Medical treatment of otosclerosis: rationale for use of bisphosphonates.

Otosclerosis is a bony dyscrasia characterized by histopathological findings of osteoclast production. Osteoclastogenesis explains the pathogenesis of otosclerosis. Basic science research in the experimental animal otic capsule has given insight into the process of evolution of otosclerosis. The normal otic capsule is preserved with very little bone turnover as a result of the production of osteoprotegerin (OPG) by the membranous inner ear that prevents the activation of osteoclasts. Animals genetically unable to produce OPG demonstrated the production of hearing loss and histopathology of the temporal bones consistent with that seen in otosclerosis. Applying the understanding of osteoclastogenesis to the treatment of otosclerosis has led to the clinical use of the class of drugs called bisphosphonates. The bisphosphonate group of drugs specifically targets osteoclasts by reducing production of osteoclasts and accelerating their early cell death. The rationale for use of bisphosphonates to treat the sensorineural hearing loss of otosclerosis is explained, with cases that illustrate the bisphosphonates treatment algorithms and the response to treatment.