Abnormalities of skull shape can arise either from external pressure exerted on the head in early life, or from intrinsic abnormalities of growth. The most common intrinsic abnormality of skull growth is called craniosynostosis, which affects about 1 in 2,500 children. Craniosynostosis is the medical term for the premature closure of one or more of the seams between the skull bones. As the brain grows during fetal life and childhood, the overlying skull also enlarges by adding new bone at these seams, which are termed sutures. The major sutures are the midline metopic (at the front) and sagittal (at the top) sutures, and the paired coronal and lambdoid sutures. The coronal sutures run across the skull in front of the ears, crossing the junction of the metopic and sagittal sutures; the lambdoid sutures divide from the back end of the sagittal suture and run obliquely forwards to end up behind the each ear.

Craniosynostosis causes distortion of the shape of the skull owing both to failure of bone growth at the prematurely closed suture, and to compensatory overgrowth at the sutures that remain open. The different types of craniosynostosis are classified by which sutures have closed prematurely. Most common (forty-five per cent) is sagittal synostosis, which gives a long, narrow head; next most frequent is coronal synostosis (twenty per cent), which may affect one side (unilateral) or both sides (bilateral) and gives a broad, flat head that is asymmetric in unilateral cases; metopic synostosis (fifteen per cent) causes a triangular-shaped forehead. Lambdoid synostosis is rare. However, not all abnormalities of skull shape are caused by craniosynostosis; a consequence of the 'back to sleep' campaign to reduce the occurrence of cot death has been a marked increase in the frequency of babies who have flat backs to their heads due to sleeping on their backs. In the absence of craniosynostosis, this condition, termed 'deformational plagiocephaly' slowly improves with age and does not require surgery.

The remaining twenty per cent of craniosynostosis is more complex and either involves the fusion of multiple sutures (five per cent), and/or is combined with additional changes in the face, limbs or other parts of the body, indicating a 'syndrome' (fifteen per cent). Over one hundred craniosynostosis syndromes have been described, most of which are extremely rare; the most common syndromes are Crouzon, Pfeiffer, Apert, Muenke, Saethre-Chotzen and craniofrontonasal syndromes. In these complex cases, there may be additional problems with the vision, breathing, hearing, teeth, learning development, facial appearance and malformation of the limbs and other organs.

Craniosynostosis has a diversity of causes, the most important of which are abnormal pressure on the fetal skull inside the womb (intrauterine factors), and alterations in the genetic makeup (mutations). Intrauterine factors that predispose to craniosynostosis include having twins, reduced amniotic fluid, an abnormally shaped womb and breech position; commonly the mother reports that there was persistent discomfort during the pregnancy or that she had a feeling of the fetal head being stuck. These factors are believed to be especially important in sagittal and metopic synostosis, for which there is usually a low risk of the condition recurring in further children.

The diagnosis, assessment and surgical/medical management of craniosynostosis requires a multidisciplinary team approach, involving plastic, maxillofacial, and neurological surgeons, eye and ear/nose/throat specialists, geneticists, psychologists and speech therapists. In England and Wales, four centres located at Birmingham, Liverpool, London (Great Ormond Street Hospital) and Oxford are accredited to undertake this work. These centres also specialise in distinguishing true craniosynostosis from deformational plagiocephaly, which can sometimes be difficult.

Inheritance patterns
Genetic mutations can be identified in about twenty-five per cent of cases, including many of the specific syndromes and also in some children with apparently non-syndromic coronal synostosis. The important genes identified to date are three of the fibroblast growth factor receptors (FGFR1, FGFR2 and FGFR3) and other genes called TWIST1 and EFNB1. Cases with a genetic cause are more likely to recur within the family. Genetic testing is available in the UK at two centres (Great Ormond Street Hospital, London and Churchill Hospital, Oxford).

Prenatal diagnosis
Prenatal diagnosis for craniosynostosis is generally only possible when a specific mutation has been identified.

Medical text written February 1994 by Dr W Reardon, Senior Registrar in Clinical Genetics, Institute of Child Health, London, UK. Last updated December 2006 by Professor A Wilkie, Nuffield Professor of Pathology, Weatherall Institute of Molecular Medicine, Oxford University, Oxford, UK.

Further Online Resources
Medical texts in The Contact a Family Directory are designed to give a short, clear description of specific conditions and rare disorders. More extensive information on this condition can be found on a range of reliable, validated web sites and links to them are included in the CD-ROM version of this Directory. Further information on these resources can be found in our Medical Information on the Internet article.

HEADLINES - CRANIOFACIAL SUPPORT

Headlines - Craniofacial Support
128 Beesmoor Road
Frampton Cotterell
Bristol BS36 2JP
Tel: 01454 850557
e-mail: info@headlines.org.uk
Web: http://www.headlines.org.uk

Originally, established in 1993 as the Craniofacial Support Group, the Group is a National Registered Charity No. 1058461 established by Contact a Family working with parents of affected children. It acts as an umbrella group for all the conditions associated with Craniosynostosis, many of which are individually listed in the index. Headlines has a full list of conditions coming under the Craniosynostosis umbrella that have been checked and approved by medical experts. It offers contact with other families with the same or similar condition where possible and has information and advice about the practical aspects of hospital visits and surgery. For UK residents, it can offer help and guidance in being referred to one of the four designated Craniofacial units. It publishes a newsletter 'Headlines' and has information available, details on request. The Group is in touch with over 1,000 people including professional workers, overseas members and over 500 families.

Group details last confirmed November 2007.