Cochlear ossification after meningitis

This study aimed to assess the pathologic processes that result in ossification of the cochlear lumen after bacterial meningitis.

The study design was a retrospective case review.

The study was conducted at a tertiary referral center.

Profoundly deaf postmeningitic patients who underwent cochlear implantation were studied.

Diagnostic and therapeutic observations were performed.

The extent of cochlear ossification is classified and related to age at which infection occurred, cerebrospinal fluid leukocyte count, Gram's stain, organism, and delay between meningitis and implantation. The extent of ossification noted on high-definition computed tomographic (CT) scan is compared with surgical findings and related to the time delays between meningitis, imaging, and surgery.

Ossification fell into three groups: gross ossification of the scala tympani and variable amounts of the scala vestibuli; partial ossification localized to the basal turn of the scala tympani; and no ossification. There was no correlation between the extent of ossification and the age when infected, type of pathogen, cerebrospinal fluid leukocyte count, and time delay between meningitis and implantation. Visualization of bacteria on Gram's stain was a highly sensitive measure of ossification (0.93) but was not specific (0.6) with positive and negative predictive values of 0.76 and 0.86, respectively. High-definition CT underestimated the extent of ossification in 50% of cases when performed within 6 months of meningitis.

Ossification is either gross or localized to the basal turn of the scala tympani. If ossification does occur, it is rapid and complete within a few months of infection. The visualization of bacteria on Gram's stain is a sensitive indicator for the presence of ossification but has low specificity. High-definition CT, if performed within the first 6 months of meningitis, can be an inaccurate diagnostic tool and therefore should be performed as close to the date of surgery as possible.