Effects of endolymphatic-perilymphatic fistula on endolymphatic hydrops inguinea pig

The endolymphatic-perilymphatic shunt operation between the scala media and scala tympani was performed in 22 guinea pigs with endolymphatic hydrops i nduced by the silver nitrate injection method 2 months before the operation . Two (n = 10), 7 (n = 6), and 28 (n = 6) days after the operation, the con dition of the fistula and the inner ear pathology were studied histopatholo gically. In half of the animals, the fistula was open, whereas in the other half, the fistula was closed. In the group examined after 2 postoperative days, the animals with open fistulas showed a slight collapse of Reissner's membrane, which might indicate that excess endolymph escaped through the f istula into the scala tympani. In the groups examined later, especially in the group examined after 28 postoperative days, the animals showed distenti on of hydrops despite preservation of the fistula. Moderate-to-severe degen erative changes of the organ of Corti, macula sacculi, and stria vascularis were observed in the vicinity of the fistula, We conclude from this study that the endolymphatic-perilymphatic fistula created inside the cochlea app arently was not sufficient to reduce the hydrops. Rather, it caused degener ative changes of the inner ear structure. This type of surgery is not suita ble for Meniere's disease.