Effectiveness of motor unit potentials classification using various parameters and indexes

Objectives: The aim of this study was to compare the effectiveness of quant ities such as amplitude, duration, area, size index, number of peaks and ir regularity coefficient applied to the classification of motor unit action p otentials (MUAPs) in neuromuscular disorders. Methods: We have analyzed 215 potentials recorded from 20 neurogenic patien ts and 240 potentials recorded from 14 myogenic patients. The statistical v alues for each parameter and correlation coefficients between parameters ha ve been analyzed. Results: The percentages of potentials unclassified by amplitude, duration, area/amplitude, area and size index were 31, 34, 28, 15 and 15%, respectiv ely. Neither the number of phases and turns nor the irregularity coefficien t may be used for the differentiation between neuro- and myogenic groups. T here was also a set of MUAPs that were not properly classified by any of th e above parameters. Among the unclassified potentials there were more poten tials from myogenic cases. These unclassified myogenic MUAPs were predomina ntly irregular, whereas most of the unclassified neurogenic MUAPs were simp le. In neurogenic cases, parameters describing the size of the potential (a mplitude, duration, area) were not significantly correlated with those desc ribing the shape (number of phases and turns), whereas in myogenic cases so me correlation between these parameters was significant. Conclusions: MUAP quantities, due to the different correlation between them in myogenic and neurogenic disorders, have different sensitivities. Indexe s were more sensitive than simple parameters and were also much more effect ive in the evaluation of atypical potentials. (C) 2000 Elsevier Science Ire land Ltd. All rights reserved.