Single Suture Craniosynostoses: Physical traits

Fusion of the Suture:
What causes sutures to abnormally fuse shut? The two most common reasons for premature closure of a skull suture are a change in one of the child’s genes, or the result of outside pressure on the skull that induces the suture to close. When only a single suture is fused shut, the most common cause is usually “environmental,” or the result of outside pressure on the skull, occurring sometime before birth. We know that it is possible to cause craniosynostosis in animals by restricting skull growth while the animal is still in the womb, and it is very likely that this is the primary cause for the majority of the single sutural synostoses in babies. The uterus, or womb, is a relatively small space. We know that sometimes babies can end up in certain positions in the uterus where they cannot move around freely (for example, the breech position). We suspect that children born with a single sutural synostosis may have been positioned in the uterus in such a way that there is continuous pressure on a certain area of the skull. This pressure can restrict the ability of the skull bones to be stretched apart by the growing brain. If the suture cannot stretch apart, it “thinks” its job is done and it fuses shut with normal bone. Abnormal skull shapes and single sutural synostoses are more commonly seen in twins than in single births, further supporting this theory of in-utero constraint. Craniosynostosis is also more common in boys than girls leading some researchers to speculate that testosterone might make suture closure more likely to occur, if there is any restriction of skull growth inside the uterus. Mothers who have delivered babies with single sutural synostosis should not feel guilty that they did anything wrong during their pregnancy to cause this condition. Craniosynostosis occurs in spite of the mother doing everything right.

In most instances, when children born with a single sutural craniosynostosis grow up, they do not pass this trait on to their own children. However, it has been reported (and we have seen cases of this, as well) of a single sutural synostosis being passed from generation to generation. When this does occur, this hereditary pattern suggests that the sutural fusion is more likely caused by a specific gene. It is possible to test for some of these genes to see if they are present in children with craniosynostosis (something that we are currently doing in Dallas). However, it should be remembered that the overwhelming majority of single sutural synostoses appear to be the product of two parents with normal genes, and a mother who has normal prenatal care. Should children born with a single sutural synostosis decide to have children of their own in adulthood, the chance of passing on the condition is estimated to be less than 2%. The chance of a couple having a second child with a single sutural synostosis is also thought to be about 2%.

Other common features of all single sutural synostoses:
Skull | Problems Caused by Sutural Fusion
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