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Craniofacial Program

Craniosynostosis

What is Craniosynostosis?

There are seven bones that make up the skull of a newborn baby. These bones are separated by spaces called sutures. The sutures meet at the fontanelles, the soft spots at the front and the back of a baby's skull. In order for the brain to grow, the sutures usually remain open and gradually grow together to form the adult skull.

Craniosynostosis is the term used to describe the premature fusion (closing) of one or more of the sutures of a baby's skull. As the brain of a baby grows, it usually exerts an even amount of pressure on all the bones of the skull. If a suture fuses prematurely, growth of the brain cannot occur evenly and an abnormal head shape results. They type of abnormal head shape that occurs depends upon which of the sutures has prematurely fused (i.e. if the sagittal suture fuses prematurely, the skull will become elongated.

Craniosynostosis occurs in about 1 in every 2500 live births. Early surgery can help to remodel the bones of the skull, leading to a more typical skull shape. Children with craniosynostosis are often followed by a multidisciplinary craniofacial team, such as the one at the Hospital for Sick Children, to address their individual medical needs.

What Causes Craniosynostosis?

All couples have a baseline risk of 3% to have a child with a birth defect that will require medical or surgical attention. Non-syndromic craniosynostosis is typically a chance event that occurs as part of this background 3% risk. Recently, a gene was identified that can cause some cases of non-syndromic craniosynostosis.

Click here for more information on the genetics of craniosynostosis.

What are the Different Types of Craniosynostosis?

Craniosynostosis can be classified into two main groups: non-syndromic craniosynostosis and syndromic synostosis. A syndrome is a collection of physical and developmental features that occur in one individual and have a common cause.

Non-Syndromic Craniosynostosis usually occurs in a non-inherited fashion (not passed on from either parent) and only involves fusion of one suture.

Syndromic Craniosynostosis includes a group of conditions that can be inherited from a parent or start as a brand new condition in a child. These conditions involve fusion of multiple sutures and are associated with additional physical differences, commonly involving the face, hands, and feet. For more information on syndromic craniosynostosis please refer to the Genetics of Syndromic Craniosynostosis pamphlet provided by the Hospital for Sick Children’s Division of Clinical and Metabolic Genetics.

What are the Types of Non-Syndromic Craniosynostosis?

Cases of non-syndromic craniosynostosis are classified according to which suture is fused.

Unicoronal Synostosis: premature closure of a coronal suture on one side of the head results in a flattening of the forehead and the brow on the fused side. The forehead is usually prominent on the unaffected side. The resulting head shape is called plagiocephaly from the Greek term "plagios" meaning slanting. Fusion of both coronal sutures can occur, but is less common. Click here for more information on unicoronal synostosis.

Metopic Synostosis: premature closure of the metopic (forehead) suture results in a triangular forehead with decreased distance between the eyes. The resulting head shape is called trigonocephaly from the Greek term "trigonos" meaning triangular. Click here for more information on metopic synostosis.

Sagittal Synostosis: premature closure of the sagittal suture, which runs from the front to the back of the head, results in a skull that is elongated and narrow. This results in a head shape that is called scaphocephaly from the Greek term "skaphe" meaning boat or skiff. Click here for more information on sagittal synostosis.

Lambdoid Synostosis: premature closure of a lambdoid suture causes flattening of the back of the head on the side where the suture has fused. The resulting head shape is called plagiocephaly from the Greek term "plagio" meaning slanting. Fusion of both lambdoid sutures can also occur, but is less common. Click here for more information on lambdoid synostosis

Rarely, the fusion of more than one suture can occur (i.e. both the coronal and lambdoid sutures).