Magnetic resonance imaging in pregnancy: study of fetal cerebral malformations

This paper reports 15 examinations by magnetic resonance imaging (MRI) performed in pregnant women whose fetuses had cerebral malformations identified by sonography. In all the cases the fetuses were immobilized by ultrasound-guided intravenous or intramuscular curarization. The diagnoses by MRI and ultrasound differed only in one case where an occipital meningocele had first been suggested. No cerebral abnormalities were demonstrated in this case by the MRI study, and this was confirmed at birth. In the remaining 14 cases, MRI confirmed the ultrasound diagnosis of cerebral malformation. In four of these cases, MRI added some additional information to the ultrasound diagnosis of ventriculomegaly by detecting agenesis of the corpus callosum in two fetuses, one Chiari malformation and one triventricular hydrocephalus. Another two ultrasound diagnoses of microcephaly actually proved to be semilobar holoprosencephaly with MRI. In the following cases, the MRI diagnoses concurred with those of ultrasound, and was therefore used unnecessarily despite providing further anatomical details of the lesions: two cases of agenesis of the corpus callosum, one case of anencephaly, a cystic hygroma of the neck, an alobar holoprosencephaly, a Dandy-Walker malformation and a mild isolated hydrocephalus associated with diaphragmatic hernia. In one case of iniencephaly, sonography offered closer approximation to the correct diagnosis. The results obtained unequivocally confirm the high sensitivity of ultrasound examinations in the prenatal screening of cerebral malformations and show that MRI proves to be complementary in uncertain cases or when more accurate anatomical detail is required.