Foramen magnum

The foramen magnum is the largest foramen of the skull and is part of the occipital bone 1. It is oval in shape with a large antero-posterior diameter 2.

Gross Anatomy

The foramen magnum is found in the most inferior part of the posterior cranial fossa 3. It is traversed by vital structures including the medulla oblongata 1. In the midline, the anterior margin is the basion and the posterior marging is the opisthion.

  • anteriorly: basilar part of occipital bone
  • anterolaterally: occipital condyles, hypoglossal canal, jugular foramen
  • posteriorly: squamous part of occipital bone with the internal occipital crest

Radiographic features

  • at the level of the foramen magnum CSF is seen to surround the medulla which is reduced or absent in tonsillar herniation

Head and neck anatomy
Edit Article Share Article

Article Information

rID: 25317
Section: Anatomy
Synonyms or Alternate Spellings:
  • Drag
    Skull base inferi...
    Figure 1: inferior view
    Drag here to reorder.
  • Drag
    Skull base superi...
    Figure 2: superior view
    Drag here to reorder.
  • Updating… Please wait.


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

    Alert_accept Thank you for updating your details.