Increased otoacoustic-emission amplitude secondary to cochlear lesions

Objective: The measurements of transient evoked otoacoustic emissions and d istortion-product otoacoustic emissions are being used increasingly, both a s an objective heating test clinically, and as a research tool to investiga te the micromechanical aspects of cochlear function. We hypothesized that l ocalized damage in the apical or middle cochlear turns may have an influenc e on the micromechanics and the function of adjacent, apparently normal coc hlea. For that purpose, we used an animal model of localized apical and mid dle-turn cochlear lesions. Method: Extent of damage was assessed by scanning electron microscopy and t he function of the damaged cochlea by change in the otoacoustic emission (O AE) levels. Results: 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. Conclusion: Explanations to this phenomenon are suggested, and possible cli nical associations such as to Meniere's disease and to sudden hearing loss are reviewed.