Cochlear ossification after meningitis

Objective: This study aimed to assess the pathologic processes that result in ossification of the cochlear lumen after bacterial meningitis. Study Design: The study design was a retrospective case review Setting: The study was conducted at a tertiary referral center. Patients: Profoundly deaf postmeningitic patients who underwent cochlear im plantation were studied. Interventions: Diagnostic and therapeutic observations were performed. Main Outcome Measures: The extent of cochlear ossification is classified an d related to age at which infection occurred, cerebrospinal fluid leukocyte count, Gram's stain, organism, and delay between meningitis and implantati on. The extent of ossification noted on high-definition computed tomographi c (CT) scan is compared with surgical findings and related to the time dela ys between meningitis, imaging, and surgery. Results: Ossification fell into three groups: gross ossification of the sca la tympani and variable amounts of the scala vestibuli; partial ossificatio n localized to the basal turn of the scala tympani: and no ossification The re was no correlation between the extent of ossification and the age when i nfected, type of pathogen, cerebrospinal fluid leukocyte count, and time de lay between meningitis and implantation. Visualization of bacteria on Gram' s stain was a highly sensitive measure of ossification (0.93) but was not s pecific (0.6) with positive and negative predictive values of 0.76 and 0.86 , respectively. High-definition CT underestimated the extent of ossificatio n in 50% of cases when performed within 6 months of meningitis. Conclusions: Ossification is either gross or localized to the basal turn of the scala tympani. If ossification does occur, it is rapid and complete wi thin a few months of infection. The visualization of bacteria on Gram's sta in is a sensitive indicator for the presence of ossification but has low sp ecificity. High-definition CT, if performed within the first 6 months of me ningitis, can be an inaccurate diagnostic tool and therefore should be perf ormed as close to the date of surgery as possible.