• Home

Home > Medical Reference > Encyclopedia (English)

Toggle: English / Spanish

Fontanelles - excessively large

• Overview

Alternative Names:

Soft spot - large

Considerations:

The skull of the newborn is made up of boney plates (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 sutures.

The bones are not joined together firmly at birth (this allows the head to pass through the birth canal). The sutures gradually harden by a process called ossification, which firmly joins the skull bones together.

In an infant, the spaces where sutures come together, but are not completely joined, is called the soft spot. It is covered by a membrane. The medical term for such spaces is fontanelle (fontanel or fonticulus). The fontanelles allow for growth of the skull during an infant's first year.

Two fontanelles are usually seen on a newborn's skull: one on the top in the middle, just forward of center; and one in the back in the middle. Like the sutures, fontanelles gradually 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, or may already be closed at birth. The anterior fontanelle (at the top of the head) usually closes sometime between 9 months and 18 months.

A wide fontanelle occurs when the fontanelle is larger than expected for the age of the baby. Slow or incomplete closure of the skull bones is most often the cause of a wide fontanelle.

Common Causes:

Delayed closure (larger-than-normal fontanelles) is most commonly caused by:

• Intrauterine growth retardation (IUGR)
• Prematurity
• Hydrocephalus
• Down syndrome
• Achondroplasia

Rarer causes:

• Hypothyroidism
• Rickets
• Osteogenesis imperfecta
• Congenital rubella (seldom seen since immunization begun with MMR -- measles, mumps, rubella -- vaccine)
• Apert syndrome
• Cleidocranial dysostosis

• Review Date: 5/10/2006
• 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.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is the first of its kind, requiring compliance with 53 standards of quality and accountability, verified by independent audit. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial process . A.D.A.M. is also a founding member of Hi-Ethics (www.hiethics.com) and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 1997-2007 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.