Otoadmittance changes following glycerol dehydration in Meniere's disease

Otoadmittance studies were undertaken in 76 patients with Meniere's disease and 8 control subjects undergoing glycerol dehydration. Baseline otoadmittance values were significantly higher in ears with fluctuant hydrops compared to the non-fluctuant ears (p less than 0.01), suggesting that there is a pathophysiological difference between these clinical Meniere's groups. Significant maximum conductance changes were seen in 53.4% of hydroptic ears, and were associated with subjective audiometric threshold shifts in 23.2%. Similar changes were not seen in the control ears. These findings provide further clinical evidence to support an underlying physical basis for the auditory symptoms of endolymphatic hydrops and the effects of glycerol dehydration on the inner ear. Objective otoadmittance changes appear to be a more sensitive indicator of reversible hydrops than conventional audiometry. Possible mechanisms to explain the somewhat paradoxical increase in the resistance to the flow of sound energy through the cochlea following reduction of the endolymphatic hydrops by glycerol dehydration are discussed.