Craniosynostosis

Craniosynostosis is a condition in which one or more of the fibrous sutures in a young infant's skull prematurely fuses by turning into bone (ossification), thereby changing the growth pattern of the skull. Because the skull cannot expand perpendicular to the fused suture, it compensates by growing more in the direction parallel to the closed sutures. Sometimes the resulting growth pattern provides the necessary space for the growing brain, but results in an abnormal head shape and abnormal facial features. In cases in which the compensation does not effectively provide enough space for the growing brain, craniosynostosis results in increased intracranial pressure leading possibly to visual impairment, sleeping impairment, eating difficulties, or an impairment of mental development combined with a significant reduction in IQ. Craniosynostosis occurs in one in 2000 births. Craniosynostosis is part of a syndrome in 15% to 40% of affected patients, but it usually occurs as an isolated condition. The term is from cranio, cranium; + syn, together; + ost, relating to bone; + osis, denoting a condition. Craniosynostosis is the opposite of metopism. Children born with craniosynostosis have a distinct phenotype, i.e., appearance—observable traits caused by the expression of a condition's genes. The features of craniosynostosis' particular phenotype are determined by which suture is closed. The fusion of this suture causes a certain change in the shape of the skull; a deformity of the skull. Virchow's law dictates that, when premature suture closure occurs, growth of the skull typically is restricted perpendicularly to the fused suture and enhanced in a plane parallel to it, thus trying to provide space for the fast-growing brain. Using this law, the pattern of skull deformity in craniosynostosis often may be predicted. An illustrative example of this phenomenon is scaphocephaly; the name providing a direct hint regarding the deformity of the skull. The literal meaning of the Greek derived word 'scaphocephaly' is boat-head.