Choroid plexus cysts--association with trisomy: prospective review of 16,059 patients

Role of Sonographic Second Trimester Soft Markers in the Era of Cell-Free DNA Screening Options: A Review

Soft markers are sonographic structural, nonspecific signs with little pathological significance, often transient, usually considered as normal variants. However, they may also be associated with chromosomal abnormalities. The most widely examined soft markers include absent or hypoplastic nasal bone (NB), intracardiac echogenic focus (IEF), ventriculomegaly (VM), thickened nuchal fold (NF), choroid plexus cyst (CPC), echogenic bowel, short long bones, and urinary tract dilation (UTD). Although the use of noninvasive prenatal testing (NIPT) has been spreading quickly in maternal–fetal medicine, it is not a diagnostic test and it still remains unavailable or cost-prohibitive for most of the population in many countries. After normal screening test results in the first trimester, there is no uniform consensus regarding the clinical significance of isolated soft markers for aneuploidy. Nowadays, the search for soft markers in an ultrasound is still part of clinical evaluation, and the interpretation of these findings is often a matter of debate. In the present review, we summarize the recent literature about the role of soft markers in the era of NIPT and propose an overview of the different clinical guidelines.

Transitory and Vestigial Structures of the Developing Human Nervous System

As with many body organs, the human central nervous system contains many structures and cavities that may have had functions in embryonic and fetal life but are vestigial or atrophic at maturity. Examples are the septum pellucidum, remnants of the lamina terminalis, Cajal-Retzius neurons, induseum griseum, habenula, and accessory olfactory bulb. Other structures are transitory in fetal or early postnatal life, disappearing from the mature brain. Examples are the neural crest, subpial granular glial layer of Brun over cerebral cortex, radial glial cells, and subplate zone of cerebral cortex. At times persistent fetal structures that do not regress may cause neurological problems or indicate a pathologic condition, such as Blake pouch cyst. Transitory structures thus can become vestigial. Examples are an excessively wide cavum septi pellucidi, suprapineal recess of the third ventricle, trigeminal artery of the posterior fossa circulation, and hyaloid ocular artery. Arrested maturation might be considered another aspect of vestigial structure. An example is the persistent microcolumnar cortical architecture in focal cortical dysplasia type Ia, in cortical zones of chronic fetal ischemia, and in some metabolic/genetic congenital encephalopathies. Some transitory structures in human brain are normal adult structures in lower vertebrates. Recognition of transitory and vestigial structures by fetal or postnatal neuroimaging and neuropathologically enables better understanding of cerebral ontogenesis and avoids misinterpretations.

Incidental Intracranial Cysts in Children

With increasing use of intracranial imaging, the diagnosis of benign intracranial cysts is becoming more frequent in the pediatric population. These lesions are usually incidentally discovered during the work-up of unrelated symptoms. Most do not require treatment and many do not even require imaging follow-up. When symptomatic, symptoms of these lesions are usually caused by local mass effect. Symptomatic lesions warrant neurosurgical evaluation, and may require surgical intervention in rare, well-selected cases. This article describes three common benign intracranial cysts found in the pediatric population: arachnoid cysts, choroid cysts, and pineal cysts.

Giant choroid plexus cysts with calvarial erosion: a case report and literature review

Choroid plexus cysts rarely grow to be symptomatic. Few large choroid plexus cysts have been reported in the pediatric population. The authors report a 15-month-old boy with increased head circumference and a bony deformity in the left parietal region due to mass effect from a giant choroid plexus cyst. The child had a craniotomy for open resection of the cyst, and made an excellent recovery. The differential diagnosis for intraventricular cysts and the literature surrounding choroid plexus cysts are discussed.

A Bayesian risk analysis for Trisomy 21 in isolated choroid plexus cyst: combining a prenatal database with a meta-analysis

OBJECTIVE

The purpose of this study was to quantify the possible additional risk of a fetus with an isolated choroid plexus cyst (ICPC) for Trisomy 21 by combining a large controlled cohort study with data from existent studies.

