Definition of Fontanelles - excessively large:

Excessively large fontanelles are larger-than-expected soft spots for the age of a baby. In an infant, the spaces where bones of the skull come together, but are not completely joined, are called soft spots or fontanelle (fontanel or fonticulus).

Considerations:

Fontanelles allows for growth of the skull during an infant's first year. Slow or incomplete closure of the skull bones is most often the cause of a wide fontanelle.

For general information, see fontanelles.

Common Causes:

Larger-than-normal fontanelles are most commonly caused by:

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

Rarer causes:

• Apert syndrome
• Cleidocranial dysostosis
• Congenital rubella
• Neonatal hypothyroidism
• Osteogenesis imperfecta
• Rickets