Cellular voids in the pathogenesis of otosclerosis

Abstract

Background: Otosclerosis is a common ear disease that causes fixation of the stapes and conductive hearing impairment. However, the pathogenesis of otosclerosis is still unknown. Otosclerosis could be associated with the unique bony environment found in the otic capsule. Normal bone remodelling is almost completely absent around the inner ear after birth allowing degenerative changes and dead osteocytes to accumulate. High levels of inner ear anti resorptive osteoprotegerin (OPG) is most likely responsible for this capsular configuration. Studies have demonstrated how osteocyte lifespan variation creates occasional clusters of dead osteocytes, so-called cellular voids, at otosclerotic predilection sites in the human otic capsule. These cellular voids have been suggested as possible starting points of otosclerosis.

Aim: To describe the cellular viability in otosclerotic lesions and compare it to that of cellular voids.

Materials and methods: The study was based on unbiased stereological quantifications in undecalcified human temporal bones with otosclerosis.

Results: Osteocyte viability was found to vary within the otosclerotic lesions. Furthermore, the results presented here illustrate that inactive otosclerotic lesions consist of mainly dead interstitial bone, much like cellular voids.

Conclusions and significance: Focal degeneration in the otic capsule may play an important role in the pathogenesis of otosclerosis.

Keywords: Otosclerosis; bone remodelling; cellular voids; undecalcified histology.