COCHLEAR FUNCTION TEST BY MEANS OF STIMULATED OTO-ACOUSTIC EMISSION

Abstract

This review gives an outline of stimulaled oto-acoustic emissions (OAEs) which are echoic oscillations from the inner ear and deals with its clinical application as a cochlear function test.
In pseudothresholds of OAE (OAE thresholds) of the subjects with normal hearing, a large difference was recognized among individuals. The intersubject difference was small as the interaural difference of OAE threshold. The interaural differences were large in the unilateral inner ear anomaly and mumps deafness but they were less than 5 dB in the cases of unilateral functional deafness. There is a positive correlation between the interaural differences of psycho-acoustic threshold and of the OAE threshold in 109 cases of unilateral sudden deafness.
An elongation of the OAE duration more than 6 ms was seen in 34% of the ears of normal subjects, whereas it was seen in all ears of tinnitus without hearing loss and of c⁵ dip deafness.
The OAE threshold is useful as an indicator not only to know the presence of inner ear impairments but also to evaluate the grade of impairments, especially in children. It is also instrumental to differenciate a cochlear mechanical tinnitus from other sensori-neural tinnitus. The cochlear function test by means of the OAE will be generalized in the near future.