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FC13.1 Muscle fiber conduction velocity spread: Validation of the interpeak latency method by model simulations
S64
Oral Communications / Clinical Neurophysiology 117 (2006) S49–S111
endogenous toxin on energy dependent Na+/K+ ATPase pump function. doi:10.1016/j.clinph.2006.06.041
FC13.2 Assessment and optimization of the number of turns as an alternative to fiber density measurements during routine EMG studies M.B. Bromberg 1, A.A. Brownell 2 1
University of Utah, Department of Neurology, USA University of Utah, Department of Biomedical Engineering, USA
2
FC13.1 Muscle fiber conduction velocity spread: Validation of the interpeak latency method by model simulations J. van der Hoeven, F. Lange, N. Maurits, T. van Weerden University Medical Hospital Groningen, Clinical Neurophysiology, The Netherlands Background: The spread of the muscle fiber conduction velocity (MFCV) is an interesting variable in physiology and some pathological conditions. There is no easy way to estimate the spread of the MFCV by non-invasive methods at high levels of recruitment. We designed a new method, the interpeak latency method to determine the spread of muscle fiber conduction velocity. Objective: It is notoriously difficult to determine the exact spread of muscle fiber conduction velocity in an interference pattern in surface EMG measurements. We designed a model to test the IPL method with respect to the spread and mean muscle fiber conduction velocity. In the present study, the results of the IPL method are compared to the spread of MFCV used as input for the model to validate the IPL method. Methods: The IPL method was described before (Lange, 2002). In the model, the myoelectric signal is measured by three surface electrodes, arranged inline on a rigid plate. The model action potential is based on a simple monopole. Important input parameters for the model such as the spread of MFCV, the mean MFCV and the number of action potentials were varied. MFCV values resulting from the IPL method were compared to model inputs and the cross-correlation method [Lange, 2002]. Results: The IPL method had a good correlation with model input parameters in case of low numbers of motor units in combination with low firing rate. When increasing the number of motor units and firing rate the spread was slightly underestimated by the IPL method. With respect to the MFCV we found a good correlation between the cross correlation method and the IPL method, while the cross correlation method is not capable of measuring the spread in MFVC. Discussion and conclusion: The technically simple IPL method is capable of measuring the spread of MFCV even at higher levels of recruitment. Sensitivity to noise could be a drawback; this has to be investigated further. Reference Lange et al. J Appl Physiol 2002. doi:10.1016/j.clinph.2006.06.042
Background: Needle electromyography (EMG) can be used to estimate the morphology of the motor unit because the motor unit action potential (MUAP) waveform reflects the local organization of the motor unit as viewed by the electrode. Changes in muscle fiber density and conduction velocity due to pathology affect MUAP waveform shape and assessment of such changes is used to determine whether pathology exists. A more sensitive measurement with single fiber EMG is not part of routine EMG studies. Aims/objectives: We hypothesize that similar information as from single fiber EMG fiber density may be obtained during routine EMG studies through visual and electronic processing of the MUAP. We focus on the number of turns in the MUAP waveform as an indication of contributions from muscle fiber action potentials. Methods: Improvements in visual processing are explored by redefining the amplitude criterion for counting the number of turns in MUAP waveforms at routine low frequency filter settings (10 Hz). Improvements in electronic processing are by raising the low frequency filter to values of 500, 1000 and 1500 Hz to emphasize high frequency components. We investigate these hypotheses using biologic muscle (normal and motor neuron disease patients) and modeled muscle with comparison to single fiber EMG fiber density. Results: We found in both biologic and modeled muscles that with 10 Hz filter settings reducing the turn criterion to as low as <25 lV did not result in significant correlations between the number of turns and fiber density. Raising the low frequency filter to 500 Hz resulted in higher correlations with fiber density, but further increases to 1000 and 2000 Hz did not further improve correlations. Discussion: We conclude that inspection of the MUAP waveform with low frequency filtering at 500 Hz and turn amplitude criterion at >25 lV can provide useful clinical information in that more turns were associated with greater fiber density values. doi:10.1016/j.clinph.2006.06.043
FC13.3 Criteria for conduction block (CB) derived from simulations with human data H. Franssen, J.T. Van Asseldonk, L.H. Van den Berg, G.H. Wieneke, J.H.J. Wokke University Medical Center Utrecht, Department of Neurology, The Netherlands
