description

dolichocephaly is a long keel-shaped skull with prominent forehead and occiput. it may be associated with craniosynostosis of the sagittal suture; it may be commonly seen in the premature infant and is more frequently a normal variant. it is more common in preterm fetuses in the breech rather than cephalic presentation and in fetuses with oligohydramnios of long duration. dolichocephalic fetuses with preterm premature rupture of membranes appear to be twice as likely to suffer respiratory distress syndrome than normocephalic infants. individuals with dolichocephaly have a decreased cephalic index of 60 to 70 (ci = head width/head length x 100; normal is 70 to 80). the skull develops from mesenchyme, with the portion surrounding the brain termed the neurocranium. the neurocranium consists of a cartilaginous portion (chondrocranium) and a membranous portion. the chondrocranium is the cartilaginous base of the skull, which develops by fusion of several cartilages. the membranous neurocranium ossifies to form the cranial vault, the bones of which are separated by connective tissue membranes known as sutures. six fibrous areas, the fontanelles, are also present. the five major sutures are the frontal, or metopic, sagittal, coronal, lambdoid and squamosal. the sutures allow for moulding to occur during the delivery process, and enlargement to accommodate normal brain growth. when the cranial bones fuse prematurely there is decreased growth potential. bone deposition occurs abnormally, with the majority being directed away from the fused bony plate. in turn, perimeter sutures adjacent to the prematurely fused suture compensate in growth to a greater extent than sutures distant to the fused area. the primary cause of synostosis may be a defect at the cranial base at the site of initial attachment of the dura; other studies suggest a vascular defect causing deficient osteoclasia. secondary craniosynostosis may occur because of brain abnormalities such as microcephaly or holoprosencephaly, or may be due to fetal constraint. craniosynostosis has been reported to be present in 0.5 to 3.4 per 1000 live births. sagittal synostosis accounts for 50%; coronal 22%; metopic 6%; and other or multiple 23%. unilateral coronal synostosis is as common as bilateral. a predominance of males is noted, particularly for sagittal involvement. craniosynostosis often causes alteration in head shape, ridging over the sutures, and/or fontanelle closure. different terms have been used to describe the head shape alterations due to craniosynostosis, with resultant shape dependent upon the suture(s) involved.