Management of fetal choroid plexus cysts

Prenatally diagnosed developmental abnormalities of the central nervous system and genetic syndromes: A practical review

Developmental brain abnormalities are complex and can be difficult to diagnose by prenatal imaging because of the ongoing growth and development of the brain throughout pregnancy and the limitations of ultrasound, often requiring fetal magnetic resonance imaging as an additional tool. As for all major structural congenital anomalies, amniocentesis with chromosomal microarray and a karyotype is the first-line recommended test for the genetic work-up of prenatally diagnosed central nervous system (CNS) abnormalities. Many CNS defects, especially neuronal migration defects affecting the cerebral and cerebellar cortex, are caused by single-gene mutations in a large number of different genes. Early data suggest that prenatal diagnostic exome sequencing for fetal CNS defects will have a high diagnostic yield, but interpretation of sequencing results can be complex. Yet a genetic diagnosis is important for prognosis prediction and recurrence risk counseling. The evaluation and management of such patients is best done in a multidisciplinary team approach. Here, we review general principles of the genetic work-up for fetuses with CNS defects and review categories of genetic causes of prenatally diagnosed CNS phenotypes.

Ultrasound screening: Status of markers and efficacy of screening for structural abnormalities

Aneuploidy is a major cause of perinatal morbidity and mortality and can have a significant impact on expecting parents and their families. With early screening and diagnosis it is important to be able to educate parents regarding the potential impact of the diagnosis. This knowledge allows parents the opportunity to consider management options early in the pregnancy, permitting more time to mentally and emotionally prepare both for the course of the pregnancy, and after the birth of the child should the pregnancy continue. Prenatal screening provides pregnant women a non-invasive risk assessment for the most common aneuploidies. Those who are considered "high-risk" then have the option for additional diagnostic (invasive) testing. Prior to the 1980s, prenatal screening consisted of risk assessment through maternal age; however, with the advent of maternal serum biochemical analysis and ultrasound, the field of prenatal screening developed significantly. As biochemical and sonographic advances continued into the 1990s, the emphasis shifted to risk assessment in the first trimester, with the combination of maternal serum analytes and sonographic evaluation of the nuchal translucency.(1) Within the last decade, the introduction of non-invasive screening (NIPT/S) has shown great impact on the expansion and evolving practice of prenatal screening. Although in many places the standard for prenatal testing continues to include maternal serum analytes and sonographic evaluation, the role of each marker alone and in combination remains important. In the era of increasingly available screening tests, especially with NIPT/(NIPS), this article attempts to review the current role of ultrasound in prenatal care and elucidate the role of ultrasound markers in prenatal screening.

Second trimester prenatal ultrasound for the detection of pregnancies at increased risk of Trisomy 18 based on serum screening

OBJECTIVE

To describe ultrasound findings in fetuses with Trisomy 18.

METHODS

Prospective population-based cohort study of second trimester ultrasound among Californian women who were at increased risk of chromosome abnormality based on serum screening between November 1999 and April 2001. Structural anomalies plus the following soft markers were assessed: nuchal fold thickening, choroid plexus cyst (CPC), echogenic intracardiac focus, echogenic bowel, renal pyelectasis, clenched hands; clinodactyly; short femur, short humerus and a single umbilical artery (SUA).

RESULTS

Overall, 8763 women underwent ultrasound evaluation, including 56 whose fetuses had Trisomy 18. Ultrasound anomalies were seen in 89% of Trisomy 18 fetuses, as compared with 14% of normal fetuses. If the genetic sonogram was normal (no structural anomaly and no soft marker), the risk was reduced by approximately 90%. The ultrasound soft markers were typically seen in conjunction with structural anomalies in affected fetuses and in the absence of a structural anomaly, most isolated ultrasound soft markers were not associated with Trisomy 18. The only exception was an isolated CPC, seen as the only finding in 11% of fetuses with Trisomy 18.

CONCLUSIONS

If the genetic sonogram is used as a sequential test following serum biochemistry, a normal ultrasound study reduces the likelihood of Trisomy 18 substantially even if a woman has abnormal serum biochemistry. The presence of an isolated CPC raises the risk, but not high enough to prompt invasive testing.

Mid-second trimester measurement of fetal nasal bone length in the Japanese population

AIM

We carried out a preliminary study to compare the nasal bone length (NBL) and biparietal diameter/NBL (BPD/NBL) ratio between the Japanese and white populations.

METHODS

Three hundred and fifty nine (359) singleton fetuses of healthy Japanese couples were examined from June 2004 to October 2005. NBL was measured by the strict midsagittal section. The reference range of NBL was established from cross-sectional data between 15 and 25 weeks' gestation.

