Craniosynostosis in neural tube defects: a theory on its pathogenesis.

BACKGROUND: In most cases, craniosynostosis is a sporadic occurrence of unknown etiology. Efforts to ascertain the exact, cause of this deformation often fall to reveal its origin and pathogenetic mechanism. Some previous reports have described isolated instances of the association of neural tube defects (NTD) and craniosynostosis, but in none of them has a causal relationship been established to explain this coincidence, apart from a fortuitous sequence of congenital defects.
METHODS: We have reviewed the clinical records of 40 patients diagnosed with craniosynostosis who were studied at our hospital over a 22-year period, for the purpose of determining the possible etiologies of this cranial deformation.
RESULTS: We found that three children with unilateral coronal synostosis had associated NTD-an incidence of 7.5%. Two children had cephaloceles and the third harbored a lumbosacral myelomeningocele. In these three cases, the craniosynostosis was noted immediately after birth and before the development or treatment of hydrocephalus.
CONCLUSION: We think that there must be an alternative explanation for the association of craniosynostosis and NTD other than overdrained hydrocephalus or chance association. We advance the hypothesis that in these cases the cause of the premature coronal synostosis was the lack of cerebral expansion. Since brain expansion and intracranial pulse pressure determine the growth and shape of the overlying cranial vault, the dampening effect of the malformation sac (myelomeningocele or cephalocele) on the intracranial pressure and on the pulse pressure may lead to close contact of the affected bones and to the premature closure of the coronal suture. The possibility of fetal head constraint because of diminished fetal activity due to the NTD as a contributory factor is also suggested.