Fontanelle

Fontanelle is a soft spot on a baby's head which, during birth, enables the bony plates of the skull to flex, allowing the child's head to pass through the birth canal. The fontanelles are usually fully hardened by a child's second birthday.

Anatomy

The human skull is made up of several 'plates' of bone which, when first born, are not tightly joined together. Instead, there are a couple of areas where these plates of bone are not yet fused - these are the fontanelles. The fontanelles allow for rapid stretching and deformation of the skull during birth. They also accommodate the rapid growth of the brain during infancy, as they can move and expand as the brain grows.

There are two main fontanelles:

• The anterior fontanelle is located on the top of the skull, towards the front. It is diamond-shaped and is the largest fontanelle. It usually closes by 18 months of age.
• The posterior fontanelle is located on the back of the skull. It is triangle-shaped and is smaller than the anterior fontanelle. It usually closes by 2-3 months of age.

Clinical significance

The fontanelles are important clinically because they can provide information about the infant's health. They are usually soft and flat, but can become tense or bulging if the infant has increased intracranial pressure, such as from a brain tumor or hydrocephalus. Conversely, they can become sunken if the infant is dehydrated.

See also

• Skull
• Infant
• Birth canal
• Brain tumor
• Hydrocephalus
• Dehydration

References

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Fontanelle

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  Human anterior fontanelle at 1 month

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  Anterior fontanelle

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  Sutures from top

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  Cranium of a baby showing fontanelle