Permeability of the Round Window Membrane in Otitis Media

A round window membrane permeability study of macromolecules in otitis media, using tritiated normal human serum albumin, was done in cats. Eustachian tube obstruction was used to induce otitis media in ten animals. Samples of perilymph in obstructed and normal control ears were studied after 25 minutes of exposure of the round window to tritiated albumin. Twelve additional animals were obstructed, and their round window membranes studied to provide histopathologic evidence for our permeability studies. In this first report of round window membrane permeability to macromolecules in otitis media, we observed an increased permeability to tritiated albumin in diseased ears. Evidence suggests a pathophysiological explanation for the association of otitis media and sensorineural hearing loss and/or endolymphatic hydrops. Proof that large molecules pass suggests the feasibility of diffusion of smaller molecules (toxins and enzymes) through the round window membrane.