It happens when one or more of the natural spaces in the infant's skull join together too early before birth or after delivery. These spaces are known as cranial sutures.
An infant's skull consists of seven bones with gaps, or cranial sutures, between them. The sutures do not normally join, or fuse, until the child is around 2 years old. This allows the brain to grow and develop without pressure from the skull.
In the United States, craniosynostosis affects around 1 in every 2,500 individuals. In most of these cases, two or more skull bones join soon after birth, according to the Centers for Disease Control and Prevention (CDC).
The bones in the skull fuse in an unusual way, and this can give the head an unusual shape.
There are four main types of craniosynostosis, depending on which bones fuse early. These can lead to different features.
- sagittal synostosis
- coronal craniosynostosis
- metopic synostosis
- lambdoid synostosis
It is possible to have just one type or a combination of them.
Each type looks different, and the symptoms can range from mild to severe. More than 180 different conditions involve some type of craniosynostosis. It can also happen by itself, without any other associated syndrome.
In this type, the sagittal suture — along the top of the head — fuses too early.
This occurs in 40 to 55 percent of cases. The head grows longer but narrower than usual. It occurs more often in boys.
This type happens when one or both of the sutures that connect the top of the head to the ears join too early. These are the coronal sutures.
It accounts for 20 to 30 percent of cases.
The person will have a flat forehead, and the eye socket might be higher on one side. If both sutures join, it affects both sides of the face. This condition more commonly affects girls. It is the second most common type.
Metopic synostosis is less common. The space that joins is between the sagittal suture and the nose. Babies with this form develop a triangular scalp.
Fewer than 10 percent of cases are of this type.
This type affects the lamboid suture, which runs across the back of the head. The back of the head will be flat. This is the rarest type of craniosynostosis.
Plagiocephaly: Sometimes, an infant can develop a flat head if they lie on their back too much. This happens because the skull bones shift, but the cranial sutures do not fuse. It is different from craniosynostosis.
A pediatrician will check an infant's head regularly in case craniosynostosis is present.
The general signs of craniosynostosis are:
- a distorted skull shape
- an unusual feel to the fontanel, or "soft spot" on the infant's skull
- early disappearance of the fontanel
- slower growth in the head compared with the body
- hard ridge forming along the suture, depending on the type of craniosynostosis
A newborn may have no symptoms or signs, but the condition may become noticeable during the first months of life.
A pediatrician will measure the infant's head and monitor their growth at every visit during the first year of life. They do this to spot this kind of condition.
The cause of craniosynostosis depends on the type. The condition can be nonsyndromic, or syndromic.
Syndromic craniosynostosis is part of a syndrome. It happens along with other birth defects.
When a gene mutates, the information it would normally carry changes. As a result, in one of the body's functions may not work correctly.
With craniosynostosis, there may be changes in a number of genes.
Researchers note that the changes can affect different parts of the body, including:
- the fingers and toes
- the skeletal system
- the heart or other organs
In this case, the cause remains unknown.
Here are some possible explanations:
- A cell defect in the sutures causes them to fuse too early.
- The fetus assumes a position in the womb that puts pressure on the head and push the plates of bone in the skull together.
Using certain treatments during pregnancy may increase the risk of problems in the baby.
The United States Food and Drug Administration (FDA) warn of this risk on the patient information for Depakote.
According to the CDC, recent research also suggests that there is a higher risk for infants whose mothers:
- had thyroid disease or treatment for thyroid disease during pregnancy
- used a fertility medication — clomiphene citrate — before pregnancy or during early pregnancy
To diagnose craniosynostosis, a pediatrician will normally look at and measure the baby's head and feel for ridges in the sutures around the skull.
Additional tests can confirm the diagnosis in more detail.
Imaging tests, such as CT scans and X-rays, can show which sutures have fused. This is important if surgery is likely.
Since there may be genetic factors, the doctor may take a sample of the baby's blood for genetic testing.
The main treatment for craniosynostosis is surgery, usually within the first year of life.
Surgery can help the skull to develop normally and allow space for the brain to develop.
Without surgery, the shape may become more unusual, and this can lead to complications.
A craniofacial surgeon and a neurosurgeon will normally work together on the procedure.
A craniofacial surgeon specializes in head and facial surgery and surgery of the jaw. A neurosurgeon specializes in the brain and the nervous system.
The doctors will use a general anesthetic, and the infant will not feel any pain.
The neurosurgeon makes an incision across the top of the infant's scalp and removes the areas of the skull that have become misshapen.
The craniofacial surgeon then reforms these sections of the skull and places them back in the head. They then sew up the opening using dissolvable stitches.
The process can last several hours, and the child will stay in the hospital for a few days after the surgery. The face is likely to swell, but this not a need for concern.
Sometimes a child needs further surgery to reshape the face, or if the craniosynostosis reappears.
After the procedure, a health professional will monitor the child's skull development.
This is less invasive. The doctor makes two small incisions in the scalp and cuts the sutures using an endoscope. This is a flexible tube that the surgeon can use to see the inside of the body during keyhole surgery.
This type of surgery is quicker, and there is less bleeding and swelling, but it is only suitable in certain cases, depending on the location of the fused suture.
Endoscopic surgery is suitable before the age of 3 months, when the bones are still soft.
After surgery, the child may need a molding helmet to help the head to grow into a suitable shape.
Without treatment, further complications can arise.
The skull will continue to grow in an unusual way, and this may affect other functions. There may be vision loss on the one side, for example.
If craniosynostosis is mild, people may not notice it until a later stage. This can cause pressure to build up on the brain — known as increased intracranial pressure — as late as the age of 8 years.
The symptoms of increased intracranial pressure include:
These symptoms do not necessarily mean that there is intracranial pressure, but it is important to seek medical help if these symptoms occur.
Without treatment, increased intracranial pressure can lead to further complications, such as brain damage, blindness, and seizures.
Symptoms of craniosynostosis can range from mild to severe.
The CDC note that with suitable treatment, most children with craniosynostosis will live a normal life, particularly if they do not have an associated genetic syndrome.
However, additional support may be necessary for those who:
- have other symptoms or changes that affect, for example, brain development
- have an unusually shaped head, even after surgery, as this can lead to problems with self esteem
Early intervention is important, and this is one reason why it is important to attend regular checkups during early childhood.