Morphologic Studies Of Round Window Membrane After Intratympanic Perfusion Dexamethasone And Dexamethasone/Hyaluronic Acid

Objective: The goal of this study was to observe the morphologic changes of round window membrane in guinea pigs after place Gelfoam in round window niche, intratympanic perfusion dexamethasone and dexamethasone/hyaluronic acid.Methods: Thirty-six healthy male guinea pigs were used in the study, these animals were divided randomly into three groups(each had 12 animals). In Group I, Gelfoam was placed in round window niche and a pipe was introduced onto the round window. In Group II, Gelfoam soaked with hyaluronic acid was placed in round window niche, and a pipe was introduced onto the round window, dexamethasone was perfused through the pipe once a day for 7 days. In Group III, Gelfoam was placed in round window niche, a pipe was introduced onto the round window, and dexamethasone was perfused once a day for 7 days. In Group IV was normal control group(n=6). The animals were sacrificed and the temporal bones were harvested at 1day or 7days after finished dexamethasone perfusion or operative procedure. The morphologic changes of round window membrane were studied by both light microscope and scanning electron microscope. The thickness of round window membrane was measured and compared with that of normal control group. Results: (1) All animals tolerated the procedure well, no one death or abnormal behavior. (2) No inflammatory reaction and bleeding was noticed in middle ear cavity. (3) Morphologic changes observed by light microscope: the three layers of round window membrane including an outer epithelial layer facing the middle ear cavity, the middle core of connective tissue, and an inner ear epithelial bordering the inner ear in group I,II and III, no statistical difference was present between groups in the thickness of round window membrane(P>0.05), no inflammatory cells infiltrated into the layers. (4) Observed by scanning electron microscope: the epithelial cells facing tympanic cavity were low cuboidal and arranged regularly, tight junctions were present near the surface, abundant microvilli were found on the cell surface and in the tight junction area, the epithelial cells lining the inner ear were squamous with long lateral extensions and irregularly arranged, microvilli are rare or absent, which did not differ morphologically from that in normal control group.Conclusions: (1) There is no obvious effect for the morphology of the round window membrane after placing the Gelfoam in round window niche. (2) Intratympanic dexamethasone and dexamethasone/hyaluronic acid perfusion is not change the morphology of round window membrane.