Applications of distortion-product emissions to an otological practice.

Abstract

The multiple clinical applications of distortion-product emissions (DPEs) to an otological practice are reviewed. Through an examination of studies involving thousands of infants, as well as adult ears, the relationships between measurements of DPEs and PTTs (PTTs) are examined. The cochlear physiology underlying generation of DPEs and the interpretation of these measurements are described in some detail. We study the contribution of phase measurements of DPEs to calculation of delay in cochlear traveling waves. The clinical applications of these measurements are described. The objective of this work is to demonstrate the clinical utility of DPEs through an examination of the correlation of the features of DPEs with PTTs in patients varying in age from newborn to the elderly. Experimental design and methodology involved careful prospective selection of large numbers of subjects in each age group, novel techniques for recording DPEs, and multivariate statistical analysis of the data. Three separate experiments encompass issues surrounding the age groups of adults, neonates, and elderly individuals. The results show that current techniques allow a 90% correct prediction of auditory PTTs for frequencies varying from 1,000 to 6,000 Hz, for patients of all ages. Techniques for measurement of DPEs currently represent an integral diagnostic component for an otological practice. The potential future application of measures of DPEs to diagnosis of tinnitus is described. With an extension of the technique for measuring DPEs to the phenomenon of reflectance, there may be promise of application to novel approaches to the treatment of tinnitus and the design of hearing aids.