CHIARI-I MALFORMATION - ASSOCIATION WITH HYPOPHOSPHATEMIC RICKETS ANDMR-IMAGING APPEARANCE

PURPOSE: To evaluate for an association between familial hypophosphate mic rickets (FHR) and Chiari I malformation (CM1). MATERIALS AND METHO DS: Sixteen patients with FHR underwent magnetic resonance (MR) imagin g of the cervicomedullary junction. Images were analyzed by three radi ologists for cerebellar tonsillar ectopia, syringohydromyelia, calvari al bone thickening, a flat posterior fossa, and cervical spinal stenos is. Final diagnoses were made by means of consensus. Tonsillar ectopia of 4 mm indicated CM1. Subjects underwent neurologic examination and completed a questionnaire. Medical records were retrospectively review ed. A two-sided Fisher exact test was used to test for independence be tween CMI and bone thickening or ventriculomegaly. RESULTS: Seven subj ects (44%) had CM1. The more severe the bone thickening, the more like ly that a CMI was present. Four subjects (25%) had cervical spinal ste nosis. CONCLUSION: Findings indicate that CM1 is associated with FHR a nd that the primary abnormality in patients with CM1 is a small. poste rior fossa caused by a bony malformation.