• Catherine Limperopoulos, Richard L Robertson, Omar S Khwaja, Caroline D Robson, Judy A Estroff, Carole Barnewolt, Deborah Levine, Donna Morash, Luanne Nemes, Linda Zaccagnini, and Adré J du Plessis.
• Fetal-Neonatal Neurology Research Program, Department of Neurology, Children's Hospital Boston and Harvard Medical School, Boston, MA, USA. catherine.limperopoulos@mcgill.ca
• AJR Am J Roentgenol. 2008 Jun 1; 190 (6): 1637-43.

ObjectiveThe first objective of our study was to describe the prevalence and spectrum of posterior fossa anomalies over 5 years in a major fetal care center where the referral diagnosis (by fetal sonography) was investigated by fetal MRI and, if confirmed, by postnatal MRI if possible. The second objective was to assess the accuracy with which fetal MRI predicts postnatal MRI findings in this population.Materials And MethodsWe retrospectively identified all cases of suspected fetal posterior fossa anomalies referred to our center from 2002 through 2006. We reviewed maternal, fetal, neonatal, and follow-up records of all cases and fetal and early postnatal imaging studies.ResultsOf the 90 cases of suspected fetal posterior fossa anomalies (by fetal sonography) referred over the study period, 60 (67%) were confirmed by fetal MRI. Of 42 live-born infants, 39 (93%) underwent postnatal MRI. There was complete agreement in fetal and postnatal MRI diagnoses in 23 infants (59%). In 16 cases (41%), fetal and postnatal MRI diagnoses disagreed; postnatal MRI excluded fetal MRI diagnoses in six cases (15%) and revealed additional anomalies in 10 cases (26%).ConclusionAlthough a valuable adjunct to fetal sonography in cases of suspected posterior fossa anomaly, current fetal MRI, particularly in early gestation, has limitations in accurately predicting postnatal MRI abnormalities. Advancing the accuracy of MRI for the diagnosis of posterior fossa anomalies will require greater understanding of normal brain development and improved tissue resolution of fetal MRI. During the interim, our findings strongly support the need for postnatal MRI follow-up in cases with suspected posterior fossa anomalies by fetal MRI.

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