Cholesteatoma - external auditory canal

Case contributed by Dr Eid Kakish

Presentation

Otorrhea and conductive hearing loss. No reported history of trauma or intervention.

Patient Data

Age: 45 years
Gender: Female

There is a rather large mass of soft tissue attenuation centered within the bony portion of the left external auditory canal, resulting in significant canal expansion and marked circumferential canal wall erosion with multiple small predominantly peripheral bony fragments.

Thinning and destructive changes of the tympanic and mastoid parts of the left temporal bone are noted, with a small amount of retained fluid within the left mastoid air cells

The mass erodes the left scutum, extending into the left middle ear cleft, encasing and slightly eroding the left middle ear ossicular chain, obliterating the left Prussak space, aditus ad antrum and mastoid antrum.

Complete obliteration of the facial recess with thinning and erosion of the posterior genu and tympanic segment of the left facial nerve canal, suggestive of facial nerve involvement. 

Case Discussion

Cholesteatomas are most commonly found in the middle ear. However, they can also be encountered in the external auditory canal (EAC), but are far less common.

External auditory canal cholesteatomas (EACC) appear as soft tissue masses within the external auditory canal, associated with erosive changes to the adjacent bony canal walls. Intralesional bony fragments are frequently seen. 

EACC can extend into the middle ear cavity, with resultant erosion of the middle ear ossicles. The facial nerve canal, mastoid air cells and tegmen tympani can also be affected by extension. Assessing for involvement of these structures is important, as this may affect management. 

One of the main differential diagnoses for EACC is keratosis obturans. The latter, however, is not associated with bony changes. 

Other differential considerations include malignant otitis externa, postinflammatory medial canal fibrosis and other neoplasms of the EAC.

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