Chro

67

CHAPTER 20 Chronic Otitis Media

Ellen G. Hoeffner

Epidemiology

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Figure 20–1 Axial computed tomography (CT) of the temporal bones was obtained in a patient with long-standing chronic otitis media. There is mucosal thickening involving both middle ear cavities that is associated with poorly pneumatized and sclerotic mastoid air cells. The sclerosis is likely due to a reactive hyperostosis due to the chronic infl ammation.

Imaging Findings

CT

Dependent middle ear opacifi cation in two perpendicular planes is characteristic of middle ear effu- sion, although the characteristics of the fl uid (serous, mucous, purulent) cannot be distinguished. Gran- ulation tissue appears as a nondependent middle ear soft tissue opacity with no ossicular displacement or bone erosion. Granulation tissue can also cause nonspecifi c mastoid opacifi cation. A middle ear cholesterol granuloma can be a complication of COM and is thought to result from eustachian tube dys- function with secondary mucosal edema and blood vessel rupture. With only middle ear involvement, cholesterol granulomas are generally not associated with bone destruction or erosion and appear on computed tomography (CT) as a nondependent middle ear opacity.

Tympanic membrane abnormalities associated with COM include thickening, calcifi cation, and re- tractions. Retractions are easily visible on CT and may involve the pars fl accida or pars tensa. Pars fl ac- cida retractions may lead to the development of an acquired cholesteatoma, which is discussed in a separate chapter.

Ossicular erosions can occur with COM in the absence of a cholesteatoma, most likely related to the action of osteoclasts and histiocytes. The most commonly affected areas are the long and lenticular processes of the incus followed by the crura of the stapes, and manubrium of the malleus. Less fre- quently erosions involve the malleus head and incus body. Widening of the incudo stapedial joint in the setting of COM is suspicious for erosion in this region with replacement by fi brous tissue. All of these changes can result in a conductive hearing defi cit (CHD).

Ossicular fi xation as a consequence of COM can also cause a CHD. Such fi xation is the result of the healing process as granulation tissue regresses and fi broblastic invasion of the submucosa develops and adhesions form. This process may take three forms: fi brous tissue fi xation, hyalinization of col- lagen, and fi bro-osseous sclerosis. Deposition of fi brous tissue may be focal or generalized and appears as nondependent soft tissue opacifi cation. A common site of involvement is the anterior superior oval window (peristapedial) with stapes fi xation. Involvement of the Prussak space results in fi xation of the malleus head and neck and can mimic an early cholesteatoma. Involvement of the round window with release of toxins may lead to sensorineural hearing loss (SNHL). Hyalinization of collagen in the middle ear results in tympanosclerosis and is evident on CT as punctate or weblike calcifi cations in the tym- panic cavity, along the tympanic membrane or on ligaments and tendons of the ossicles. Finally fi bro- osseous sclerosis results in new bone formation, most commonly in the epitympanum. This appears on CT as a dense bone mass often encasing the ossicles ( Fig. 20–1 , Fig. 20–2 , and Fig. 20–3 ).

20 CHRONIC OTITIS MEDIA 69

MRI

Magnetic resonance imaging (MRI), although not helpful in assessing the osseous structures of the middle ear, may be helpful in determining the etiology of soft tissue opacifi cation seen on CT. Middle ear effusions have typical fl uid signal on T1- and T2-weighted images with no enhancement. Granula- tion tissue may have a similar appearance on T1- and T2-weighted MRI, but usually enhances intensely.

A cholesteatoma, however, does not enhance, and, if recurrent, may have high signal on diffusion weighted images. Finally, a cholesterol granuloma of the middle ear is hyperintense on T1- and T2- weighted images.

Intracranial complications can develop with COM, similar to those discussed in the chapter on acute otomastoiditis, and are generally best assessed with MRI.

PE ARL S

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Middle ear effusions or nonspecifi c opacifi cation are common fi ndings with COM. Nondependent opacifi cation may be secondary to granulation tissue, cholesterol granuloma, cholesteatoma, or fi - brous tissue.

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Ossicular erosions can result from COM in the absence of cholesteatoma formation.

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Ossicular fi xation may appear as a soft tissue, calcifi c or osseous mass in the middle ear.

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Figure 20–2 Axial CT obtained through the left temporal bone performed in a patient with chronic otitis media shows mucosal thickening surrounding the long process of the incus.

