Health Encyclopedia

Fontanelles - sunken

Definition

Sunken fontanelles are an obvious curving in of the "soft spot" in an infant's head.

Alternative Names

Sunken fontanelles; Soft spot - sunken

Considerations

The skull is made up of many bones. There are 7 bones in the skull itself and 14 bones in the facial area. They join together to form a solid, bony cavity that protects the brain and supports 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 get through the birth canal. The sutures gradually gain minerals and harden, firmly joining the skull bones together. This process is called ossification.

In an infant, the space where two sutures join forms a membrane-covered "soft spot" called a fontanelle (fontanel). The fontanelles allow for the skull to grow 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 ossify 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 or 2 months old. The fontanelle at the top of the head (anterior fontanelle) usually closes within 7 - 19 months.

The fontanelles should feel firm and should curve inward slightly to the touch. A noticeably sunken fontanelle is a sign that the infant does not have enough fluid in his or her body.

Common Causes

Dehydration
Malnutrition
Normal variant

Call your health care provider if

A sunken fontanelle CAN BE A MEDICAL EMERGENCY and a health care provider should check it right away.

What to expect at your health care provider's office

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

When did you first notice that the fontanelle looked sunken?
How severe is it? How would you describe it?
Which "soft spots" are affected?
What other symptoms are present?
Has the baby been ill, especially with vomiting, diarrhea, or excessive sweating?
Is the skin turgor poor?
Is the baby thirsty?
Is the baby alert?
Are the baby's eyes dry?
Is the baby's mouth moist?

Tests may include:

Blood chemistries
CBC
Urinalysis
Tests to check the baby's nutritional status

You might be referred to a place that can provide intravenous (IV) fluids if the sunken fontanelle is caused by dehydration.

Review Date:8/15/2007
Reviewed By:Rachel A. Lewis, MD, FAAP, Columbia University Pediatric Faculty Practice, New York, NY. Review provided by VeriMed Healthcare Network.

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