AUDITORY AND CYTOCOCHLEAR CORRELATES OF INNER-EAR DISORDERS

Pure-tone threshold audiograms showing sensorineural hearing loss, whe n plotted on a data-based anatomic frequency scale, show a close spati al correlation with their respective cytocochleograms. Whereas most of the cochleae show pathology of several different cell types, a suffic ient number show losses that involve predominantly a single cell type, which permits the following deductions: (I) focal lesions of the orga n of Corti are strongly tonotopic and are responsible for those instan ces of abrupt pure-tone threshold losses; (2) lesions of the stria vas cularis show no tonotopic organization but lead to flat pure-tone thre shold losses; and (3) the principal effect of neuronal losses is a dim inished capability for word recognition. There is an indeterminate gro up where no pathologic correlate can be identified by light microscopy .