METHODS

We searched our prenatal database between 2000 and 2014 for all singleton pregnancies between 18 + 0 and 26 + 6 gestational weeks with either an isolated choroid plexus cyst (study group) or no abnormality found in the detailed ultrasound scan (control group). We assessed all prenatal karyotyping results if invasive testing was performed and attempted to collect the postnatal outcome reports of all patients. The prevalence of Down syndrome was calculated. By using previous studies that met our inclusion criteria, a meta-analysis following the Bayesian Independent Model was created. From this meta-analysis, we computed the posterior predictive distribution of the probability (Trisomy 21 | ICPC) = P1 including posterior means, standard deviations, quantiles (2.5, 50, and 97.5%). By calculating the posterior of the difference (Δ) between the probability (Trisomy 21 | ICPC) and the probability (Trisomy 21 | Normal Ultrasound) = P2, we investigated the additional risk of an ICPC (ΔB = P1-P2).

RESULTS

Overall, we detected 1220 fetuses with an isolated plexus cyst at 19-27 weeks of gestational age (GA). In our study group, the prevalence of Trisomy 21 was 2/1220 (0.16, 95% CI: 0.1-0.6%). The median of the pooled probability of Trisomy 21 given isolated PC across the studies included in the meta-analysis was 0.2% (CI: 0.1-0.4%). In the given periods (GA and time), 66,606 (74.8%) out of 89,056 investigated fetuses met the inclusion criteria and had a normal ultrasound result without any abnormality. The Δ between our study group and the control group was 0.08% (CIΔA: 0-0.5%). Including the meta-analysis, the median of the posterior distribution of Δ between P1 and P2 was 0.08% (CIΔB: 0-0.4%) (ΔB = P1-P2).

CONCLUSION

The posterior distribution of Δ between P1 and P2 including the meta-analysis corresponds to showing no difference between the cases and controls (95% CIΔB: 0-0.4%). The additional risk of a fetus with an ICPC for Trisomy 21 is 97.5% likely to be lower than 0.4% (about 1/250). However, in our collective, the positive predictive value of ICPC for Down syndrome was 0.16% (about 1/625). In prenatal counseling, the additional risk should be added to the individual risk (based on maternal age, earlier screening test results, and sonographic markers) and the diagnostic options including fetal DNA and diagnostic procedures should be discussed according to the posterior individual risk.

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.

Incidental findings on brain and spine imaging in children

In recent years, the utilization of diagnostic imaging of the brain and spine in children has increased dramatically, leading to a corresponding increase in the detection of incidental findings of the central nervous system. Patients with unexpected findings on imaging are often referred for subspecialty evaluation. Even with rational use of diagnostic imaging and subspecialty consultation, the diagnostic process will always generate unexpected findings that must be explained and managed. Familiarity with the most common findings that are discovered incidentally on diagnostic imaging of the brain and spine will assist the pediatrician in providing counseling to families and in making recommendations in conjunction with a neurosurgeon, when needed, regarding additional treatments and prognosis.

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.

The trisomy 18 syndrome

The trisomy 18 syndrome, also known as Edwards syndrome, is a common chromosomal disorder due to the presence of an extra chromosome 18, either full, mosaic trisomy, or partial trisomy 18q. The condition is the second most common autosomal trisomy syndrome after trisomy 21. The live born prevalence is estimated as 1/6,000-1/8,000, but the overall prevalence is higher (1/2500-1/2600) due to the high frequency of fetal loss and pregnancy termination after prenatal diagnosis. The prevalence of trisomy 18 rises with the increasing maternal age. The recurrence risk for a family with a child with full trisomy 18 is about 1%. Currently most cases of trisomy 18 are prenatally diagnosed, based on screening by maternal age, maternal serum marker screening, or detection of sonographic abnormalities (e.g., increased nuchal translucency thickness, growth retardation, choroid plexus cyst, overlapping of fingers, and congenital heart defects ). The recognizable syndrome pattern consists of major and minor anomalies, prenatal and postnatal growth deficiency, an increased risk of neonatal and infant mortality, and marked psychomotor and cognitive disability. Typical minor anomalies include characteristic craniofacial features, clenched fist with overriding fingers, small fingernails, underdeveloped thumbs, and short sternum. The presence of major malformations is common, and the most frequent are heart and kidney anomalies. Feeding problems occur consistently and may require enteral nutrition. Despite the well known infant mortality, approximately 50% of babies with trisomy 18 live longer than 1 week and about 5-10% of children beyond the first year. The major causes of death include central apnea, cardiac failure due to cardiac malformations, respiratory insufficiency due to hypoventilation, aspiration, or upper airway obstruction and, likely, the combination of these and other factors (including decisions regarding aggressive care). Upper airway obstruction is likely more common than previously realized and should be investigated when full care is opted by the family and medical team. The complexity and the severity of the clinical presentation at birth and the high neonatal and infant mortality make the perinatal and neonatal management of babies with trisomy 18 particularly challenging, controversial, and unique among multiple congenital anomaly syndromes. Health supervision should be diligent, especially in the first 12 months of life, and can require multiple pediatric and specialist evaluations.

