Quantitative Measurement of Laryngeal Electromyography Using Motor Unit Action Potential in Unilateral Vocal Cord Paralysis

BACKGROUND AND OBJECTIVES: Laryngeal electromyography (LEMG) is valuable to evaluate the innervation status of the laryngeal muscles and the prognosis of vocal fold paralysis (VFP). However, there is a lack of agreement on quantitative interpretation of LEMG. The aim of this study is to measure the motor unit action potentials (MUAP) quantitatively in order to find cut-off values of amplitude, duration, phase for unilateral vocal fold paralysis patients. MATERIALS AND METHOD: Retrospective chart review was performed for the unilateral VFP patients who underwent LEMG from March 2016 to May 2018. Patient's demography, cause of VFP, vocal cord mobility, and LEMG finding were analyzed. The difference between normal and paralyzed vocal folds and cut-off values of duration, amplitude, and phase in MUAP were evaluated. RESULTS: Thirty-six patients were enrolled in this study. Paralyzed vocal fold had significantly longer duration (p=0.021), lower amplitude (p=0.000), and smaller phase (p=0.012) than the normal. The cut-off values of duration, amplitude, and phase in MUAP for unilateral VFP were 5.15 ms, 68.35 µV, and 1.85 respectively. CONCLUSION: An analysis of MUAP successfully provided quantitative differences between normal and paralyzed vocal folds. But, additional research is needed to get more available cut-off value which is helpful to evaluate the status of laryngeal innervations.

A new approach for multi-channel surface EMG signal simulation

Simulation models are necessary for testing the performance of newly developed approaches before they can be applied to interpreting experimental data, especially when biomedical signals such as surface electromyogram (SEMG) signals are involved. A new and easily implementable surface EMG simulation model was developed in this study to simulate multi-channel SEMG signals. A single fiber action potential (SFAP) is represented by the sum of three Gaussian functions. SFAP waveforms can be modified by adjusting the amplitude and bandwidth of the Gaussian functions. SEMG signals were successfully simulated at different detected locations. Effects of the fiber depth, electrode position and conduction velocity of SFAP on motor unit action potential (MUAP) were illustrated. Results demonstrate that the easily implementable SEMG simulation approach developed in this study can be used to effectively simulate SEMG signals.

The loss of motor unit and it's influencing factors in patients with middle cerebral artery infarction / 中国神经精神疾病杂志

Objective To investigate the loss of motor unit and it's influencing factors in the lower motor neurons after middle cerebral artery infarction. Method Forty patients with first onset and unilateral middle cerebral artery infarction were divided into cortical-basal ganglia(26)and basal ganglia(14)groups and 10 healthy controls were served as control group.All included patients were scored by National Institute of Health stroke scale(NIHSS),modified Rankin scale (mRS), Fugl-Meyer Assessment (FMA) at 48 hours of admission. Nerve conduction study on the limb and motor unit number estimation (MUNE) on abductor pollicis brevis were performed at 2-4 weeks after onset, and the data of single motor action potential (SMUAP) were collected. SPSS 20.0 software was used to statistical analysis. Result The MUNE on were significantly lower and the amplitude and area of SMUAP were significantly increased in ipsilateral than contralateral sides (cortical-basal ganglia group:95.85±26.82 vs. 143.65±38.86, P<0.001; basal ganglia group: 126.71± 44.13 vs. 157.36±56.72, P=0.001). The affected MUNE was significantly decreased in the cortex-basal ganglia than in basal ganglia groups (95.85±26.82 vs.161.40±48.90,P=0.027). The MUNE was negatively correlated with NIHSS score (r=-0.362,P=0.022)and mRS score(r=-0.339,P=0.032).NIHSS score(β=-1.603,P=0.032,95%CI:-3.064~-0.142)and mRS score(OR=2.885,P=0.025,95%CI:1.139~7.158)on admission could predict the loss of MUNE on the affected side. Conclusion This study reveals the loss of motor unit and the compensation of remained motor unit on the affected side after middle cerebral artery infarction,NIHSS score and mRS score on admission may predict the loss of MUNE after stroke.

A Study on the Decomposition of Surface EMG Signals Based on Second Order Non-stationary Source Separation / 航天医学与医学工程

Objective To investigate the decomposition method of surface EMG(sEMG)signals based on Blind Source Separation and to detect the the motor unit action potential(MUAP)information.Methods Utilizing the sEMG signals recorded at low muscle contraction force(10% MVC),the methods of second order non-stationary source separation(SEONS)and FastICA were explored to analyze the sEMG signals decomposition.Results The experiment results showed that the MUAP information could be acquired by spike detection and pattern recognition after the decomposition of recorded sEMG signals using the proposed algorithm and FastICA method,but a little difference occurred due to the complexity of sEMG signals.Conclusion The non-stationary characteristic of sEMG signals is considered by the SEONS algorithm,and the proposed method can be applied in the sEMG signals decomposition.

