Visualization and evaluation of the tympanic membrane is best performed with otoscopy. However, some findings which are typical for chronic inflammation, are well visible with CT and they usually inform the radiologist of some more profound changes within the middle ear and mastoid.

Tympanic membrane thickening and/or perforation is pathognomonic for chronic inflammation. It is evaluated with otoscopic imaging; on CT thickened membrane is visible as grey line of soft tissue density (Fig. 3).

Tympanic membrane retraction is the condition, when a part of the tympanic membrane is pulled inwards within the middle ear, usually due to negative pressure in the middle ear. It is also best evaluated with otoscopy. If the retraction is profound, it may become adherent to the stapes head (Fig. 4) (Mafee et al. 1986).

The term Myringosclerosis stands for the formation of the hyalinized collagen in the tympanic membrane. In most cases changes are clinically significant and cause little or no hearing loss. On CT myringosclerosis is visible as thickened and calcified (Fig. 5) tympanic membrane (Lemmerling et al. 2009).

Post-inflammatory ossicular chain fixation (PIOF) is a common problem in patients with COM and in many cases it results with conductive hearing loss. It usually takes three pathologic forms (Swartz et al. 1985, Lemmerling et al. 2008, 2009):

Fibrous tissue fixation appears on CT as noncalcified, soft-tissue debris encasing some or all of the ossicular chain. It is usually present in the niche of oval window, forming so called “peristapedial tent” (Fig. 6), but may also be present anywhere in meso- and epitympanum. On CT it is usually presented as a subtle mass of soft tissue density. Therefore, diagnosis of fibrous tissue fixation based on sole CT appearance should not be made, since fixation cannot be determined by imaging and the density of the mass is similar to other middle ear substances, like fluid and cholesteatoma. Diagnosis of fibrous tissue fixation can be suggested, if a soft tissue mass is seen in the setting of COM, in patient with dry ear and conductive hearing loss (Swartz et al. 1985).

Tympanosclerosis reflects deposits of hyalinized collagen in the tympanic cavity. It appears as unifocal or multifocal punctate or weblike calcifications in the middle ear cavity (Fig. 7) or on the tympanic membrane (myringosclerosis). In the tympanic cavity, it may be present in any location, visible as focal calcified densities in the middle ear cavity, along tendons, also in direct apposition to the ossicular chain. If the debris is not in a position to compromise the ossicular chain function, conductive hearing loss will not take place. On CT changes may be subtle—increased thickening of stapedial crura—or more profound (Swartz et al. 1985; Lemmerling et al. 2009). Since calcification of tendons and ligaments is a characteristic for tympanosclerosis, knowledge of normal anatomy and anatomical variants is mandatory in order to evaluate the exact location and extent of the disease. Normal eminences, prominent bone ridges, and tendons should not be mistaken for pathological changes (Lemmerling et al. 1997; Petrus 1997).

New bone formation has been identified mostly in the epitympanum and is the least common manifestation of PIOF. It is visible as lamellar structures of high density (Fig. 8), thick bony webs, or generalized bony encasement (Lemmerling et al. 2008).

In general, CT of the temporal bone plays an important role in the evaluation of the extent of PIOF. It also enables differential diagnosis which includes other causes of conductive hearing loss, like otosclerosis, ossicular chain erosion, post-traumatic changes, developmental abnormalities. In case of suspected cholesteatoma MRI is the modality of choice (De Foer et al. 2007; Lemmerling et al. 2009).

Post-inflammatory ossicular chain erosion is not very frequent in case of a non-cholesteatomatous disease, but does occur, and will affect first the incus long process and lenticular process, followed by stapes head.