Evaluating the incidence and likelihood ratios for chromosomal abnormalities in fetuses with common central nervous system malformations

OBJECTIVE

To determine the incidence and likelihood ratios for chromosomal abnormalities in fetuses with common central nervous system malformations on ultrasound.

STUDY DESIGN

A database derived retrospective cohort study of all patients referred for ultrasound and genetic evaluation from 1990-2006. Fetal karyotypes were delineated by prenatal diagnosis or postnatal examination. The incidence and likelihood ratios were calculated for the association of each central nervous system abnormality with trisomy 13, 18, and 21.

RESULTS

Of 62,111 women included, 587 (0.9%) had major fetal central nervous system abnormalities. The only central nervous system anomalies associated with trisomy 21 were ventriculomegaly and choroid plexus cysts. When isolated, only spina bifida, holoprosencephaly, and agenesis of the corpus callosum were significantly associated with trisomy 13, anencephaly with trisomy 18, and ventriculomegaly with trisomy 21. Likelihood ratios positive range from 2-20 depending on the central nervous system malformation and aneuploidy type.

CONCLUSION

Central nervous system malformations detected on ultrasound are strongly associated with and predictive of chromosomal abnormalities, especially trisomy 13 and 18.

Sonographic findings of trisomy 18 in the second trimester of pregnancy

OBJECTIVE

The purpose of this study was to examine the sonographic findings in fetuses with trisomy 18 in the second trimester of pregnancy.

METHODS

A retrospective review of the cytogenetic laboratory databases at 6 tertiary referral centers identified all cases of trisomy 18. The prenatal sonographic studies in fetuses at 15 to 21 weeks' gestation, done before invasive testing for the karyotype, were reviewed for anatomic and biometric findings. We defined abnormal fetal biometric findings as a biometric measurement (biparietal diameter, abdominal circumference, or femur length) below the fifth percentile in the second trimester.

RESULTS

Of 98 fetuses with trisomy 18, 95 (97%) were detected sonographically; an anomaly was found in 92 (94%). A biometric measurement below the fifth percentile was noted in 50 (51%). Cardiac (63%) and central nervous system (34%) anomalies were most frequently detected. Although choroid plexus cysts were commonly seen, no fetuses with trisomy 18 and isolated choroid plexus cysts were found.

CONCLUSIONS

Targeted sonography identified abnormal fetal anatomy or abnormal biometric findings in 97% of fetuses with trisomy 18 in the second trimester. A biometric measurement below the fifth percentile was noted in half of the cases in the second trimester.

Anterior choroid plexus cysts: distinction from germinolysis by high-resolution sonography

BACKGROUND

The aim of the present paper was to develop criteria identifying anterior choroid plexus cysts (ACPC) and distinguish these from germinolytic pseudocysts.

METHODS

Cerebral sonography was performed in 2200 neonates with mean gestational age 40 completed weeks (range 23-42 weeks) and mean birthweight of 3450 g (range 340-4610 g). In the last 300 neonates cystic formations in the caudothalamic groove were studied prospectively using a high-resolution ultrasound system with linear scanhead, and the previous results were re-evaluated.

RESULTS

In 22 neonates choroid plexus cysts outside the typical location in the choroid plexus glomus could be attributed to the anterior part of the choroid plexus in the lateral ventricles (prospectively analyzed in 16 of 300 neonates: 5% prevalence on high-resolution sonography). ACPC were located medial and behind germinolytic pseudocysts and best realized during sweep of the scanhead through the caudothalamic groove. In contrast to germinolytic pseudocysts, they had a spherical form, no septation and a thick, partial double wall. Larger cysts seemed to bounce.

