Midline prosencephalic development by 3D Ultrasound

[e-mail]

Objective:

Detection of midline prosencephalic structures in the developing fetus is considered an important part of a targeted ultrasound examination of the fetal brain. The aim of this study was to determine the normal appearance and development of the corpus callosum and cavum septi pellucidi by 3D ultrasound. Another aim of this study was to create reference ranges and tables for different corpus callosum measurements between 18 and 41 weeks of gestation studied by 3D ultrasound. An additional task was to detect and record fetal corpus callosum pathologies.

Methods:

For the present study a total of 604 pregnant women refered for level III sonographic examination at the DEGUM level III Center for Prenatal Diagnosis and Therapy at Krankenhaus Nordwest, Frankfurt/Main was recruited to undergo a specific sonographic examination during 17 and 41 weeks of gestation. From 604 cases, a total of 466 cases was used to developed the growth charts and tables for the normal corpus callosum. Exclusion criteria were fetuses with 17 weeks of gestation (small corpus callosum), multiple pregnancy and fetuses with structural and chromosomal anomalies. In addition, 18 cases of corpus callosum pathology were detected. Gestational age was determined on the basis of the last menstrual period and confirmed at least by one ultrasound examination during the first trimester of pregnancy. All 466 threedimensional sonographic volumes of normal fetal brains were analysed offline using a dedicated computer software. Measuremets of the corpus callosum included the length of the entire structure and height (=thickness) of the rostrum, genu, body and splenium.

Results:

Using 3D ultrasound we were able to demonstrate the corpus callosum as a thin anechoic structure starting from 17 weeks of gestation. However, at this time the corpus callosum is too small to enable a precise differentiation among the four anatomical parts. After 20 weeks of gestation the corpus callosum should be sonographically visualized under routine conditions. The corpus callosum development involves horizontal and vertical changes. In our study we observed between 18 and 41 weeks of gestation an approximately four-fold increase in the different corpus callosum lengths, a three-fold increase in the rostrum height (=thickness), a four-fold increase in the genu height, a two-fold increase in the body height and a three-fold increase in the splenium height. Regarding the echogenicity of the corpus callosum, we found a hypoechoic structure of the corpus callosum with a clear demarcation from the cavum septi pellucidi throughout the entire observation time.

Conclusion:

3D neurosonography serves as an excellent tool to detect normal growth pattern of fetal midline prosencephalic structures. Understanding the normal growth pattern may enhance the early detection of midline anomalies.

fetal neurosonography - 3D ultrasound - corpus callosum - cavum septi pellucidum