Distortion-Product Otoacoustic Emissions and Cochlear Microphonics: Relationships in Patients With and Without Endolymphatic Hydrops

Objectives Because endolymphatic hydrops causes cochlear malfunction, and both otoacoustic emissions and cochlear microphonics measure specific cochlear activities, some insight into the pathology of Meniere's disease might be gained by using these two test modalities. Specifically, the involve...

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Veröffentlicht in:The Laryngoscope 2001-06, Vol.111 (6), p.946-954
1. Verfasser: Fetterman, Bruce L.
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Sprache:eng
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Zusammenfassung:Objectives Because endolymphatic hydrops causes cochlear malfunction, and both otoacoustic emissions and cochlear microphonics measure specific cochlear activities, some insight into the pathology of Meniere's disease might be gained by using these two test modalities. Specifically, the involvement of cochlear outer hair cells in patients with endolymphatic hydrops may be detected. Furthermore, it is hoped that these two tests might help determine which regions of the cochlea are affected by endolymphatic hydrops, as well as where along the auditory pathway abnormalities are present. Study Design Data were gathered prospectively on patients presenting to a private, tertiary referral otology/neurotology practice. Methods From February 1999 to April 2000, clinical information was collected on patients presenting with vertigo, hearing loss (HL), sudden HL, fluctuant HL, aural fullness, and/or tinnitus. Data included demographics, diagnosis, pure‐tone and speech audiometry, tympanometry, summating potential, action potential, cochlear microphonic, and distortion‐product otoacoustic emissions. Descriptive statistics were calculated, and relationships between distortion‐product otoacoustic emissions and cochlear microphonics in patients with hydrops (defined as summating potential to action potential ratio ≥0.40) and without hydrops were analyzed. Results Distortion‐product otoacoustic emissions were present more often and had larger amplitudes at the lower frequencies. No differences were found in the presence of distortion‐product otoacoustic emissions across the frequencies for the two groups, but larger mean amplitudes were found for hydropic ears at 7966 Hz. As hearing levels worsened, both hydropic and nonhydropic ears were less likely to have emissions present; however, 18% of hydropic ears had emissions unexpectedly present when the pure‐tone thresholds were ≥50 dB. The cochlear microphonic from the hydrops group tended to be smaller, but this was not statistically significant. Analysis of variance showed a small negative correlation between summating potential to action potential ratio and level of emission at 1968 Hz in hydropic ears; otherwise, there was no relationship between the ratio and emissions. The only statistically significant finding when analyzing the relationship between cochlear microphonic and otoacoustic emission was a small positive correlation between level of microphonic and level of emission at 1406 Hz in hydropic ears. No signific
ISSN:0023-852X
1531-4995
DOI:10.1097/00005537-200106000-00004