Skull Base Cholesterol Granuloma: A Distinct Entity?

Objective: Cholesterol granulomas (CG) are the most common benign lesions of the petrous apex (PA) and have very distinct computed tomography (CT) and magnetic resonance imaging (MRI) characteristics. On CT, CGs of the PA (PACG) present as expansile lesions with erosion of bony trabeculae. On MRI, these lesions are hyperintense on T1- and T2-weighted images and do not enhance with gadolinium. The objective of this study is to describe the radiographic features of CGs of the skull base that do not arise from the PA.

Methods: Retrospective review of the clinical presentation, radiographic features, and pathology results in three patients with skull base CG not originating in the PA.

Results: Three patients were operated on for suspected recurrent endolymphatic sac tumor, intracranial cholesteatoma, and recurrent sphenoid wing meningioma based on CT and MRI findings. Pathology results were consistent with CG in all the three cases. All patients had bone erosion on CT. These skull base CGs did not demonstrate similar MRI features. These lesions were hyperintense, iso- to hyperintense, and hypointense on T1-weighted MRI, respectively. These CGs were hyperintense in two cases and iso- to hyperintense in one case on T2-weighted MRI. In addition, these lesions either demonstrated central or rim enhancement after gadolinium administration.

Conclusion: Skull base CGs that do not arise from the PA demonstrate a broad spectrum of radiographic characteristics on MRI that are not typical of PACG. Skull base CGs not originating from the PA may represent different pathophysiologic entities from PACGs.

Keywords

cholesterol granuloma - petrous apex - skull base - MRI - CT