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Early structural tympanic membrane ractions to myringotomy: A study in an acute otitis media model.
Umeå University, Faculty of Medicine, Clinical Sciences, Otorhinolaryngology.
Umeå University, Faculty of Medicine, Clinical Sciences, Otorhinolaryngology.
Umeå University, Faculty of Medicine, Clinical Sciences.
2002 (English)In: Acta Oto-Laryngologica, ISSN 0001-6489, Vol. 122, no 5, 479-487 p.Article in journal (Refereed) Published
Abstract [en]

Myringotomy (Myr) is one of the most frequently performed surgical procedures in children. However, events occurring in the early phases, i.e. a matter of hours, following Myr in the acute otitis media (AOM) model have not been described. The aim of the present study was to evaluate the early otomicroscopic and histopathologic reactions of the tympanic membrane (TM) after Myr during the course of AOM (AOM-Myr). The left tympanic bulla from 36 healthy Sprague-Dawley rats was inoculated with Streptococcus pneumoniae type 3. Forty-eight h later, at Day 0, 4 randomized animals were immediately sacrificed and the remaining animals were treated with bilateral Myr. Otomicroscopy and sacrifices were performed in series of 4 animals at 3, 6, 9, 12, 24 and 48 h, and 4 and 7 days. The AOM-Myr TMs were compared to non-infected Myr TMs (non-AOM-Myr). The TMs were then dissected free and routinely processed for light and electron microscopy. AOM developed in all inoculated ears at Day 0. In the pars tensa of the AOM-Myr TMs the reaction of the keratinocyte layer of the perforation border was already evident at 6 h. The lamina propria exhibited a strong inflammatory reaction, which became more organized from 12 h onwards. At Day 4 the perforations were closed in three-quarters of cases. At Day 7 all perforations were healed with a distorted scar. In the non-AOM Myr TMs a strong degranulation of mast cells and edema were found in the pars flaccida at 6 h. A keratin spur at the perforation border was not seen until 24 h. All perforations were patent on Day 7 and myringosclerotic deposits were abundant in these TMs. The infected TMs regenerated faster and closed their perforations at an earlier stage. These findings favor the hypothesis that there is a low risk of chronic perforations when myringotomizing AOM TMs.

Place, publisher, year, edition, pages
2002. Vol. 122, no 5, 479-487 p.
National Category
Medical and Health Sciences
URN: urn:nbn:se:umu:diva-3349PubMedID: 12206255OAI: diva2:142011
Available from: 2004-01-19 Created: 2004-01-19 Last updated: 2010-04-12Bibliographically approved
In thesis
1. Developing otitis media: experimental studies in particular regarding inflammatory changes in the tympanic membrane
Open this publication in new window or tab >>Developing otitis media: experimental studies in particular regarding inflammatory changes in the tympanic membrane
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Otitis media (OM), one of the commonest of childhood diseases, causes much suffering. OM exists in a variety of forms, two of which are acute otitis media (AOM) and otitis media with effusion (OME). The clinical courses of these conditions differ, AOM usually presenting with earache, fever and/or aural discharge, and the OME usually with hearing impairment. The tympanic membrane (TM) mirrors the events in the middle ear cavity, and pars flaccida (PF) is the initial site of inflammatory changes in the TM. PF is rich in mast cells (MCs), which by releasing various mediators, may trigger TM inflammation.

The aims of the present studies were to investigate early inflammatory changes in the TM in rat models of OM; after mast cell degranulation, in response to AOM, and OME, after myringotomy in AOM and in normal ears. Furthermore, we developed a new rat AOM model, that excludes surgical trauma and resembles the natural route of infection in man.

AOM and OME elicited the first inflammatory response in PF of the TM. The response to OME was discrete, but a slight increase in macrophages was found. During the first 48 hours of AOM, the inflammatory response was intense, following a bimodal pattern. This reaction is similar to that found after MC degranulation. In AOM, macrophages were the predominant cell in PF, while in pars tensa (PT), polymorphonuclear cells (mainly neutrophils) predominated.

When myringotomy was performed in AOM ears, the healing time was shorter than that of myringotomy in normal ears. The highly inflamed lamina propria seemed to promote healing.

During early AOM, as well as following myringotomy, fibrin extravasates into PF and PT. This fibrin deposition may be involved in regulating the inflammatory response.

Repeated nasal challenge with the otitis media pathogen Streptococcus pneumoniae provoked AOM and concomitant TM stimulation reduced the number of AOM cases. This new rat AOM model has the advantage of avoiding trauma in the middle ear cavity, while eliciting an intense inflammatory response in the middle ear cavity (MEC).

56 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 871
Otorhinolaryngology, otitis media with effusion, acute otitis media, myringotomy, tympanic membrane, rat, Streptococcus pneumoniae, compound 48/80, mast cell, Otorhinolaryngologi
National Category
Research subject
urn:nbn:se:umu:diva-180 (URN)91-7305-580-8 (ISBN)
Public defence
2004-02-13, Sal D (grå salen), 1D, Tandläkarhögskolan, Norrlands Universitetssjukhus, Umeå, 09:00 (English)
Available from: 2004-01-19 Created: 2004-01-19 Last updated: 2010-04-12Bibliographically approved

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