Pathogenesis of Middle Ear Adhesions

Abstract

Middle ear adhesions are well-known to the ear surgeon, although data on etiology, pathogenesis, and significance are lacking in current literature. This study on experimental acute otitis media presents histopathological data on these aspects. Pneumococci were inoculated in the right middle ear bulla of 25 rats; the left ear served as control. At days 4, 8, 16, 90, and 180, respectively, 5 rats were decapitated, and the bullae were removed, opened, and stained with periodic acid-Schiff (PAS)/alcian blue. The entire middle ear mucosae were dissected from the bone, embedded as whole mounts in colophonium chambers, and examined by light microscopy. Representative parts of the mucosae were sectioned and examined in the same way. All inoculated ears from day 8 and later (20 in total), contained mucosal adhesions of various sizes, shapes, and locations. None were found in control ears. The site of predilection for the development of adhesions was the hypotympanum, followed by the anterior epitympanum, the attic, the drum, the interossicular spaces, and the tubal orifice. Based on present histopathological findings, we conclude that the middle ear adhesion is a pathological phenomenon caused by infection, and we propose a six-stage hypothesis of pathogenesis: 1. Localized epithelial rupture; 2. Prolapse of subepithelial tissue; 3. Epithelialization of the prolapse; resulting in a polypous/fold-like prominence; 4. Growth and elongation of the prominence; 5. Fusion of the end/tip of the prominence with another part of the mucosa; 6. Formation of an adhesion.

Structural properties of the mastoid using image analysis and visualization

“…In the second case, see Fig. 3.9(B), the mucosa has recovered its original geometry in most places excepted at the level of the narrow conduit where a strand is created, similar to the ones found in [11]. It should be noted that the occluded air cell may also become diploic or sclerotic.…”

“…In Chapter 9, illustrations of these mucosal strands will be provided for real cases. Though they have been reported previously in [11,74], they have not been illustrated in the bone in 3D. Before proceeding, it should be noted that this process does not occur in all the air cells at the same time, and all cells are not necessarily hampered with the same degree.…”

“…Epithelial cells form along these bridges, leading to mucosal strands. Mucosal strands are also found from a study performed by P. Cayé-Thomasen et al [11] and described as adhesions. Such mucosal strands may eventually form sheets obstructing an air cell completely from the rest of the air cell system, or form some sort of ropes.…”

“…Per Cayé-Thomasen et al [11] reported the formation of bone in the presence of a pathological bone, such as in chronic otitis media. To investigate whether the bony spicules result from the original bone formation, or from a remodelling due to chronic pathology, more clinical work needs to be done and is beyond the scope of this work.…”

Tissue remodelling in upper airways: where is the link with lower airway remodelling?

“…Adhesions often do not produce any symptoms, though if they are extensive they can cause obstruction. However, adhesions in the upper airways, even in middle ear, are likely to obstruct mucociliary clearance and thus enhance the risk of prolonged and recurrent infection (38).…”