Distortion-product Otoacoustic Emissions in Idiopathic Sudden Deafness

Distortion-product otoacoustic emissions (DPOAEs) at three F2 frequencies (1, 2and 4kHz) were recorded from 43 ears with idiopathic sudden deafness (ISD). The potential of DPOAEs as a clinical test to predict the hearing prognosis of ISD was investigated. At the first visit within 2 weeks after onset, DPOAEs were detected in several ears with hearing loss of 40dBHL or more at the corresponding frequencies to F2. In most of these ears, hearing at the DPOAE-detected frequencies was recovered to 30dBHL or less after treatment. The incidence of DPOAEs, however, was low in the ears with severe hearing loss and in mid-frequency range, and there were many ears in which hearing was recovered even though DPOAEs were not detected. Moreover, DPOAEs were not detected or their output was not increased before hearing was changed during the course of hearing recovery. From these results, it was considered that the prognosis seemed good in the ears with DPOAEs at an early stage of ISD, but that there were many problems and limitations for clinical application of DPOAE testing with respect to accurate and reliable prediction of prognosis.