Objective: Human neonatal temporal bones frequently show the formation of granulation tissue provoked by amniotic fluid keratin contents, desquamated keratinized epithelial cells and lanugo hair. Similar histopathologic findings have been produced previously in a short-term animal model. To test the hypothesis that those short-term pathologic observations could have theoretical relevance for ear disease in older patients, a longer term animal model study was necessary.
Methods: Into the right bulla of 10 chinchilla pups was placed an aliquot of autogenous, nonviable epidermal scrapings and hair. Into the left bulla was placed 1 mm2 viable autogenous epidermal tissue. Animals were killed at intervals up to 11 months and then studied by light microscopy.
Results: Chronic ear histopathologic changes such as granulation tissue, osteoneogenesis, adhesions, and cholesteatoma were present. Over time, these secondary pathologic changes became more obvious than the initial keratin implant.
Conclusions: The authors conclude that chronic pathologic changes resembling human ear disorders persist and that this model further extends the hypothesis that prenatally acquired keratin eventually could account for some cases of human ear disease.