Discriminant analysis of various concentric needle EMG and macro-EMG parameters in detecting myopathic abnormality.

OBJECTIVES: The aim of the study was to evaluate the effectiveness of various concentric needle electromyography (EMG) motor unit action potentials (cnMUPs) and macro-EMG motor unit potentials (mMUPs) parameters for differentiation between myopathic motor unit action potentials (MUPs) and normal MUPs.

METHODS: We have analyzed 112 cnMUPs and 84 mMUPs recorded from 7 patients with myopathy and 256 cnMUPs, 256 mMUPs from 14 healthy subjects. Biceps brachii muscle was investigated. Evaluated variables were duration, amplitude, area, number of phases, area/amplitude ratio, size index and area/number of phases ratio for cnMUPs, area and amplitude for mMUPs. Univariate statistical analysis and discriminant analysis for each parameter were performed.

RESULTS: The variable 'area ' gave rather good discrimination than duration, amplitude, number of phases, area/amplitude ratio, and size index. As demonstrated by discriminant analysis, area/phase ratio is more useful than area alone if myopathic MUPs had to be discriminated from normal MUPs. Discriminant efficiency of mMUP parameters were lower than all cnMUP parameters except number of phases.

CONCLUSIONS: The new parameter area/number of phases ratio seemed to be promising, since it produced a better yield in detecting of myopathic abnormality than other investigated parameters in discriminant analysis. Discriminating ability of macro-EMG was lower than that of cnEMG.