The round-window membrane (RWM) is extremely thin and is the only soft-tissue barrier between the middle ear and the inner ear. Under inflammatory conditions of the middle ear the various layers of the triple-layered RWM undergo characteristic changes parallel to the changes of the middle-ear mucosa. Several studies report that bacterial products, exo- and endotoxins, from bacteria invading the middle ear may result in profound inflammatory changes in the inner ear, followed by severe damage to the inner-ear function. The present review, in which we summarized experimental and clinical observations, on bacterial products in interactions between the middle and inner ear, focused on: 1. Bacteria and bacterial products in an inflamed middle ear that may influence inner-ear function. 2. RWM structure and RWM permeability under the influence of bacteria and bacterial products. 3. Morphological and functional inner-ear effects of bacterial infection of the middle ear, and the possible mechanisms involved. 4. Future studies to be directed in this field.

The localization of alpha-atrial natriuretic polypeptide (alpha-ANP) in the rat cochlea was studied by immunohistochemical technique, using a polyclonal antibody against synthetic rat alpha-atrial natriuretic polypeptide (alpha-rANP). The spiral ligament of the lateral cochlear wall exhibited pronounced immunoreactivity to atrial natriuretic polypeptide (ANP), whereas the stria vascularis displayed almost no immunoreaction. ANP immunoreactivity (IR) was also intense in the spiral limbus region. IR was observed in the fibroblast-like cells and in the extracellular matrix, in particular along its fibrous bundles, of both the spiral ligament and the spiral limbus. These results indicate that ANP may participate in the regulation of the water electrolyte balance at these sites, which may imply a role for ANP in the regulation of cochlear fluids.

The distribution of rat alpha-atrial natriuretic polypeptide (ANP) was studied in the adult inner ear of the Sprague-Dawley rat using immunohistochemical methods. Immunostaining, in particular of the subepithelial stroma cells of the spiral ligament, the spiral prominence and below neuroepithelial areas of all five vestibular organs, was identified. We hypothesize that alpha-ANP is involved in perilymphatic dynamics rather than generating endolymph. The strong staining for alpha-ANP of outer hair cells indicates specific mechanisms for volume control as compared with inner hair cells and vestibular hair cells which all lack this immunostaining. The functional significance of the specific staining of nerve calyces in only the three cristae ampullares but not in the two maculae remains to be clarified. The positivity of epithelial cells in the endolymphatic sac supports a previous hypothesis which looks upon this organ as a pressure regulation system in the inner ear.

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of ear infections. We attempted to evaluate the clinical usefulness of arbekacin in treating chronic suppurative otitis media (CSOM) by comparing its clinical efficacy and toxicity with those of vancomycin. Efficacy was classified according to bacterial elimination or bacteriologic failure and improved or failed clinical efficacy response. Ninety-five subjects were diagnosed with CSOM caused by MRSA. Twenty of these subjects were treated with arbekacin, and 36 with vancomycin. The bacteriological efficacy (bacterial elimination, arbekacin vs. vancomycin: 85.0% vs. 97.2%) and improved clinical efficacy (arbekacin vs. vancomycin; 90.0% vs. 97.2%) were not different between the two groups. However, the rate of complications was higher in the vancomycin group (33.3%) than in the arbekacin group (5.0%) (P=0.020). In addition, a total of 12 adverse reactions were observed in the vancomycin group; two for hepatotoxicity, one for nephrotoxicity, eight for leukopenia, two for skin rash, and one for drug fever. It is suggested that arbekacin be a good alternative drug to vancomycin in treatment of CSOM caused by MRSA.