Fontanelle: Meaning, Development and Clinical Relevance
The fontanelle is a soft, not yet ossified spot on the skull of newborns and infants. It allows for childbirth and supports brain growth during early development.
Things worth knowing about "Fontanelle"
The fontanelle is a soft, not yet ossified spot on the skull of newborns and infants. It allows for childbirth and supports brain growth during early development.
What Is the Fontanelle?
The fontanelle (also spelled fontanel) refers to the soft, membranous gaps between the incompletely fused skull bones in newborns and infants. Because the brain grows rapidly during the first months and years of life, these flexible areas of the skull allow for sufficient expansion. The fontanelles also play an important role during childbirth by allowing the skull bones to slightly overlap, making it easier for the baby's head to pass through the birth canal.
Types of Fontanelles
Newborns have several fontanelles, but two are of particular clinical importance:
- Anterior (front) fontanelle: Located at the top of the head at the junction of the frontal and parietal bones. It is diamond-shaped and approximately 2–3 cm in size in newborns. It typically closes between 9 and 18 months of age, and no later than 24 months.
- Posterior (back) fontanelle: Located at the back of the skull, between the parietal and occipital bones. It is considerably smaller and usually closes within the first few weeks to 3 months of life.
Clinical Significance and Examination
The fontanelle serves as an important diagnostic window for pediatricians. During routine check-ups, it is regularly palpated and assessed. Key features evaluated include:
- Tension: At rest, the fontanelle should feel slightly sunken or flat. A tense, bulging fontanelle may indicate raised intracranial pressure.
- Sunken appearance: A markedly sunken fontanelle is a warning sign for dehydration, for example in cases of severe diarrhea.
- Size and closure timing: Premature closure (craniosynostosis) or delayed closure may indicate developmental disorders or underlying medical conditions.
When to Seek Medical Advice
Parents should consult a doctor promptly if they notice any of the following:
- The fontanelle is visibly bulging and tense even when the child is calm and lying down.
- The fontanelle is markedly sunken and the child appears lethargic or is not feeding well.
- The skull is growing unusually fast or unusually slowly.
- The fontanelle closes very early, before 3 months of age.
Handling and Care
Many parents worry about touching or injuring their baby's fontanelle. In fact, the fontanelle is protected by a tough layer of connective tissue and can be touched safely during normal care activities such as hair washing. However, strong impacts or direct pressure to this area should always be avoided.
Development and Closure
The natural closure of the fontanelles occurs through the progressive ossification of the skull bones -- a process known as ossification. The anterior fontanelle is typically fully closed between 12 and 18 months of age. Either premature or delayed closure should be evaluated by a physician, as it may be associated with conditions such as rickets (vitamin D deficiency), Down syndrome, or craniosynostosis.
References
- Sadler T.W. - Langman's Medical Embryology. Lippincott Williams and Wilkins, 14th Edition (2019).
- American Academy of Pediatrics (AAP) - Pediatric Clinical Practice Guidelines and Policies (2022).
- World Health Organization (WHO) - Child Growth Standards and Development Guidelines. WHO Press (2021).
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