The long-standing chronic infl ammatory process has resulted in reactive sclerosis of the long process of the incus ( straight arrow ). Note the normal attenuation of the manubrium of the malleus ( curved arrow ). In addition, there is diffuse sclerosis of poorly pneumatized mastoid air cells.

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Figure 20–3 Coronal CT performed in a patient with chronic otitis media shows diffuse mucosal thickening, which has scalloped and remodeled that mastoid air cells ( small arrows ).

Note the adjacent sclerosis of the surrounding bone ( large ar- rows ), which is due to the long-standing chronic process. In this case, the fi ndings were due to coalescent mastoiditis but similar fi ndings may also be seen with cholesteatoma.

70 III MIDDLE EAR AND MASTOID

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MRI may be helpful in differentiating the cause of nondependent middle ear opacifi cation seen on CT.

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Intracranial complications are better assessed with MRI.

Suggested Readings

Brook I . Microbiology and management of chronic suppurative otitis media in children. J Trop Pediatr 2003 ; 49 : 196 – 199

Canalis RF , Lambert PR . Chronic otitis media and cholesteatoma. In: Canalis RF, Lambert PR, eds. The Ear: Comprehensive Otology. Philadelphia: Lippincott Williams & Wilkins, 2000 : 409 – 431

Gates GA . Otitis media with effusion. In: Hughes GB, Pensak ML, eds. Clinical Otology, 2nd ed. New York: Thieme, 1997 : 205 – 214

Maheshwari S , Mukherji SK . Diffusion-weighted imaging for differentiating recurrent cholesteatoma from granulation tissue after mastoidectomy: case report. AJNR Am J Neuroradiol 2002 ; 23 : 847 – 849

Maroldi R , Farina D , Palvarini A , et al . Computed tomography and magnetic resonance imaging of pathologic conditions of the middle ear. Eur J Radiol 2001 ; 40 : 78 – 93

Nemzek WR , Swartz JD . Temporal bone: infl ammatory disease. In: Som PM, Curtin HD, eds. Head and Neck Imaging, 4th ed. St. Louis: Mosby, 2003 : 1173 – 1229

Swartz JD , Harnsberger HR . The middle ear and mastoid. Imaging of the Temporal Bone, 3rd ed. New York: Thieme, 1998 : 47 – 169

71

CHAPTER 21 Acquired Cholesteatoma

Ellen G. Hoeffner

Epidemiology

Most acquired cholesteatomas result from complications of chronic middle ear infections. Loss of col- lagen fi bers and structural support of the tympanic membrane along with negative middle ear pressure results in a retraction pocket lined with squamous epithelium. Continued negative middle ear pressure and accumulation of epithelial cells, keratin, and cellular decay expand the pocket. Bone destruction of the tympanum and ossicles ensues secondary to direct pressure from the expanding cholesteatoma, biochemical factors related to chronic infl ammation and the cholesteatoma itself, and osteoclastic activity. Most cholesteatomas involve the weaker pars fl accida with less common involvement of the pars tensa.

Other potential etiologies of cholesteatoma formation include epithelial invasion through a tympanic membrane perforation, squamous metaplasia of middle ear epithelium, and basal cell hyperplasia.

Clinical Features

Otorrhea and a conductive hearing loss are the most common complaints associated with a choles- teatoma. Patients often have a history of multiple earaches in childhood followed by chronic ear prob- lems. Physical exam demonstrates retraction of the eardrum, often with a perforation, and surrounding bony erosion. Patients with ossicular erosion typically present with a 30- to 60-dB conductive hearing loss. On otoscopic examination, the characteristic clinical fi nding is the presence of a “pearly white mass” behind the tympanic membrane. However, the tympanic membrane often becomes scarred and retracted in chronic infl ammation and the otologist may not be able to accurately assess the middle ear cavity.

Pathology

Cholesteatomas are lined by stratifi ed squamous epithelium and contain desquamated keratin and purulent material.

Treatment

Surgical excision or exteriorization is the treatment of choice. In patients who cannot tolerate surgery, disease can be controlled with repeated cleansing under a surgical microscope.

Imaging Findings

CT

Computed tomography (CT) is the preferred modality when imaging cholesteatomas, as the defi ning feature is bone destruction. Cholesteatomas typically present as a nondependent middle ear soft tissue mass in a characteristic location associated with bone and ossicular erosion.

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