Long-Term Morphological and Electrophysiological Effects of Small Mechanical Lesions in the Guinea Pig Cochlea

This paper reports the results on chronic morphological and electrophysiological effects of small lesions in 6 guinea pigs. The lesions were made on the external wall on one of the three scalae of the basal cochlear turn. Following a 6-week recovery period the round window was exposed using a postauricular approach and a platinum iridium ball electrode was placed on the round window. Measurements of the CM were made at ten frequencies. Following completion of the electrophysiological measurements, the animals were perfused with Prussian blue solution and their temporal bones removed, fixed and stained, decalcified and prepared for microscopy. In general, electrophysiological responses of the cochlea were depressed following discrete mechanical lesioning. Morphologically there was little influence segmentally limited on the vasculature at the site of the lesion. Little histopathological effect was seen on the organ of Corti. Although no consistent relationship was found between individual mechanical lesions primarily restricted to one scala and subsequent electrophysiological effects, findings of this study do indicate that restricted mechanical damage to the cochlea results in restricted histopathology and a restricted effect on cochlear function.