CONCLUSIONS

ACPC are not rare and are identified by their location, form, and movement.

Prenatal ultrasonographic findings may be useful in predicting the prognosis of trisomy 18

OBJECTIVE

This study was conducted to determine whether specific ultrasonographic findings in the prenatal period were associated with survival of children affected with trisomy 18.

METHOD

Between October 1987 and July 2004, we collected 24 cases with trisomy 18. We investigated the relationship of prenatal ultrasonographic findings, gestational age at delivery, the Apgar score, the mode of delivery, and the neonatal treatment strategies, with survival time.

RESULTS

17 of the 24 neonates died within 1 month after birth (Group 1), 5 died within 12 months (Group 2), and 2 survived for more than 1 year (Group 3). Severe polyhydramnios was more frequent in group 1. In groups 2 and 3, the fluid in fetal stomach was visible in all cases. Severe cardiac anomalies were more frequent in group 1. In groups 2 and 3, all neonates were girl.

CONCLUSION

Prenatal ultrasonographic findings associated with survival less than 1 month included severe polyhydramnios, absence of the fluid in the stomach, severe cardiac anomaly and male sex.

Women's response to fetal choroid plexus cysts detected by prenatal ultrasound

OBJECTIVES

To determine maternal responses to detection of a minor structural variant, the choroid plexus cyst (CPC), in their fetus on prenatal ultrasound.

STUDY DESIGN

We interviewed 34 pregnant women with an isolated CPC detected on mid-pregnancy ultrasound about their objective experience at diagnosis, emotional response and subsequent reactions. Audiotaped, transcribed responses were evaluated by two independent raters and analyzed qualitatively and quantitatively.

RESULTS

All women reported negative emotional responses including shock, distress, fear and decreased attachment, despite counseling by 82% of providers that the CPC was probably benign. Three women underwent amniocentesis purely for reassurance after CPC detection. Most (79%) sought information beyond what their physician provided, frequently on the internet. One half of women reported that intense negative responses were temporary. However, weeks after diagnosis, 62% continued to believe that the CPC presented some danger to their baby.

CONCLUSIONS

Detection of CPC prenatally can evoke profound, negative maternal emotional responses despite accurate provider counseling. Practitioners should consider these responses when counseling parents about these and other structural variants of unclear functional significance.

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.

Antenatal neurosurgical counseling: approach to the unborn patient

The detection and diagnosis of structural anomalies of the fetal central nervous system has become commonplace. Therefore, the pediatric neurosurgeon who will eventually care for a child postnatally can be called upon to interpret the meaning of diagnostic studies and advise the prospective parents prenatally. This article discusses some principals of prenatal counseling as they relate to neurosurgical conditions, reviews the diagnostic armamentarium for defining neurosurgical fetal conditions, and describes the common antenatal diagnoses that may be encountered by the neurosurgeon.

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.

Prenatal diagnosis for detection of aneuploidy: the options

The value of all noninvasive prenatal tests must be viewed with the perspective of the consequences of invasive testing. Regarding second trimester noninvasive testing, biochemical screening is more accurate in establishing risk than maternal age alone. One or more major ultrasound abnormalities, nuchal thickening, or a shortened humerus should raise concern for Down syndrome regardless of the patient's a priori risk based on age or biochemical markers. Isolated minor ultrasound markers should not be used in calculating risk in low-risk patients regarding Down syndrome unless the biochemical profile already places the patient at risk or in a borderline risk zone. If the ultrasound finding is hyperechoic bowel, problems other than aneuploidy may be the cause, including cystic fibrosis, infection, or hemorrhage, and these problems must be considered if hyperechoic bowel is an isolated finding. Improved risk adjustment seems to be applicable to a priori high-risk patients with completely normal sonograms. Genetic sonograms with specific risk adjustment schemata may be used to adjust a priori risk (either maternal age or biochemical screening results) at centers in which this has proven to be accurate, but whether this is statistically sound remains to be determined. The goal of second trimester ultrasound screening is to identify at-risk fetuses better and offer invasive testing to a more select group of patients. As the value of first trimester screening becomes more evident and practical, and if the risk of chorionic villus sampling becomes an acceptable norm, the patient population that reaches the second trimester of pregnancy will be select. Therefore, we can anticipate that second trimester screening and invasive testing may be needed only in a minority of cases, and the practice standards of prenatal testing and sonography (including minor ultrasound markers) will change entirely.

