Approximation of motor unit structure from the analysis of motor unit potential

Objectives: The aim of this simulation study was to approximate certain features of motor unit structure on the basis of motor unit potential (MUP) analysis. Methods: The principle of the approximation method has been to invert the procedure used in the simulation of the MUP. An algorithm has been developed that analyses the recorded potential and estimates the number of fibers that contribute to the MUP, their diameters and localization relative to the electrode. These parameters have been determined by minimizing the differences between the recorded and modeled potentials. Results: The method has been tested on MUPs recorded in the muscles of healthy and diseased subjects. The evaluated range of fiber diameters and densities in a healthy muscle was consistent with its morphological characteristics. In pathological cases, the results of the analysis indicated changes of fiber diameters and densities typical of a given pathological process. Conclusion: Preliminary results of simulations suggest that the proposed method is a potentially useful tool for the approximation of morphological features of muscle fibers contributing to the MUP. Significance: The analysis of MUPs, in addition to the evaluation of the electrical activity of the muscle with the use of the proposed approximation method, may also permit characterization of muscle morphology, and therefore it may improve the diagnostic value of electromyography.