The Study In Treatment For Animal's Damage Inner Ear Caused By Irradiation

Objective: the protective effects of dexamethasone against irradiation damage to inner ears in the guinea pigs were observed for providing the experiment evidence for preventing and treating irradiation damage to inner ears in OHNS clinical.Methods: 120 guinea pigs were divided into three groups randomly. (1)Simply irradiated group (45 guinea pigs) : only treated with irradiation (total does 70Gy, finished in two days). (2)Drug treatment group (45 guinea pigs): treated with irradiation (the same dose as simply irradiated group),and topically applied of injection dexamethasone through an intact RWM on right ear for one time on the day after irradiation .(3)The control group (30 guinea pigs): treat with irradiation, and topically applied of normal saline through an intact RWM on right ear for one time. Auditory brainstem response(ABR) was measured before irradiation,3^rd day,two weeks and two months after treatment. The guinea pigs were killed at 3^rd day,two weeks and two months after treatment respectively. The middle ear mucosa was observed simultaneously .The Corti's organs were observed by the scanning electron microscope(SEM) .The soft sample preparation of cochlea were observed by the microscope in order to analyze for hair cells damage or loss.Results: The ABR thresholds were raising with time went by in all groups, but drug treatment group was better than the other two groups at two weeks and two months's time (P<0.05).There was no difference in the ABR thresholds between simply irradiated group and the control group in the same time. There were no changes in the latency of waves III(80dB) in all groups compared to the normal animal.Under the scanning electron microscope ,hair cells were seen some damage in all groups , and there were some hair cells lost too, but the hair damage and loss in drug treatment group were less than the other groups. There was no difference in the ABR thresholds and hair loss between simply irradiated group and the control group in the same time.Conclusions : The study shows that topically applied of dexamethasone through an intact RWM reduces the extent of irradiation induced hearing loss.