Fontanelles - excessively large
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 area 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 (this process is called ossification), firmly joining the skull bones together.
In an infant, the spaces where sutures intersect but don't completely touch is called the "soft spot", a membrane coverd area also called a fontanelle (fontanel or fonticulus). The fontanelles allow for growth of the skull during an infant's first year.
There are typically two fontanelles that are normally evident on a newborn's skull, primarily at the top in the midline just forward of center and in the back in the midline.. 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 between 9 months and 2 years old.
A wide fontanelle occurs when the fontanelle is larger in size than expected for the age of the baby. Slow or incomplete ossification of the skull bones is most often the cause of a wide fontanelle.
Common causes:
The more common causes:
The rarer causes:
- hypothyroidism
- rickets
- osteogenesis imperfecta
- congenital rubella (seldom seen since immunization begun with MMR vaccine--measles, mumps and rubella)
- Apert syndrome
- Cleidocranial dysostosis
Note: There may be other causes of large fontanelles. This list is not all inclusive, and the causes are not presented in order of likelihood. The causes of this symptom can include unlikely diseases and medications. Furthermore, the causes may vary based on age and gender of the affected person, as well as on the specific characteristics of the symptom such as location, quality, time course, and associated complaints. Use the Symptom Analysis option to explore the possible explanations for an excessively large fontanelle, occurring alone or in combination with other problems.
Update Date: 02/09/00
Updated by: J. Gordon Lambert, MD, Associate Medical Director,
Utah Health Informatics and adam.com
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