A comparison of two commercial quantitative electromyographic algorithms with manual analysis

Concentric Needle Quantitative EMG of Pubovisceralis Muscle Group: Normative Data from Asymptomatic Nulliparous Women

OBJECTIVES: The muscles of the pelvic floor closest to the vaginal opening are subject to the greatest degree of stretch during vaginal childbirth. We aim to define normative quantitative EMG (QEMG) parameters for the pubovisceralis (PV) muscle in nulliparous women, and compare them to the external anal sphincter (EAS). METHODS: In 31 asymptomatic nulliparous women, concentric Needle EMG of the PV and the EAS was performed. Multi-motor unit action potential (Multi-MUAP) and interference pattern (IP) algorithms were utilized to obtain QEMG parameters. We used paired t-tests to compare PV and EAS parameters. RESULTS: The motor units for the PV were of greater duration (p < 0.002) and had more turns (p = 0.03) than the paired motor units in the EAS. The EAS demonstrated more turns/second (p = 0.02), greater activity (p = 0.01), and more short segments (p = 0.009) than the PV. CONCLUSIONS: The PV has longer and more complex motor units than the EAS. This knowledge continues to improve our ability to detect neuropathic changes in this vulnerable muscle area following childbirth or in women with pelvic floor dysfunction. In addition, the PV muscle group appears less responsive to requests for increased neuromuscular activity than the EAS. This needs to be further evaluated, as it may be associated with understanding which portion of the muscle functionally shortens to maintain the closure of the levator hiatus.

Motor Unit Action Potential Duration, I: Variability of Manual and Automatic Measurements

The aim of this work is to analyze the variability in manual measurements of motor unit action potential (MUAP) duration and to evaluate the effectiveness of well-known algorithms for automatic measurement. Two electromyographists carried out three independent duration measurements of a set of 240 MUAPs. The intraexaminer and interexaminer variabilities were analyzed by means of the Gage Reproducibility and Repeatability method. The mean of the three closest manually marked positions was considered the gold standard of the duration markers positions (GSP). The results of four well-known automatic methods for estimating MUAP duration were compared to the GSP. Manual measurements of duration showed a lot of variability, with the combined intraoperator and interoperator variability greater than 30%. The greatest difference between manual positions was 11.2 ms. The mean differences between the GSP and those obtained with the four automatic methods ranged between 0.6 and 8.5 ms. Both manual and automatic measurements of MUAP duration show a high degree of variability. More precise methods are needed to improve the accuracy and reliability of the estimates of this parameter.

The role of different EMG methods in evaluating myopathy

For the diagnosis of myopathy, EMG may have an important role along with blood tests, muscle biopsies and genetic testing. This review evaluates different EMG methods in the diagnosis of myopathy. These include manual analysis of individual motor unit potentials and multi-motor unit potential analysis sampled at weak effort. At high effort, turns-amplitude analyses such as the cloud analysis and the peak ratio analysis have a high diagnostic yield. The EMG can seldom be used to differentiate between different types of myopathy. In the channelopathies, myotonia, exercise test and cooling of the muscle are helpful. Macro-EMG, single-fibre EMG and muscle fibre conduction velocity analysis have a limited role in myopathy, but provide information about the changes seen. Analysis of the firing rate of motor units, power spectrum analysis, as well as multichannel surface EMG may have diagnostic potential in the future. EMG is of great importance in the diagnosing of patients with myopathy, preferably a needle electrode and quantitative analyses should be used. A combination of a method at weak effort as well as a method at stronger effort seems optimal.

Comparison of three algorithms for multi-motor unit detection and waveform marking

Quantitative EMG (QEMG) techniques include automated motor unit action potential (MUAP) detection and marking of clinically useful waveform metrics. Different computer algorithms are available on modern EMG machines to perform these operations rapidly. However, the efficiency and accuracy of available algorithms are rarely directly compared. We have assessed three commercially available algorithms using both synthesized and biologic interference patterns and found differences among algorithms, some of which are clinically significant. Our results point out the importance of assessing for duplicate MUAPs (same waveform detected as two separate waveforms) and accuracy of markings used to determine MUAP metrics.