Myringotomy delays the tympanic membrane recovery in acute otitis media: a study in the rat model.

Background/hypothesis: Acute otitis media is a major cause of visits to pediatric health care providers. Myringotomy in uncomplicated acute otitis media is debatable today. The study addressed this problem through the otomicroscopic and histopathological observations of the events occurring in the tympanic membrane during the first week after myringotomy.

Study Design: Randomized study in an experimental animal model.

Methods: Under anesthesia, the left middle ear of 36 Sprague-Dawley rats was inoculated with Streptococcus pneumoniae type 3. Forty-eight hours later, at day 0, four animals were immediately killed and the remaining animals were randomly assigned into a myringotomy group (n = 16, myringotomy on the left ear) and a non-myringotomy group (n = 16, otomicroscopy without myringotomy). Otomicroscopy and killings were performed in series of four animals from each group at days 1, 2, 4, and 7 after myringotomy. Tympanic membranes were collected after fixation and processed for light and electron microscopy.

Results: All inoculated ears showed a manifest acute otitis media at day 0. An intense infiltration by inflammatory cells and edema distorted severely the tympanic membrane structure. These findings decreased the following days. However, inflammation as evaluated by the thickness and the cytoarchitecture of the tympanic membrane layers, recovered significantly faster in the membranes in the non-myringotomy group. At day 7, all tympanic membranes in the myringotomy group were closed by a hypertrophic keratinizing epithelium and a remodeling connective tissue layer, whereas the animals in the non-myringotomy group had a residual edema in the lamina propria.

Conclusions: The present infectious model induced an intense inflammatory reaction within the entire structure of the tympanic membrane. Myringotomy provoked a delayed recovery from the inflammatory process within the tympanic membrane. Therefore, if applicable to human conditions, the use of myringotomy in the management of acute otitis media should be restricted to selected cases of acute otitis media.