S4A-17 SESSION 4A: GENERALITIES IN CRANIOSYNOSTOSIS – PART I LESSONS LEARNED FROM X-LINKED HYPOPHOSPHATEMIC RICKETS RELATED CRANIOSYNOSTOSIS:

Abstract

Introduction: X-linked hypophosphatemic rickets (XLH) represents the most common form of hypophosphatemia and leads to vitamin D resistant rickets in children. Early closure of the cranial sutures leading to cranial vault and craniovertebral anomalies of potential craniofacial interest have been observed in XLH, the actual incidence of such anomalies is not yet established. Aim of this study is to describe and analyze the incidence of cranial and cervico-occipital junction (COJ) in children with XLH. Methods: Retrospective study of CT scans of the head and skull in 44 XLH children. The patency of the sutures was noted. The cranial index was calculated and the position of the cerebellar tonsils was analyzed Results: Forty-four XLH children, 15 boys and 29 girls, age 8.7 ± 3.9 years at time of CT scan. 25% of XLH children showed protrusion of the cerebellar tonsils (7 children > 5 mm and 3 children < 5 mm). 59% of XLH children had a complete or partial fusion of the sagittal suture and craniosynostosis was associated with abnormal descent of cerebellar tonsils. A history of dental abscesses was associated with craniosynostosis. Only 36% XLH children presented a cranial index <75%. Patients with craniosynostosis had a smaller cranial index compared to patients without craniosynostosis Conclusion: Sagittal suture fusion and Chiari malformation are two common complications of XLH. The association between the two entities underlines the potential consequences of a long lasting synostosis in this population. This study also highlights the particularities of metabolic synostosis that despite a mild deformation may have severe consequences. Because the diagnosis can be underestimated on a purely clinical basis, radiological studies should be considered in XLH children if a proper diagnosis is warranted.