oculi and O oris). The MUAP findings in O oculi occurred independently from neuromuscular blocking on single fibre EMG (SFEMG) in the same muscle. On turns amplitude analysis (TAA), 50% of MuSK-MG patients and 42% of AChR-MG patients had a pattern in O oculi which was similar to that in the myopathic control group, and 62% of MuSK-MG patients and 50% of AChR-MG patients had a pattern in O oris that was also similar to that in the myopathic control group. The TAA findings for O oculi and O oris in both MG cohorts were different from those obtained from the neurogenic control group. ConclusionsFacial muscle atrophy in MuSK-MG patients is not neurogenic and the pathophysiological changes are akin to a myopathic process. The selected AChR-MG patients also show evidence of a similar pathophysiological process in the facial muscles albeit to a lesser degree. SignificanceWe propose that muscle atrophy in MuSK-MG is a myopathic process consisting of either muscle fibre shrinkage or loss of muscle fibres from motor units. The duration of disease and long-term steroid treatment may be further contributory factors.

Turns amplitude analysis of the orbicularis oculi and oris muscles

Objective The aim of the study was to determine whether ‘clouds’ from turns amplitude analysis obtained from the orbicularis oculi and oris muscles without force monitoring can be used to differentiate pathological processes affecting the face. Methods The interference pattern from orbicularis oculi and orbicularis oris was studied using a concentric needle electrode. Data-points from 20 normal subjects were plotted on a logarithmic scale of mean amplitude between turns versus turns/second, from which linear regression analysis defined the 95% confidence intervals. This enabled us to draw the boundaries of the normal cloud on a linear plot. Data-points from the interference pattern in two pathological cohorts, of 6 patients receiving botulinum toxin injections (representing a neurogenic model), and 6 patients with a muscle dystrophy (representing a myopathic model) were plotted against the normal cloud. These findings were compared and correlated with the mean durations obtained on motor unit action potential analysis from these same two facial muscles. Results The majority of patients receiving botulinum toxin injections into their facial muscles showed a pattern of high amplitude with low turns/s, or low amplitude with a low-to-normal range of turns/s in both facial muscles. These findings were associated with high-duration motor unit action potentials in most cases. In the myopathic group of patients 66% showed a pattern of low amplitude with low-to-normal range of turns/s in O oculi and O oris. This correlated with short-duration motor unit action potentials in both facial muscles. Conclusions We have demonstrated that turns amplitude analysis without force monitoring can be used to study the interference pattern from facial muscles and can be applied to differentiate primary neurogenic from myopathic pathological processes. Significance Turns amplitude analysis without force monitoring in the facial muscles can be used as an effective and practical method of interference pattern analysis to complement findings from conventional motor unit action potential analysis.

Turns-amplitude analysis of the electromyographic recruitment pattern following upper motor neuron lesions

To assess the pattern of motor unit recruitment of weak muscles in upper motor neuron (UMN) lesions. Ten patients underwent turns-amplitude analysis (TAA) on the paretic and healthy brachial biceps muscles, in the acute and subacute stages of hemiparesis. The control group comprised 10 age- and sex-matched subjects. Although absent in the acute stage, five patients developed a myogenic cloud pattern in their paretic extremities in the subacute stage; which was statistically significant when compared with controls (P = 0.033). Mean amplitude was reduced in both acute and subacute stages of the hemiparesis compared with controls (P = 0.000). The turns/mean amplitude ratio in the subacute stage was increased compared with both the paretic limbs examined in the acute stage (P = 0.000) and to controls (P = 0.000). Abnormalities in the recruitment of motor units in UMN lesions give rise to a myogenic cloud pattern in the TAA, which is prominent in the third month after the initial insult. This may result from the increase in motor unit activity, while the recruitment of bigger motor units is still defective.

Turns-amplitude analysis and motor unit potential analysis in myasthenia gravis.

