Effects of a perilymphatic fistula on the passive vibration response of the basilar membrane

In this study, a three-dimensional finite-element model of the passive human cochlea was created. Dynamic behavior of the basilar membrane caused by the vibration of the stapes footplate was analyzed considering a fluid-structure interaction with the cochlear fluid. Next, the effects of a perilymphatic fistula (PLF) on the vibration of the cochlea were examined by making a small hole on the wall of the cochlea model. Even if a PLF existed in the scala vestibuli, a traveling wave was generated on the basilar membrane. When a PLF existed at the basal end of the cochlea, the shape of the traveling wave envelope showed no remarkable change, but the maximum amplitude became smaller at the entire frequency range from 0.5 to 5kHz and decreased with decreasing frequency. In contrast, when a PLF existed at the second turn of the cochlea, the traveling wave envelope showed a notch at the position of the PLF and the maximum amplitude also became smaller. This model assists in elucidating the mechanisms of hearing loss due to a PLF from the view of dynamics.

Round window membrane in Ménière's disease: a human temporal bone study

OBJECTIVES

To disclose the histopathologic findings of the thickness of the round window membrane and the presence of false round window membrane in Ménière's disease.

METHODS

Twelve temporal bones from 6 patients with bilateral Ménière's disease, 44 temporal bones from 23 patients with unilateral Ménière's disease, and 102 age-matched normal temporal bones from 56 individuals were histopathologically examined. The thickness of the round window membrane was calculated from 3 different places. In addition, the presence of false round window membrane was investigated in temporal bones with Ménière's disease and compared to the normal temporal bones.

RESULTS

A significant difference in the mean thickness of the round window membrane was observed in temporal bones with Ménière's disease compared with normal temporal bones. There was no significant difference in the thickness of the round window membrane between the diseased side and contralateral side in patients with unilateral Ménière's disease. A false round membrane was observed in 9 (25.7%) of 35 Ménière's disease cases and in 5 (4.9%) of 102 normal temporal bones.

CONCLUSION

The thickened nature of the round window membrane and the frequent presence of false round window membrane in patients with Ménière's disease may impede the intratympanic injection treatments. The thickened middle layer of the round window membrane may be related to perilymphatic pressure changes observed in patients with Ménière's disease.