Otoprotective effects of dexamethasone in the management of pneumococcal meningitis: an animal study.
OBJECTIVE
To determine whether treating pneumococcal meningitis with a combined antibiotic and steroid regime will prevent cochlear damage, a common pneumococcal meningitis side effect.


METHODS
Prospective animal study.


METHODS
Gerbils were randomly assigned to three experimental groups. Animals in group 1 received intrathecal saline injections. Animals in groups 2 and 3 received intrathecal injections of Streptococcus pneumoniae to induce meningitis. Group 2 was treated for 7 days with intraperitoneal penicillin injections (48,000 units). Animals from group 3 received intraperitoneal dexamethasone (0.5 mg/kg) injections for 4 days in addition to 7 days of intraperitoneal penicillin. Three months after the meningitis was induced, the animals' cochlear functions were determined using auditory brainstem responses (ABRs). After measuring cochlear function, the animals were sacrificed for cochlear histopathology. Spiral ganglion cell densities at Rosenthal's canal were determined.


RESULTS
ABR thresholds were significantly elevated in animals from group 2 when compared with the animals in groups 1 and 3 (P < .05). ABR thresholds for animals from group 3 and group 1 were similar (P > .05). Damage of cochlear structures was detected in animals from group 2. The degree of the damage varied: one animal in group 2 had no identifiable hair cells and pillar cells and showed damage of the tectorial membrane. Spiral ganglion density in the basal turn was significantly less in animals from group 2 when compared with controls (P < .05). Although spiral ganglion cell density was less in the dexamethasone-treated group (group 3) when compared with group 1 (control group), but greater than observed in animals treated with antibiotics only (group 2), the differences were statistically not significant (P > .5). Nuclear diameters of the spiral ganglion cells decreased on average from 7.24 +/- 0.48 microm (group 1) to 6.28 +/- 0.76 microm (group 3, animals that received dexamethasone) to 5.57 +/- 0.82 microm (group 2, animals that received antibiotics only). Differences were significant (P < .05). Differences in stria vascularis thickness were not significant among the animals.


CONCLUSIONS
Dexamethasone has a protective effect on the cochlea when given together with antibiotics in the treatment of pneumococcal meningitis.
Kim
Harold H
HH
Wilson Ear Clinic, Portland, Oregon 97209, USA. galbey@yahoo.com
Addison
John
J
Suh
Eul
E
Trune
Dennis R
DR
Richter
Claus-Peter
CP
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology* / Q000627:therapeutic use; D002452:Cell Count; D003051:Cochlea / Q000187:drug effects*; D003907:Dexamethasone / Q000494:pharmacology* / Q000627:therapeutic use; D004359:Drug Therapy, Combination; D016057:Evoked Potentials, Auditory, Brain Stem; D005849:Gerbillinae; D006319:Hearing Loss, Sensorineural / Q000517:prevention & control; D007274:Injections, Intraperitoneal; D008586:Meningitis, Pneumococcal / Q000188:drug therapy* / Q000382:microbiology; D010406:Penicillins / Q000627:therapeutic use; D011446:Prospective Studies; D011897:Random Allocation; D013136:Spiral Ganglion / Q000473:pathology; D013296:Streptococcus pneumoniae / Q000472:pathogenicity; D013680:Tectorial Membrane / Q000382:microbiology / Q000473:pathology
D000893:Anti-Inflammatory Agents; D010406:Penicillins; D003907:Dexamethasone