Mastoid fontanelle

Last revised by Assoc Prof Craig Hacking on 17 May 2020

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.

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Cases and figures

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