Abnormalities of skull shape can arise either from external pressure applied on the head in pregnancy or infancy, or from problems when the skull is growing. The most common abnormality of skull growth is called craniosynostosis, which occurs due to the early closure of one or more of the seams between the skull bones called sutures.
Last updated October 2018 by Professor A Wilkie, Nuffield Professor of Pathology, Weatherall Institute of Molecular Medicine, Oxford University, Oxford, UK.
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As the brain grows during fetal life (in the womb) and childhood, the overlying skull also enlarges by adding new bone at these sutures. Craniosynostosis causes distortion of the shape of the skull due to 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:
- sagittal synostosis – which gives a long, narrow head
- coronal synostosis – may affect one side (unilateral) or both sides (bilateral) and gives a broad, flat head that is asymmetric in unilateral cases
- metopic synostosis – causes a triangular-shaped forehead.
- lambdoid synostosis – causes flattening at the back of the head.
The remaining 30 per cent of craniosynostosis is more complex and either involves the fusion of multiple sutures, and/or is combined with additional changes in the face, limbs or other parts of the body, or developmental problems, indicating a syndrome.
Over 100 craniosynostosis syndromes have been described – the most common are Crouzon, Pfeiffer, Apert, Muenke, Saethre-Chotzen and craniofrontonasal syndromes, together with TCF12-, ERF-, and SMAD6-related craniosynostosis.
Intrauterine factors (within the womb) that increase the likelihood of craniosynostosis include having twins, reduced amniotic fluid (the fluid around the baby), an abnormally shaped womb and breech position (baby feet first rather than head first).
Syndromes that cause craniosynostosis may be due to a change in genetic information (DNA). Genetic mutations can be identified in about 25 per cent of cases, including many of the specific syndromes and also in some children with apparently non-syndromic synostosis. Important genes identified to date are three of the fibroblast growth factor receptors (FGFR1, FGFR2 and FGFR3) and other genes called TWIST1, EFNB1, TCF12, ERF and SMAD.
The diagnosis, assessment and surgical/medical management of craniosynostosis requires a multidisciplinary team approach, involving plastic, maxillofacial (focussing on the mouth, jaws, face and neck), and neurological surgeons. Also involved may be ear/nose and throat specialists, geneticists, orthoptists (specialise in diagnosing and treating visual problems involving eye movement and alignment), psychologists and speech and language therapists.
In England and Wales, four centres located at Birmingham, Liverpool, London (Great Ormond Street Hospital) and Oxford can undertake this work.
If craniosynostosis is due to a genetic syndrome then the pattern of inheritance will conform to that syndrome. Especially in more severe cases, the syndrome may be caused by a new mutation, i.e. arising in the family for the first time in the affected child (sporadic mutation).
Prenatal diagnosis for craniosynostosis is only normally possible when a specific mutation in a family has been identified. In selected cases, non-invasive prenatal diagnosis (using a blood sample from the pregnant mother) is now technically possible. Affected families should be referred to their genetics centre for information and support. Ultrasound scanning during pregnancy often fails to detect craniosynostosis, except in severe cases.
Headlines – Craniofacial Support
The Group is a Registered Charity in England and Wales No. 1058461. It provides information and support to all those affected by Craniosynostosis (both syndromic and non-syndromic) and associated conditions. The Group hosts an annual family weekend and has online forums for members.
Group details last updated October 2018.