Craniosynostosis

Skull deformities are a very common reason for referral to pediatric neurosurgery.Premature fusion of cranial suture closure is called craniosynostosis.

Incidence and Aetiology :
Isolated craniosynsostosis occurs due to the premature fusion of a single suture or multiple sutures. The overall prevalence of craniosynostosis is around 1 in 2500 live births, with ranges of 1 in 709 to 1 in 3225 of births. The wide variation seen is due to differences in the various criteria under which one labels craniosynsostosis. Isolated craniosynostosis is far more common than multiple ‘syndromic’ synostosis.Sagittal seems to be commonest, followed by coronal and metopic. True lambdoid synostosis appears rare and is difficult to distinguish from deformational posterior asymmetry, which is considered to be because of positional molding of the cranium.

Common Syndromic Craniosynostosis like Apert and Crouzon have prevalence of about 1 in 65000, each about 4-6 per cent of all craniosynostosis. There is evidence of FGFR2 mutation in Apert Syndrome, FGFR3 in Crouzon syndrome and FGFR1 in Pfeiffer syndrome. Almost all Aperts and about 50 per cent of Crouzons arise de novo and there is a correlation with increase in paternal age. The prevalence of Pfeiffer syndrome is lower than others but there is no definite percentage data.

Apart from this there are rarer types of single gene syndromes associated with other malformations, metabolic storage disorders and learning disabilities.There are chromosomal aberrations of which craniosynostosis may be a feature. There are teratogenic causes associated with anticonvulsants, (Valproate, Hydantoin)cytotoxic agents, (Methotraxate, Cyclophosphomide, Cytarabine) abortifacients, and nitrosatable drugs(Chlorpneramine,Nitrofurantoin, Chlordiazepoxide and Fluconazole).

Classification and Terminology
Over the years, the nomenclature for various craniofacial deformities has remained constant, but with the entry of molecular genetics, there have been additional terms given to the complex multi sutural synostosis. However, in simple terms these deformities can be classified into three different varieties.