Quantitative Needle Electromyography Research Articles

P88-T Clinical and neurophysiologic characterization of the diabetic truncal mononeuropathy

Background Thoraco-abdominal or truncal nerves can be selectively affected in diabetic patients. The clinical picture shows predominantly sensory symptoms like pain, paresthesia, and occasional motor involvement. This mononeuropathy can be misdiagnosed with different thoracic-abdominal conditions (herpes zoster, angor pectoris, acute abdomen, intraabdominal tumours,…). It usually occurs between the 5th and 6th decades, with an insidious or subacute onset. We present a series of 4 cases in which electrodiagnostic testing was decisive for the diagnosis. Material and methods All the patients presented a long history of type 2 diabetes, and complained of poorly defined abdominal pain, without finding a cause that justified the symptoms in a prior extensive clinical investigation (including analytics and imaging studies). The neurophysiologic study consisted on motor and sensory conduction studies and quantitative needle electromyography of the rectus abdominis and external abdominal oblique muscles. Results In every case electromyography showed a subacute-chronic neurogenic pattern, characterized by complex and long-duration motor unit potentials, with an increased percentage of polyphasic potentials. In three cases we found spontaneous activity (fibrillation potentials or positive sharp waves). The study was compatible with the diagnosis of truncal neuropathy/radiculopathy. In half of the patients it was associated with a mixed sensory-motor polyneuropathy. Conclusions Truncal mononeuropathy in diabetic patients is most likely underdiagnosed, probably because the unspecific clinical presentation, including very variable sensory symptoms that mimic other conditions. Once the diagnosis of presumption is stablished, it is easily confirmed neurophysiologically, with electromyography being the technique that provides the most information for the diagnosis.

Motor unit number estimation and quantitative needle electromyography in stroke patients

ObjectiveTo evaluate the effect of upper motor neuron damage upon motor units’ function by means of two separate and supplementary electrophysiological methods. MethodsThe abductor digiti minimi muscle of the non-paretic and the paretic side was studied in forty-six stroke patients with (a) motor unit number estimation (MUNE) – adapted multiple point stimulation method and (b) computerized quantitative needle electromyography (EMG) assessing the configuration of voluntary recruited motor unit potentials. Main outcome comparisons were focused on differences between non-paretic and paretic side. ResultsOn the affected hands mean MUNE value was significantly lower and mean area of the surface recorded single motor unit potentials was significantly larger than the corresponding ones on the non-paretic hands. EMG findings did not reveal remarkable differences between the two sides. Neither severity nor chronicity of stroke was related to MUNE or EMG parameters. DiscussionMUNE results, which suggested reduced motor unit numbers in stroke patients, in conjunction with the normal EMG features in these same muscles has given rise to different interpretations. In a clinical setting, reinnervation type changes in the EMG similar to that occurring in neuronopathies or axonal neuropathies should not be expected in muscles with central neurogenic lesion.

Bayesian aggregation versus majority vote in the characterization of non-specific arm pain based on quantitative needle electromyography.

BackgroundMethods for the calculation and application of quantitative electromyographic (EMG) statistics for the characterization of EMG data detected from forearm muscles of individuals with and without pain associated with repetitive strain injury are presented.MethodsA classification procedure using a multi-stage application of Bayesian inference is presented that characterizes a set of motor unit potentials acquired using needle electromyography. The utility of this technique in characterizing EMG data obtained from both normal individuals and those presenting with symptoms of "non-specific arm pain" is explored and validated. The efficacy of the Bayesian technique is compared with simple voting methods.ResultsThe aggregate Bayesian classifier presented is found to perform with accuracy equivalent to that of majority voting on the test data, with an overall accuracy greater than 0.85. Theoretical foundations of the technique are discussed, and are related to the observations found.ConclusionsAggregation of motor unit potential conditional probability distributions estimated using quantitative electromyographic analysis, may be successfully used to perform electrodiagnostic characterization of "non-specific arm pain." It is expected that these techniques will also be able to be applied to other types of electrodiagnostic data.

