Questioning the relationship between cochlear otosclerosis and sensorineural hearing loss: a quantitative evaluation of cochlear structures in cases of otosclerosis and review of the literature.

BACKGROUND

The literature provides conflicting information regarding the prevalence and cause of sensorineural hearing loss (HL) in individuals with otosclerosis.

OBJECTIVE

The purpose of this study was to further evaluate the association between involvement of the cochlear endosteal layer with otosclerosis and sensorineural HL.

METHODS

Retrospective case review.

METHODS

Temporal bones and audiograms from five individuals with otosclerosis were evaluated. The cochlear elements were quantified. The location and extent of the cochlear element loss was correlated with the location and extent of endosteal involvement with otosclerosis.

RESULTS

A reduction in the population of cochlear elements was observed in most individuals; however, the reduction was not proportional to the extent of endosteal involvement with otosclerosis. The cochlear elements remained normal adjacent to some areas of endosteal involvement with otosclerosis. One individual with extensive cochlear otosclerosis had normal hearing and predominantly normal cochlear elements.

CONCLUSIONS

This study demonstrates a variable amount of degeneration of the cochlear elements in individuals with otosclerotic involvement of the endosteum. The reduction in the population of cochlear elements was not related to the extent and location of endosteal involvement with otosclerosis. These findings suggest that factors that limit the effect of otosclerotic endosteal involvement on the cochlear elements or processes that effect the cochlear elements directly and are independent of bone involvement may be present.