A cholesteatoma is histologically equivalent to a epidermoid cyst and is composed of desquamated keratinized squamous epithelium forming a mass.
The mass is lined by epithelium (facing inwards) which continues to grow, thereby shedding additional cells into the mass. Their high cholesterol content is responsible for their name, although 'keratoma' is probably a more apt term.
Cholesteatomas of the temporal bone and middle ear are divided into two main types:
- congenital cholesteatoma : accounting for only 2%
acquired cholesteatoma : 98%
- primary (no history of chronic otomastoiditis)
- secondary (vast majority)
Occasionally they can arise in relation to the external ear : see : external ear canal cholesteatoma
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.
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 1000s/mm2 a cholesteatoma becomes apparent as a hyperintense area. The signal intensity should be higher than visible on the DWI images with b-value 0s/mm2. On the ADC-map a low signal should be visible in the same area, confirming the presence of diffusion-restriction.
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.
- cholesterol granuloma
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
- 1. Swartz JD, Loevner LA. Imaging of the Temporal Bone. Thieme Medical Pub. (2008) ISBN:1588903451. Read it at Google Books - Find it at Amazon
- 2. Dubrulle F, Souillard R, Chechin D et-al. Diffusion-weighted MR imaging sequence in the detection of postoperative recurrent cholesteatoma. Radiology. 2006;238 (2): 604-10. doi:10.1148/radiol.2381041649 - Pubmed citation
- De foer B, Vercruysse JP, Bernaerts A et-al. 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. doi:10.1148/radiol.10091140 - Pubmed citation
Synonyms & Alternative Spellings
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