Normal and abnormal appearance of fetal ganglionic eminence at second-trimester three-dimensional ultrasound

Objectives: To describe the appearance and size of the ganglionic eminence (GE) in normal fetuses at mid trimester three-dimensional (3D) neurosonography and to report the association between GE alterations (cavitation or enlargement) and malformations of cortical development (MCD). Methods: This was a prospective multicenter cohort study, with retrospective analysis of pathological cases. From January to June 2022, patients attending our tertiary centers for expert fetal brain scan were recruited for the purpose of the study. A 3D volume of the fetal head, starting from the sagittal plane, was acquired in apparently normal fetuses transabdominally or transvaginally. Stored volume datasets were then independently evaluated by two expert operators. Two measurements (longitudinal diameter or D1 and transverse diameter or D2) of the GE in the coronal view were taken twice by each operator. Intra- and interobserver variation was calculated. Normal reference ranges for GE measurements were calculated in the normal population. Previously stored volume dataset of 60 cases with MCD were also independently analyzed by the two operators using the same method, in order to assess if GE abnormalities (cavitation or enlargement) were present. Postnatal follow-up was obtained in all cases. Results: In the study period, 160 normal fetuses between 19 and 22 weeks of gestation were included in the study. The GE was visible in the coronal plane at 3D ultrasound in 144 (90%) cases, not clearly visible in the remaining 16 cases. The intra- and interobserver agreement were almost perfect for D1, with an ICC of 0.90 (95% CI, 0.83-0.93) and an ICC of 0.90 (95% CI, 0.86-0.92), respectively, and substantial for D2, with an ICC of 0.80 (95% CI, 0.70-0.87) and an ICC of 0.64 (95% CI, 0.53-0.72), respectively. A retrospective analysis of 50 cases with MCD in the second trimester showed that GE enlargement was bilaterally present in 14 cases and GE cavitation in four cases. Conclusions: A systematic assessment of the GE in fetuses at 19-22 weeks is feasible at 3D brain ultrasound with good reproducibility in normal cases. Cavitations or enlargement of the GE can be demonstrated in fetuses with MCD. This article is protected by copyright. All rights reserved.