The aims of this study were to investigate myopathic changes in myasthenia gravis (MG) by using turns-amplitude analysis (TAA) and quantitative motor unit potential duration analysis (MUPan), to correlate myopathic changes with severity and duration of the disease and the results of diagnostic tests including repetitive nerve stimulation test (RNS), single fiber electromyography (SFEMG), and anti-acetylcholine receptor antibody (AChR-ab), and to compare the sensitivities of these two methods in detecting myopathic changes in MG. We studied both MUPan and TAA in 32 patients with MG. The MUPan study showed myopathic changes in 12 patients (37.5%); TAA revealed a myopathic pattern in 4 (12.5%) and a neurogenic pattern in 4 cases (12.5%). Two of the 4 patients with a myopathic change by TAA also had short-duration mean MUP on the MUPan. No statistically significant association was found between the myopathic changes either by MUPan or TAA, and the various clinical and laboratory features. We conclude that MUPan is a more sensitive method than TAA in showing myopathic changes in MG, and that TAA is of limited help in demonstrating them.

Diagnostic value of turns-amplitude analysis in neuromuscular disease

We describe a new method of turns-amplitude analysis of electromyography interference patterns, modified from the original Stålberg’s method. Ten samples were obtained from one muscle at maximum voluntary contraction. As indices of amplitude (A), the average of the three highest and three lowest values from the ten samples was calculated. Similar indices were calculated for turns (T) and the T/A ratio. A total of six indices were evaluated. Criteria for abnormalities in these six indices were determined through a control study of healthy volunteers. The test-retest reliability of the six indices was confirmed in the extensor digitorum communis muscle, and the Pearson product–moment correlation coefficients ranged from 0.767 to 0.907 (P < 0.01). The clinical usefulness of this method was evaluated in 21 patients with mild or moderate neuromuscular disorders. Abnormalities in the T/A indices were found in 77.8%-100% of the patients, a higher incidence of abnormality than for the other indices. Two of the three criteria were found to be abnormal in 80% of patients with myopathy and in 78.6% of those with neuropathy. The diagnostic sensitivity of our method in these patients was 79.2% (19 of 24 studies [in 3 patients with myopathy, two muscles were examined]). The clinical usefulness of our method of analysis appears to be similar to that in other reports of turns-amplitude analyses.

Turns-amplitude analysis assessment of myopathies in HIV-infected patients

Electromyographic interference patterns during a gradual increase in force were studied by means of the turns-amplitude analysis in a series of HIV-infected patients with and without clinical, biological and histological signs of myopathy. Different parameters were evaluated to determine their sensitivity for the diagnosis of the myopathies that occur in this context. The studied parameters were the number of turns (NT), the mean amplitude of the turns (MA) and the ratio NT MA (RTA). For each parameter, we compared the interest of mean values, calculated at moderate contraction, to that of peak values. In addition, the shape of the cloud of MA plotted versus NT data points was analyzed. The sensitivity of the turns-amplitude analysis was 95% for the diagnosis of myopathy when NT, MA and RTA were taken together into account, versus 80% in the cloud studies. Peak values were the most sensitive criteria, but mean values abnormalities were observed in some cases of zidovudine myopathy, indicating a potential usefulness of this quantitative EMG method in the differential diagnosis among myopathies in HIV-infected patients.

Quantitative EMG in botulinum toxin treatment of cervical dystonia. A double-blind, placebo-controlled study

We used turns-amplitude analysis of the EMG as a guidance for botulinum toxin (BT) treatment in 19 patients with cervical dystonia. At the first examination, muscles showing abnormal activity (>100 turns/sec at rest) were given BT 75 units (10 patients) or placebo (9 patients). At subsequent examinations, about 6, 12 and 18 weeks after the start, BT 75 units were given to all hyperactive muscles. Six weeks after the first BT treatment the sternocleidomastoid muscle contralateral to the involuntary head rotation and the ipsilateral and contralateral posterior neck muscles (PNM) showed a reduction of involuntary activity, as indicated by reduced turns/sec and mean amplitude at rest. Similar changes were seen when comparing BT treatment with placebo. The reduction was greater in the contralateral sternocleidomastoid muscle than in PNM, suggesting that PNM need higher doses of BT. At maximal voluntary contraction, BT treated muscles showed unchanged turns/sec (5/6 tests), decreased mean amplitude and increased ratio (turns/amplitude). This may reflect a functional random loss of muscle fibres, combined with inability to activate all motor units. At high (89%) clinical success rate with BT therapy was obtained, and it is concluded that quantitative EMG is a useful tool for the precise identification of hyperactive muscles, for optimal placing of the injection cannula and for unbiased monitoring of the treatment effect.

