OP12.04: Screening for fetal CNS anomalies: are the actual standards sensitive enough?

The standard anatomic 2nd trimester survey of the fetal brain includes 3 axial planes, 6 anatomical structures and 4 biometric measurements. Recent studies propose widening the scope of the axial assessment to increase the screening positive rate in case of CNS anomalies. Our aim was to assess the maximum performance of the actual and expanded screening criteria in hands of experts in fetal neurosonography. Two blinded experts reviewed data of consecutive cases of CNS anomalies diagnosed in the 2nd and 3rd trimesters at our fetal neurology clinic. First, only 3 axial planes were provided, and the parameters of the standard screening were noted. Second, anterior complex structures, Sylvian and parieto-occipital fissure, and brain symmetry parameters were assessed. If final diagnosis could not be achieved with standard or expanded axial views, sagittal and coronal planes were provided. Findings in all planes and suggested final diagnosis were noted. We included 37 consecutive cases of brain anomalies, selected by the highest quality of 2D images stored. In 29/37 (78.4%) the experts agreed and could detect an abnormality in the extended axial planes. In 21% even when using the extended axial views, the experts could not detect an abnormality and needed additional planes. Expert A requested additional imaging to reach the full diagnosis in 30/37 (81.1%) of cases, while Expert B requested it in 35/37 (94.6%) of cases. Both experts reach an accurate diagnosis. The use of the extended axial views by our experts led to high suspicion rate of fetal brain anomalies. However, it's acknowledged that additional planes are necessary for a comprehensive assessment and full diagnosis. Hence, we advocate for further research into extended views of axial planes and recommend considering the addition of supplementary planes to fetal brain imaging whenever feasible.