Last revised by Derek Smith on 19 Jun 2022

The opisthion is the median (midline) point of the posterior margin of the foramen magnum.

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

Related pathology

Various lines and measurements using the opisthion are made in the diagnosis of atlanto-occipital dissociation (AOD) injuries, platybasia and basilar invagination:

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Cases and figures

  • Figure 1: skull landmarks images
    Drag here to reorder.