Disorders of the Skull Vault

Craniosysostosis is a disorder that involves premature fusion of the cranial vault sutures causing abnormal and disproportionate growth of the cranial bones during development (see Fig. 1). When a suture is fused there is no growth in a plane perpendicular to the line of the suture. Growth of the remainder of the skull is affected as it attempts to compensate for lack of expansion in the synostosed, or fused area.

Normal cranial vault growth is directly related to brain development. Problems in brain development can affect growth of the skull, and skull dysmorphogenesis can affect the brain. The skull as a whole grows most rapidly from birth to the 7th year. The cranial vault increases the most during the first year, corresponding with the rapid growth of the brain during that period. The brain completes its maximum growth at about two years of age.

Craniosynostosis can occur prenatally, or later in infancy or childhood, with the impact on cranial growth being less severe the later its occurrence. Craniosynostosis can be classified as isolated or syndromic.
     In isolated craniosynostosis, there is premature fusion of either single or multiple sutures. There are no other associated abnormalities, aside from those produced secondarily as a result of premature sutural fusion. These cases are usually not familial, and except for certain cases of unicoronal synostosis, a genetic basis has not been discovered.
     In syndromic craniosynostosis, fusion of sutures is combined with other systemic abnormalities, such as hearing loss or polysyndactyly. This type of craniosynostosis has a genetic basis and is often familial. (Cohen, 1986)