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[Diagnosis of endolymphatic hydrops with low tone masked otoacoustic emissions]
K Nubel1, E Kabudwand, G Scholz
1Hals-Nasen-Ohren-Klinik im Virchow-Klinikum der Humboldt-Universität Berlin.
Background:
A new method of diagnosis of endolymphatic hydrops by recording low-tone masked evoked otoacoustic emissions (TEOAE) is presented.
Methods:
A short acoustic stimulus and a masker tone of 30 Hz are applied in an adjustable phase relation simultaneously to the same ear. In the normal hearing ear the masker shows little influence on the TEOAE at 0 degrees, whereas the suppression at phase 270 degrees (maximal rarefaction at the eardrum) is nearly complete. However, in cases of endolymphatic hydrops this masking effect is reduced or absent, indicating impaired mobility of the basilar membrane.
Results:
The masked TEOAE were recorded of patients with normal hearing, Menière's disease, and sudden hearing loss without vertigo. In Menière cases with supposed endolymphatic hydrops, the amplitude modulation of the emissions was found to be much less than in the other groups.
Conclusions:
Where TEOAE can be recorded, low-tone masking is a quick, objective, and noninvasive method for the diagnosis of endolymphatic hydrops.