Craniosynostosis, or simply synostosis, is the early growing together (or fusion) of two or more bones of the skull. A newborn's skull is made up of many separate bones that are not yet fused together. Because the brain grows quickly in the first two years of life, it is important that the skull bones remain open. In fact, complete fusion of the bones normally occurs late in the teen years. Synostosis interferes with normal growth of the brain and skull.
What Is Normal Development?
A suture is a hinge of bony edges that are united by a thin layer of soft tissue. During normal development, interdigitations (folds of the membranes) develop between the bones and form a definitive suture. Later, the open cranial and facial sutures close by forming bony bridging.
At birth, the open sutures allow a lot of flexibility in craniofacial molding of bones to allow the newborn to pass through the birth canal. This molding usually normalizes with one to two weeks after birth. Normal craniofacial growth occurs through two processes: bone displacement and bone remodeling.
Shape of the Head
An abnormal head shape (plagiocephaly) can occur as a result of abnormal forces on the skull before or after birth. This can happen before birth:
- When the baby descends into the pelvis
- If the mom has an abnormally shaped uterus
- If the fetus is in an odd position
- If the mom is having twins (or triplets, etc.)
After birth, abnormal head shape is most commonly a result of gravity, when the patient lies in one position for long periods of time.
Most of these problems will "fix themselves" within the first few months after birth due to rapid brain growth or with frequent repositioning of the baby.
Molding helmets may be used for those newborns who are not showing improvement in head shape with repositioning techniques. It is important to distinguish positional plagiocephaly (a non-surgical condition) from lambdoid synostosis or unilateral coronal synostosis, which require surgery to correct the problem.