The inion (plural: inia/inions)  is the tip of external occipital protuberance (EOP), the midline bony prominence in the occipital bone where the ligamentum nuchae and trapezius muscle attaches. 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
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Article information

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

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Cases and figures

  • Figure 1: skull landmark images
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  • Case 1: massive EOP
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