O. Spandow et S. Hellstrom, ANIMAL-MODEL FOR PERSISTENT TYMPANIC MEMBRANE PERFORATIONS, The Annals of otology, rhinology & laryngology, 102(6), 1993, pp. 467-472
Topically applied hydrocortisone was used to develop an animal model f
or persistent tympanic membrane (TM) perforations. Hydrocortisone susp
ension was applied on the margins of TM perforations of standardized s
ize in rats once daily for 10 days. The healing patterns of the TMs we
re mapped weekly and, when the perforations were about to close, daily
. After 50 days, all hydrocortisone-treated perforations were open, wh
ereas the controls closed within 9 to 12 days. At 3 months, when one t
hird of the perforations still were open, the TMs were studied by otom
icroscopy and light microscopy. All TMs were thickened and covered by
keratin and wax. The thickened epidermal layer at the border of the TM
perforations that remained open also draped the surface of the perfor
ation facing the middle ear cavity. The thickened connective tissue la
yer contained abundant fibroblasts with their axes of length oriented
at random. Both application of 1.4% hyaluronan and wounding of the per
foration border enhanced the healing rate of the hydrocortisone-induce
d chronic TM perforation.