RESULTS

The success rate of obtaining reliable NBL was 93% (333/356). There were 330 fetuses (93%) available for constructing a reference range from the population. The median NBL increased from 3.2 mm at 15 weeks' to 7.6 mm at 25 weeks' gestation. The median of BPD/NBL ratio was 9.01.

CONCLUSIONS

We demonstrated that NBL was significantly shorter and BPD/NBL was significantly greater in the Japanese population than those in the white and black populations.

Occurrence of fetal choroid plexus cysts in siblings: Concerns regarding recurrence and chromosomal abnormality

Choroid plexus cysts (CPC) are a well-known ultrasound aneuploidy marker easily detectable at second-trimester ultrasound examination. However, their genetic etiology is totally unknown. We report two cases of Japanese mothers who carried two and three siblings respectively; all the fetuses that had CPC were noticed at second trimester. Genetic amniocentesis revealed that each fetus had different karyotypes, that is, trisomy 18 and 46,XX in the case of one mother, and trisomy 18, 46,XY and trisomy 21 in the case of the other. These observations indicate that the genetic basis of the cysts is not linked to abnormal chromosomes. We propose that careful ultrasound observation and genetic counseling of the siblings should be offered to patients who have previously had a baby with CPC, despite that baby having a normal karyotype.

Controversial ultrasound findings

This article has reviewed a few of the more controversial findings in the field of obstetric ultrasound. For each one evidence-based strategies for the management of affected pregnancies have been suggested, derived from what the authors believe is the best information available. In some cases, this information is very limited, which can make counseling these patients extremely difficult. Some physicians find using specific likelihood ratios helpful in these complex discussions. An example of the relative likelihood ratios for several markers of trisomy 21 is illustrated in Table 10. Although the management of each of the findings discussed in this article is different, a few generalizations can be made. To begin with, the detection of any abnormal finding on ultrasound should prompt an immediate detailed ultrasound evaluation of the fetus by someone experienced in the diagnosis of fetal anomalies. If there is more than one abnormal finding on ultrasound, if the patient is over the age of 35, or if the multiple marker screen is abnormal, an amniocentesis to rule out aneuploidy should be recommended. Of the six ultrasound findings reviewed here, the authors believe that only echogenic bowel as an isolated finding confers a high enough risk of aneuploidy to recommend an amniocentesis in a low-risk patient. The other findings in isolation in a low-risk patient seem to confer only a modest increased risk of aneuploidy, if any, and this risk is certainly less than the risk of unintended loss from amniocentesis. Wherever possible, modifiers of this risk, such as maternal age, history, and first and second multiple marker screening, should be used to define more clearly the true risk of aneuploidy. As obstetric ultrasound moves forward, particularly into the uncharted waters of clinical use of three- and four-dimensional ultrasound, one can expect a whole new crop of ultrasound findings with uncertain clinical significance. Clinicians are well advised to await well-designed studies to determine the clinical significance of these findings before altering clinical care.

Karyotyping of fetuses with isolated choroid plexus cysts is not justified in an unselected population

OBJECTIVE

The main objective of this study was to determine whether isolated choroid plexus cysts are a risk factor for trisomy 18.

METHODS

A total of 12,672 unselected patients were examined, and the outcome of fetuses with choroid plexus cysts was assessed. The cases with choroid plexus cysts were selected from the 12,672 patients and further divided into cases with minor markers of aneuploidy and cases with associated structural anomalies. Previous similar work was reviewed, analyzed, and, where possible, compared with the results of this study.

RESULTS

The findings revealed 366 fetuses with choroid plexus cysts (2.9%). Thirty-three percent of fetuses with trisomy 18 had choroid plexus cysts, and, in every case, structural anomalies were also present. From the 12 cases with choroid plexus cysts in addition to major associated anomalies, amniocentesis revealed 2 cases of trisomy 18. Forty-three patients who had choroid plexus cysts and minor anomalies within our population had normal outcomes.

CONCLUSIONS

These results indicate that the risk of amniocentesis is not acceptable if isolated choroid plexus cysts are isolated findings. More data are needed to establish whether choroid plexus cysts and other soft signs independently increase the risk of aneuploidy.

Second-trimester sonography and trisomy 18: the significance of isolated choroid plexus cysts after an examination that includes the fetal hands

OBJECTIVE

To estimate the risk of trisomy 18 with the finding of isolated choroid plexus cysts after a standard sonographic examination that is extended to include the fetal hands.

METHODS

Aretrospective chart review was performed on all fetuses with choroid plexus cysts on second-trimester sonographic examinations. When choroid plexus cysts were identified, our standard protocol for fetal evaluation was expanded to include the hands. If no other findings were noted on completion of this examination, the choroid plexus cysts were classified as "isolated." These results were correlated with the presence or absence of trisomy 18 to determine the impact of this approach for the detection of fetuses with this aneuploidy.

