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Cholesterol Granuloma

Summary

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  • Cholesterol granuloma is a benign, expansile cystic lesion containing cholesterol crystals, haemosiderin, and fibrous tissue
  • Typically occurs in the temporal bone, particularly the petrous apex
  • Imaging shows a well-defined, expansile lesion with characteristic MRI signal intensities1

Pathophysiology

  • Believed to result from a foreign body reaction to cholesterol crystals
  • Proposed mechanisms:
    • Obstruction of pneumatised air cells leading to haemorrhage and inflammation
    • Chronic haemorrhage into a confined space (e.g., mucosal retention cyst)
  • Cholesterol crystals form from degraded blood products
  • Surrounding granulation tissue develops, leading to expansion and bone remodelling

Demographics

  • Can occur at any age, but most common in adults
  • Slight male predominance (male:female ratio approximately 1.5:1)
  • No known racial predilection

Diagnosis

  • Often asymptomatic and discovered incidentally
  • When symptomatic, presentation depends on location:
    • Petrous apex: hearing loss, tinnitus, vertigo, facial nerve palsy
    • Orbit: proptosis, diplopia, visual disturbances
    • Paranasal sinuses: nasal obstruction, facial pain
  • Differential diagnosis includes:
    • Cholesteatoma
    • Mucocele
    • Arachnoid cyst
    • Epidermoid cyst

Imaging

  • CT findings:
    • Well-defined, expansile lesion with smooth margins
    • Bone remodelling without destruction
    • Variable density, often isodense to brain
    • May show fluid-fluid levels
  • MRI findings :
    • T1-weighted: Hyperintense due to protein content and methaemoglobin
    • T2-weighted: Heterogeneous, often hyperintense
    • Gradient echo: Susceptibility artefact due to haemosiderin
    • Post-contrast: Thin peripheral enhancement
  • Characteristic "motor oil" appearance on MRI due to T1 hyperintensity and T2 heterogeneity

panels-1

  • A 50-year-old patient presented with a headache.
  • CT showed a well-marginated lesion in the left petrous apex.
  • T1-hyperintensity within the lesion was consistent with a cholesterol granuloma.
  • Following enlargement and worsening headaches, the lesion was drained (not shown).

Treatment

  • Asymptomatic lesions are observed; symptomatic lesions are surgically drained/marsupialised

Differential diagnosis

Differential Diagnosis Differentiating Feature
Cholesteatoma (petrous apex) T1 hypo/intermediate with restricted diffusion, unlike the T1-hyperintense cholesterol granuloma
Acoustic neuroma Enhancing IAC/CPA mass rather than a T1-bright expansile petrous apex lesion
Meningioma Usually enhances strongly with contrast on MRI
Arachnoid cyst Follows CSF signal on all MRI sequences
Epidermoid cyst Restricted diffusion on DWI
Mucocele Lacks T1 hyperintensity characteristic of cholesterol granuloma
Petrous apex effusion Lacks expansile nature and chronic symptoms
Metastasis Often multiple lesions; bone destruction with irregular margins

  1. Hoa et al. Petrous apex cholesterol granuloma: pictorial review of radiological considerations in diagnosis and surgical histopathology. 2013. The Journal of laryngology and otology - Open in new tab. ↩