Diagnostic Usefulness of Outliers Count in Quantitative EMG

Park, Seung Hyun; Moon, Jae Ho; Kang, Seoung Woong

Abstract

The reference values of motor unit action potentials(MUAP) of first dorsal interosseous and tibialis anterior muscles were measured in 50 healthy subjects. The MUAPs were recorded with a concentric needle electrode and extracted with a decomposition method. Sixty six patients with neuropathy were also studied in the same way with a count of outliers and measurement of mean values. The mean values of amplitude, area, duration and thickness were 667.74+/-204.34 V, 992.26+/-253.18 Vms, 9.75+/-1.95 ms and 1.49+/-0.26 ms, respectively in the first dorsal interosseous muscles, and 612.88+/-140.13 V, 1172.84+/-199.21 Vms, 11.41+/-2.48 ms and 1.93+/-0.34 ms respectively in the tibialis anterior muscles. There was no significant difference in age and gender of normal subjects. The amplitude was the most sensitive parameter to detect abnormality in a count of outliers and measurement of mean values. The outliers count in duration showed a higher sensitivity than the measurement of mean values(p<0.05), but not in amplitude, area or thickness. Based on the results of this study, the count of outliers was more sensitive than the measurement of mean values in the diagnosis of patients with neuropathy. Further more, less numbers of MUAPs were needed for the evaluation of the outliers count. Through this method we could save the evaluation time and the patients felt more comfortable.