Chronic Otitis Media

Chronic otitis media is characterized by the presence of intractable tissue pathology such as granulation tissue, fibrosis, cholesterol granuloma, cholesteatoma, ossicular erosin, or new bone formation, with or without associate middle ear effusion.  This is the most serious form of otitis media and at present can only be corrected by surgical intervention.

The etiology of chronic otitis media is repeated episodes of the other forms previously described.  Although this classification was previously based on the presence of a perforated tympanic membrane, it is currently accepted that chronic otitis media can exist behind an intact and normal appearing tympanic membrane “silent otitis media”.  The following are examples of chronic otitis media showing intractable tissue pathology.

Granulation Tissue

Granulation tissue is the most common form of pathologic tissue in otitis media (Figure 1).  The term granulation tissue derives from its pink, soft granular appearance.  Its histologic appearance is characterized by the proliferation of blood vessels and fibroblasts.  Macrophages are almost always present in granulation tissue, eating up extracellular debris, fibrin, and other foreign matter. Neutrophils, eosinophils, mast cells, and lymphocytes may also be seen.  In later stages there is an increase in collagen and a decrease in the number of active fibroblasts and new vessels.  The end result of granulation tissue is a fibrous type of scar tissue composed of dense collagen and inactive-appearing fibroblasts with few vessels.

Figure 1. Granulation tissue in the round window area.

Cholesterol granulomas result from a foreign body reaction to cholesterol crystals (Figure 2).  These crystals are believed to be the result of the breakdown of blood or tissue products.  They are most commonly seen in the petrous apex.  Histologically they are characterized by the presence of large pointed crystals and giant cells.  Overtime the granulomas may enlarge, however, they generally remain silent unless they impinge on the cranial nerves.

Figure 2. There is a large cholesterol granuloma filling the mastoid cavity.  

Tympanic membrane retraction

The tympanic membrane  is thickened and atalectatic.