It happens when one or more of the infant's cranial sutures fuses too early. The cranial sutures are the natural cracks in the skull.
An infant's skull is made up of seven bones with gaps, or cranial sutures, between them. The sutures do not normally fuse until the child is approximately 2 years old, and this allows the brain to grow and develop.
In the United States, craniosynostosis affects 1 in every 2,500 individuals. The majority of these are due to early fusion of one of more skull bones in a baby after they are born. It occurs equally in boys and girls.
If the plates of the skull fuse too early, a child might have craniosynostosis.
There are four major types of craniosynostosis:
- Sagittal synostosis
- Coronal craniosynostosis
- Metopic synostosis
- Lambdoid synostosis.
It is possible to have just one type or a combination of them.
The appearance for each type of craniosynostosis can differ. More than 180 different conditions are linked to some type of craniosynostosis.
In sagittal synostosis, the sagittal suture, located at the top of the head, fuses too early. This occurs in 40 percent to 60 percent of cases. The head grows long but its width is restricted. It mostly occurs in boys.
Coronal craniosynostosis happens due to early fusion of one or both of the sutures that connect the top of the head to the ears, known as the coronal sutures. It accounts for 20 percent to 30 percent of cases.
It results in a flat forehead and possibly a higher eye socket on the affected side. If both sutures fuse, both sides of the face are affected. This is known as biconal synostosis. This kind of craniosynostosis occurs mostly in girls and is the second most common type.
Metopic synostosis is a much rarer form of craniosynostosis. This suture that fuses is located 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.
Lambdoid synostosis affects the lamboid suture, the suture that runs across the back of the head. It causing flatness in this area. This is the rarest type of craniosynostosis.
Sometimes, a flat head can happen if an infant lies on their back too much. This happens due to a shifting of the skull bones without fusion of the cranial sutures, and it is called plagiocephaly. It is not craniosynostosis.
Unlike craniosynostosis, plagiocephaly is not due to early fusion of cranial sutures.
The general symptoms of craniosynostosis are:
- A distorted skull shape
- The fontanel on the infant's skull feels unusual and disappears sooner than is usual
- The baby's head grows more slowly than the body, or not at all
- Hard ridge forms along the suture, depending on the type of craniosynostosis.
A newborn may have no symptoms, but the condition may become apparent during the first months of life. The pediatrician will measure the infant's head and monitor its growth at every visit during the first year of life, in order to spot this kind of condition.
The cause of craniosynostosis depends on the type. The condition can be nonsyndromic, or syndromic. Syndromic craniosynostosis occurs with other birth defects.
When a gene mutates, the information it carries is mixed up, resulting in one of the bodily functions not working correctly. A number of genes are thought to mutate, resulting in craniosynostosis.
The cause of nonsyndromic craniosynostosis has not been identified.
It may be due to a cell defect in the sutures that causes them fusing too early.
Sometimes, the fetus assumes an irregular position in the womb, potentially putting pressure on the head and pushing the plates of bone in the skull together. This can cause the sutures to fuse.
A pediatrician will normally diagnose craniosynostosis by performing a visual assessment and feeling for ridges in the sutures around the baby's skull. This kind of test is usually enough to detect the condition, but additional tests can confirm the diagnosis in more detail.
Imaging tests, such as CT scans and X-rays, can reveal which sutures have fused. This is important if surgery is to be performed.
As craniosynostosis can be caused by hereditary genetic mutations, a sample of the baby's hair, blood, or saliva might be taken for genetic testing.
The primary treatment method of craniosynostosis is surgery, which is best done within the first year of the child's life.
It normally takes around 2 years for an infant's skull to fuse.
The main goal of the surgery is to let the cranial vault develop normally.
Without surgery, the condition can get worse and the skull deformity may increase.
Surgery normally involves a craniofacial surgeon and a neurosurgeon. A craniofacial surgeon specializes in head and facial surgery and surgery of the jaw. A neurosurgeon specializes in the brain and nervous system.
Surgery is performed under general anesthetic. The infant does 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 skull and places them back in the head. The opening is then sewn up using dissolvable stitches.
The process can last several hours, and the child will stay in hospital for a few days after the surgery. The face is likely to swell, but this not a need for concern.
Sometimes further surgery is required to reshape the face. Sometimes the craniosynostosis reappears, also requiring further surgery.
After the procedure, the child's skull development will be monitored.
Endoscopic surgery offers a less invasive approach. Two small incisions are made in the scalp and the sutures are cut with the help of an endoscope, a flexible tube that can be used 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 recommended before the age of 3 months, because the bones are still soft. After surgery, the child may need a molding helmet to help the head to grow into a suitable shape.
If not treated, craniosynostosis can lead to further complications. The skull will continue to grow abnormally, and this may affect other functions, for example, vision loss on the affected side, known as amblyopia.
If craniosynostosis is mild, it might not be spotted until later, leading to intracranial pressure (ICP) in the skull as late as the age of 8 years.
The symptoms of intracranial pressure include:
These symptoms do not necessarily mean that there is intracranial pressure, but if these symptoms occur, medical attention should be sought. Untreated, ICP can lead to further complications, such as brain damage, blindness, and seizures.Written by Mike Paddock