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78th Annual Meeting of the German Society of Oto-Rhino-Laryngology, Head and Neck Surgery

German Society of Oto-Rhino-Laryngology, Head and Neck Surgery

16.05. - 20.05.2007, Munich

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The Endolymphatic Hydrops and its Influence On Low-frequency Modulation Of Distortion Products Of Otoacoustic Emissions – a Study in Guinea Pigs

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German Society of Oto-Rhino-Laryngology, Head and Neck Surgery. 78th Annual Meeting of the German Society of Oto-Rhino-Laryngology, Head and Neck Surgery. Munich, 16.-20.05.2007. Düsseldorf, Köln: German Medical Science; 2007. Doc07hno030

The electronic version of this article is the complete one and can be found online at: http://www.egms.de/en/meetings/hno2007/07hno030.shtml

Published: August 8, 2007

© 2007 Anft et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.

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Introduction: Low frequency modulation of distortion product otoacoustic emissions (TTDPOAE) can help to diagnose Menière´s disease. But like all other methods for this purpose, we can only assume to detect an endolymphatic hydrops (EH). We do not have the evidence of it, as it is not possible to find out in humans as long as they are alive. Therefore we studied the method and the effects in guinea pigs.

Methods: To confirm an initial normal hearing ABR threshold was measured following DPOAE and TTDPOAE registrations. Some of the animals were treated with the antidiuretic hormon ADH distributed by an osmotic pump. After a period of 14 days DPOAE and TTDPOAE were registrated again. Afterwards these guinea pigs had been sacrificed and the cochleae were removed for histology either to demonstrate a normal cochlea or an ADH induced EH.

Results: Due to the difficulty to position the probe into the earcanal, only some measurements were valid. Animals without ADH showed a sufficient DPOAE carrier any bigger than the noise, while TTDPOAE measurements showed a slight decrease of the DPOAE carrier, the modulation was bigger than the noise. Because of the induced EH the ADH treated animals did show neither a DPOAE Carrier nor a modulation. This is different from the measurements in humans with Menière´s disease symptoms, in which the DPOAE Carrier was reduced but still visible.

Conclusion: Our first results show a dependency of modulation and ADH influence on EH. So TTDPOAE seems to be suitable to detect an EH. But we will collect more data on this subject to confirm our suggestions.