Cholesterol granuloma

Cholesterol granulomas can occur in any obstructed air cells. They often arise from the apex of the petrous bone and may enlarge enough to expand in the posterior cranial fossa and produce nerve disturbances.

• Mucocele
• Dermoid/Epidermoid

The imaging findings are

• At CT, cholesterol granulomas appear as sharply and smoothly marginated expansile lesions in the temporal bone, isoattenuating with brain tissue and nonenhancing.
• At MR imaging, they characteristically have a large central region of increased signal intensity and a thin peripheral rim of decreased signal intensity on both T1- and T2-weighted images. The latter finding corresponds to expanded cortical bone and hemosiderin deposits.
• Spontaneous and homogeneous central high signal intensity on T1-weighted images is very suggestive of a cholesterol granuloma.

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