The Course and Neonatal Outcome of Choroid Plexus Extension to the Anterior Horn at the Routine Anatomy Scan

OBJECTIVES

Our objective was to examine the pregnancy course and immediate neonatal outcome of fetuses with an isolated extension of choroid plexus (CP) to the anterior horn during the second trimester.

METHODS

We prospectively collected the cases referred to us between July 2012 and January 2021 with isolated finding of CP extension to the anterior horn. Relevant clinical and demographic information was recorded, and a full anatomy scan including a comprehensive neurosonogram was performed. In cases of confirmed isolated extension of CP to the anterior horns, women were offered further investigation including fetal MRI, and ultrasound follow up.

RESULTS

We collected 29 eligible cases for analysis. The mean gestational age (GA ± SD) for diagnosis and referral was 19.24 ± 2.3 weeks. No other intracranial anomalies were detected in any of the cases, and the finding resolved at 25 ± 2.6 weeks. The average extension length and width to the anterior horn were 0.7 ± 0.3 cm, and 0.5 ± 0.1 cm, respectively. Eleven fetuses (38%) had choroid plexus cyst (CPC) in addition to the extension. Ten patients (35%) completed a fetal brain MRI, with no identified abnormalities. Gross neurological exam and Apgar score at birth were normal.

CONCLUSION

Extension of CP to anterior horn with or without CPC at mid-trimester seems to have spontaneous resolution with likely a good prognosis and no further implications.

Association of Fetal Choroid Plexus Cysts With Trisomy 18 in a Population Previously Screened by Nuchal Translucency Thickness Measurement

OBJECTIVE

The study's aim was to determine any association between choroid plexus cysts (CPCs) and trisomy 18 in a population of fetuses previously screened by nuchal translucency (NT) thickness measurement.

METHODS

During the study period (May 1999 to December 2004), 7,795 fetuses had an NT scan and second-trimester fetal anatomical scan at our institution. The prevalence of trisomy 18 was determined among four types of pregnancies: 1) those with isolated CPCs, 2) those with CPCs and enlarged NT, 3) those with CPCs and other ultrasound markers, and 4) those with CPCs, enlarged NT, and other ultrasound markers. The fetal outcome according to NT and presence of CPCs was calculated. Incidence rates of enlarged NT and CPCs in fetuses with trisomy 18 and fetuses with normal chromosomes were also evaluated.

RESULTS

For the entire population, ten trisomy 18 cases were diagnosed prenatally (prevalence, 0.13%). Among fetuses with enlarged NT, the likelihood ratio of trisomy 18 was significantly increased in fetuses with CPCs compared with fetuses without such cysts (333.6 versus 15.2, P = .002). However, among fetuses with normal NT, no significant difference was demonstrated for likelihood ratio of trisomy 18 between fetuses with and without CPCs.

CONCLUSION

In pregnancies complicated by isolated CPCs, fetal karyotyping is not indicated when no additional anomaly is detected on ultrasonographic examination and first-trimester NT results are normal.

Bifid choroid plexus: always a normal fetal brain structure variant?

Choroid plexus, a fetal organ developing approximately from the sixth week of gestation, plays a fundamental role in developing fetal brain organization. As relatively little is known about the relationship between anomalies of choroid plexuses structure and their role in brain function, we examined cases of bifid choroid plexus (BCP) and discussed their potential association with lateral ventriculomegaly, other abnormal ultrasound findings, and their potential role as markers of fetal chromosomal abnormalities. In the present study, we described 23 cases of fetal BCP found in 2145 routine second trimester ultrasounds. For each patient 2D and 3D ultrasound volumes were acquired. BCP was defined as a choroid plexus whose body was divided into two portions (arms) differently located and oriented on the three spatial axes in correspondence to the lateral ventricle, in one or both sides. The entity of the separation and reciprocal orientation of the two arms was examined. The presence of BCP in a low-risk population of pregnant women undergoing routine second trimester ultrasound was showed. Lateral ventricles significantly increased in the presence of BCP. Malformations were found in four of 23 fetuses with BCP. Pregnancy outcome was favorable only in one of these four cases. We suggest that in the presence of mono or bilateral BCP without associated abnormal ultrasound findings, a closer look at fetal brain or extra-cranial structures is recommended. If no related abnormalities are found, serial prenatal and postnatal sonographic follow-up should be considered. In the presence of concomitant abnormal findings, genetic counseling, fetal karyotyping and magnetic resonance imaging, if possible by gestational age, are strongly advised.

