The ultrastructure of the round window membrane of humans, monkeys, felines, and rodents discloses three basic layers: an outer epithelium, a middle core of connective tissue, and an inner epithelium. Interspecies variations are mainly in terms of thickness, being thinnest in rodents and thicker in humans. Morphologic evidence suggests that the layers of the round window participate in absorption and secretion of substances to and from the inner ear, and that the entire membrane could play a role in the defense system of the ear. Different substances, including antibiotics, local anesthetics, and tracers such as cationic ferritin, horseradish peroxidase, and 1 μ latex microspheres, are placed in the middle ear side traverse the membrane. Cationic ferritin and 1 micron microspheres placed in perilymph become incorporated by the inner epithelial cells of the membrane. Permeability is selective; factors include size, concentration, liposolubility, electrical charge, and thickness of the membrane. Passage of substances through the round window membrane is by different pathways, the nature of which is seemingly decided at the outer epithelium of the round window membrane. Microsc. Res. Tech. 36:201–211, 1997. © 1997 Wiley‐Liss, Inc.

The ultrastructure of the round window membrane of humans, monkeys, felines, and rodents discloses three basic layers: an outer epithelium, a middle core of connective tissue, and an inner epithelium. Interspecies variations are mainly in terms of thickness, being thinnest in rodents and thicker in humans. Morphologic evidence suggests that the layers of the round window participate in absorption and secretion of substances to and from the inner ear, and that the entire membrane could play a role in the defense system of the ear. Different substances, including antibiotics, local anesthetics, and tracers such as cationic ferritin, horseradish peroxidase, and 1 mu latex microspheres, are placed in the middle ear side traverse the membrane. Cationic ferritin and 1 micron microspheres placed in perilymph become incorporated by the inner epithelial cells of the membrane. Permeability is selective; factors include size, concentration, liposolubility, electrical charge, and thickness of the membrane. Passage of substances through the round window membrane is by different pathways, the nature of which is seemingly decided at the outer epithelium of the round window membrane.

The aim of the National Quality Registries is to monitor the outcome of healthcare given to patients. The Swedish Quality register for otosclerosis surgery is one of the nine official national registers for ear, nose and throat diseases in Sweden. Since 2004, surgical and audiological results and patient satisfaction scores have been systematically collected from a majority of the ear, nose and throat clinics performing stapes surgery in Sweden. The results of 1688 patients who underwent primary operations for otosclerosis were evaluated for 24 out of totally 26 clinics performing stapes surgery, between 2004 and 2010. The most common surgical technique reported was stapedotomy accomplished in an overnight stay. A majority of patients experienced improved hearing, and were satisfied with the preoperative counselling. Successful surgery, defined as an ABG closure ≤10 dB HL, was achieved in 69%, improvement in AC by ≥20 dB in 63% and BC not worsened by more than ≥5 dB in 93% of the patients. An overall low incidence of postoperative complications was reported. The outcome for ABG and BC was demonstrated to be independent of the number of operations performed by each clinic. An evaluation of the register and the results from the SQOS revealed that stapes surgery is a safe procedure with good hearing outcomes, low complication rates and a high rate of patient’s satisfaction on a national level.

By the use of computer-assisted morphometric analysis of the organ of Corti and/or measurements of action potential threshold changes, inner ear changes in chinchillas were evaluated 4 weeks after application on the round window membrane of a Pseudomonas aeruginosa exotoxin A solution. Severe inner ear damage was detected after application of 50 ng (5 microL at a concentration of 10 micrograms/mL) exotoxin A, whereas application of 5 ng exotoxin did not cause measurable inner ear damage. Perilymph concentrations of exotoxin A were measured with an enzyme-linked immunosorbent assay 1.5 to 19 hours after 50 ng, 0.5 micrograms, or 5 micrograms of exotoxin A was applied on the round window membrane. Only the highest concentration produced measurable levels of exotoxin in the inner ear fluids. It is concluded that exotoxin A present on the round window membrane of the chinchilla has the ability to penetrate into the inner ear and cause irreversible inner ear changes.

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