Relationship between Endolymphatic Hydrops and Symptoms of Meniere Disease in Acoustic Hearing

Hypothesis: The endolymphatic hydrops (EH) does not affect hearing loss significantly at low frequencies, whereas the hydrops affects the diplacusis. Background: There have been many arguments whether the EH cause the Meniere disease. Despite a lot of experimental studies to investigate the Meniere disease, there have been little modeling studies, which are helpful to understand the mechanism. Methods: A 3D finite element model of the human cochlea and the middle ear was used for investigation of the relationship between EH and hearing loss at low frequencies and diplacusis (2 specific symptoms of Meniere disease). While the cochlear geometry was simplified as a tapered box shape, the middle ear was based on the real geometry obtained from mu CT images. EH is implemented by prestress on the basilar membrane surface in the simulation. Results: The EH did not cause significant hearing loss at low frequencies in both air- and bone-conducted hearing. Rather, this disorder caused a shift in best frequency (BF) position to the base at low frequencies below about 250 Hz. The BF shift can explain the diplacusis because a low-frequency sound can be perceived as a slightly higher frequency so that Meniere patients can perceive 2 different frequency sounds corresponding to a given single-frequency sound. Conclusion: The EH cannot be a sufficient condition for Meniere disease, whereas the hydrops can cause the diplacusis.