Fetal Brain Structure and CNS Anomalies

Abstract

As the brain is an organ that must be understood as a three-dimensional (3D) structure, and because the fetal skull ossifies in late pregnancy, it is difficult to depict detailed structures in the brain using conventional horizontal cross-sectional images captured by transabdominal ultrasound. However, there are large spaces such as anterior/posterior fontanels and sagittal sutures in the fetal skull. By using these spaces as a window for ultrasound, it becomes easier to observe the brain structure. Transvaginal fetal 3D neurosonography and transvaginal ultrasound have made it possible to observe congenital brain structural abnormalities and cortical dysgenesis in more detail. Transvaginal 3D ultrasound imaging has been reported to be effective in the evaluation of fetal brain structure. Images of normal brain development, intracerebral vascular architecture, brain malformations, brain disorders such as intracerebral hemorrhage and stroke, and abnormalities in cortical development have gradually revealed the previously unknown development and pathology of the fetal brain. Fetal 3D neurosonography provides information on the orientation of the fetal brain, brain development during pregnancy, the exact location of brain lesions, and the inner structure of the lesions. Detailed neuroimaging is now available for diagnosis of the central nervous system, and genetic tests such as chromosomal microarrays, exome sequencing, and genome sequencing add information on genetic causative factors. The combination of detailed neurosonography and molecular genetics has established a new interdisciplinary field of fetal neurology called “neurosonogenetics,” which will enable accurate perinatal management and care in the future.