Inion

Dr Daniel J Bell and Dr Craig Hacking et al.

The inion (plural: inia/inions) is the tip of the external occipital protuberance (EOP), the midline bony prominence in the occipital bone from which the ligamentum nuchae and trapezius muscle attach. It is usually easily palpable.

It is the surface marking of the internal attachment of the tentorium cerebelli.

It is one of the skull landmarks, craniometric points for radiological or anthropological skull measurement.

Anatomy: Head and neck
Share article

Article information

rID: 40397
System: Head & Neck
Section: Anatomy
Synonyms or Alternate Spellings:
  • Inions
  • Inia
  • External occipital protuberance

Support Radiopaedia and see fewer ads

Cases and figures

  • Figure 1: skull landmark images
    Drag here to reorder.
  • Case 1: massive EOP
    Drag here to reorder.
  • Updating… Please wait.

     Unable to process the form. Check for errors and try again.

     Thank you for updating your details.