Craniosynostosis 

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.