Comparison of Interference Pattern between Normal and Myopathy Group used by Quantitative EMG

J Korean Assoc EMG Electrodiagn Med 2007;3(1):13-19.
Published online May 10, 2007.

Abstract

Objectives : The aim of this study was to compare with interference pattern of normal and myopathy group. Methods : Sixteen control subjects and nine patients were included. Patients were diagnosed as myopathy by physical examination, history taking, muscle biopsy, laboratory studies including muscle enzyme and polymerase chain reaction for progressive muscular dystrophy. We recorded EMG interference pattern from the biceps muscle, vastus medialis muscle, tibialis anterior muscle. Interference pattern was measured at each electrode position while the subject contracted muscle at different levels of maximal force. The number of turns, mean amplitude, activity, envelope, number of small segments (NSS) were measured from interference pattern recorded at each force level at each site and calculated turns/amplitude ratio, envelope/activity ratio, NSS/activity ratio. Results : The results of this study revealed stastically significant difference in turns/amplitude ratio, envelope/activity ratio, NSS/activity ratio between 2 groups. Increased turns/amplitude ratio, decreased envelope/activity ratio, inc0reased NSS/activity ratio were shown in myopathy group (p<0.01). Conclusion : Automatic interference pattern analysis may contribute to diagnose myopathy in incooperable patients such as young children.

Key Words: Quantitative electromyography, Myopathy, Interference pattern analysis, turns/amplitude ratio, envelope/activity ratio, NSS/activity ratio