The inion is the most prominent projection of the occipital bone at the lower rear part of the skull. The ligamentum nuchae and trapezius muscle attach to it.

The term external occipital protuberance (protuberantia occipitalis externa) is sometimes used as a synonym, but more precisely the term "inion" refers to the highest point of the external occipital protuberance.


The word "inion" is the Greek word for the occipital bone.

Anatolian bump

An Anatolian bump is a protuberance on the back of the skull said to be related to Asian ancestry, it is an unusually large external occipital protuberance.

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