Prospective ranking of the sonographic markers for aneuploidy: data of 2143 prenatal cytogenetic diagnoses referred for abnormalities on ultrasound

OBJECTIVE

To design a scheme to rank sonographic anomalies as indicators of aneuploidy and record the distribution of data from 2143 prenatal amniotic fluid/chorionic villous sample diagnoses referred for karyotyping because of fetal anomalies detected with ultrasound.

METHODS

In all cases the records of sonographic anomalies were obtained prior to karyotyping. A cascade of seven prospective categories of ultrasound anomalies was chosen and the data were included in the highest compatible sonography category. The categories were in descending order: (I) combined central nervous system (CNS)/cranial shape and cardiac anomalies (excluding spina bifida and anencephaly); (II) key anomaly present (exomphalos/ intrauterine growth restriction/duodenal atresia/cystic hygroma/fetal hydrops/talipes--with other multiple anomalies); (III) CNS +/- other abnormality (excluding choroid plexus cyst, spina bifida, anencephaly); (IVa) increased nuchal translucency--first trimester +/- other abnormality; (IVb) increased nuchal thickening--second trimester +/- other abnormality; (V) cardiac anomaly +/- other abnormality; (VI) other markers of aneuploidy (pyelectasis/two vessel cord/echogenic bowel/short femur); and (VII) other (mostly isolated) malformations.

RESULTS

There were 412/2143 (19.2%) chromosome abnormalities detected in this sonographically abnormal group. Overall, the prevalence of aneuploidy significantly ranged from 51 to 3% according to the above I-VII ultrasound categories and from approximately 1-80% for individual ultrasound anomalies. Likelihood ratios were derived for many ultrasound anomalies for several aneuploidy groups: trisomies of 13; 18; and 21; 45,X and 45,X mosaics; triploidy; other autosomal duplications and/or deletions; and other (than 45,X) sex chromosomal aneuploidies.

CONCLUSION

It is suggested this data could be used to assist pre-procedural counselling of patients after the ultrasound scan in tertiary referral centres for prenatal cytogenetic diagnosis.

Clinically significant persistence and enlargement of an antenatally diagnosed isolated choroid plexus cyst

Isolated choroid plexus cysts are usually diagnosed at the time of screening ultrasonography during the second trimester. While they raise the question of underlying chromosomal abnormalities, their clinical course is almost invariably benign with complete resolution often by the third trimester. We report the highly unusual case of a choroid plexus cyst diagnosed at 14 weeks of gestational age with subsequent further enlargement of the cyst, necessitating postpartum neurosurgical intervention.

Isolated choroid plexus cyst in low-risk women less than 35 years old

OBJECTIVE

The purpose of this study was to determine the incidence of trisomy 18 in women who are <35 years old and who have sonographically detected isolated choroid plexus cyst.

STUDY DESIGN

A meta-analysis of prospective trials that were published in the English language between 1990 and 2000 was performed. Each trial met the following inclusion criteria: (1) prospective trial, (2) total population screened during the study period reported, (3) maternal age (either numeric or descriptive) reported, and (4) pregnancy/neonatal outcomes reported. An isolated choroid plexus cyst for the purpose of this study was defined as absence of sonographically detected structural abnormalities and normal serum analyte screens, if reported.

RESULTS

Eight trials met the criteria and were used for analysis. A total of 106,732 women were screened through articles that were published between 1990 and 2000. The total number of fetuses with choroid plexus cysts that were identified in second-trimester scans were 1,235 (incidence, 1.2%). The incidence of isolated choroid plexus cysts in women who were <35 years old was 1.0% (n = 1,017 women). There were no cases of trisomy 18 in women with isolated choroid plexus cyst who were <35 years old. Four structural abnormalities were noted on postnatal examination; all four neonates had normal karyotypes.