Sonography of fetal choroid plexus cysts: detection depends on cyst size and gestational age

OBJECTIVE

To establish diagnostic criteria for the diagnosis of fetal choroid plexus cysts across gestation.

METHODS

Prenatal sonographic images of 166 fetuses without choroid plexus cysts were prospectively collected from 13 weeks to term. Texture characteristics of the choroid plexus regions were analyzed to quantify changes as a function of gestational age. A set of 20 fetal sonographic images with choroid plexus cysts were used to create cyst prototypes (1.5-2.5 mm), which were randomly embedded into normal choroid plexus images from varying gestational ages. A test set of 544 images was created, which included 408 images with choroid plexus cysts and 136 images without choroid plexus cysts. Four observers following a blinded study design evaluated the presence of choroid plexus cysts in the images. The influence of cyst size and gestational age on the detection of cysts was measured with receiver operating characteristic analysis and analysis of variance. Observer agreement was characterized by agreement kappa statistics.

RESULTS

Texture analysis indicated greater echo texture heterogeneity at earlier gestational ages. The receiver operating characteristic analysis showed a corresponding decrease in diagnostic accuracy for cyst detection at earlier gestational ages. The cyst detection threshold (area under the receiver operating characteristic curve, 0.8) was 2.4 mm (SE, 0.2 mm) for 13 to 21 weeks' gestation and decreased to 1.9 mm (SE, 0.17 mm) for 22 to 38 weeks' gestation. Average interobserver and intraobserver kappa statistics were 0.37 and 0.53, respectively.

CONCLUSIONS

Because of the changing echo texture of the choroid plexus through gestation, choroid plexus cysts must be at least 2.5 mm in diameter for confident diagnosis before 22 weeks' gestation and at least 2 mm after 22 weeks.

Some observations of the structure of the choroid plexus and its cysts

The structure of the choroid plexus was studied in five normal human embryos, three normal fetuses and three fetuses with choroid plexus cysts. These were detected by ultrasound and the fetuses were karyotypically normal. The choroid plexus appears in the lateral cerebral ventricles at the seventh developmental week. The early structure is lobulated with vessels running in the mesenchymal stroma and forming capillary nets under the single-layered ependymal epithelium. This embryonal structure is converted into the fetal type during the ninth developmental week as the embryonal capillary net is replaced by elongated loops of wavy capillaries that lie under regular longitudinal epithelial folds. The choroid plexus cysts exhibited accumulation of fluid within distended mesenchymal stroma and did not show the wavy folds on this surface, which was smooth. Within this connective tissue of the cyst wall were distended angiomatous interconnecting thin-walled capillaries. Therefore, filled cavities were not lined by any epithelium. We suggest that fetal choroid plexuses cysts (at least in many cases) are in fact pseudocysts exhibiting angiomatous patterns of capillaries in their walls.

Antenatal screening for aneuploidy

There are several methods of antenatal screening for aneuploidy. Most are aimed at the identification of women at increased risk of Down syndrome, the most common abnormal karyotype conferring a significant risk of serious long-term morbidity. Traditional maternal-age-based screening has largely been replaced by programmes based on biochemical markers in maternal serum in the second trimester of pregnancy. However, in recent years there has been a considerable drive towards earlier screening such that there are now a range of potential programmes based on various combinations of maternal age, serum markers and ultrasound findings. There is currently much debate as to which are the most effective methods of screening for aneuploidy.