Magnetic resonance of the fetus. Part II: Pathologic features

This paper reports the results of 27 prenatal fetal MR. The materials and methods have been published in a separate part of this study. The different pathological features have been grouped in 7 different sections. The first comprises a case of an encephaly in which MR findings failed to add significant information to previous ultrasound investigation, although images were very similar to the anatomo-pathological findings from the aborted fetus. The same section includes two cases of microcephalus, one of which was part of a complex series of malformations and the other caused by true Evrard's microcephaly with histological confirmation of a depleted germinative matrix. This group also comprises a rare case of iniencephaly in which only MR examination of the aborted fetus and anatomo-pathological examination allowed correct interpretation of the malformation, a posteriori. The second section includes 2 cases of alobar oloprosencephaly and 2 of semilobar oloprosencephaly. In the first, the MR findings were suggestive but failed to add any significant data to the ultrasound images which remained diagnostic. In contrast, MR findings in the two cases of semilobar oloprosencephaly gave additional morphological information on the malformation; one case was confirmed at anatomo-pathological observation and the other at post-natal CT. The third section comprises 5 cases of agenesis of the corpus callosum. When transvaginal echography is not possible, MR may be the only procedure to identify this malformation accurately and rule out any associated CNS abnormalities. In 2 of our cases isolated agenesis of the corpus callosum was diagnosed and pregnancy continued to term. In the other 3 cases agenesis of the corpus callosum was accompanied by Chiari's malformation in one case, microcephaly with schizencephaly in another and large interhemispheric cysts in the third: pregnancy was terminated and the anatomo-pathological findings are available. This section arbitrarily includes a septum pellucidum and cavum Vergae cyst confirmed at post-natal CT. The group of cystic malformations of the posterior cranial fossa comprises a classic Dandy-Walker malformation, a Dandy-Walker variant and a megacisterna magna. In these forms fetal MR was diagnostic for a minor malformation in terms of deciding whether or not pregnancy was to proceed. The cases of Chiari's malformation were type I with caudal ectopia of the tonsillae cerebelli and dilated ventricular system. Pregnancy was terminated in both cases and diagnosis confirmed at autopsy. The hydrocephalus section also includes two cases of severe hydrocephalus, one associated with encephalic malformation (Chiari I and agenesis of the corpus callosum), the other being a case of evolutive hydrocephalus in which only repeated MR scans led to a correct diagnosis. The final section comprises extracranial pathology.