Craniosynostosis

Page last reviewed: 13/07/2011

Craniosynostosis is a rare type of birth defect where a baby is born with an abnormally shaped skull or develops one during growth. This is because the normal development of the skull is disrupted.

The human skull

Many people think of the human skull as a single section of bone that is similar to the shell of an egg. However, the skull is more like a football. It consists of a number of plates of bone that fit together to create a sphere.

In between the plates of bone are narrow openings called sutures. The sutures give the bone plates flexibility so that the skull is able to grow along with the brain. This is important because the human brain grows rapidly following birth, literally doubling in size during the first three years of life, and the skull must grow to accommodate this growth.

After the skull and brain have grown to their full adult size, the sutures fuse together to create a single structure of bone. However, in cases of craniosynostosis, one or more sutures fuse together before birth or shortly afterwards.

The premature fusion means that the skull is unable to grow in the affected areas. When one area of the skull is prevented from growing, other areas may "over grow" to compensate and to limit the pressure that is developing around the brain. A lack of growth in some areas and compensatory growth in other areas will result in an altered head shape.

Syndromic and nonsyndromic

Craniosynostosis can either be:

  • syndromic - where the condition is one of a number of birth defects to affect a child
  • nonsyndromic - where the condition develops in isolation and the child has no other birth defects

How common is craniosynostosis?

Craniosynostosis is a rare condition. It is estimated that one in every 1,800 to 3,000 children is born with the condition. Three out of every four cases affect boys.

Nonsyndromic craniosynostosis is the most common form of the condition, accounting for 80%-95% of all cases. The cause of nonsyndromic craniosynostosis is unknown.

There are more than 150 different syndromes that can cause syndromic craniosynostosis, all of which are very rare. A syndrome describes a range of different symptoms that are all related to a common cause, which is usually (but not always) genetic.

Syndromes that can cause craniosynostosis include:

  • Apert's syndrome, which affects one in every 10,000 children and disrupts the normal growth of bone before birth, resulting in deformities of the head, hands, feet and face
  • Crouzon syndrome, which affects one in every 60,000 children and disrupts the normal growth of bone in both the skull and the face, often resulting in severe facial disfigurement
  • Pfeiffer syndrome, which affects one in every 100,000 children and disrupts bone growth, resulting in deformities of the head and face; it also causes big toes, wide thumbs and webbed hands and feet
  • Saethre-Chotzen, a condition of unknown origin that affects around in 1 every 50,000 births and can cause a wide range of disfigurements, including facial defects

Intracranial pressure (ICP)

Craniosynostosis does not just pose a cosmetic problem, it can also lead to health and developmental problems in the medium to long term. This is because without treatment there will not be enough room for the infant's brain to develop as they get older.

If moderate to severe cases of craniosynostosis are left untreated, the bones may begin to squeeze the brain, increasing the pressure on the brain. The pressure around the brain is known as intercranial pressure (ICP). Children with two or more fused sutures are particularly at risk of developing raised ICP.

If raised ICP is left untreated it can cause:

  • persistent headaches
  • learning difficulties
  • brain damage
  • visual disturbances
  • respiratory problems

Surgery during the first year of life is usually recommended for the most severe cases of craniosynostosis. There is a range of techniques to correct the appearance and development of the skull.

Outlook

The outlook for children with craniosynostosis is generally good. Most children respond well to surgery and the appearance of their skull improves significantly. However, around one in 15 children may have further problems with their skull's development as they get older, which will require further surgery to correct.

Page last reviewed: 13/07/2011

Types of craniosynostosis

There are four main types of craniosynostosis that may occur in isolation or together. They are:

  • sagittal synostosis
  • coronal craniosynostosis
  • metopic synostosis
  • lambdoid synostosis

The different types of craniosynostosis are outlined below.

Sagittal synostosis

Sagittal synostosis is the most common type of craniosynostosis, accounting for around half of all of cases. In occurs when the suture at the top of the skull (the sagittal suture) fuses. This leads to a lack of growth in width and compensatory growth in length, resulting in a long, narrow skull.

