Cholesteatoma

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Diagnosis Definition

A Cholesteatoma is a central collection of desquamated keratinized cells bound by a thin layer of squamous epithelial cells
Generally an acquired lesion in the setting of chronic otitis media and uncommonly a congenital lesion
Most common site is the lateral epitympanum (Prussak space is a sub-site), associated with the pars flaccida of the tympanic membrane
Locally destructive lesion that erodes bone/ossicles, presenting with conductive hearing loss and ear drainage

Imaging Findings

The findings of a cholesteatomas on CT is most typically soft tissue in the lateral epitympanic space (which includes Prussak space)
On T2-weighted MR images, Cholesteatomas are hyperintense
On T1 pre-contrast images, cholesteatomas are typically hypointense; which helps to distinguish them from cholesterol granulomas
T1 post-contrast images may show a thin rim of enhancement, however, no central enhancement should be seen
DWI images, key for identification, show central restricted diffusion; nonecho planar diffusion-weighted imaging (such as HASTE) has improved sensitivity over conventional DWI because of proximity to air in mastoid/middle ear

Pearls

Differential considerations include cholesterol granuloma (T1 bright and will not restrict diffusion), paraganglioma, and vascular malformation (will enhance)
Look for bone destruction on temporal bone CT and restriction on HASTE diffusion
Can also occur in the mastoid air cells and petrous apex

References

De Foer B, Vercruysse JP, Bernaerts A, Meersschaert J, Kenis C, Pouillon M, De Beuckeleer L, Michiels J, Bogaerts K, Deckers F, Somers T. Middle ear cholesteatoma: non–echo-planar diffusion-weighted MR imaging versus delayed gadolinium-enhanced T1-weighted MR imaging—value in detection. Radiology 2010 255(3):866-72
Chapman PR, Shah R, Curé JK, Bag AK. Petrous apex lesions: pictorial review. American Journal of Roentgenology 2011 196(3_supplement):WS26-37

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