(Over)training effects on quantitative electromyography and muscle enzyme activities in standardbred horses

Too intensive training may lead to overreaching or overtraining. To study whether quantitative needle electromyography (QEMG) is more sensitive to detect training (mal)adaptation than muscle enzyme activities, 12 standardbred geldings trained for 32 wk in age-, breed-, and sex-matched fixed pairs. After a habituation and normal training (NT) phase (phases 1 and 2, 4 and 18 wk, respectively), with increasing intensity and duration and frequency of training sessions, an intensified training (IT) group (phase 3, 6 wk) and a control group (which continued training as in the last week of phase 2) were formed. Thereafter, all horses entered a reduced training phase (phase 4, 4 wk). One hour before a standardized exercise test (SET; treadmill), QEMG analysis and biochemical enzyme activity were performed in muscle or in biopsies from vastus lateralis and pectoralis descendens muscle in order to identify causes of changes in exercise performance and eventual (mal)adaptation in skeletal muscle. NT resulted in a significant adaptation of QEMG parameters, whereas in muscle biopsies hexokinase activity was significantly decreased. Compared with NT controls, IT induced a stronger adaptation (e.g., higher amplitude, shorter duration, and fewer turns) in QEMG variables resembling potentially synchronization of individual motor unit fiber action potentials. Despite a 19% decrease in performance of the SET after IT, enzyme activities of 3-hydroxyacyl dehydrogenase and citrate synthase displayed similar increases in control and IT animals. We conclude that 1) QEMG analysis is a more sensitive tool to monitor training adaptation than muscle enzyme activities but does not discriminate between overreaching and normal training adaptations at this training level and 2) the decreased performance as noted in this study after IT originates most likely from a central (brain) rather than peripheral level.

7. Parametric and non-parametric statistics in quantitative needle electromyography

7. Parametric and non-parametric statistics in quantitative needle electromyography

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.

Paraspinal Mapping

This was a case series with intervention performed by masked investigators. To determine values for normal subjects on quantified needle electromyography of the paraspinal muscles compared with a previous sample of patients with clear evidence of radiculopathy. Diagnosis of radicular back pain is difficult, even with modern imaging studies, partly due to the large percentage of imaging abnormalities in asymptomatic persons. Electromyography has been shown to be as sensitive as imaging studies in diagnosing radicular pain. An electromyographic study of the low back has never been done in normal subjects. We have previously anatomically validated and clinically demonstrated a method of quantitative needle electromyography in the paraspinal muscles called paraspinal mapping. Thirty-five subjects free of back pain or polyneuropathy were intermixed with volunteers referred for electromyography of radicular back pain. One electrodiagnostician punctured the skin at five predetermined locations and obtained paraspinal mapping scores in one of these. An electromyographer who was masked to the study's nature then performed a complete paraspinal mapping study. A total "sensitivity" score was compared to scores of previously tested patients who had pain complaints and clear evidence for radiculopathy on either radiologic or traditional electromyographic studies. Mean score in normal subjects was 1.11 (SD 1.49). Mean score for abnormal subjects averaged 12.18 (SD 12.03). Differences between examiners were insignificant. Normal persons have few, if any electromyographic abnormalities in the paraspinal muscles. This is in contrast to computed tomography, magnetic resonance imaging, or myelographic results in normal subjects. Persons with radiculopathy have significantly different scores. Needle electromyographic examination of the paraspinal muscles is useful in distinguishing false-positive radiologic studies.

Quantitative needle electromyography during sustained maximal effort

We describe changes in time domain as well as in frequency domain of the electromyographic (EMG) signal during sustained maximal effort. The anterior tibial muscle in five subjects and the brachial biceps muscle in eight subjects were examined with needle electrodes. The forces exerted decreased exponentially with time to ∼50% of the initial values after 1 min of sustained maximal effort. The mean and median power frequency declined exponentially with time. The decrease in number of spikes (turns, zero crossings) and amplitude (mean amplitude, integrated electrical activity) of the electrical activity in fatigued muscle, as compared with initial values can be explained in part by a dropout of some motor units and a decrease in firing rate. During the first minute, a decrease in number of turns and an increase in amplitude occurred in fatigued muscle as compared with values at the same force level in fresh muscle, probably owing to a decrease in conduction velocity along the fatigued muscle fiber and synchronous firing. This was consolidated by a linear relationship between the decrease in number of turns and the decrease in mean power frequency. After the first minute, a continued increase in amplitude only suggested contractile element fatigue. This order of physiologic changes was the same as that previously observed at sustained submaximal force.