Chiari I malformation: association with hypophosphatemic rickets and MR imaging appearance.
OBJECTIVE
To evaluate for an association between familial hypophosphatemic rickets (FHR) and Chiari I malformation (CM1).


METHODS
Sixteen patients with FHR underwent magnetic resonance (MR) imaging of the cervicomedullary junction. Images were analyzed by three radiologists for cerebellar tonsillar ectopia, syringohydromyelia, calvarial bone thickening, a flat posterior fossa, and cervical spinal stenosis. 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 reviewed. A two-sided Fisher exact test was used to test for independence between CM1 and bone thickening or ventriculomegaly.


RESULTS
Seven subjects (44%) had CM1. The more severe the bone thickening, the more likely that a CM1 was present. Four subjects (25%) had cervical spinal stenosis.


CONCLUSIONS
Findings indicate that CM1 is associated with FHR and that the primary abnormality in patients with CM1 is a small posterior fossa caused by a bony malformation.
Caldemeyer
K S
KS
Department of Radiology, Indiana University School of Medicine, University Hospital, Indianapolis 46202-5253, USA.
Boaz
J C
JC
Wappner
R S
RS
Moran
C C
CC
Smith
R R
RR
Quets
J P
JP
D000293:Adolescent; D000328:Adult; D001139:Arnold-Chiari Malformation / Q000150:complications / Q000175:diagnosis*; D001921:Brain / Q000473:pathology*; D002648:Child; D003388:Cranial Fossa, Posterior / Q000473:pathology; D005260:Female; D006801:Humans; D007015:Hypophosphatemia, Familial / Q000150:complications*; D008279:Magnetic Resonance Imaging; D008297:Male; D011446:Prospective Studies; D013116:Spinal Cord / Q000473:pathology*