Craniosynostosis
From bonepath
Craniosynostosis refers to the premature closure or fusion of a cranial vault suture (Wilkie 1997). As the vault sutures are the intramembranous growth sites responsible for enlargement of the bony vault (Opperman, 2000), synostoses can result in a variety of somewhat predictable cranial shapes (Virchow, 1852, cited in Alden et al., 1999; Oostra et al., 2005). It is unclear whether craniosynostosis impedes and influences the growth of the underlying brain and meninges, or whether abnormalities in growth of the brain and meninges are responsible for synostoses (see Matic and Vander Kolk, 2002).
Craniosynostosis is associated with a variety of etiologies. Non-syndromic causes include artificial cranial deformation (O’Loughlin, 1996), abnormal brain growth (Wilkie, 1997), and perinatal trauma (Roberts and Manchester, 2005). However, synostoses are also associated with congenital diseases, perhaps most notably Crouzon’s, Pfeiffer’s, and Apert’s syndromes (Rutland et al., 1995; Wilkie et al., 1995; Wilkie, 1997; Alden et al., 1999). Some 64 mutations on six genes (MSX2, FGRF1-3, FBN1, TWIST) have been associated with craniosynostosis and related syndromes; indeed, synostosis is a symptom of over 100 such conditions (Wilkie, 1997).
Because of the varied associations of craniosynostosis, it is difficult to tell to what extent other cranial abnormalities are a result of the synostosis, or other outcomes of an associated syndrome. Clinical manifestations of craniosynostosis and concomitant abnormal cranial growth include increased “intracranial pressure, impaired cerebral blood flow, airway obstruction, impaired vision and hearing, learning difficulties and psychological defects” (Wilkie, 1997: 1647). O’Loughlin (1996) also found that synostotic crania tended to have larger and deeper venous sinuses underlying the early-closed suture.
Early fusion at a given suture prevents enlargement of the vault in that region, which results in compensatory growth in other regions of the cranial vault (Oostra et al., 2005, summarized below). This results in fairly predictable cranial vault shapes: synostosis of the sagittal suture prevents enlargement of the vault at the parietals, resulting in an antero-posteriorly long vault (dolichocephaly); synostosis of the metopic suture results an a narrow, pointed frontal and a broad posterior vault (trigonocephaly); a relatively broad cranium (brachiocephaly) is caused by bilateral early fusion of the coronal suture (or of the lambdoidal suture, though this is less common). Unilateral fusion of either the coronal or lambdoidal sutures results in an asymmetrical vault (plagiocephaly). Finally, synostosis of multiple sutures can result in superior-ward compensatory growth, resulting in a ‘high’ vault (acrocephaly).
It is estimated that some form of craniosynostis occurs in anywhere from three to five of every 2500 people (Wilkie, 1997; Oostra et al., 2005). The most common type is sagittal synostosis, followed by coronal (Oostra et al., 2005; Richtsmeier et al., 2006). Craniosynostosis occurs about three to four times more often in men than in women (Oostra et al., 2005). However, Richtsmeier and colleagues (2006) noted that the occurrence of coronal synostosis (uni- or bilateral) is about twice as high in females as in males. These authors further note that unilateral coronal synostosis is usually nonsyndromic, whereas bicoronal synostosis is usually syndromic.
[edit] Examples from Ford Collection
[edit] Additional Resources
[edit] References
Alden TD, Lin KY, Jane JA. 1999. Mechanisms of premature closure of cranial sutures. Child's Nervous System 15:670-5
Matic D, Vander Kolk CA. The Ptolemaic Concept versus the Copernican System: Rethinking the Etiology and REsults of Treatment in Craniosynostosis in 2002. Plastic and Reconstructive Surgery 111:929 - 933
O'Loughlin VD. 1996. Comparative endocranial vascular changes due to craniosynostosis and artificial cranial deformation. Am J Phys Anthropol 101:369-85
Oostra RJ, van der Wolk S, Maas M, Hennekam RC. 2005. Malformations of the axial skeleton in the museum Vrolik: II: craniosynostoses and suture-related conditions. Am J Med Genet A 136A:327-42
Opperman LA. 2000. Cranial sutures as intramembranous bone growth sites. Dev Dyn 219:472-85
Richtsmeier JT, Aldridge K, DeLeon VB, Panchal J, et al. 2006. Phenotypic integration of neurocranium and brain. J Exp Zool B Mol Dev Evol 306:360-78
Roberts C, Manchester K. 2005. The Archaeology of Disease. Ithaca: Cornell University Press
Rutland P, Pulleyn LJ, Reardon W, Baraitser M, et al. 1995. Identical mutations in the FGFR2 gene cause both Pfeiffer and Crouzon syndrome phenotypes. Nature genetics 9:173-6
Wilkie AOM. 1997. Craniosynostosis: genes and mechanisms. Human molecular genetics 6:1647
Wilkie AOM, Slaney SF, Oldridge M, Poole MD, et al. 1995. Apert syndrome results from localized mutations of FGFR2 and is allelic with Crouzon syndrome. Nature genetics 9:165-72
