Quantitative Turns/Amplitude Analysis of Interference Pattern in Neuromuscular Diseases

ABSTRACT

The present study was designed to evaluate the diagnostic efficacy and the clinical usefulness of quantitative analysis of interf erence pattern in differentiating the neuromuscular diseases. To obtain the normal control value, the automatic turns/amplitude analysis of interference pattern in biceps brachii and tibialis anterior muscle was done in 30 healthy normal subjects. The same procedure was performed in 16 patients with myopathy and 14 neuropathy to determine the diagnostic sensitivity of this method. Original pairs of turns/amplitude data obtained from controls converted into the logarithmic scale and linear regression equation, were calculated. Boundary of normal cloud was defined by the + 2 S. D. lines, maximum turn and amplitude. The result was considered abnormal if two or more turns/amplitude values were outside the zone normal cloud. The values of myopathic patients shifted toward the right lower quadrant meaning high turns and small amplitudes, but those of neuropathic patients shifted toward the left upper quadrant meaning few turns and large amplitudes. In all subjects of each patient group, at least two turns/amplitude values were outside the zone of normal cloud. In addition, the sequential changes of mean turns/amplitude ratio were well correlated with the disease activity. These results suggest that this method of automatic turns/amplitude analysis could be used not only as a supplementary diagnostic tool in differentiating the neuromuscular disorders, but also a parameter of monitoring the disease activity.