Ultrasonographic Characteristics of Cortical Sulcus Development in the Human Fetus between 18 and 41 Weeks of Gestation

Abstract

Background: Fetal brain development is a complicated process that continues throughout pregnancy. Fetal sulcus development has typical morphological features. Assessment of fetal sulcus development to understand the cortical maturation and development by prenatal ultrasound has become widespread. This study aimed to explore a reliable method to assess cortical sulcus and to describe the normal sonographic features of cortical sulcus development in the human fetus between 18 and 41 weeks of gestation.

Methods: A cross-sectional study was designed to examine the fetal cortical sulcus development at 18-41 weeks of gestation. Ultrasound was used to examine the insula, sylvian fissure (SF), parieto-occipital fissure (POF), and calcarine fissure (CF). Bland-Altman plots were used for assessing the concordance, and the intraclass correlation coefficient was used for assessing the reliability.

Results: SF images were successfully obtained in 100% of participants at 22 weeks of gestation, while the POF images and CF images could be obtained in 100% at 23 weeks of gestation and 24 weeks of gestation, respectively. The SF width, temporal lobe depth, POF depth, and the CF depth increased with the developed gestation. The width of uncovered insula and the POF angle decreased with the developed gestation. By 23 weeks of gestation, the insula was beginning to be covered. Moreover, it completed at 35 weeks of gestation. The intra- and inter-observer agreements showed consistent reproducibility.

Conclusions: This study defined standard views of the fetal sulcus as well as the normal reference ranges of these sulcus measurements between 18 and 41 weeks of gestation. Such ultrasonographic measurements could be used to identify fetuses at risk of fetal neurological structural disorders.

Figure 1

Schematic diagram of the SF image (a). (b) A photograph of the medial hemispheric surface of a fetal brain at 27 weeks of gestation. The red line represents the anatomic level at which the axial view of the biparietal diameter is taken. The black line represents the anatomical level at which the axial view through the SF is taken. (c) Ultrasound image (axial view) of the fetal head at 27 weeks of gestation demonstrating measurement of the temporal depth (dotted line). (d) The same ultrasound image (axial view) of the fetal head at 27 weeks demonstrating measurement of the SF width (longer dotted) and uncovered insular width (shorter dotted line). AC: Anterior commissure; CSP: Cavum septum pellucidum; GCC: Genu of corpus callosum; LVAH: Left anterior horn of lateral ventricle; SF: Sylvian fissure; T: Thalamus; TV: Third ventricle. 1: Temporal depth; 2: SF depth; 3: SF width; 4: Uncovered insula width.

Figure 2

Schematic diagram of POF image (a). (b) A photograph of the medial hemispheric surface of a fetal brain at 27 weeks of gestation. The red line represents the anatomic level at which the axial view of the biparietal diameter is taken. The black line represents the anatomic level at which the axial view through the POF is taken. (c) Ultrasound image (axial view) of the fetal head at 27 weeks of gestation demonstrating measurement of the POF depth (short dotted line). (d) The same ultrasound image (axial view) of the fetal head at 27 weeks demonstrating measurement of the POF angle. POF: Parietal-occipital fissure; CeF: Cerebral falx; CeS: Centrum semiovale; f: POF depth; g: POF width.

Figure 3

Schematic diagram of CF image (a). (b) A photograph of the medial hemispheric surface of a fetal brain at 27 weeks of gestation. The red line represents the anatomic level at which the axial view of the biparietal diameter is taken. The black line represents the anatomic level at which the coronal view through the CF is taken. (c) Ultrasound image (coronal view) of the fetal head at 29 weeks of gestation demonstrating measurement of the CF depth (dotted line). CF: Calcarine fissure; CeF: Cerebral falx; CH: Cerebellar hemisphere; CM: Cisterna magnum; CT: Cerebellar tentorium; CV: Cerebellar vermis; FV: Fourth ventricle; POF: Parieto-occipital fissure; 7: CF depth.

Figure 4

Schematic model of normal fetal cortical sulcus development between 18 and 41 weeks of gestation. Cartoons show the changing appearance on prenatal ultrasound of the sylvian fissure (a), parieto-occipital fissure (b), and calcarine fissure (c) throughout gestation. w: Weeks.

Figure 5

Mean difference and 95% limits of agreement between paired measurements: SF width (a), temple lobe depth (b), SF depth (c), Uncovered width of insula (d), POF depth (e), POF angle (f), and CF depth (g). These were performed by two different observers using the same stored images (n = 60). POF: Parieto-occipital fissure; CF: Calcarine fissure; SF: Sylvian fissure.