Coronal craniosynostosis

Coronal craniosynostosis is the second most common type of craniosynostosis after sagittal synostosis, accounting for around one in four cases.

In coronal craniosynostosis, the fusion occurs in one or both of the two sutures that run from the top of the ear to the top of the skull. These are known as the coronal sutures.

If only one coronal suture is fused, the infant will develop a flattened forehead on the affected side. They may also have a raised eye socket and a crooked nose. If both coronal sutures are fused, the infant will develop a flat and elevated (prominent) forehead and brow. 

Metopic synostosis

Metopic synostosis is an uncommon type of craniosynostosis, occuring in between 4%-10% of cases of craniosynostosis. The fusion occurs in the metopic synostosis, which is the suture that runs from the nose to the top of the skull. Infants with metopic synostosis will develop a pointed scalp that looks triangular.

Lambdoid synostosis

Lambdoid synostosis is the rarest type of craniosynostosis and occurs in about 2%-4% of cases. Fusion occurs in the lambdoid suture, which runs along the back of the head. Infants with lambdoid synostosis will develop a flattened head at the back.

However, not all children with a flattened head at the back have Lambdoid synostosis. It is common and normal for babies to have some flatness at the back of their head as a result of lying on their backs for prolonged periods of time. This type of flattening is known as positional plagiocephaly and often resolves with further development. See the box to the left for more information about positional plagiocephaly.

Intracranial pressure (ICP)

If your child has mild craniosynostosis, it may not be spotted until they begin to experience problems due to an increase in intercranial pressure (ICP) in their skull. This usually occurs when a child is between four to eight years old.

The symptoms of ICP usually begin with:

  • a persistent headache, which is usually worse in the morning and last thing at night
  • vision problems, such as double vision, blurred vision or a "greying out" of vision
  • an unexplained decline in the child's academic abilities

If your child complains of any of the above symptoms, take them to see your GP as soon as possible. In most cases, these symptoms are unlikely to be caused by raised ICP but they do require further investigation.

Left untreated, other symptoms of raised ICP can include:

  • vomiting
  • irritability
  • sluggishness and unresponsiveness
  • swollen eyes, or the eyes find it difficult to follow a moving object
  • hearing difficulties
  • breathing difficulties
Suture
A suture is a seam-like join between the bones in the skull.

Positional plagiocephaly

Parents sometimes think that their child has craniosynostosis when, in fact, they have positional plagiocephaly. This is also known as "flat head syndrome", is where the back or side of a baby's head becomes flattened.

Positional plagiocephaly usually occurs when an infant is encouraged to sleep on their back. Infants should always been encouraged to sleep on their back because it is one of the best ways to prevent sudden infant death syndrome (SIDS).

Positional plagiocephaly is quite a common condition and it does not cause any health problems. Although an infant’s head may become flattened during the first few months of life, the shape of their head will usually correct itself by their first birthday.

It can sometimes be difficult for people who are not healthcare professionals to tell the difference between craniosynostosis and positional plagiocephaly. Talk to your GP if you are uncertain about whether your child has craniosynostosis or positional plagiocephaly. They will be able to confirm whether or not your child has either one.

Page last reviewed: 13/07/2011

Causes of nonsyndromic craniosynostosis

The cause of nonsyndromic craniosynostosis is unknown. However, a number of theories have been suggested.

One theory is that nonsyndromic craniosynostosis may be caused by the baby adopting an unusual position in the womb. For example, if the baby's head is pushed down by their mother's ribcage, this will place pressure on their skull. This extra pressure may push the plates of bone together, causing the sutures in the skull to fuse too soon.

Another theory about what might cause nonsyndromic craniosynostosis is that a (as yet unidentified) defect in the cells that make up the suture causes them to fuse prematurely.

Most cases of syndromic craniosynostosis do not appear to be connected to anything that a mother does during pregnancy. An exception to this is women who take a medication called valproic acid (sodium valproate), which is used to treat epilepsy.

