Labyrinthitis ossificans due to chronic otitis media.

Histopathology of two cases of unilateral labyrinthitis ossificans in the presence of bilateral chronic suppurative otitis media is presented. In both cases, ossification and fibrosis were limited to the scala tympani of the lower basal turn, apparently due to inflammation entering through the round window membrane. The round window was occluded by new bone and fibrous tissue presumably resulting in a conductive hearing loss in addition to the conductive loss due to middle ear lesions. Degeneration of the hair cells of the organ of Corti was limited to the lower basal turn where ossification and fibrosis occurred.