Spontaneous healing of various tympanic membrane perforations in the rat

Objectives - To investigate the spontaneous healing process of various types of perforation and the location of the epithelial generation center in the tympanic membrane of rats. Material and methods - Various types of perforation were made in the ears of 50 rats and the healing process was observed using light and electron microscopy. Results - Epithelia hyperplasia could not be seen at the edge of the perforations, but occurred in the annulus and handle of malleus regions during the early stage of healing. There was no correlation between the healing time and the size of the perforations. When one ear was perforated, no changes were observed in the intact ear on the other side. The epithelium did not migrate into the tympanic cavity in the posterior marginal perforations. All the perforations healed, although the manubria of the malleus were damaged. Conclusions - The perforations healed by means of epithelial migration. The epithelial generation center was located near the annulus and the handle of the malleus, and therefore protection of these two regions is very important in middle ear surgery.