Increased otoacoustic-emission amplitude secondary to cochlear lesions.
The measurements of transient evoked otoacoustic emissions and distortion-product otoacoustic emissions are being used increasingly, both as an objective hearing test clinically, and as a research tool to investigate the micromechanical aspects of cochlear function. We hypothesized that localized damage in the apical or middle cochlear turns may have an influence on the micromechanics and the function of adjacent, apparently normal cochlea. For that purpose, we used an animal model of localized apical and middle-turn cochlear lesions. Extent of damage was assessed by scanning electron microscopy and the function of the damaged cochlea by change in the otoacoustic emission (OAE) levels. We found that localized damage to the apical or middle turn may be accompanied by an increase in OAE measured from adjacent apparently normal cochlea. Explanations to this phenomenon are suggested, and possible clinical associations such as to Meniere's disease and to sudden hearing loss are reviewed.