A morphological analysis of the macro motor unit potential

The technique of macro EMG is used to investigate the motor unit architectu re in a number of pathological conditions. Amplitude and area are the most commonly used criteria, but these parameters alone are not sufficient to as sess the complexity of the macro MUP morphology. In an attempt to examine t he morphology of the macro MUP in more detail, additional measures were inv estigated including, (i) average power, (ii) duration, and (iii) number of phases. Macro MUP duration was defined as the time parameter that contains a particular fraction (90%) of the total power of the potential. The above mentioned parameters were evaluated for normal subjects and for patients su ffering with motor neuron disease (MND), spinal muscular atrophy (SMA), and Pecker's muscular dystrophy (BMD). It is shown that high amplitude and ave rage power macro MUPs give shorter macro MUP duration than macro MUPs with normal amplitude. In contrast, in low amplitude macro MUPs there is a tende ncy towards a higher duration measure, as compared with the duration of the normal amplitude macro MUPs. Also, t-test results for the duration measure gave a significant difference between the NOR-MND, and no significant diff erence between the NOR-BMD and NOR-SMA groups at P<0.05. Significant differ ence between the NOR and the three disease groups investigated was obtained for the parameters log amplitude, log area, and log average power. The num ber of phases was not significantly different between the NOR and the rest of the groups. In conclusion, the average power and duration parameters can possibly be used as additional discriminators to detect abnormalities of t he macro motor unit potential in both needle and surface EMG but further in vestigation is necessary. (C) 2000 IPEM. Published by Elsevier Science Ltd. All rights reserved.