RESULTS

From March 1990 to the end of 2001, 49,435 fetuses that were subsequently delivered at our hospital were scanned between 16 and 25 menstrual weeks. At least 1 choroid plexus cyst was detected in 1209 fetuses (2.3%), of which 1060 were isolated. No fetuses with isolated choroid plexus cysts had trisomy 18. However, 3 fetuses with trisomy 18 had choroid plexus cysts and abnormal hands as their only abnormal findings.

CONCLUSIONS

Fetuses with an apparently isolated finding of choroid plexus cysts can be further evaluated by extending the standard examination to include the hands. If no other findings are identified, the risk of trisomy 18 appears to be low.

Second-trimester sonography and trisomy 18

OBJECTIVE

This report presents the findings seen on initial second-trimester sonography in a large group of fetuses with trisomy 18. The object of this study was to describe the types and frequencies of abnormal sonographic findings seen and to further evaluate those cases in which no abnormal findings were noted.

METHODS

A retrospective chart review of the prenatal sonograms in cases of trisomy 18 was conducted.

RESULTS

Forty-nine fetuses with trisomy 18 were examined by second-trimester sonography. Multiple fetal anomalies were seen in most cases. The most frequent structural findings involved the brain (82%), heart (55%), and upper extremities (53%). Growth abnormalities occurred in 39% of these fetuses. Choroid plexus cysts were the most common individual findings. Larger cysts increased the likelihood of trisomy 18, although no fetuses with trisomy 18 had isolated choroid plexus cysts. Seven fetuses (14%) had no anomalies seen on their initial scans. In each of these scans, the fetal anatomy was incompletely visualized because of technical constraints. Six had subsequent scans approximately 2 weeks later, which showed abnormal sonographic findings.

CONCLUSIONS

Most fetuses with trisomy 18 were identified by structural anomalies, typically seen in the brain, heart, and upper extremities. Larger choroid plexus cysts were associated with this aneuploidy. Technical factors, which limit fetal visualization, were noted in all cases in which no sonographic abnormalities were detected during the initial sonographic examinations. Detection of abnormal cases will rely on a completed evaluation of a routine fetal anatomic survey.

Second trimester choroid plexus cysts and trisomy 18

OBJECTIVES

In this study, the aims were to reveal the incidence of isolated choroid plexus cyst in our population, and to discuss the accuracy of distinguishing either an isolated or non-isolated choroid plexus cyst.

METHODS

The study population was consisted of 10594 pregnant women. The patients with choroid plexus cysts were classified into two groups: isolated and non-isolated. Detailed ultrasonographic examination and genetic counseling were performed and triple screening test was ordered. The incidence, sensitivity, specificity, false-positive rate and likelihood ratio of cases with isolated choroid plexus cyst for trisomy 18 were determined.

RESULTS

Choroid plexus cysts were identified in 109 patients (109/10594; 1.02%). In 102 patients isolated choroid plexus cysts, and in seven patients additional fetal anomalies supporting trisomy 18 were detected. Trisomy 18 was detected in four patients, and one of them had isolated choroid plexus cyst. The likelihood ratio in cases of isolated choroid plexus cysts for trisomy 18 was 9.51 (95% confidence interval, 0.2-41).

CONCLUSIONS

According to the study the individual risk for trisomy 18 in isolated choroid plexus cyst should be calculated by using the likelihood ratio. These data allows the physician to express the individual risk of trisomy 18 and permits more accurate genetic counseling.

Choroid plexus cysts in the mid-trimester fetus--practical application suggests superiority of an individualized risk method of counseling for trisomy 18

OBJECTIVES

Analysis of a referral population of patients with choroid plexus cysts (CPCs) was performed to compare an average risk method of counseling to an individualized risk method.

METHODS

A total of 395 patients referred to a Prenatal Diagnosis Center were included, of whom 341 had isolated CPCs and 54 had associated ultrasound abnormalities. For isolated CPCs, an average risk of 1/150 for aneuploidy was compared to an individualized risk assessment [prior risk as determined by maternal age or serum screening multiplied by the likelihood ratio established by Gupta et al. (1997)]. Accuracy, cost, and procedure-related losses were assessed.

RESULTS

Both methods resulted in 100% sensitivity. The individualized method resulted in greater specificity, decreased costs, and (theoretically) fewer procedure-related pregnancy losses.

CONCLUSIONS

An individualized risk method of counseling utilizing the likelihood ratios established by Gupta et al. (1997) was superior to an average risk method for assessing trisomy 18 risk in the setting of CPC detected in mid-trimester.

