感音難聴における誘発耳音響放射の臨床応用

Abstract

The aim of this study is to investigate the clinical usefulness of stimulated oto-acoustic emission (OAE) recording in sensorineural hearing loss. The OAE was recorded by the double barreled acoustic probe which consisted of a subminor earphone and a subminiature microphone. The stimulus sounds were tone bursts (rise-fall time 1ms, total duration 3ms) with the frequency between 1kHz and 2kHz. The responses were averaged 256 times with the analysis time of 20ms. Based upon the analysis of OAE recording in 17 normal hearing subjects, the interaural difference of OAE pseudothreshold was found out as a most excellent clinical indicator. The reproducibility of various OAE parameters such as configuration of wave form, the resonance frequency, the pseudothreshold, the latency and the input-output function was also found to be excellent in repeated tests of 41 ears. The OAE was examined in various kinds of unilateral moderate and profound sensorineural hearing loss which included congenital deafness, mumps deafness, functional deafness and sudden deafness. The interaural difference of OAE pseudothreshold was more than 35dB in all cases of congenital deafness and mumps deafness which were considered as the inner ear deafness. In contrast with this, the interaural difference of OAE pseudothreshold was nil in all cases of functional deafness. Furthermore in sudden deafness, the positive correlation existed between the interaural difference of psychoacoustic threshold and that of OAE pseudothreshold and also the interaural difference of OAE pseudothreshold became smaller along with the recovery of psychoacoustic threshold. From these results, we concluded that the OAE could be usful as an excellent clinical tool to investigate the inner ear function.