A normal skull consists of several plates of bone that are separated by sutures, or fibrous joints. The sutures are found between the bony plates in the head. As an infant grows and develops, the sutures close forming a solid piece of bone, called the skull.
Craniosynostosis is a condition in which the sutures close too early, causing problems with normal brain and skull growth. Premature closure of the sutures may also cause pressure inside of the head to increase and the skull or facial bones to change from a normal, symmetrical appearance.
Causes of Craniosynostosis
Craniosynostosis occurs in one out of 2,200 live births and affects males slightly more often than females.
Craniosynostosis is most often sporadic. In some families, craniosynostosis is inherited in one of two ways:
Autosomal Recessive: Autosomal recessive means that two copies of the gene are necessary to express the condition, one inherited from each parent, who is obligate carriers. Carrier parents have a one in four or 25 percent chance, with each pregnancy, to have a child with craniosynostosis. Males and females are equally affected.
Autosomal Dominant: Autosomal dominant means that one gene is necessary to express the condition, and the gene is passed from parent to child with a 50/50 risk for each pregnancy. Males and females are equally affected.
Craniosynostosis is a feature of many different genetic syndromes that have a variety of inheritance patterns and chances for reoccurrence, depending on the specific syndrome present. It is important for the child as well as family members to be examined carefully for signs of a syndromic cause, or inherited genetic disorder of craniosynostosis such as limb defects, ear abnormalities, or cardiovascular malformations.
Types of Craniosynostosis
There are numerous types of craniosynostosis. Different names are given to the various types, depending on which suture, or sutures, is involved, including the following:
Plagiocephaly involves fusion of either the right or left side of the coronal suture that runs from ear to ear. This is called coronal synostosis and it causes the normal forehead and the brow to stop growing. Therefore, it produces a flattening of the forehead and the brow on the affected side, with the forehead tending to be excessively prominent on the opposite side. The eye on the affected side may also have a different shape.
There may also be flattening of the back area, or occipital. Unilateral lambdoidal suture synostosis may cause plagiocephaly, as well. Deformational, or positional plagiocephaly refers to the misshapen, asymmetrical head from repeated pressure to the same area of the head. This is not a true synostosis. It can result when the part of the skull, or occipital bone that is dependent, or in one position flattens out due to pressure, as when sleeping on that part of the skull. The number of infants with deformational plagiocephaly has risen over the past several years. This increase may be the result of the "Back to Sleep" campaign promoted by the American Academy of Pediatrics to help prevent sudden infant death syndrome (SIDS), but other factors can cause this type of plagiocephaly. Specific treatment will be determined by your child's doctor based on the severity.
Trigonocephaly is a fusion of the metopic, or forehead suture. This suture runs from the top of the head down the middle of the forehead, toward the nose. Early closure of this suture may result in a prominent ridge running down the forehead. Sometimes, the forehead looks quite pointed, like a triangle, with closely placed eyes also known as hypotelorism.
Scaphocephaly is an early closure of fusion of the sagittal suture. This suture runs from front to back, down the middle of the top of the head. This fusion causes a long, narrow skull. The skull is long from front to back and narrow from ear to ear.