Sonographic developmental milestones of the fetal cerebral cortex: a longitudinal study

OBJECTIVE: To identify sonographic landmarks of normal fetal cortical development. METHODS: Serial ultrasound examinations were performed every 2 weeks from 18 weeks of gestation until term. In each session a detailed examination of the fetal brain was performed and the appearance of the main sulci and gyri was recorded. RESULTS: Twenty-two pregnant women volunteered to participate in the study. The fetal cortex followed an orderly pattern of development. By the time of the first ultrasound examination, at 18 weeks, the major fissures were present. The first sulci could be demonstrated as early as 18 weeks. Main landmarks, represented by the parieto-occipital fissure and the cingulate and calcarine sulci, were present between 22-24 weeks. The central sulcus was present in all cases by 28 weeks. By 30-32 weeks most of the main sulci could be demonstrated. CONCLUSIONS: Prenatal sonographic examinations can accurately demonstrate structures of the fetal cortex. Comparison of our results with those of both magnetic resonance imaging and other sonographic studies shows similarities in the order of appearance of the sulci and gyri, with only minor differences in the exact gestational age at which they are detected. Accurate knowledge of the ultrasound appearance of the fetal cortex at different stages of gestation is important in order to be able to diagnose in-utero malformations of cortical development.