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Topic

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Petrous part of temporal bone

The petrous part of the temporal bone is a dense, pyramid-shaped portion of the temporal bone located at the base of the skull, wedged between the sphenoid and occipital bones. It houses critical structures such as the inner ear (cochlea and vestibular apparatus) and the internal auditory canal, and provides passage for the facial and vestibulocochlear nerves. Its unique anatomy makes it highly significant in neuroimaging and skull base pathology.

Synonyms

  • Petrous temporal bone

  • Petrous pyramid

  • Pars petrosa ossis temporalis

  • Petrosal part of temporal bone

MRI Appearance

  • Proton Density (PD) Sequence

    • The petrous part of the temporal bone appears as a homogeneously hypointense (dark) structure due to its high mineral (osseous) content and lack of mobile protons.

    • The internal auditory canal and cochlea may be seen as small areas of relative hyperintensity due to fluid content.

  • Short Tau Inversion Recovery (STIR) Sequence

    • The bone itself remains hypointense (very dark), as STIR is used to suppress fat and highlight fluid or edema.

    • Any marrow pathology (e.g., edema, tumor) within the petrous apex may appear as hyperintense (bright) signal, contrasting sharply with the normal dark bone.

  • T1-Weighted Sequence

    • The petrous bone is very hypointense (black) due to the dense cortical bone and minimal fat within the medullary cavity.

    • The internal auditory canal and adjacent CSF spaces are hyperintense (bright) relative to the bone.

MRI images

Petrous part of temporal bone