RESUMO
Objective To establish a model of immune-mediated inner ear disease(IMIED) and to compare the efficacy of dexamethasone between systemic application and round window adminstration. Methods The guinea pigs were injected with keyhole limpet hemocyanin(KLH) mixed with complete Freund's adjuvant subcutaneouly in the back,and were boosted with KLH mixed with incomplete Freund's adjuvant two weeks later.Meanwhile,a small piece of gelatin sponge full of KLH was delivered on the round window through operation.Thus established a model of IMIED.Micro-osmotic pumps were used to deliver dexamethasone through the round window(PBS control group also set),and systemic application was implemented by intraperitoneal injection.The efficacy was compared by recording auditory brain-stem response(ABR) before and after the treatment. Results None of the 6 guinea pigs in the control group experienced significant hearing loss,while 22 of the 39 guinea pigs in the experiment group suffered from hearing loss beyond 10 dB.Seventeen guinea pigs with hearing loss no less than 15 dB were divided into three groups randomly and were given different treatment.Those(n=6) treated by local application through the round window enjoyed the efficacy and the mean ABR threshold decreased 13.3 dB.Four out of the 6 treated by systemic application enjoyed the efficacy and the mean ABR threshold decreased 13.7 dB.No efficacy was observed in the PBS group. Conclusion The model of IMIED can be successfully induce by KLH through the round window,and dexamethasone administered through the round window is as efficacious as systemic application.