Diagnostic value of ultrasound in fetal posterior fossa anomalies at 11-13 + 6 gestational weeks / 中华超声影像学杂志

ABSTRACT

Objective:To explore the diagnostic value of ultrasound in posterior fossa anomalies (PFA) at 11-13 + 6 gestational weeks by measuring brainstem (BS), brainstem-to-occipital bone (BSOB) diameter and BS/BSOB ratio. Methods:A total of 209 normal fetuses (control group) were randomly selected from Beijing Obstetrics and Gynecology Hospital, Capital Medical University, between March 2018 and November 2021. Reference ranges for BS, BSOB diameter and BS/BSOB ratio were obtained on the mid-sagittal view of the fetal profile and the relationship of three parameters and crown-rump length (CRL) was investigated. The intra- and inter-observer reliabilities were determined by intraclass correlation coefficient (ICC) in 30 normal fetuses. Fourteen fetuses diagnosed with PFA in the same period including 10 cases of cystic posterior fossa malformations (cPFM) and 4 cases of open spine bifida (OSB) were retrospectively selected to compare BS, BSOB diameter and the BS/BSOB ratio with control group.Results:BS and BSOB diameters were successfully obtained in all control fetuses (100%), and the intra- and inter-observer reliabilities for BS and BSOB diameters were good (ICC=0.877, 0.846 and 0.939, 0.895). In the control group, BS and BSOB diameter linearly correlated with CRL ( r=0.867, 0.794; all P<0.001), while the BS/BSOB ratio was 0.75 (0.71, 0.79). There were significant differences of BSOB diameter and BS/BSOB ratio between control group and PFA group (all P<0.05). Except for one isolated vermian hypoplasia (VH), the BSOB diameters in 9 (90%) cases of cPFM were above the 95th percentile of the calculated normal range and were below the 5th percentile in 4(100%) cases of OSB.Except for one isolated VH, the BS/BSOB ratio in 9 (90%) cases of cPFM was below the 5th percentile of the calculated normal range. The BS/BSOB ratio in 4 (100%) cases of OSB was above the 95th percentile of the calculated normal range. Conclusions:The measurements of BS and BSOB diameter are feasible with good repeatability. Abnormal BSOB diameter and BS/BSOB ratio are suggestive for PFA. The posterior fossa of isolated VH can be normal in the first trimester.