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

Abstract

Background and purpose: Few investigators have analyzed the MR imaging patterns of fetal gyration. Our purpose was to establish, with a large prospective series, the normal sulcation landmarks according to gestational age by using in utero MR imaging and to correlate our findings with established neuroanatomic 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 coronal, axial, and sagittal slices were obtained for each fetus and systematically analyzed. The sequential development of the different fissures and sulci of the cerebral cortex with respect to gestational age were tabulated.

Results: Sulcation of the medial, lateral, and inferior surfaces of the brain was depicted, and a timetable for the MR depiction of the primary and secondary sulci was established for the 22- to 38-week gestational period. This timetable was in good agreement with the neuroanatomic standards of reference, with a mean lag time of 1 week.

Conclusion: This analysis of fetal brain sulcation in a large series of fetuses contributes to a better understanding of the maturation of the fetal cortex on MR imaging studies. It furthermore provides a standard of reference that can be used to assess the normality of fetal sulcation and to diagnose gyrational abnormalities with prenatal MR imaging.

fig 1.

Distribution of fetuses by gestational age (GA)

fig 2.

Slice no. 1. T2-weighted midline sagittal image (20/9.2/12) (31 weeks' gestation). 1, parietooccipital fissure; 2, calcarine fissure; small arrow, marginal sulcus; large arrow, cingular sulcus.fig 3. Slice no. 2. T2-weighted parasagittal image (20/9.2/12) at the level of the sylvian fissure (28 weeks' gestation). Opercularization of the insula is completed posteriorly (arrow). Anteriorly, the insula (star) is wide open

fig 4.

Slice no. 3. T2-weighted anterior coronal image (20/9.2/12) at the anterior part of the frontal lobes (35 weeks' gestation). 1, superior frontal sulcus; 2, inferior frontal sulcus.fig 5. Slice no. 4. T2-weighted coronal image (20/9.2/12) at the level of the third ventricle (35 weeks' gestation). Large arrow, cingulate sulcus; small arrow, callosal sulcus (barely visible); 1, superior temporal sulcus (anterior part); 2, inferior temporal sulcus; 3, external occipital temporal sulcus; 4, collateral sulcus.

fig 6.

Slice no. 5. T2-weighted coronal image (20/9.2/12) at the level of the temporal horns (33 weeks' gestation). Large arrow, cingulate sulcus; small arrow, callosal sulcus (barely visible); 1, superior temporal sulcus (posterior part); 2, collateral sulcus; 3, hippocampal fissure.fig 7. Slice no. 6. T2-weighted coronal image (20/9.2/12) at the level of the ventricular atria (33 weeks' gestation). 1, collateral sulcus; 2, intraparietal sulcus

fig 8.

Slice no. 7. T2-weighted transverse image (20/9.2/12) at the level of the vertex (31 weeks' gestation). 1, precentral sulcus; 2, central sulcus (almost abutting the hemispheric fissure); 3, postcentral sulcus.fig 9. Slice no. 8. T1-weighted transverse image (300/15/4) at the level of the third ventricle (29 weeks' gestation). The insula (star) is wide open