title: Structural changes in the tympanic membrane after repeated tympanostomy tube insertion.
abstract: In an animal model (rat) a polyethylene tympanostomy tube was repeatedly inserted (four periods lasting 2 weeks) into the upper rear quadrant of the right tympanic membrane (TM). The intervals between the different tubulation periods (TPs) lasted 3 weeks. The corresponding quadrant of the left TM was subjected to repeated myringotomies (four times). The structural changes in the TMs were evaluated otomicroscopically and by histological techniques 3 weeks and 3 months after the final TP. Repeated tympanostomy tube insertion caused a dramatically thickened pars tensa. The thickened areas were characterized by a scar tissue exhibiting sclerotic plaques and a dense connective tissue with bone-like formations. Occasionally, islands of keratinizing stratified squamous epithelium were noted within the thickened pars tensa as well as interrupting the epithelial lining facing the tympanic cavity. Similar structural changes occurred after myringotomy without tube insertion, but they were not so pronounced as after repeated tympanostomy tube insertion. The changes were not restricted to the manipulated quadrants, but also affected the untouched anterior quadrants. Throughout the observation period the anterior quadrants improved, while the rear quadrants remained severely affected.
mesh_terms: D000818:Animals; D003238:Connective Tissue / Q000473:pathology; D008297:Male; D008854:Microscopy, Electron; D008876:Middle Ear Ventilation / Q000009:adverse effects*; D011095:Polyethylenes; D051381:Rats; D011919:Rats, Inbred Strains; D012086:Reoperation / Q000009:adverse effects; D013997:Time Factors; D014432:Tympanic Membrane / Q000473:pathology*
chemical_list: D011095:Polyethylenes