Occult craniosynostosis in normocephalic children with Chiari I malformation

There are numerous theories regarding the development of paediatric Chiari I malformation. We hypothesise a subset may be related to early calvarial suture closure, which may occur too late to cause an abnormal head shape but early enough that changes in intracranial pressure lead to the development of tonsillar descent. Isolated single suture craniosynostosis is not typically associated with Chiari I malformation. We assessed our series of children with Chiari I malformation to establish what proportion harboured an undiagnosed craniosynostosis.

This was a single-centre retrospective review of all children with Chiari I malformation from 2012 to 2022. Imaging was reviewed for the presence of a craniosynostosis. Clinical records of synostotic patients were reviewed to establish whether they had a craniofacial disorder or were under the care of the craniofacial team. If neither applied then they were considered to have an 'incidental craniosynostosis'.

The study included six-hundred-and-nineteen patients with Chiari I malformation, with a mean age at diagnosis of 8.7 years. 13.4 % of patients had radiological evidence of an incidentally-detected craniosynostosis, most commonly the sagittal suture (95.7 %). Incidental craniosynostosis was mostly observed in normocephalic children, but dolichocephaly was associated with an increased risk of concurrent sagittal craniosynostosis.

Craniosynostosis in normocephalic children with a Chiari I malformation is an under-diagnosed phenomenon. Given the high rate of correlation we recommend assessing specifically for craniosynostosis in all children with a 'simple' Chiari I malformation prior to any intervention.