The mechanism of healing of tympanic membrane perforations. A two-dimensional histological study in guinea pigs.

The healing of small perforations, made in 60 tympanic membranes (30 guinea pigs) with either a thermal myringotome or a needle was observed over a 10-day period using an operating microscope. Thirty-six of these were sectioned either parallel with the handle of the malleus, or at right angles to it, and the closing perforations studied by light microscopy. The epidermis closed the perforations first, in the direction of surface migration. This process began within 48 hours and was complete within 9 days. A fibrous reaction occurred, starting at 3 days, and this was seen on the side of the perforation adjacent to the malleus or bony tympanic annulus. There was no response visible in the middle ear mucosa. The conclusion of this study is that the epidermis is the first layer to close a perforation because of its migratory function, and the direction of closure is the direction of migration. Healing of the fibrous layer occurs secondarily, and the site of the response in this layer is related to the vascular distribution in the tympanic membrane.