Cranial sutures and fontanels
Joints made of strong, fibrous tissue (cranial sutures) hold the bones of your baby's skull together. The sutures meet at the fontanels, the soft spots on your baby's head. The sutures remain flexible during infancy, allowing the skull to expand as the brain grows. The largest fontanel is at the front (anterior).
Craniosynostosis (kray-nee-o-sin-os-TOE-sis) is a disorder present at birth in which one or more of the fibrous joints between the bones of your baby's skull (cranial sutures) close prematurely (fuse), before your baby's brain is fully formed. Brain growth continues, giving the head a misshapen appearance.
Usually, during infancy the sutures remain flexible, allowing a baby's skull to expand as the brain grows. In the front of the skull, the sutures meet in the large soft spot (fontanel) on top of the head. The anterior fontanel is the soft spot felt just behind a baby's forehead. The next largest fontanel is at the back (posterior). Each side of the skull has a tiny fontanel.
Craniosynostosis usually involves premature fusion of a single cranial suture, but it can involve more than one of the sutures in a baby's skull (multiple suture craniosynostosis). In rare cases, craniosynostosis is caused by certain genetic syndromes (syndromic craniosynostosis).
Treating craniosynostosis involves surgery to correct the shape of the head and allow for brain growth. Early diagnosis and treatment allow your baby's brain adequate space to grow and develop.
Although neurological damage can occur in severe cases, most children develop as expected in their ability to think and reason (cognitive development) and have good cosmetic results after surgery. Early diagnosis and treatment are key.
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The signs of craniosynostosis are usually noticeable at birth, but they become more apparent during the first few months of your baby's life. Signs and severity depend on how many sutures are fused and when in brain development the fusion occurs. Signs and symptoms can include:
- A misshapen skull, with the shape depending on which of the sutures are affected
- Development of a raised, hard ridge along affected sutures, with a change in the shape of the head that's not typical
Types of craniosynostosis
There are several types of craniosynostosis. Most involve the fusion of a single cranial suture. Some complex forms of craniosynostosis involve the fusion of multiple sutures. Multiple suture craniosynostosis is usually linked to genetic syndromes and is called syndromic craniosynostosis.
The term given to each type of craniosynostosis depends on what sutures are affected. Types of craniosynostosis include:
- Sagittal (scaphocephaly). Premature fusion of the sagittal suture that runs from the front to the back at the top of the skull forces the head to grow long and narrow. This head shape is called scaphocephaly. Sagittal craniosynostosis is the most common type of craniosynostosis.
- Coronal. Premature fusion of one of the coronal sutures (unicoronal) that run from each ear to the top of the skull may cause the forehead to flatten on the affected side and bulge on the unaffected side. It also leads to turning of the nose and a raised eye socket on the affected side. When both coronal sutures fuse prematurely (bicoronal), the head has a short and wide appearance, often with the forehead tilted forward.
- Metopic. The metopic suture runs from the top of the bridge of the nose up through the midline of the forehead to the anterior fontanel and the sagittal suture. Premature fusion gives the forehead a triangular appearance and widens the back part of the head. This head shape is also called trigonocephaly.
- Lambdoid. Lambdoid synostosis is a rare type of craniosynostosis that involves the lambdoid suture, which runs along the back of the head. It may cause one side of a baby's head to appear flat, one ear to be higher than the other ear and tilting of the top of the head to one side.
Other reasons for a misshapen head
A misshapen head doesn't always indicate craniosynostosis. For example, if the back of your baby's head appears flattened, it could be the result of spending too much time lying on one side of the head. This can be treated with regular position changes, or if significant, with helmet therapy (cranial orthosis) to help reshape the head to a more balanced appearance.
When to see a doctor
Your health care provider will routinely monitor your child's head growth at well-child visits. Talk to your pediatrician if you have concerns about your baby's head growth or shape.
Often the cause of craniosynostosis is not known, but sometimes it's related to genetic disorders.
- Nonsyndromic craniosynostosis is the most common type of craniosynostosis. Its cause is unknown, although it's thought to be a combination of genes and environmental factors.
- Syndromic craniosynostosis is caused by certain genetic syndromes, such as Apert syndrome, Pfeiffer syndrome or Crouzon syndrome, which can affect a baby's skull development. These syndromes usually also include other physical features and health problems.
If untreated, craniosynostosis may cause, for example:
- Permanently misshapen head and face
- Poor self-esteem and social isolation
The risk of increased pressure inside the skull (intracranial pressure) from simple craniosynostosis is small if the suture and head shape are fixed surgically. But babies with an underlying syndrome may develop increased intracranial pressure if their skulls don't expand enough to make room for their growing brains.
If untreated, increased intracranial pressure can cause:
- Developmental delays
- Cognitive impairment
Sept. 15, 2022