In its simplest form, craniosynostosis occurs when one of the normal joints of the skull fuses or closes prematurely, leading to abnormal skull growth. These skull joints (or sutures) act as expansion joints, allowing the skull to grow rapidly in the first years of life. This rapid growth is driven in part by the brain, which typically grows to 70-80 percent of adult size in the first two years. Normally, the sutures begin closing after the major period of brain growth, when a child is around 2-3 years of age. This normal closure process continues into adulthood.
When one of the sutures fuses prematurely, however, the skull cannot grow normally in response to the expanding brain. This leads to characteristic patterns of abnormal skull growth depending upon which suture or combination is fused.
Usually, a child diagnosed with craniosynostosis has only one suture fused. However, some children may have complex patterns of craniosynostosis where multiple sutures fuse prematurely. This condition occurs most commonly in connection with craniofacial syndromes such as Apert, Crouzon or Pfeiffer syndromes.
Craniosynostosis is probably caused by a combination of environmental, hormonal and genetic factors that make the skull suture a little more likely to fuse. However, our understanding of what causes craniosynostosis is not complete.
For children having craniosynostosis involving a single suture, probably the most common cause is environmental. While a baby is in the womb, the head may become wedged in a tight spot, putting pressure on the skull and impairing skull expansion. This may signal to the skull bones that growth is nearing completion and it is time to begin fusing the suture. This theory is supported by the finding that craniosynostosis is slightly more likely to occur during twin pregnancies, where the babies are tightly constrained within the uterus.
Although it is rare for single suture craniosynostoses to be passed from generation to generation in families, some reports suggest heredity may play a role. A number of genes have been identified which may lead to an increased risk of craniosynostosis. However, it seems most likely that these genes serve a "helper" role, perhaps making the sutures a little more likely to fuse when other necessary conditions are present. Genes are more likely to play a role in complex pattern craniosynostosis.
Single suture craniosynostosis occurs more frequently in boys than girls, suggesting a possible hormonal connection.
While our understanding of what causes craniosynostosis is still evolving, it does seem clear that single suture craniosynostosis is not caused by anything the parents have done or neglected to do. The vast majority of children with single suture craniosynostosis will grow up to lead normal, happy, productive lives.
Signs include an abnormally shaped skull, ridging of the suture and early closure of the fontanels (soft spot). In addition, children with craniosynostosis may feel increased pressure on their brains and may report symptoms of headaches.
The possibility of elevated intracranial pressure and the worrisome effect it may have on development and intelligence of a child continues to be an area of interest for researchers and a driving force behind surgical treatment. Most children with single suture craniosynostosis have normal development and intelligence.
Diagnosing craniosynostosis can be challenging, even for experienced pediatricians. Craniosynostosis is frequently confused with another common cause of abnormal skull shape in infants known as deformational or positional plagiocephaly. Since craniosynostosis leads to predictable and characteristic patterns of abnormal skull growth, the diagnosis is best made after a physical exam by an experienced craniofacial surgeon.
During a physical exam, your craniofacial surgeon will assess the overall shape of the skull, measure the circumference of the head and feel the soft spots (or fontanels) to see if they are open or closed. In addition, your surgeon will check for any visible ridging over the sutures of the skull. Ridging refers to raised areas of bone that follow the line of the sutures. As a suture begins to fuse, ridging that may be seen or felt is a common diagnostic sign of craniosynostosis. However, the lack of visible or palpable ridging does not rule out craniosynostosis.
While most craniosynostosis diagnoses may be made by physical exam alone, X-ray studies may help confirm a diagnosis when it is unclear whether a suture is fused. In these rare instances, a CT scan of the skull is probably the best radiology test for evaluating cranial sutures.
However, we encourage parents to have their child seen by a craniofacial surgeon prior to any diagnostic imaging since these studies may be unnecessary.
When multiple sutures are involved or a craniofacial syndrome is suspected, genetic testing and consultation may be recommended.
Surgical correction of craniosynostosis is most often done when the baby is 6 to12 months of age. Following surgery, your baby will spend at least one night in the pediatric intensive care unit prior to being transferred to a regular pediatric bed. You can anticipate that your baby will spend anywhere from 2-5 days in the hospital following surgery.
When only one suture is fused, it is likely that only one surgery will be required to correct the abnormal skull shape. When multiple sutures are involved, as in craniofacial syndromes, children often require several skull surgeries.