Cholesteatoma
Updates to Article Attributes
Cholesteatoma is histologically equivalent to a epidermoid cyst and is composed of desquamated keratinizing stratified squamous epithelium forming a mass. They usually present with conductive hearing loss.
Pathology
The mass is lined by epithelium (facing inwards) which continues to grow, thereby shedding additional cells into the mass. Their cholesterol content (which is not always present) is responsible for their name, although 'keratoma' is probably a more apt term.
Cholesteatomas of the temporal bone and middle ear are divided into:
- congenital cholesteatoma: accounting for only 2%
-
acquired cholesteatoma: 98%
- primary (no history of chronic otomastoiditis)
- secondary (vast majority):
- pars flaccida
- pars tensa
- external ear canal cholesteatoma
- mural cholesteatoma
Radiographic features
MRI
Conventional non-contrast MR imaging with diffusion-weighted imaging is recommended in all patients with a suspicion of cholesteatoma. Especially in patients with previous surgery for cholesteatoma an MRI should be performed since recurrence or residual tumour can be detected with great accuracy. If negative it can avoid a "second look" surgery. It's important to prepare the patient before the examination (clear the external auditory canal or the postoperative cavity) to avoid false positive diagnosis.
Standard examination is a T2 weighted series in the coronal and axial plane, followed by a non-EP DWI series (b-values 0, 1000). On the DWI images with b-value 1000 s/mm2 a cholesteatoma becomes apparent as a hyperintense area. The signal intensity should be higher than visible on the DWI images with b-value 0 s/mm2. On the ADC-map a low signal should be visible in the same area, confirming the presence of diffusion restriction.
CT
CT-scan should be added in those cases where a cholesteatoma is detected with MRI. CT is needed for preoperative planning (reconstruction of ossicles if needed) and to exclude perforation of the bony tegmen.
Pars flaccida cholesteatoma starts in Prussak's space and usually extends posteriorly.
Pars tensa cholesteatoma starts in posterior mesotympanum and usually extends posteromedially.
Differential diagnosis
- cholesterol granuloma
- inflammation
In contrast with cholesteatoma these show high signal on the ADC map. With these findings recurrent cholesteatoma can be detected with 100% specificity. Cholesteatomas up to a size of 2 mm can be detected with this technique on a 1.5T machine.
Further differential diagnosis is to be made with:
- cerumen: which shows similar image characteristics to cholesteatoma but is located in the external ear
- abscess formation in the middle ear: can also show similar imaging findings but has a completely different clinical appearance
Practical points
Important CT features to comment on when reporting a cholesteatoma:
- erosions of the
- dehiscense of the
- integrity of the
- epitympanum
- aditus ad antrum and mastoid antrum
- oval and round window
- presence of cholesteatoma in sinus tympani (which is the most hidden recess of the middle ear) - to avoid residual disease
-<li><a href="/articles/tegment-tympani">tegment tympani</a></li>- +<li><a href="/articles/tegment-tympani">tegmen tympani</a></li>
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