Involvement of the skull base and vault in chronic idiopathic hyperphosphatasia.

Chronic idiopathic hyperphosphatasia (CIH) is a rare generalised skeletal dysplasia in childhood. The clinical, radiographic and cerebral MR findings in a 5-year-old girl with the severe infantile form of CIH are reported. In spite of cranial enlargement, the intracranial space and the skull base were markedly reduced, the whole brain was compressed and a Chiari I malformation was present. Normal flow in the dural venous sinuses was documented. The patient showed no detectable cranial nerve involvement or hydrocephalus. Cranial MR in this patient enabled us to confirm that CIH involves the skull base and vault.