Petrous apex mucocele

Last revised by Henry Knipe on 2 Aug 2021

Petrous apex mucoceles are a rare complication that can occur in patients who have a pneumatized petrous apex. The pathology is similar to mucocele formation elsewhere in other sinuses in that these air cells become obstructed causing mucous secretions to accumulate. The trapped secretions cause bony expansion of the structure that it’s located in.

An expanding mucocele can lead to the patient developing pain or ipsilateral cranial neuropathy 1. However, these are non-specific and can be experienced in many lesions of the petrous apex.

Smooth expansile lesion of the petrous apex with loss of the normal bony septations.

  • T1: low to intermediate signal
  • T2: high signal
  • T1+ Gd: no central enhancement; may have peripheral enhancement; favored to be due to adjacent secondary inflammatory response 1
  • DWI/ADC: no abnormal diffusion restriction

The management can vary; serial imaging to assess for change or surgical drainage can be performed 2.

The principal differential is a cholesterol granuloma, which can appear similar on CT, however, MRI is the main imaging modality in differentiating the two apart.  A mucocele is low/intermediate on T1 imaging and a cholesterol granuloma is hyperintense on T1.

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