Thickness of the human round window membrane in different forms of otitis media.

The thickness and morphologic characteristics of the round window membrane were evaluated in temporal bones from normal subjects as well as those with serous otitis media, purulent otitis media, and chronic otitis media. Temporal bones were studied in chronological order in six age ranges to determine the possibility of age-related differences. No significant difference in the mean thickness of the round window membrane was observed in terms of age groups in normal temporal bones or temporal bones from patients with otitis media; however, a significant difference in the mean thickness was observed in the various forms of otitis media compared with the normal round window membrane in all age groups. The membrane was thickest in patients with chronic otitis media when compared with that in normal subjects or those with serous or purulent otitis media. The epithelial layer (including the subepithelial space) and the fibrous layer were measured individually to determine in which layer the change in mean thickness occurred. These measurements showed an involvement of all layers of the round window membrane in those groups with otitis media, with maximal involvement of the combined epithelial layer and subepithelial space.