What is the normal timeframe for fontanelle closure in a child?

Normal Fontanelle Closure Timeframe in Children

The anterior fontanelle typically closes at a mean age of 13.8 months, with normal closure occurring between 7-24 months of age. 1

Anterior Fontanelle Development and Closure

• The anterior fontanelle is the largest of the six fontanelles present at birth and the most important for clinical evaluation 1
• At birth, the average size of the anterior fontanelle is approximately 2.1 cm 1
• The fontanelle reaches its maximum size at around 1 month of age (approximately 2.2 cm) and then gradually decreases with age 2
• By 12 months of age, the average size decreases to approximately 0.6-1.0 cm 3, 2

Normal Closure Timeline

• The mean fontanelle closure time is 9.7 ± 5.0 months, with slight gender differences (girls: 10.3 ± 4.7 months, boys: 9.2 ± 5.1 months) 4
• According to more recent data from a large Chinese study (104,147 children), the mean age for anterior fontanelle closure is 14.5 months (95% CI 14.4-14.6) 3
• The 3rd and 97th percentiles for closure are 6.6 months and 22.4 months respectively, indicating the normal range of variation 3
• Closure rates by age:
  • 0.1% at 3 months 3
  • 3% at 6 months 2
  • 26.5% at 12 months 2
  • 67.5% at 15-17 months 3
  • 93.0% at 24 months 2

Factors Affecting Fontanelle Size and Closure

• There is significant individual variation in fontanelle size and closure time 5
• Gender differences: Boys tend to have slightly smaller fontanelles and earlier closure despite having larger head circumferences, though this difference is not always statistically significant 5, 3
• Growth parameters: While some studies show positive correlation between fontanelle closure and height/weight 3, others found no significant correlation between fontanelle size and growth parameters (weight, length, head circumference) 2

Clinical Implications

• Abnormal fontanelle size or delayed closure may indicate underlying conditions such as achondroplasia, hypothyroidism, Down syndrome, increased intracranial pressure, or rickets 1
• A bulging fontanelle can indicate increased intracranial pressure or intracranial/extracranial tumors 1
• A sunken fontanelle is typically a sign of dehydration 1
• Children with fontanels measuring above the 95th percentile should be monitored closely and investigated for potentially associated diseases 4
• Early fontanelle closure is not necessarily associated with microcephaly 4

Measurement Techniques

• Both traditional and oblique measurement techniques can be used, as they provide equally accurate results 4
• The fontanelle dimensions are commonly represented by oblique diameters in clinical pediatric practice 2