Fetal cerebral lobes development between 20 and 28 weeks gestational age: a postmortem MR study

To investigate the fetal cerebral lobes development between 20 and 28 weeks gestational age, 36 fetus specimen without CNS abnormality, with 4 fetuses in each gestation week, were scanned with 3.0T MR. Lobular parameters were measured, including the parenchyma thickness of the frontoparietal and the temporal lobes, the margin length of frontoparietal, the insula and the temporal lobes, the Sylvian fissure and the perimeter of hippocampus, on the plane perpendicular to the longitudinal axis of hippocampus body across the base of cerebral peduncle. The relative value of parenchyma thickness and the lobes' length ratios to the same side hemisphere were calculated and their correlation with gestational weeks was analyzed. All measured parameters were positively correlated with gestational age. No significant tendency was found for relative value of the parenchyma thickness (P>0.05). The temporal lobe length ratio increased while the frontoparietal ratio decreased before 24 weeks GA and then the two reversed. The Sylvian fissure length ratio increased (P<0.001) and the hippocampus decreased (P<0.001) throughout this period. In conclusion, the early fetal cerebrum lobes developed asynchronously during this period, the 24 weeks GA could be a turning point for cerebrum development pattern changing from primitive to mature.