Feasibility and agreement of including anterior-posterior complexes and landmarks of the proximal hemisphere into basic examination of the fetal brain: A prospective study

Feasibility of neurosonography in CHD-fetuses and controls in a clinical tertiary setting

Objective

Ultrasonographic examination is the first-tier test to detect abnormal development of central nervous system (CNS). In optimal conditions, neurosonography can detect all important hallmarks of CNS development. It is, however, not known how the performance of this modality is in a routine setting. We aimed to evaluate the feasibility of neurosonography in a time-limited routine setting.

Study design

We have performed a prospective study in which we have included a group of pregnant women carrying a fetus with an isolated congenital heart defect (CHD), and a control group of fetuses without structural anomalies. We have performed basic neurosonography examination according to the guideline 'how to perform a basic screening examination of the CNS', published by the international society of ultrasound in obstetrics and gynecology in both groups. In all these examinations, 9 brain structures were scored in 3 different planes, by researchers that were blinded for group allocation. A sufficient neurosonogram was performed when 7 or more out of 9 CNS structures were clearly visible during the off-line scoring of the examination.

Results

A total of 574 neurosonographic examinations were performed in 151 fetuses, 90 in the CHD-group and 61 in the control group. A sufficient neurosonogram could be performed in 79% (234/294) of cases in a clinical setting (CHD cases) and in 90% (253/280) of control pregnancies. Higher maternal BMI (>30), maternal age, fetal cephalic position, fetal gender and placental position did not significantly influence neurosonography scores.

Conclusion

In clinical setting, basic fetal neurosonography can be sufficiently performed in the majority of cases. This was not significantly influenced by maternal or fetal factors. The optimal gestational age for neurosonography is between 22 and 34 weeks.

Neurosonographic Measurements of the Fetal Anterior Complex in Singleton Pregnancies

OBJECTIVE

To construct reference ranges of the fetal cerebral anterior complex, including ventricular index (VI), anterior horn of lateral ventricle width (AW), and cavum septi pellucidi (CSP) width, as a function of gestational age (GA), in Thai fetuses.

METHODS

Low-risk pregnancies were recruited to measure fetal anterior complex on axial transventricular and coronal transcaudate planes using transabdominal ultrasound. The downside and upside hemisphere were defined as cerebral hemisphere located distal and proximal to the transducer, respectively. The five variables, downside/upside VI, downside/upside AW and CSP width, were measured from each fetus. Best-fit models in predicting mean and standard deviation for each value as a function of GA were constructed, using regression analysis. Distributions of Z-scores of all values based on GA were created to evaluate the fitness of models. Intraclass correlation coefficients were used to assess inter-/intraobserver variability.

RESULTS

A total of 395 fetuses were measured for anterior complex. All parameters changed with GA with quadratic function. The models for predicting means and standard deviation of the five parameters as well as percentile charts were created. All models were proven well-fitted. The intra-/interobserver reliability coefficients of all values showed excellent agreement.

CONCLUSION

The reference ranges of the fetal anterior complex, including VI, AW, and CSP, in axial transventricular and coronal transcaudate planes have been established and available for clinical use.

Feasibility of extended ultrasound examination of the fetal brain between 24 and 37 weeks' gestation in low-risk pregnancies

OBJECTIVES

To assess the feasibility of identifying fetal brain structures and anatomic landmarks included in the anterior complex (AC) and posterior complex (PC), as well as the proximal hemisphere (PH).

METHODS

This was a prospective observational multicenter study of healthy pregnant women evaluated by ultrasound screening at 24 to 36 + 6 weeks' gestation. Six physicians performed transabdominal ultrasound, to obtain the planes required to visualize the AC, PC, and PH. Blind analysis by an expert and non-expert operator in fetal neurosonography was used to assess the structures included in each plane view.

RESULTS

In the population studied (n=366), structure detection rates for AC were over 95 %, with an agreement of 96 % when comparing expert and non-expert examiners. Visualization of the corpus callosum crossing the midline was detected in over 97 and 96 % of cases for the AC and PC, respectively, with an agreement of over 96 %. The PH plane, particularly through the posterior access via the mastoid fontanelle, enabled visualization of the proximal anatomical structures in almost 95 % of cases. Detection of the corpus callosum through the AC and PC, both proximal/distal germinal matrix (AC) and proximal Sylvian fissure through the anterior access (PH) in the 24-25 + 6, 26-31 + 6 and 32-36 + 6 weeks' gestation groups were successful in over 96 % of cases with high level of agreement.

CONCLUSIONS

Inclusion of AC, PC, and PH later in pregnancy proves feasible with a high level of agreement between both expert and non-expert operators.

Role of Fetal Magnetic Resonance Imaging in Differentiating Isolated Septal Agenesis from Septo-Optic Dysplasia: Case Study and Review

INTRODUCTION

The detection of absent septi pellucidi (ASP) during obstetric ultrasound is a rare event. However, the clinical implications of this finding are significant. ASP can be associated with severe central nervous system anomalies such as holoprosencephaly, agenesis/dysgenesis of the corpus callosum, schizencephaly, severe ventriculomegaly, and open neural tube defects. In such cases, the prognosis is poor. When no such anomalies are identified, isolated ASP usually carries a good prognosis. However, some fetuses thought to have isolated ASP actually have septo-optic dysplasia (SOD), which is associated with optic nerve hypoplasia, hypothalamic-pituitary dysfunction, and developmental delay.

CASE PRESENTATION

A case in which fetal 3.0 Tesla magnetic resonance imaging (MRI) was considered crucial to definitively diagnose isolated ASP is presented. A review of the literature was conducted and analyzed to determine the role of MRI in the evaluation of fetuses with ASP, with special consideration on the differential diagnosis between isolated ASP and SOD.

CONCLUSION

Differentiating isolated ASP from SOD is imperative for adequate prenatal counseling. Unfortunately, making a prenatal diagnosis of SOD requires visualization and evaluation of the fetal optic nerves, chiasm, and pituitary gland, which is very demanding and not always possible using ultrasound. Fetal MRI has the potential of obtaining high-quality images of the fetal brain, and therefore this technique can be used for establishing the differential diagnosis in utero.

WAPM-World Association of Perinatal Medicine Practice Guidelines: Fetal central nervous system examination

These practice guidelines follow the mission of the World Association of Perinatal Medicine in collaboration with the Perinatal Medicine Foundation, bringing together groups and individuals throughout the world, with the goal of improving the ultrasound assessment of the fetal Central Nervous System (CNS) anatomy. In fact, this document provides further guidance for healthcare practitioners for the evaluation of the fetal CNS during the mid-trimester ultrasound scan with the aim to increase the ability in evaluating normal fetal anatomy. Therefore, it is not intended to establish a legal standard of care. This document is based on consensus among perinatal experts throughout the world, and serves as a guideline for use in clinical practice.