OC06.03: Reduced Hippocampal Volume in Human Fetal Brains with Agenesis of the Corpus Callosum Revealed by Magnetic Resonance Imaging

As one of the most common human brain malformation, agenesis of the corpus callosum (ACC) occurs either in isolated form or associated with other brain anomalies. Since ACC can modify brain morphology, we aimed to determine which consequence has this congenital defect on prenatal development of the human hippocampus. We analysed 81 in vivo fetal brain MRI ranging between 20 gestational weeks (GW) to 38 GW which were divided into three groups; control group (49 cases), 15 cases with isolated ACC and 17 cases with ACC associated with other brain anomalies. Segmentation of both hippocampi was performed manually and values of intracranial volume (ICV) was obtained from automated segmentations on a 3D reconstructed MRI from a set of 2D axial, coronal and sagittal T2-weighted images. Obtained data were statistically analysed and presented as a power regression model for each of three groups and for both hemispheres. The volumes of both hippocampi in all three groups display similar values as well as the same slope of growth curve in the first phase of the analysed period. Moreover, after 25th GW there was a significant decrease in hippocampal volume in CCA associated group compared to controls (p = 0.02), and this difference were pronounced even more in the later developmental period. Absolute hippocampal volumes in isolated CCA group start to differ significantly after 28th GW, first for the left hippocampus (p = 0.007), and after 29th GW for the right hippocampus and this difference were more pronounced after 30th GW. Growth curves of ICV for control and isolated CCA group overlap during analysed period while ICV of CCA associated group was lagging behind. Our data indicate an arrest of the normal process of the hippocampal development in fetuses with ACC, which was detected first in associated forms of ACC (after the 25th GW) and later in isolated forms (after 28th GW) onwards, suggesting that this restricted hippocampal growth could affect memory functions in later life of these infants.