Fetal and neonatal neurologic consultations: identifying brain disorders in the context of fetal-maternal-placental disease

Pediatric neurologists provide an important consultative role for the fetus or neonate with a suspected brain disorder. Although most consultations are initiated after birth, neonatal neurologic dysfunction may be reflective of fetal brain damage or maldevelopment. Maternal or placental/cord disease states can predispose the fetus or neonate to brain disorders during the antepartum, intrapartum, or early postpartum periods. Neurologists must therefore consider maternal, placental, and fetal conditions on which a neonatal encephalopathy may be superimposed, with or without recent brain injury. This review suggests how the pediatric neurologist can contribute more effectively to fetal and neonatal neurologic evaluations regarding etiologies and mechanisms of brain injury; their role will enhance diagnostic services composed of maternal-fetal specialists, placental and pediatric pathologists, neonatologists, neurosurgeons, geneticists, and other pediatric subspecialists. Selected examples of structural markers during fetal life, and functional markers during neonatal life, illustrate the wide spectrum of disease states that are highly dependent on the timing and location of brain injury. The pediatric neurologist has the opportunity to integrate these complementary lines of investigation into a responsive consultative opinion, which is both medically accurate and ethical, responsible to the welfare of the mother and child.

Central nervous system anomalies

Fetal central nervous system abnormalities encompass a variety of lesions. Most of the anomalies are seen in association with an increased incidence of fetal aneuploidy and an increase in other anomalies both within and outside of the central nervous system. These associated findings and the underlying lesion all have a role in the eventual prognosis for the ongoing pregnancy. The antenatal diagnosis of a central nervous system abnormality should prompt a careful search for other defects, and consideration should be given for genetic evaluation and testing.

Isolated fetal choroid plexus cysts: role of ultrasonography in establishment of the risk of trisomy 18

OBJECTIVE

The significance of isolated choroid plexus cysts found by ultrasonographic scan during the second trimester as a marker for trisomy 18 is still debated. We analyzed our data and reviewed the series published in the English-language literature to calculate the likelihood ratio of trisomy 18 in the presence of isolated choroid plexus cysts; that is, the factor by which the individual risk of trisomy 18 is increased in the presence of isolated choroid plexus cysts.

STUDY DESIGN

Likelihood ratios were calculated as ratio of the sensitivity to the false-positive rate. Sensitivity was defined as the rate of isolated choroid plexus cysts detected at midgestation among fetuses with trisomy 18. False-positive rate was defined as the rate of choroid plexus cysts detected at midgestation in the population without trisomy 18. The sensitivities of all published series reporting rates of choroid plexus cysts at the time of the first ultrasonographic examination between 14 and 24 weeks' gestation in populations with trisomy 18 and in low-risk populations were included in the analysis. To these we added all cases of trisomy 18 diagnosed at our institution during the period January 1, 1988, through June 30, 1998, in which prenatal ultrasonographic examination was performed between 14 and 24 weeks' gestation.

RESULTS

The prevalence of second-trimester ultrasonographic detection of isolated choroid plexus cysts among fetuses with trisomy 18 was 6.7% (13/194), whereas that in the population without trisomy 18 was 0.9% (752/79,583). The likelihood ratio associated with isolated choroid plexus cysts was therefore 7.09 (95% confidence interval, 3.97-12.18).

CONCLUSION

The presence of isolated second-trimester choroid plexus cysts increases the base risk of trisomy 18 by a factor of 7.09. This likelihood ratio can be multiplied by the risk calculated according to maternal age to obtain the individual risk of trisomy 18 and thus permit more accurate counseling of the patient.

Ultrasound screening for fetal chromosome anomalies

Ultrasound evidence for aneuploidy may be found in almost every organ of the fetus and can be used to modify the risk of aneuploidy. The diagnosis of these minor anomalies on second-trimester ultrasonography will increase the risk of an abnormal karyotype whereas the absence of these findings may reduce this danger. The most specific and most ominous isolated markers for fetal aneuploidy are nuchal findings (edema or cysts), indicating the need to obtain a fetal karyotype in all cases irrespective of maternal age or results of biochemical serum screening. Hyperechoic fetal bowel is apparently also a strong indicator of fetal aneuploidy. Other isolated sonographic markers may increase the risk of an abnormal karyotype three- to ninefold. Most sonographic markers for aneuploidy specify an increased risk for Down syndrome, but choroid plexus cysts are apparently more specific for trisomy 18. Along with other screening methods, ultrasound screening for fetal aneuploidy should be used routinely to identify additional pregnancies at need for evaluation of fetal karyotype.