Visualization of caudothalamic groove at expert fetal neurosonography.

Objectives: To describe the sonographic features of the caudothalamic groove in the third trimester of pregnancy in a group of structurally normal fetuses and to report a small series of cases with abnormal appearance of the caudothalamic groove at antenatal cranial ultrasound.

Methods: This was an observational study conducted at two fetal medicine referral units in Italy. A non-consecutive cohort of pregnant women with a singleton non-anomalous pregnancy were recruited prospectively and underwent three-dimensional (3D) ultrasound assessment of the fetal brain at 28-32 weeks' gestation. At offline analysis, the ultrasound volumes were adjusted in the multiplanar mode, according to a standardized methodology, until the caudothalamic groove was visible in the parasagittal plane. To evaluate interobserver agreement, two operators were asked independently to indicate if the caudothalamic groove was visible unilaterally or bilaterally on each volume and Cohen's kappa (κ) coefficient was calculated. The digital archives of the two centers were also searched retrospectively to retrieve cases with abnormal findings at the level of the caudothalamic groove on antenatal cranial ultrasound that were confirmed postnatally.

Results: A total of 180 non-consecutive cases were included. At offline analysis of the 3D ultrasound volumes, the caudothalamic groove was identified in the parasagittal plane by both operators at least unilaterally in 176 (97.8%) cases and bilaterally in 174 (96.7%) cases. The κ-coefficient for the agreement between the two independent operators in recognizing the caudothalamic groove was 0.89 and 0.83 for one and both hemispheres, respectively. The retrospective search of our archives yielded five cases with an abnormal appearance of the caudothalamic groove at antenatal cranial ultrasound, including two cases of hemorrhage and three cases of cyst.

Conclusions: The caudothalamic groove is consistently seen in normal fetuses on multiplanar neurosonography in the third trimester, and abnormal findings in this region may be detected antenatally. © 2024 International Society of Ultrasound in Obstetrics and Gynecology.