The round window membrane: otological observations.

The membrane of the round window serves as a barrier between the middle and inner ear and has a well-established role in cochlear physiology. It is important in many otological conditions: otitis media, otosclerosis, trauma, sequelae to drugs reaching the middle ear, tumors, congenital dysplasia, sudden deafness. We here describe the first electron microscopic findings in round window membranes from adult humans, and various conditions in reference to these findings. Since surgical lesions are made in this membrane during cochlear implantation, and by some otologists in treating vertigo, preliminary findings of a lesioning experiment in animals are presented. Interestingly, early healing resulted from a mesothelial cellular reaction in the adjacent scala tympani, with formation of clots, while in the middle ear the epithelial cellular layer sealed the edges of the perforation, leading to formation of an indentation ("pocket"). Subsequently, the middle layer of the membrane contributed to healing.