Osteogenesis Imperfecta Tarda and Otosclerosis a Temporal Bone Histopathology Report

The histopathology of the temporal bones in a 59-year-old female with osteogenesis imperfecta tarda (OIT), complicated by otosclerosis, is presented. Advanced conduction and sensorineural deafness in the left ear and absence of a response to sound in the right ear had been recorded before she died and the temporal bones were acquired for histological study. Histopathological examination revealed a marked degree of porosity of the labyrinthine capsule, enlarged vascular spaces, and a deficiency in number and size of bony trabeculae in the marrow of the petrous apex. All layers of the otic capsule had been extensively replaced by otosclerotic material including the bony semicircular canals and the cochlear and vestibular walls. In the right ear, which had a profound hearing loss, the outline of the space which had been occupied by a piston prosthesis in the oval window was evident; in addition, a layer of new bone (labyrinthitis ossificans was present in the scala tympani in the region of the round window. In the left ear the stapedial footplate was otosclerotic with the base of the crura slightly displaced but fixed in the window. The severity of the OIT in this case was demonstrated by the patient's history of repeated fractures, marked porosity of the nonotosclerotic areas of the labyrinthine capsule, and possibly by the female's relatively early death at age 59. The unique features of the otosclerosis in this case were the extensive replacement of all layers of the cochlear and vestibular capsules and the relatively large areas of an osteoporotic type of degeneration in the more central areas of the otosclerotic bone While the etiology of otosclerosis remains unknown it is apparent that both the incidence and severity of the disorder as it occurs in association with OIT bear some as yet unknown but definite relationship to the pathologies occurring with OIT.