CONCLUSION

There is no evidence that detection of isolated choroid plexus cyst in women who are <35 years of age increases the risk of trisomy 18. Therefore, amniocentesis is not warranted because of the inherent risk of pregnancy loss that is associated with the procedure. Better algorithms are needed to screen women who have a low risk for trisomy 18.

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.

The value of minor ultrasound markers for fetal aneuploidy

As a result of improvements in ultrasound image quality and scanning technique, an increasing number of subtle morphological changes in fetal anatomy have been identified in the second trimester. Most of these ultrasound features were originally described as normal variants of development with no clinical significance. However, subsequent studies in high-risk populations showed that some of these variants were more prevalent in fetuses with chromosomal defects and therefore proposed as prenatal markers for the detection of aneuploidy. The implications for pregnancy management when one of these so-called minor ultrasound markers is detected have been a matter of continuous controversy in the field of prenatal diagnosis and yet the definitive answer on their clinical significance in the low-risk population is still debated.

Sonographic markers of fetal aneuploidy

A variety of ultrasound findings can be identified in fetuses with fetal aneuploidy. Typical findings vary with both the chromosome abnormality and gestational age at time of the ultrasound examination. Increased NT is the primary marker during the first trimester, whereas a variety of markers may be seen during the second trimester. The presence of ultrasound markers increases the risk for fetal aneuploidy, whereas a normal ultrasound reduces the risk. Optimal risk assessment includes consideration of other risk factors including maternal age, family history, and biochemical markers. It is expected that combined risks, incorporating ultrasound findings and biochemistry, will be available in the near future. How first-trimester screening is integrated with second-trimester screening remains to be determined.

Parental decision-making differences between patients in two healthcare systems for choroid plexus cysts

We evaluated the medical-sociological implications of parental perception of risk and decision-making choices for prenatally ascertained choroid plexus cysts (CPC) between two obstetric populations. The Wayne State University (WSU) Reproductive Genetics database and the Madigan Army Medical Center (MAMC) experience were reviewed to compare the rates of aneuploidy and invasive testing for cases with CPC. Aneuploidy rates were compared between those with isolated CPC, CPC with advanced maternal age (AMA), and CPC associated with multiple anomalies. In the WSU cohort 186 cases were identified, of whom 27 (15%) declined invasive fetal testing. In the remaining 159 cases, aneuploidy was present in 2/132 (1.5%) isolated CPC, 3/11 (27%) CPC with AMA, and 15/16 (93%) CPC with multiple anomalies. In the MAMC cohort 107 cases were identified, of whom 99 (92%) declined invasive fetal testing. No aneuploidy cases were found in the 3/12 AMA cases or 5/95 non-AMA cases that underwent amniocentesis. The two cases of aneuploidy with isolated CPC cannot be ignored, and provide an estimated attributable risk of at least 0.8%, a higher risk than 38 years of age. However, the parental sociologic context may be as important for decision-making as the genetic-prognostic risk.

Second trimester markers of aneuploidy

The risks of aneuploidy associated with identification of a sonographic marker in the low risk population is controversial. Prior risk estimates have been derived usually from high risk populations. Screening programmes in the first trimester, second trimester and combined first and second trimester will undoubtedly alter the second trimester scan as a screening tool for aneuploidy. This chapter reviews the current sonographic markers and the difficulties in their application to the general population.

Prenatal ultrasound findings in affected and unaffected pregnancies that are screen-positive for trisomy 18: the California experience

This study investigated whether significant differences in ultrasound findings exist between trisomy 18 affected and unaffected pregnancies positive by serum screening. Ultrasound reports were reviewed for 335 screen-positive women. This represented 65% of all trisomy 18 screen-positive patients who had follow-up services at any of 117 Californian state-approved Prenatal Diagnosis Centers during a six-month period from November 1, 1995 to April 30, 1996. Ultrasound reports were available for 100% of trisomy 18 fetuses diagnosed during the six month period (n=23). Ultrasound findings were reported as normal in 35% of the fetuses affected with trisomy 18. The number and type of abnormalities observed in the affected and unaffected groups are described. When compared to unaffected cases, the trisomy 18 affected fetuses had a greater re-dating discrepancy on follow-up ultrasound evaluation and significantly lower femur length to biparietal diameter (FL/BPD) ratio measurements. We recommend that all women who are screen positive for trisomy 18 be encouraged to have amniocentesis, regardless of ultrasound findings, since affected fetuses may not be detected otherwise.