Oral Communications / Clinical Neurophysiology 117 (2006) S49–S111
endogenous toxin on energy dependent Na+/K+ ATPase pump function. doi:10.1016/j.clinph.2006.06.041
FC13.2 Assessment and optimization of the number of turns as an alternative to fiber density measurements during routine EMG studies M.B. Bromberg 1, A.A. Brownell 2 1
University of Utah, Department of Neurology, USA University of Utah, Department of Biomedical Engineering, USA
2
FC13.1 Muscle fiber conduction velocity spread: Validation of the interpeak latency method by model simulations J. van der Hoeven, F. Lange, N. Maurits, T. van Weerden University Medical Hospital Groningen, Clinical Neurophysiology, The Netherlands Background: The spread of the muscle fiber conduction velocity (MFCV) is an interesting variable in physiology and some pathological conditions. There is no easy way to estimate the spread of the MFCV by non-invasive methods at high levels of recruitment. We designed a new method, the interpeak latency method to determine the spread of muscle fiber conduction velocity. Objective: It is notoriously difficult to determine the exact spread of muscle fiber conduction velocity in an interference pattern in surface EMG measurements. We designed a model to test the IPL method with respect to the spread and mean muscle fiber conduction velocity. In the present study, the results of the IPL method are compared to the spread of MFCV used as input for the model to validate the IPL method. Methods: The IPL method was described before (Lange, 2002). In the model, the myoelectric signal is measured by three surface electrodes, arranged inline on a rigid plate. The model action potential is based on a simple monopole. Important input parameters for the model such as the spread of MFCV, the mean MFCV and the number of action potentials were varied. MFCV values resulting from the IPL method were compared to model inputs and the cross-correlation method [Lange, 2002]. Results: The IPL method had a good correlation with model input parameters in case of low numbers of motor units in combination with low firing rate. When increasing the number of motor units and firing rate the spread was slightly underestimated by the IPL method. With respect to the MFCV we found a good correlation between the cross correlation method and the IPL method, while the cross correlation method is not capable of measuring the spread in MFVC. Discussion and conclusion: The technically simple IPL method is capable of measuring the spread of MFCV even at higher levels of recruitment. Sensitivity to noise could be a drawback; this has to be investigated further. Reference Lange et al. J Appl Physiol 2002. doi:10.1016/j.clinph.2006.06.042
Background: Needle electromyography (EMG) can be used to estimate the morphology of the motor unit because the motor unit action potential (MUAP) waveform reflects the local organization of the motor unit as viewed by the electrode. Changes in muscle fiber density and conduction velocity due to pathology affect MUAP waveform shape and assessment of such changes is used to determine whether pathology exists. A more sensitive measurement with single fiber EMG is not part of routine EMG studies. Aims/objectives: We hypothesize that similar information as from single fiber EMG fiber density may be obtained during routine EMG studies through visual and electronic processing of the MUAP. We focus on the number of turns in the MUAP waveform as an indication of contributions from muscle fiber action potentials. Methods: Improvements in visual processing are explored by redefining the amplitude criterion for counting the number of turns in MUAP waveforms at routine low frequency filter settings (10 Hz). Improvements in electronic processing are by raising the low frequency filter to values of 500, 1000 and 1500 Hz to emphasize high frequency components. We investigate these hypotheses using biologic muscle (normal and motor neuron disease patients) and modeled muscle with comparison to single fiber EMG fiber density. Results: We found in both biologic and modeled muscles that with 10 Hz filter settings reducing the turn criterion to as low as <25 lV did not result in significant correlations between the number of turns and fiber density. Raising the low frequency filter to 500 Hz resulted in higher correlations with fiber density, but further increases to 1000 and 2000 Hz did not further improve correlations. Discussion: We conclude that inspection of the MUAP waveform with low frequency filtering at 500 Hz and turn amplitude criterion at >25 lV can provide useful clinical information in that more turns were associated with greater fiber density values. doi:10.1016/j.clinph.2006.06.043
FC13.3 Criteria for conduction block (CB) derived from simulations with human data H. Franssen, J.T. Van Asseldonk, L.H. Van den Berg, G.H. Wieneke, J.H.J. Wokke University Medical Center Utrecht, Department of Neurology, The Netherlands