First trimester ultrasound of the cerebral lateral ventricles in fetuses with open spina bifida: a retrospective cohort study.

ABSTRACT

BACKGROUND: Beyond 18 weeks of gestation an increased size of the fetal lateral ventricles is reported in the majority of fetuses with open spina bifida. At 1st trimester, the definition of ventriculomegaly is based on the ratio between the size of the choroid plexus and that of the ventricular space or of the entire fetal head. However, contrary to what is seen from midtrimester, in most fetuses with open spina bifida at 11-13 weeks the amount of fluid in the ventricular system seems to be reduced rather than increased. OBJECTIVE: To compare the biometry of the lateral ventricles at 11+0-13+6 weeks between normal fetuses and those with a confirmed open spina bifida. STUDY DESIGN: Retrospective cohort study including all cases of isolated open spina bifida detected at 11+0-13+6 weeks of gestation over a period of 5 years and a group of structurally normal fetuses attending at our Centre over a period of 1 year for the aneuploidies screening as controls. The transventricular axial views of the fetal brain obtained among cases and controls were extracted from the archive for post-hoc measurement of the cerebral ventricles. The ratios between choroid plexus and lateral ventricle lenghts (CPVLr) and areas (CPVAr), the ratio between the sum of both choroid plexus areas and fetal head area (CPHAr) and the ratio between the mean of choroid plexus lengths and occipito-frontal diameter (CPHLr) were calculated for both groups. Measurements obtained from the two groups were compared, and the association of each parameter with open spina bifida was investigated. RESULTS: Ten fetuses with open spina bifida were compared with 358 controls, showing significantly smaller size of the cerebral ventricles measurements as expressed by larger values of CPVAr (0.72 vs 0.49, p<0.001), CPVLr (0.79 vs 0.70, p<0.001), CPHAr (0.33 vs 0.28, p=0.006) and CPHLr (0.60 vs 0.52, p<0.001) compared with controls. CPVAr was found to be the most accurate predictor of OSB showing an area under the curve of 0.88 with a sensitivity of 90% and a specificity of 82%. CONCLUSIONS: At 11+0-13+6 weeks' gestation open spina bifida is consistently associated with a reduced amount of fluid in the lateral cerebral ventricles of the fetus, as witnessed by significantly increased CPVLr, CPVAr, CPHAr and CPHLr.