ESPE Abstracts

Background: X-linked hypophosphatemic rickets (XLH) represents the most common form of hypophosphatemia and leads to vitamin D resistant rickets in children. Even though cranial vault and craniovertebral anomalies of potential neurosurgical interest, namely early closure of the cranial sutures and Chiari type I malformation- have been observed in XLH patients their actual incidence is not established.

Aim: Describe and analyze the incidence of cranial and cervico-occipital junction (COJ) in children with XLH.

Patients and methods: Retrospective study of CT scans of the head and skull in 44 XLH children followed at the French Reference Center for Rare Diseases of the Calcium and Phosphate Metabolism. 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 in whom XLH was diagnosed and treatment initiated at 2.4±2.1 years were analyzed. 25% of XLH children showed protrusion of the cerebellar tonsils (seven children > 5 mm and 3 children <5 mm). 59% of XLH children had a complete or partial fusion of the saggital suture and craniosynostosis was associated to abnormal descent of cerebellar tonsils. A history of dental abcesses was associated to craniosynostosis. 36% of XLH children presented scaphocéphalie (cranial index <75%). Patients with craniosynostosis had a smaller cranial index compared to patients without craniosynostosis.

Conclusion: This study highlights that sagittal suture fusion and Chiari malformation are two possible complications of XLH. The incidence of sagittal synostosis in patients affected by XLH is actually extremely high and it has been probably underestimated in previous reports. Chiari malformation is also relatively common in this population. 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. Further studies are needed to better assess the clinical impact of these complications in this population.