Craniosynostosis (plural: craniosynostoses) refers to the premature closure of the cranial sutures. The skull shape then undergoes characteristic changes depending on which suture(s) close early.
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Epidemiology
There is a 3:1 male predominance with an overall incidence of 1 in 2000-2500. 8% of cases are syndromic or familial.
Associations
Most occur as isolated anomalies but syndromic associations can be seen in a small proportion of cases (~10%):
Pathology
Aetiology
Primary forms are either sporadic or familial. Secondary craniosynostosis occurs in relation to a variety of causes:
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endocrine disorders
hypophosphataemia
hypercalcaemia
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haematologic disorders causing bone marrow hyperplasia
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inadequate brain growth
shunted hydrocephalus
Ages of normal sutural/fontanelle closure
metopic: 3-9 months
anterior fontanelle: 18-24 months
sphenosquamosal: 6-10 years
sphenofrontal: approximately 15 years
occipitomastoid: approximately 16 years
sagittal: approximately 22 years
coronal: approximately 24 years
lambdoid: approximately 26 years
squamosal: approximately 60 years
Types
brachycephaly: bicoronal and/or bilambdoid sutures
scaphocephaly/dolichocephaly: sagittal suture
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plagiocephaly: unilateral coronal and lambdoid sutures
frontal plagiocephaly: unilateral coronal suture
occipital plagiocephaly: unilateral lambdoid suture
pachycephaly: lambdoid suture
oxycephaly/turricephaly: sagittal, coronal and lambdoid sutures (tower like skull)
cloverleaf skull/Kleeblattschädel: intrauterine sagittal, coronal, lambdoid sutures (most severe)
harlequin eye: ipsilateral coronal suture
progressive postnatal pansynostosis: a rare form of craniosynostosis which involves late (postnatal) fusion of all cranial sutures 9
The sagittal suture is most commonly involved (≈50%), where the lateral growth of the skull is arrested while anteroposterior growth continues, producing a narrowly elongated skull known as scaphocephaly (meaning boat-shaped) or dolichocephaly (from the ancient Greek for long, δολιχός: dolichos).
The next most common sutures in terms of involvement are:
coronal (~20%)
lambdoid (~5%)
metopic (~5%)
Radiographic features
Restriction of skull growth is perpendicular to the affected suture line. Characteristic dysmorphic head shapes are associated with each type of craniosynostosis.
Ultrasound
Ultrasound can be used as a screening tool or in clinically-subtle cases and can reduce radiation exposure in infants to cases with inconclusive findings 11.
General features include:
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sutures are normally hypoechoic
there may be a loss of normally decreased echogenicity in the region of the fusion
lack of suture patency
ridging of the sutures
CT
Low-dose CT with 3D image reformations is the best modality for the evaluation of skull sutures 5.
Treatment and prognosis
Treatment is often with a cranioplasty. Abnormal intracranial pressure may affect neurocognition.
History and etymology
Craniosynostosis was first accurately characterised by Rudolph Virchow in 1851 10.