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.

Utility of minor ultrasonographic markers in the prediction of abnormal fetal karyotype at a prenatal diagnostic center

OBJECTIVE

This study was undertaken to assess the value of minor ultrasonographic markers in predicting significant karyotypic abnormalities.

STUDY DESIGN

A total of 2743 fetuses (14-24 weeks' gestation) prospectively underwent a detailed ultrasonographic survey before genetic amniocentesis. Criteria for 8 minor ultrasonographic markers were established. Odds ratios for significant karyotypic abnormalities in the presence of minor ultrasonographic markers were calculated with the chi(2) and Fisher exact tests.

RESULTS

Of the fetuses, 14.6% had a single minor ultrasonographic marker, 2.1% had >/=2 minor ultrasonographic markers, and 2.7% had >/=1 major ultrasonographic abnormality. One hundred four fetuses (3.8%) had an abnormal karyotype. Compared with a normal ultrasonographic examination result a single minor ultrasonographic marker increased the risk of karyotypic abnormality 5.7-fold (95% confidence interval, 3.5-9.3), whereas multiple minor markers increased the risk of an abnormal karyotype 12-fold (95% confidence interval, 5.5-26.5). When they were identified ultrasonographically in isolation, echogenic bowel, 2-vessel umbilical cord, echogenic intracardiac foci, choroidal separation, and choroid plexus cysts were statistically associated with an abnormal karyotype. When minor markers were identified in clusters of >/=2, echogenic bowel, short femur, 2-vessel umbilical cord, echogenic intracardiac foci, and mild ventriculomegaly were significantly predictive of karyotypic abnormality. With respect to the a priori aneuploidy risk of 1:26 and the a priori Down syndrome risk of 1:50, a normal ultrasonographic examination result reduced the risks to 1:67 and 1:120, respectively. The use of minor ultrasonographic markers in addition to major ultrasonographic abnormalities increased the detection of karyotypic abnormality from 27.9% to 68.3%. For trisomy 21 the sensitivity rose from 16.4% to 67. 3%.

CONCLUSIONS

Significant karyotypic abnormality risk assessment by ultrasonography was greatly enhanced by the addition of minor ultrasonographic markers. Further, clusters of minor ultrasonographic markers greatly increased the likelihood of karyotypic abnormality compared with a single minor marker. A completely normal ultrasonographic examination result reduced the risk of an abnormal karyotype by 62%. Inclusion of minor ultrasonographic markers in the genetic sonogram in a high-risk population will allow the detection of 68% of fetuses with karyotypic abnormalities with a false-positive rate of 17%.

Obstetric sonography. Who to scan, when to scan, and by whom

Most patients in the United States have an indication for and receive sonography during pregnancy. The issue of routine sonography for low-risk women continues to be contentious even though the randomized trials have not been able to demonstrate a clear benefit. Clinics that routinely offer sonography for all pregnancies usually schedule such a procedure at 16 to 20 weeks of gestation. Although great progress is being made in the first-trimester diagnoses of congenital anomalies, most targeted studies are performed at 18 to 20 weeks of gestation. Although many private obstetricians perform in-office sonography, the highest rates of detection of congenital anomalies are seen in tertiary care settings such as a university medical center. In difficult or otherwise high-risk cases, a consulting perinatologist is commonly the physician most likely to integrate the ultrasound findings with a rational management plan for the remainder of the pregnancy and for delivery.

Choroid plexus cysts and aneuploidy

The association of choroid plexus cysts with fetal aneuploidy, particularly trisomy 18, was first noted in 1986. Through the years there have been numerous reports on this subject, but no consensus has been reached with regard to chromosomal risk. In this review, we attempt to summarise published reports on second trimester choroid plexus cysts, with an emphasis on the strengths and weaknesses of each report. Based on these reports, additional malformations are a significant risk factor for aneuploidy and an indication for determination of fetal karyotype. The management of isolated choroid plexus cysts remains controversial.

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.