Craniosynostosis (kray-nee-o-sin-os-TOE-sis) is a birth defect in which one or more of the joints between the bones of your baby's skull close prematurely, before your baby's brain is fully formed. When your baby has craniosynostosis, his or her brain can't grow in its natural shape and the head is misshapen.
Craniosynostosis can affect one or more of the joints in your baby's skull. In some cases, craniosynostosis is associated with an underlying brain abnormality that prevents the brain from growing properly.
Treating craniosynostosis usually involves surgery to separate the fused bones. If there's no underlying brain abnormality, the surgery allows your baby’s brain adequate space to grow and develop.