Experimental grafting of the round window membrane: Part I

The histology and permeability of cats’ round window membranes were described following surgical grafting with gelatin foam or fascia. An increase in the thickness of the round window membrane due to fibrosis, neovascularization, and epithelial metaplasia was observed 2 months following grafting with gelatin foam. Grafting with fascia did not increase the thickness of the round window membrane, but did form a thick layer of granulation tissue adjacent to and overlying the round window membrane, with occasional adhesions between. The layer of granulation tissue consisted of cuboidal or columnar ciliated epithelial cells, fibrous tissue, lipid, and undigested grafted material. The granulation tissue did not always completely cover the round window membranes. Horseradish peroxidase placed in the round window niche of cats with grafts on the round window membrane remained a significant distance further from the inner ear when compared to its migration through nongrafted membranes.