Passage through the round window membrane and inner ear function

The round window membrane (RWM) is an anatomical barrier between the aerated middle ear and the fluid (perilymph) compartments of the cochlea. Permeability of the RWM is regarded as an accident and not as a function of the membrane because of its anatomical characteristics, location and the high prevalence of middle ear disease. This paper provides a review of the effects on cochlear function following experimental exposure of bacterial toxins into the round window niche. Hearing loss is correlated with RWM morphology in experimental chronic otitis media. Following exposure to bacterial toxins there is a time‐dependent response of both the middle ear mucosal changes and the morphological alterations in the epithelium of the endolymphatic duct and sac. Otoprotectants, such as nitric oxide inhibitors, dexamethasone and neurotrophic factors, prevent toxic effects of Pseudomonas aeruginosa exotoxin A. In spite of a limited knowledge on the permeability of the RWM the application of therapeutic substances into...