Imaging of labyrinthine fibrosis and ossification

Bacterial meningitis is the most common cause of bilateral labyrinthine ossification. Frequently ossification predominates within the scala tympani of the basal turn. Fibrosis may precede ossification and zones of fibrosis and ossification may coexist. Normally in implant surgery the electrode-array is inserted within the scala tympani through the round window or a cochleostomy. Bilateral cochlear fibrosis and ossification do not represent contraindication to implantation in deaf children, but they are factors that can modify surgical approach. Both CT and MR are mandatory in preoperative diagnostic protocol of cochlear implant candidate children. CT shows very well labyrinthine ossification; both axial and coronal images should be acquired in order to avoid misdiagnosis of subtle basal turn calcifications. In labyrinthine fibrosis without ossification CT findings are usually normal, but T2- weighted images demonstrate lack of fluid of the inner ear. Enhancement of fibrosis on post-contrast T1-weighted images means that fibrosis is still proliferative and suggests performing quickly a cochlear implantation.