As of the latest update, Google Chrome and Microsoft Edge have made a breaking change to how file uploads are handled. Once your system installs this update, you will not be able to upload new images. Please use another browser until we can get it fixed.

Mastoid fontanelle

The mastoid or posterolateral fontanelles are paired bilateral soft membranous gaps (fontanelles) at the junction of the parietomastoidoccipitomastoid, and lambdoid sutures. Each mastoid fontanelle persists until the second year of life, after which it is known as the asterion. It can be used as an additional sonographic window for performing cranial ultrasound to improve the visualization of the posterior fossa.

Anatomy: Head and neck

Anatomy: Head and neck

Share article

Article information

rID: 62359
Section: Anatomy
Synonyms or Alternate Spellings:
  • Mastoid fontanelle
  • Mastoid fontanels
  • Mastoid fontanel
  • Posterolateral fontanelles
  • Posterolateral fontanels
  • Posterolateral fontanelles
  • Posterolateral fontanel

Support Radiopaedia and see fewer ads

Cases and figures

  • Figure 1
    Drag here to reorder.
  • Figure 2
    Drag here to reorder.
  • Updating… Please wait.

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

     Thank you for updating your details.