Cochlear preservation after meningitis: an animal model confirmation of adjunctive steroid therapy.

Objective/hypothesis: The objective of the present study was to determine whether treating pneumococcal meningitis with a combined antibiotic and steroid regime will prevent cochlear damage, a common pneumococcal meningitis side effect.

Study Design: This was a prospective animal study.

Methods: Gerbils were randomly assigned to three experimental groups. Animals in group 1, the control animals, received intrathecal saline injections. Animals in groups 2 and 3 received intrathecal injections of Streptococcus pneumoniae to induce meningitis. Although group 2 solely was treated for 7 days with intraperitoneal penicillin injections (48,0000 units), group 3 received, in addition to the antibiotic for 4 days, 0.5 mg/kg intraperitoneal dexamethasone injections. Three months after the meningitis was induced, the animals' cochlear function was determined using auditory brainstem responses (ABRs). Fifteen frequencies were tested, five octaves at three steps per octave between 2 and 50 kHz.

Results: ABR thresholds were significantly elevated only in group 2. When compared with group 1, ABR thresholds were 19 dB higher (P<.05). Frequencies at the low-frequency end of the hearing range were affected more than the midfrequencies. Animals that received dexamethasone had 2-dB higher thresholds than the control group (P>.05).

Conclusions: Dexamethasone therapy in conjunction with antibiotic therapy preserves cochlear function in cases of S. pneumoniae meningitis in the Mongolian gerbil model.