Cochlear osteoneogenesis after meningitis in cochlear implant patients: a retrospective analysis.

Study Design: Retrospective clinical study.

Setting: Academic tertiary referral center at the Medical University of Hannover.

Patients: Computed tomographic findings of 126 patients (95 children and 31 adults) profoundly deafened by meningitis during a period of 20 years were evaluated. Children were defined as up to 12 years old at the onset of meningitis. No patients showed any relevant bilateral auditory brainstem response thresholds at the time of admission to our clinic.

Interventions: Patient histories, surgical findings, and imaging results were analyzed by experienced surgeons/neuroradiologists.

Results: Of 95 children, 30 (32%) displayed symptoms of labyrinthitis ossificans, whereas 11 (36%) of 31 adults showed changes of the bony structure of the cochlea. High-resolution computed tomography (HRCT) evaluation indicated that the ossification was detected more frequently if there was a larger time interval between onset of meningitis and high-resolution computed tomographic scan. Bilateral ossification at various stages was observed in 67% of children and 55% of adults with obliteration. In the comparison of cochlear ossification found in computed tomographic scans and intraoperative obliteration, HRCT showed a specificity of 73% and a sensitivity of 88%. The intraoperative evaluation revealed various stages of cochlear obliteration in 44% of children and 39% of adults.

Conclusion: In our study, the earliest onset of labyrinthitis ossificans was found in high-resolution computed tomographic scans as early as 4 weeks after the onset of meningitis. In most cases, ossification occurred bilaterally with predominantly asymmetric involvement of both ears. The rate of osteoneogenesis increases significantly over time after meningitis. This leads to the conclusion that cochlear ossification can start very early and increase over time with unpredictable speed. Cochlear ossification typically develops bilaterally. From these results, we conclude that cochlear implantation should be performed bilaterally as soon as possible after meningitis and deafness have been diagnosed. HRCT offers good specificity but only limited sensitivity. Preoperative diagnostics should include magnetic resonance imaging to optimize preparation for cochlear implantation.