[Clinical aspects of the osteolytic (inflammatory) phase of cochlear otosclerosis].

During the last years it has been demonstrated that the active stage of otosclerosis (French: otospongieuse) is caused by an osteolytic inflammation associated with a measles-virus infection. Under influences that are not yet well understood (e.g. estrogens), the osteolytic process is arrested and changed to osteoblast activity accompanied by new bone formation. This latter process can be understood as a scar formation. If the process takes place within the area of the oval window, it results in fixation of the stapes and conductive hearing loss. When the otosclerotic process is restricted to the cochlea, clinical signs are not well defined. We report on exemplary cases of progressive bilateral sensorineural hearing loss caused by otosclerosis, restricted to the cochlea. The characteristics of the clinical course include: 1. Bilateral asymmetric sensorineural hearing loss. 2. Roaring tinnitus. 3. Episodes of sudden hearing loss. 4. Excellent response to prednisolone therapy. 5. In the late stage of the disease a small but transitory conductive hearing loss. High resolution computed tomography in such cases reveals diffuse osteolytic foci within the cochlear walls. In severe cases of such progressive deafness we discuss an antiproliferative (immunosuppressive) therapy with cyclosporine and/or a radionuclide therapy with Sn-117 m, an isotope with a very small irradiation radius.