Alternative names
Sunken fontanelles; Fontanelles - sunken

Definition
Sunken fontanelles describe a concave deformity of the “soft spot” in an infant.

Considerations
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 space 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 sometime within the range of 7 - 19 months.

The fontanelles should feel firm and very slightly concave 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 should be evaluated promptly by a physician.

What to expect at your health care provider’s office
The medical history will be obtained and a physical examination performed.

Medical history questions documenting sunken fontanelles in detail may include:

 
• 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 also 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 eyes dry?  
• Is the mouth moist?

DIAGNOSTIC TESTS may include:

 
• Blood tests such as CBC, blood chemistries, and urinalysis  
• An assessment of the nutritional status

Treatment may include referral to a facility that can provide intravenous hydration (IV fluids) if the sunken fontanelle is associated with dehydration.

After seeing your health care provider:
You may want to add a diagnosis related to sunken fontanelles to your personal medical record.

Medical Encyclopedia

All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.