Quantification of the relation between electrophysiologic and morphologic changes in experimental endolymphatic hydrops.

The degree of hydrops in guinea pig ears that had undergone unilateral endolymphatic sac and duct obliteration was quantified. For 15 guinea pigs from a prior study, the correlation between the degree of hydrops and several electrophysiologic measures of the functional state of the cochlea was determined. A significant correlation between the degree of hydrops and a reduction in the low-frequency cochlear microphonic evoked by a 29-Hz tone was found. No correlation was found between the degree of hydrops and the magnitude of the summating potential evoked by 8-kHz probes. A weak correlation was found between the degree of hydrops and a reduction in the compound action potential evoked by 2-kHz probes. Possible differences in the way the endolymphatic duct obliteration exerts its effect on the different cochlear potentials are discussed.