Considerations

The skull is made up of many bones, seven in the skull itself and 14 in the face area. They join together to form a solid, bony cavity that protects and supports the brain. 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 change shape to help it pass through the birth canal. The sutures get minerals added to them over time and harden, firmly joining the skull bones together.

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

There are normally several fontanelles on a newborn's skull, mainly at the top, back, and sides of the head. Like the sutures, fontanelles harden over time and become closed, solid bony areas.

• The fontanelle in the back of the head (posterior fontanelle) usually closes by the time an infant is 1 - 2 months old.
• The fontanelle at the top of the head (anterior fontanelle) usually closes between 7 - 19 months.

The fontanelles should feel firm and very slightly curved inward to the touch. A tense or bulging fontanelle occurs when fluid builds up in the brain or the brain swells, causing increased pressure inside the skull.

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.

Causes

• Encephalitis -- swelling (inflammation) of the brain, most often due to infections
• Hydrocephalus -- a buildup of fluid inside the skull
• Increased intracranial pressure
• Meningitis -- infection of the membranes covering the brain

Home Care

If the fontanelle returns to normal appearance when the child is calm and head-up, it is not a truly bulging fontanelle.

When to Contact a Medical Professional

Immediate, emergency care is needed for any infant who has a truly bulging fontanelle, especially if it occurs along with fever or excess drowsiness.

What to Expect at Your Office Visit

The health care provider will perform a physical examination and ask questions about the child's medical history, such as:

• Does the "soft spot" return to normal appearance when the infant is calm or head-up?
• Does it bulge all the time or does it come and go?
• When did you first notice this?
• Which fontanelles bulge (top of the head, back of the head, or other)?
• Are all the fontanelles bulging?
• What other symptoms are present (such as fever, irritability, lethargy)?

Diagnostic tests that may be done are:

• CT scan of the head
• MRI scan of the head
• Spinal tap (lumbar puncture)

Alternative Names

Soft spot - bulging; Bulging fontanelles

References

Kinsman Sl, Johnston MV. Congenital anomalies of the central nervous system. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 592.

Update Date: 1/24/2012

Reviewed by: Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.