Analysis of the Hyalinization Reaction in Otosclerosis.

IMPORTANCE Otosclerotic bone has been observed to penetrate the endosteal layer of the cochlea, resulting in direct contact with the soft-tissue structures of the inner ear. Sensorineural hearing loss has been observed in some, but not all, of these cases. The development of histologic changes occurring in the cochlear soft tissues at the site of otosclerotic endosteal penetration has been descriptively referred to as a hyalinization reaction. The role of the hyalinization reaction in the development of hearing loss is unknown. OBJECTIVE To evaluate the composition of these hyalinized soft tissues using immunostaining techniques. DESIGN, SETTING, AND PARTICIPANTS Retrospective review in a human temporal bone histopathology research laboratory of 3 specimens from patients with endosteal otosclerotic involvement. INTERVENTIONS Evaluation of human temporal bone pathology findings. MAIN OUTCOMES AND MEASURES Human temporal bone sections with endosteal otosclerotic involvement were studied using immunostaining techniques to identify collagen I, chondroitin sulfate, and keratan sulfate deposition in the hyalinization reaction tissue. RESULTS Intense collagen I staining was demonstrated within the hyalinization reaction in an onionskin-like layered fashion. In addition, dual immunofluorescence-stained sections for proteoglycans revealed both chondroitin sulfate and keratan sulfate deposition in the hyalinized tissue. CONCLUSIONS AND RELEVANCE The tissue of the hyalinization reaction appears to be composed of collagen I, chondroitin sulfate, and keratan sulfate, which are known to act as molecular barriers. This observation suggests that the hyalinization reaction may limit the diffusion of toxic substances produced by otosclerotic bone into the soft tissues and fluids of the cochlea.