Motor Unit Action Potentials of the Rectus Abdominis Muscle according to Changes of Abdominal Pressure

OBJECTIVE: In current urodynamic studies, rectal catheters can cause erroneous result affecting detrusor pressure, and the catheter itself is not comfortable to the patients. To reduce these problems we investigated the relationship between the motor unit action potentials (MUAP) of rectus abdominis muscle and the abdominal pressure measured by rectal catheter. METHOD: Healthy seven men and three women volunteers (mean age: 49 years) with no neurological abnormality were enrolled. Possible maximal abdominal pressure (Pmax) was attained by Valsalva maneuver for 5 seconds. The MUAPs of the rectus abdominis muscle were recorded with surface electrodes for analysis. These recordings were done on 100, 80, 60, 40, and 20% of Pmax. The parameters of MUAP such as mean frequency, median frequency, turns, mean amplitude, and RMS (root mean square) were measured. RESULTS: Turns, mean amplitude, and RMS were increased in a proportion to the increment of abdominal pressure in all subjects(R=0.840, 0.879, and 0.984, respectively). CONCLUSION: These findings suggested that the surface MUAP of rectus abdominis muscle might be used indirectly for more convenient measurement of the abdominal pressure.

Contribution of single motor unit action potential to surface myo-electric signals / 体力科学

In the present study, we attempted to reconstruct the surface myo-electric signals from monopolarly recorded motor unit action potentials (MUAPs), and to construct a method of analysis for extracting information from surface ME signals on the recruitment behavior among motor units.<BR>1) The waveform of a single MUAP of a surface electrode recorded monopolarly consisted of three phases : first, a positive, second, a negative transient and, third, a positive phase except for the end-plate region. The appearance of each phase could be interpreted from the field potential in the volume conductor produced by conduction of action potentials from the end-plate to the myotendinous junction.<BR>2) Waveforms of MUAPs indicated that the positive phase and the negative phase are the same in area. In surface ME signals, coincidence of the phase areas was observed. Therefore, it was inferred that all the motor units producing the interfered surface ME signal showed a tendency to coincide with respect to the area between the two phases.<BR>3) The fact that MUAPs consisted of three phases during conduction means that the contribution potential for a recorded electrode changes according to the position of the action potential on the muscle fiber (s) . Therefore, the potential of a surface myoelectric signal represents the sum of the contributed potentials from activated motor units.<BR>4) The amplitude of surface ME potentials tended to be other than 0V as tension increased.<BR>5) Considering the reconstruction of a surface ME signal involving many activated motor units from the contribution potential, the surface ME potential depends on the number of recruited motor units with a different waveform, in addition to the magnitude of synchronization and grouping discharge among motor units.

Diagnostic Usefulness of Outliers Count in Quantitative EMG

The reference values of motor unit action potentials(MUAP) of first dorsal interosseous and tibialis anterior muscles were measured in 50 healthy subjects. The MUAPs were recorded with a concentric needle electrode and extracted with a decomposition method. Sixty six patients with neuropathy were also studied in the same way with a count of outliers and measurement of mean values. The mean values of amplitude, area, duration and thickness were 667.74+/-204.34 V, 992.26+/-253.18 Vms, 9.75+/-1.95 ms and 1.49+/-0.26 ms, respectively in the first dorsal interosseous muscles, and 612.88+/-140.13 V, 1172.84+/-199.21 Vms, 11.41+/-2.48 ms and 1.93+/-0.34 ms respectively in the tibialis anterior muscles. There was no significant difference in age and gender of normal subjects. The amplitude was the most sensitive parameter to detect abnormality in a count of outliers and measurement of mean values. The outliers count in duration showed a higher sensitivity than the measurement of mean values(p<0.05), but not in amplitude, area or thickness. Based on the results of this study, the count of outliers was more sensitive than the measurement of mean values in the diagnosis of patients with neuropathy. Further more, less numbers of MUAPs were needed for the evaluation of the outliers count. Through this method we could save the evaluation time and the patients felt more comfortable.

Changes of Electromyographic Signals Following Peripheral Nerve Injury

Quantitative analysis of abnormal spontaneous activities, motor unit action potentials and interference patterns were recorded in 55 subjects with traumatic peripheral nerve injury to understand the changes of electromyographic signals. We analyzed amplitudes of fibrillation potentials and positive sharp waves at rest, amplitude, duration, spike duration and polyphasicity of motor unit action potentials at minimal contraction, and the root mean square(RMS), and mean rectified voltage (MRV) at maximal contraction. The amplitudes of fibrillation potentials and positive sharp waves had negative correlations with the duration of peripheral nerve injury but the amplitudes of motor unit action potentials, RMS, and MRV had positive correlations. Therefore electromyographic evaluation could be used for the estimation of the duration of peripheral nerve injury.