Quantitative EMG in botulinum toxin treatment of cervical dystonia. A double-blind, placebo-controlled study

We used turns-amplitude analysis of the EMG as a guidance for botulinum toxin (BT) treatment in 19 patients with cervical dystonia. At the first examination, muscles showing abnormal activity (>100 turns/sec at rest) were given BT 75 units (10 patients) or placebo (9 patients). At subsequent examinations, about 6, 12 and 18 weeks after the start, BT 75 units were given to all hyperactive muscles. Six weeks after the first BT treatment the sternocleidomastoid muscle contralateral to the involuntary head rotation and the ipsilateral and contralateral posterior neck muscles (PNM) showed a reduction of involuntary activity, as indicated by reduced turns/sec and mean amplitude at rest. Similar changes were seen when comparing BT treatment with placebo. The reduction was greater in the contralateral sternocleidomastoid muscle than in PNM, suggesting that PNM need higher doses of BT. At maximal voluntary contraction, BT treated muscles showed unchanged turns/sec (5/6 tests), decreased mean amplitude and increased ratio (turns/amplitude). This may reflect a functional random loss of muscle fibres, combined with inability to activate all motor units. At high (89%) clinical success rate with BT therapy was obtained, and it is concluded that quantitative EMG is a useful tool for the precise identification of hyperactive muscles, for optimal placing of the injection cannula and for unbiased monitoring of the treatment effect.

Quantitative EMG analysis and longitudinal nerve conduction studies in a Refsum's disease patient

A patient with aosmia and night blindness had repeated clinical and electrophysiological examinations during a 21-year period. Within the first 11 years, he experienced two subacute episodes of numbness with weakness and ataxia. Over the 10 ensuing years, no additional functional disability appeared. We looked retrospectively for a correlation between repeated manual muscle scoring and different nerve conduction parameters. Further studies were done in order to estimate reinnervation in proximal and distal muscles and to assess autonomic functions. A direct relationship was found between the magnitude of muscle weakness and the amplitude of compound muscle action potentials, whereas nerve conduction velocities were inhomogeneously reduced but almost unchanged over time. Parasympathetic tests were normal but sympathetic skin responses were absent. As estimated by macro-EMG and turns-amplitude analysis the compensatory reinnervation was very high. We conclude that, in Refsum's disease, recurrent segmental demyelination of a significant portion of the motor units can occur in parallel with exacerbations of weakness, and that a considerable degree of progressive motor and sudoromotor axonal loss can be found although there is an apparent long-term clinical stabilization of the neuropathy.

Turns-amplitude analysis of the electromyographic recruitment pattern disregarding force measurement. I. Method and reference values in healthy subjects.

We used turns-amplitude analysis to characterize the EMG recruitment pattern disregarding force measurement. The electrical muscle pattern of the brachial biceps (BB), abductor pollicis brevis (APB), medial vastus (MV), and anterior tibial (AT) muscles was analyzed during progressive increase in force from rest to maximum using the mean amplitude as an indicator of the force of the muscle. The following parameters were obtained on-line: the maximal ratio of turns to mean amplitude (peak-ratio, PR), the mean amplitude, and the number of time intervals (TI) between turns at PR and at near maximum force (NMF). The highest PR values were obtained in BB, the lowest in MV. Analysis of the distribution of the TI between turns at different degrees of voluntary contraction showed fewer spikes with short duration and small amplitude at high force compared with low force.

Turns‐amplitude analysis of the electromyographic recruitment pattern disregarding force measurement. II. Findings in patients with neuromuscular disorders

Turns-amplitude analysis of the electromyographic recruitment pattern was performed on-line in the brachial biceps muscle of 46 patients with neuromuscular disorders using the mean amplitude as an indicator of force. The parameters, peak-ratio (PR) and number of time intervals (TI) from 0 to 1.5 ms, were increased in patients with myopathy. In patients with neurogenic involvement, the characteristic pattern was a decreased PR and a decreased incidence of TI between 0 and 1.5 ms. The results indicate that the two parameters supplement each other as some of the patients were identified only by one or the other. In patients with myopathy, the method had a higher diagnostic yield than the individual motor unit action potential analysis. The method is objective, fast, and reliable.