Fetal cerebral cortex: Normal gestational landmarks identified using prenatal MR imaging

BACKGROUND AND PURPOSE: Few investigators have analyzed the MR imaging patt erns of fetal gyration. Our purpose was to establish, with a large prospect ive series, the normal sulcation landmarks according to gestational age by using in utero MR imaging and to correlate our findings with established ne uroanatomic timetables. METHODS: A standardized fetal cerebral MR examination was performed in 173 normal fetuses at 22 to 38 weeks' gestation. Eight T1- and T2-weighted coro nal, axial, and sagittal slices were obtained for each fetus and systematic ally analyzed. The sequential development of the different fissures and sul ci of the cerebral cortex with respect to gestational age were tabulated. RESULTS: Sulcation of the medial, lateral, and inferior surfaces of the bra in was depicted, and a timetable for the MR depiction of the primary and se condary sulci was established for the 22- to 38-week gestational period. Th is timetable was in good agreement with the neuroanatomic standards of refe rence, with a mean lag time of 1 week. CONCLUSION: This analysis of fetal brain sulcation in a large series of fet uses contributes to a better understanding of the maturation of the fetal c ortex on MR imaging studies. It furthermore provides a standard of referenc e that can be used to assess the normality of fetal sulcation and to diagno se gyrational abnormalities with prenatal MR imaging.