From the Research
Cholesterol granulomas on MRI typically appear as well-defined, expansile lesions with high signal intensity on both T1 and T2 sequences, as demonstrated in a recent case report of a giant cholesterol granuloma of the petrous apex 1.
Key MRI Findings
- High signal intensity on T1-weighted images due to high protein and methemoglobin content
- High signal intensity on T2-weighted images, reflecting fluid components
- Lack of significant enhancement following gadolinium contrast administration, with only peripheral rim enhancement sometimes observed
- No restricted diffusion on diffusion-weighted imaging
- Often demonstrates a fluid-fluid level due to layering of different blood degradation products
Clinical Context
Cholesterol granulomas most commonly occur in the petrous apex of the temporal bone but can also be found in the middle ear, mastoid, or paranasal sinuses. The characteristic MRI appearance reflects the underlying pathology of these lesions, which contain cholesterol crystals, hemosiderin, granulation tissue, and inflammatory cells resulting from chronic hemorrhage and impaired drainage. A recent study highlighted the importance of MRI in diagnosing and managing cholesterol granulomas, particularly in distinguishing them from other lesions such as epidermoid cysts, acoustic neuromas, or meningiomas 1.
Diagnostic Considerations
While other studies have reported variable MRI findings for cholesterol granulomas, such as different signal intensities on T1 and T2 sequences 2, 3, the most recent and highest quality study suggests that high signal intensity on both T1 and T2 sequences is a characteristic feature of these lesions 1. Additionally, the use of T1-weighted dynamic contrast-enhanced MRI (DCE-MRI) has been shown to be useful in distinguishing cholesterol granulomas from other lesions, such as invasive ductal carcinoma of the breast 4. However, in the context of petrous apex lesions, the MRI findings described in the recent case report 1 are the most relevant and reliable.