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82nd Annual Meeting of the German Society of Oto-Rhino-Laryngology, Head and Neck Surgery

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

01.06. - 05.06.2011, Freiburg

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Influence of the individual growth behaviour of distortion product otoacoustic emissions (DPOAEs) on alterations of their levels due to minor conductive hearing loss (CHL)

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  • corresponding author presenting/speaker Bernhard Olzowy - Department of Otorhinolaryngology, Head and Neck Surgery, University of Munich Medical Center, München, Germany
  • author Christoph Deppe - Department of Otorhinolaryngology, Head and Neck Surgery, University of Munich Medical Center, München, Germany
  • author Peter Kummer - Department of Otorhinolaryngology, Head and Neck Surgery, University of Regensburg, Regensburg, Germany

German Society of Oto-Rhino-Laryngology, Head and Neck Surgery. 82nd Annual Meeting of the German Society of Oto-Rhino-Laryngology, Head and Neck Surgery. Freiburg, 01.-05.06.2011. Düsseldorf: German Medical Science GMS Publishing House; 2011. Doc11hno37

doi: 10.3205/11hno37, urn:nbn:de:0183-11hno374

Published: August 3, 2011

© 2011 Olzowy et al.
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Outline

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Introduction: Even minor CHL can strongly influence DPOAE levels, since both the primary tones during forward transmission and the distortion product during backward transmission are damped. DPOAEs are evoked using two simultaneously applied stimulus tones that differ slightly in frequency (f1 and f2) and level (L1 and L2). Optimal DPOAE levels are generated with an exactly defined level difference, which is larger for low level primaries and decreases towards higher primary tone levels (scissors paradigm). A CHL damps both primary tones to a similar extent so that inner ear stimulation is no longer optimal. The presented data shows possible effects of this mechanism on DPOAE level alteration due to minor CHL.

Methods: A minor CHL was induced in guinea pigs by filling the middle ear space with saline solution, in humans by head-down-positioning on a tilting table. DPOAEs (2f1-f2, f1/f2=1,2, guinea pigs f2=8 kHz, humans f2=2 kHz) were measured before and after induction of the CHL with constant L2 and variation of L1 in small steps.

Results: The largest variation of DPOAE levels was found in a guinea pig with a CHL of 4 dB. Depending on L1, DPOAE level alteration varied between –32 and +9 dB, i. e. certain level combinations produced a paradox increase of DPOAE levels. Comparable level variations were found in humans due to head-down-positioning.

Conclusion: Alteration of DPOAE levels due to minor CHL strongly depends on the primary tone level combination and the individual DPOAE growth behaviour.