[Topography of the round window and its significance for the surgical therapy of perilymph fistulas].

The clinical findings concerning the diagnosis of a rupture of the round window membrane vary widely. Therefore, microtopography of the round window was studied using 45 serially sectioned human temporal bones of the Wittmaack Collection, ENT Clinic, University of Hamburg. Our morphometrical data show a great variety in respect of the dimension of the round window membrane and the angle between the window membrane and the tympanic membrane. The extension and the microtopography of the promontory are as variable as the mucosal folds in the round window niche. It can be concluded that a direct view of the round window membrane is possible only in rare cases. Surgical manipulations to improve the view of the round window should be avoided because of the danger of an iatrogenic lesion of the inner ear.