Bilateral Cholesterol Granulomas

Findings:

Axial T1 weighted MR images without contrast demonstrate ovoid expansile hyperintense lesions within the bilateral petrous apices. A postoperative nasal septal defect is present and there is heterogeneous signal abnormality of the clivus with zones of soft tissue thickening due to postoperative change. The left sided expansile lesion encroaches on the internal auditory canal. The right internal auditory canal is normal.

Discussion/Differential Diagnosis:

With this case, it would be easy for the uninitiated to think that these are bilateral enhancing CP angle masses in association with the IAC and therefore representing schwannomas in the setting of NF2. However, there is no contrast administered based on an absence of enhancement of normal structures like the nasal mucosa. The pathophysiology is similar to mucocele, with obstruction of an air cell and accumulation of material causing expansion and pressure erosion. Additional case and discussion:            -Cholesterol Cyst

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