Research found that women who take valproic acid during pregnancy are seven times more likely to give birth to a child with craniosynostosis than women who do not take any medication. However, in general terms, due to the rarity of nonsyndromic craniosynostosis, this increase in risk is still very small - around one in 500.

Causes of syndromic craniosynostosis

Most cases of syndromic craniosynostosis are caused by one of four genetic mutations. A genetic mutation occurs when the instructions that are carried in certain genes (a unit of genetic material) become scrambled. This means that some of the body's processes do not work in the normal way.

Examples of mutated genes are:

  • FGFR1, FGFR2 and FGFR3 (three related genes)
  • TWIST gene

The FGFR group of genes seem to make a protein called fibroblast growth factor receptor work less effectively. As this protein is involved in regulating cell growth, particularly the growth of bones, it is thought that the FGFR mutation disrupts the development of the skull.

The mutated TWIST gene seems to totally block the effects of fibroblast growth factor receptors, so birth defects that are associated with this gene are often wide-ranging.

Genetic
Genetic is a term that refers to genes, the characteristics inherited from a family member.
Suture
A suture is a seam-like join between the bones in the skull.

Page last reviewed: 13/07/2011

A paediatrician (specialist in treating children) will usually be able to diagnose craniosynostosis by carrying out a simple visual examination of your baby's head. 

Any severe distortions of the skull or face will be apparent, and the existence of ridges over fused sutures or misalignment of the ears will also provide evidence of craniosynostosis.

An X-ray of the skull may be taken to confirm a diagnosis of craniosynostosis.

Computerised tomography (CT) scan

A computerised tomography (CT) scan is the most detailed method of assessing the condition of your child's skull. A CT scan involves taking a series of X-rays and using a computer to reassemble them into a more detailed image.

CT scans are usually only required to plan some types of surgery or if the diagnosis of craniosynostosis is in doubt.

If your child has other birth defects that suggest that craniosynostosis may be part of a wider syndrome, such as Apert's disease, a sample of their blood, hair or saliva may be taken and tested for any genetic mutations. Apert's disease is a genetic disorder that causes deformities of the head, hands, feet and face.

Genetic
Genetic is a term that refers to genes, the characteristics inherited from a family member.
Suture
A suture is a seam-like join between the bones in the skull.
X-ray
An X-ray is a painless way of producing pictures of inside the body using radiation.

Page last reviewed: 13/07/2011

Surgery

Surgery is the main type of treatment for craniosynostosis. It is usually recommended that surgery is carried out in the first 12 months following birth.

Surgery for craniosynostosis is usually carried out by a team of two surgeons who each have their own speciality. These are:

  • a neurosurgeon - a specialist in the nervous system and brain
  • a craniofacial surgeon - a specialist in surgery of the face, head and jaws

The procedure

Surgery for craniosynostosis is carried out under a general anaesthetic, which means that your child will be asleep during the procedure and will not feel any pain.

The neurosurgeon will make an incision (cut) across the top of your child's scalp. This will leave a scar but it will be hidden by their hair. The neurosurgeon will remove the affected areas of skull.

The removed pieces of bone will be reshaped by the craniofacial surgeon before being returned to a normal position in the skull. The incision will then be sealed using dissolvable stitches.

After the operation

Surgery for craniosynostosis is not dangerous, although extra precautions always have to be taken in cases where surgery involves very young children.

Therefore, after the operation it is likely that your child will be transferred to an intensive care unit (ICU) for one or two days so that their condition can be carefully monitored. Most children are well enough to leave hospital around five days after surgery.

Following surgery, most children will only experience mild pain but it is common for them to develop significant swelling around their eyes. The swelling can often prevent them from opening their eyes. Your child may find this annoying or distressing, but the swelling does not present a health risk and it should subside after a few days.

After having surgery for craniosynostosis, it is likely that your child will be asked to attend regular check-ups so that the future development of their skull can be monitored. The check-ups will be quite frequent at first, such as every six weeks, before becoming less frequent as your child gets older. Most children will only require an annual check-up once they reach the age of six.

Incision
An incision is a cut made in the body with a surgical instrument during an operation.
Suture
A suture is a seam-like join between the bones in the skull.

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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