Human skull provides a cavity and support system for the brain structure and is composed of many bones that are joined together through fibrous joints called sutures. At the time of birth, in an infant, these bones are not fused together because the skull needs to expand as brain develops with developing age of the infant. The sutures allow the bones of brain to be flexible enough to move as the brain grows larger. Within few years, when the brain is fully grown, all the sutures close up and bones fuse together to form a solid skull. In some infants, one or some of the suture are already closed at the time of birth. This premature fusion of bones in the skull is termed as Craniosynostosis.
Closure of a single suture does not allow the skull to expand from that specific area, but, to provide enough intracranial space for the growing brain, skull expands from some other portion resulting in an abnormally shaped head. Closure of multiple sutures causes increase in intracranial pressure, resulting in certain neurological disorders along with non-symmetrical head shape.