Fontanelles - bulging

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Bulging fontanelles

Skull of a newborn

A bulging fontanelle is an outward curving of an infant's soft spot (fontanelle).

Soft spot - bulging; Bulging fontanelles

The skull is made up of many bones, 7 in the skull itself and 14 in the facial area. They join together to form a solid, bony cavity protecting the brain and supporting the structures of the head. The areas where the bones join together are called the sutures.

The bones are not joined together firmly at birth. This allows the head to accommodate passage through the birth canal. The sutures gradually accumulate minerals and harden, firmly joining the skull bones together. This process is called ossification.

In an infant, the spaces where two sutures intersect form a membrane-covered "soft spot" called a fontanelle (fontanel). The fontanelles allow for growth of the skull during an infant's first year.

There are several fontanelles that are normally present on a newborn's skull, primarily at the top, back, and sides of the head. Like the sutures, fontanelles gradually ossify and become closed, solid bony areas. The posterior fontanelle (in the back of the head) usually closes by the time an infant is 1 or 2 months old. The anterior fontanelle at the top of the head usually closes within the range of 7 - 19 months.

The fontanelles should feel firm and very slightly concave (curved inward) to the touch. A tense or bulging fontanelle occurs when fluid accumulates in the skull cavity or when pressure increases in the brain (increased intracranial pressure).

When the infant is crying, lying down, or vomiting, the fontanelles may look like they are bulging, but they should return to normal when the infant is in a calm, head-up position.

• Hydrocephalus
• Increased intracranial pressure (associated with meningitis and other disorders)

Review Date: 10/27/2005
Reviewed By: Daniel Rauch, MD, FAAP, Director, Pediatric Hospitalist Program, Associate Professor of Pediatrics, NYU School of Medicine, New York, NY. Review provided by VeriMed Healthcare Network.