Abstract:
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Purpose: To assess the appearance of the fetal corpus callosum using MR and relate these findings to gestational age and CNS dysmorphology.
Methods and Materials: Retrospective review of our fetal MR database was performed to select those cases in which views of the fetal brain had been performed using a T2-weighted SSFSE sequence in axial, coronal and sagittal projections orthogonal to fetal lie. MR images were assessed for adequacy of sagittal images in demonstrating midline CNS structures. The cases were reviewed for the presence of the genu, body, splenium and rostrum of the fetal corpus callosum, based upon the presumed embryologic development of this structure. The fetal gestational age and type of CNS dysmorphology, if present, were also noted. A t-test analysis was performed to evaluate the relationship of gestational age to the appearance of the corpus callosum.
Results: Fetal MR studies were reviewed in 60 cases. Ten cases demonstrated no CNS dysmorphology. Fourteen cases were diagnosed with a Chiari II malformation, 10 with isolated ventriculomegaly, 4 cases with porencephaly, 3 with Dandy-Walker malformation and 2 with hydranencephaly. The remaining cases were diagnosed with less frequent CNS abnormalities. In normal cases the ability to identify the corpus callosum increased with increasing gestational age (p=0.05) and followed the expected embryologic pattern of development. In cases of Chiari II malformation the corpus callosum was identified in 9 of 14 cases. In cases of isolated ventriculomegaly, the corpus callosum was visualized in only 5 of 10. Two of those 5 with non-visualization were in 17 and 19-week fetuses; in the other three callosal agenesis was suspected. The corpus callosum was not visualized in either case of hydranencephaly nor in one case of aqueductal stenosis. The genu of the corpus callosum was seen in 2 of 4 cases of porencephaly. No significant trend was seen within the abnormal groups related to gestation.
Conclusion: 1. The ability to adequately evaluate the corpus callosum of the fetus with MRI is significantly dependent on gestational age in fetuses assessed to have normal central nervous system findings. 2. The corpus callosum may be recognized in its entirety as early as 24 weeks; caution is advised in suggesting agenesis based on non-visualization before 24 weeks. 3. Underlying CNS dysmorphology causing ventriculomegaly or hydrocephalus may hinder identification of the fetal corpus callosum but this does not necessarily imply agenesis or hypoplasia.
Gouvion MD, M,
MR Evaluation of the Fetal Corpus Callosum in Relation To Gestational Age and CNS Dysmorphology. Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL.
http://archive.rsna.org/2003/3102505.html
