A fontanelle is a gap between the bones of an infant’s skull covered by a tough membrane, created because the skull bones have not yet fully fused. The anterior fontanelle, located at the top of the head where the frontal and parietal bones meet, is the largest and most clinically significant. It typically closes between 12 and 18 months of age. In neonatal sonography, the anterior fontanelle is the primary acoustic window used for cranial ultrasound because it allows sound waves to pass through to the brain without being blocked by bone. The posterior fontanelle and mastoid fontanelles can also be used as supplementary windows to image different regions of the brain from additional angles.
Sonography Term