From the Guidelines
The anterior fontanelle typically closes between 12 to 18 months of age, while the posterior fontanelle closes between 1 to 3 months of age. When considering the closure of fontanelles in infants, it's essential to understand the normal anatomical features and developmental milestones. The provided evidence, although focused on the use of point-of-care ultrasound (POCUS) in critically ill neonates and children 1, indirectly highlights the importance of fontanelles in pediatric care. Key points to consider include:
- The anterior fontanelle closure time can vary, but average closure occurs around 12-14 months of age.
- The posterior fontanelle closes much earlier, usually within the first few months of life.
- Fontanelles are membrane-covered spaces where the skull bones haven't yet fused together, allowing for brain growth and slight compression of the skull during childbirth.
- Closure occurs as ossification progresses and the separate skull bones grow together.
- Premature closure (craniosynostosis) or significantly delayed closure may indicate underlying medical conditions and should be evaluated by a healthcare provider 1.
- During well-child visits, pediatricians routinely check fontanelle size and closure timing as part of normal development assessment.
- Parents should not be concerned about gently touching these areas, as they are protected by a tough membrane, though they should avoid applying direct pressure. It's crucial to prioritize the assessment of fontanelle closure in the context of overall infant development and to address any concerns or abnormalities promptly.
From the Research
Fontanelle Closure
- The anterior fontanelle closure rates were 25% at 4-6 months, increasing to 47% at 10-12 months and 80% at 13-18 months in the Māori/Pasifika group 2.
- The posterior fontanelle was clinically unfused in 17% of the Māori/Pasifika group aged <1 month and in 7% of the 1-3-month-old group 2.
- No specific information on the exact time of closure for the posterior fontanelle was found in the provided studies, but it is known that the posterior fontanelle typically closes earlier than the anterior fontanelle.
Fontanelle Size and Variation
- The pooled mean size of the anterior fontanelle was 2.58 cm (95% CI: 2.31,2.85 cm) among term newborns 3.
- There was a statistically significant mean difference in anterior fontanelle size between male and female newborns, with males having a larger mean size 3.
- The size and closure of fontanelles can vary among different populations and ethnic groups 2, 3.
Diagnostic Use of Fontanelles
- Posterior fontanelle sonography can be used to improve visualization of brain lesions, particularly in the posterior supratentorial and infratentorial structures 4, 5.
- The posterior fontanelle can be used as an acoustic window into the neonatal brain, allowing for better assessment of certain brain structures and lesions 4.