Changes of Click-evoked Otoacoustic Emissions and Electrocochleographyin Experimental Endolymphatic Hydrops in Guinea Pigs

Jung, Ha Won; Chang, Sun O; Yu, Won Seok

Abstract

BACKGROUND AND OBJECTIVES: Despite the continued research on the pathology of Meniner's disease, it still remains largely uncertain. Since endolymphatic hydrops is known to occur in Meniner's disease, this study was conducted with experimentally induced endolymphatic hydrops. We evaluated the usefulness of click evoked otoacoustic emissions (CEOAE) and electro-cochleogram (ECoG) in studying endolymphatic hydrops.
MATERIALS AND METHODS
Animal endolymphatic hydrops was induced in giunea pigs by mechanically obliterating the right endolympatic sacs and their ducts. The left ears were used as controls. In twelve weeks following the induction of endolymphatic hydrops, CEOAE and ECoG were measured.
RESULTS
1) The endolymphatic hydrops induced group responded to CEOAE with 33.3% positivity, whereas the control group responded with 87.6% positivity. The echo response and reproducibility were significantly low in the endolymphatic hydrops group, for which the negative echo response was more pronounced. For the CEOAE positive endolymphatic hydrops group, the average peak frequency of the response curves was shifted significantly to a higher frequency. 2) The tone burst stimulated ECoG response showed the permanant summating potential. The tone bursts with the intensity of 95 dB and frequencies of 4 or 8 kHz were found to be suitable stimuli for the study of endolymphatic hydrops. On click stimulation, the latency of the first negative peak (AN1) in the endolymphatic hydrops group was prolonged. The ratios of the summating potential amplitude to the action potential were observed to be significantly high.