Chiari 1 malformation and untreated sagittal synostosis: a new subset of complex Chiari?

Chiari 1 malformation (CM1) is a well-known association with complex craniosynostosis (CC), while it has been rarely reported in association with monosynostosis. The aim of the present study is to investigate on the association between CM1 and untreated sagittal synostosis (USS).

The study included 48 cases of sagittal synostosis (SS), untreated for misdiagnosis and associated with CM1. The children were firstly diagnosed for CM1 by MRI (mean age 9) than for SS (mean age 10.5) by three-dimensional computerized tomography (3D-CT), which documented the absence of the sagittal suture, in the presence of residual indentation of all the other sutures. Syndromic cases were diagnosed by clinical evaluation and molecular studies.

Of the 48 children harboring CM1 plus USS, 21 were asymptomatic for CM1 and are still on follow-up, while 27 children were operated for syringomyelia and scoliosis and/or occurrence of symptoms, three of them had an acute presentation (two papilledema and one sleep apneas) and 11 children had a documented increase of preoperative ICP. Craniovertebral decompression (CVD) was the first-line surgery in 24 children, 16 with duroplasty and five without and eight had also cerebellar (CBL) tonsil coagulation. A cranial vault remodelling was firstly performed in three children. Fifteen percent of children submitted to CVD needed a revision for cerebrospinal fluid (CSF) collection, while two needed both the supra- and infratentorial decompressive procedure and another two needed a treatment for the associated hydrocephalus.

The present study identified an USS in 27 (15.5%) of 174 CM1 children operated for a symptomatic CM1. We suggest to define this association CM1 plus USS, a new subtype of complex CM1. For the high percentage of complications and multiple procedures needed to solve the CM1, we advise to identify by 3D-CT scan these children before performing CVD. Our finding suggests also that, if left untreated, SS may lead to the delayed occurrence of a challenging subset of CM1.