A 33-year-old G1 presents for a fetal anatomic survey at 20 weeks 2 days’ gestation. A unilateral choroid plexus cyst is noted; no other sonographic markers of aneuploidy or structural malformations are identified.
What are isolated choroid plexus cysts and how common are they?
A choroid plexus cyst is a small fluid-filled structure within the choroid of the lateral ventricles of the fetal brain. Sonographically, choroid plexus cysts appear as echolucent cysts within the echogenic choroid (Figure 1). Choroid plexus cysts may be single or multiple, unilateral or bilateral, and most often are less than 1 cm in diameter. Choroid plexus cysts are identified in approximately 1% to 2% of fetuses in the second trimester and they occur equally in male and female fetuses.1
What are the major clinical implications of an isolated choroid plexus cyst?
When a choroid plexus cyst is identified, the presence of structural malformations and other sonographic markers of aneuploidy should be assessed with a detailed fetal anatomic survey performed by an experienced provider. Detailed examination of the fetal heart (4-chamber view and outflow tracts view) and hands (for “clenching” or other abnormal positioning) should be included, as well as fetal biometry for assessment of intrauterine growth restriction. If no other sonographic abnormalities are present, the choroid plexus cyst is considered isolated.
A choroid plexus cyst is not considered a structural or functional brain abnormality. Most choroid plexus cysts are isolated and occur in otherwise low-risk pregnancies.2 The only association of some significance between an isolated choroid plexus cyst and a possible fetal problem is with trisomy 18. Choroid plexus cysts are present in 30% to 50% of fetuses with trisomy 18. Trisomy 18 is characterized by major structural abnormalities and abnormal sonographic findings.3 When a fetus is affected by trisomy 18, multiple structural anomalies are almost always evident, including structural heart defects, clenched hands, talipes deformity of the feet, growth restriction, and polyhydramnios. When a structural anomaly is present in addition to choroid plexus cysts, the probability of trisomy 18 is 37%.4
In the absence of associated sonographic abnormalities, the likelihood of trisomy 18 is extremely low in otherwise low-risk pregnancies. Studies from the 1990s reported that the risk of trisomy 18 with isolated choroid plexus cysts was approximately 1 in 200 to 1 in 400.5,6
Based on a meta-analysis of 14 studies published before 2000, Ghidini et al suggested utilization of a composite (+) likelihood ratio of 7.09 (95% CI, 3.97-12.18).4 A large, single-center cohort study (N=1111 cases of isolated choroid plexus cyst) published in 2008 reported much lower risk.7 Given the considerable improvements in imaging technology and aneuploidy screening in recent years, the risk of trisomy 18 in the setting of isolated choroid plexus cysts is now believed to be much lower.
When an isolated choroid plexus cyst is detected, how is counseling different for women with a normal screen versus those whose screening indicates increased risk?
Counseling for a woman after prenatal identification of a fetal choroid plexus cyst should be guided by the presence or absence of other sonographic markers or structural abnormalities, results of maternal screening for risk of trisomy 18 (if performed), and maternal age (Figure 2).
In women who screen negative for trisomy 18 (either first- or second-trimester screening) and in whom no other fetal structural abnormalities are visualized on a detailed ultrasound, the finding of an isolated choroid plexus cyst does not require additional genetic testing. Some experts suggest that it is unnecessary for a physician to discuss such a finding with a patient because it can be considered a normal variant.8 If it is discussed, the patient can be reassured about the extremely low risk of trisomy 18.
Genetic counseling should be offered to women whose screening (eg serum or combined) indicates an increased risk of trisomy 18. If serum screening was not performed or was declined, it can be performed at this time. Counseling should include a discussion of the association between choroid plexus cysts and trisomy 18, and diagnostic testing should be offered.9
Noninvasive prenatal testing may be a reasonable option for women who are concerned about the procedure-related risk of pregnancy loss.10
Ultrasound characteristics of choroid plexus cysts (size, complexity, laterality, and persistence) should not be used to further modify risk because these factors do not significantly impact the likelihood of trisomy 18. The presence of a choroid plexus cyst does not alter the risk of trisomy 21, and the finding should not be used to modify a patient’s risk of trisomy 21.11
How should a woman with anisolated choroid plexus cyst be followed throughout pregnancy?
More than 90% of choroid plexus cysts resolve, most often by 28 weeks.12,13 Studies evaluating neurodevelopmental outcomes in euploid children born after a prenatal diagnosis of choroid plexus cysts have not shown differences in neurocognitive ability, motor function, or behavior.14-16
Therefore, neither serial antenatal ultrasounds nor post-natal evaluation are clinically useful.
1. Landy HJ. Association of sex of the fetus in isolated fetal choroid plexus cysts. J Ultrasound Med.1999;18(11):769-771.
2. Bronsteen R, Lee W, Vettraino IM, Huang R, Comstock CH. Second-trimester sonography and trisomy 18: the significance of isolated choroid plexus cysts after an examination that includes the fetal hands. J Ultrasound Med. 2004;23(2):241-245.
3. Nyberg DA, Kramer D, Resta RG, et al. Prenatal sonographic findings of trisomy 18: review of 47 cases. J Ultrasound Med. 1993;12(2):103-113.
4. Ghidini A, Strobelt N, Locatelli A, Mariani E, Piccoli MG, Vergani P. Isolated fetal choroid plexus cysts: role of ultrasonography in establishment of the risk of trisomy 18. Am J Obstet Gynecol. 2000;182(4):972-977.
5. Gross SJ, Shulman LP, Tolley EA, et al. Isolated fetal choroid plexus cysts and trisomy 18: a review and meta-analysis. Am J Obstet Gynecol. 1995;172(1 pt 1):83-87.
6. Walkinshaw S, Pilling D, Spriggs A. Isolated choroid plexus cysts—the need for routine offer of karyotyping. Prenat Diagn. 1994;14(8):663-667.
7. Goetzinger KR, Stamilio DM, Dicke JM, Macones GA, Odibo AO. Evaluating the incidence and likelihood ratios for chromosomal abnormalities in fetuses with common central nervous system malformations. Am J Obstet Gynecol. 2008;199(3):285.e1-285.e6.
8. Filly RA, Benacerraf BR, Nyberg DA, Hobbins JC. Choroid plexus cyst and echogenic intracardiac focus in women at low risk for chromosomal anomalies. J Ultrasound Med. 2004;23(4):447-449.
9. American College of Obstetricians and Gynecologists. ACOG practice bulletin no. 88, December 2007. Invasive prenatal testing for aneuploidy. Obstet Gynecol. 2007;110(6):1459-1467.
10. American College of Obstetricians and Gynecologists Committee on Genetics. Committee opinion no. 545: noninvasive prenatal testing for fetal aneuploidy. Obstet Gynecol. 2012;120(6):1532-1534.
11. Yoder PR, Sabbagha RE, Gross SJ, Zelop CM. The second-trimester fetus with isolated choroid plexus cysts: a meta-analysis of risk of trisomies 18 and 21. Obstet Gynecol. 1999;93(5 pt 2):869-872.
12. DeRoo TR, Harris RD, Sargent SK, Denholm TA, Crow HC. Fetal choroid plexus cysts: prevalence, clinical significance, and sonographic appearance. AJR Am J Roentgenol. 1988;151(6):1179-1181.
13. Chitkara U, Cogswell C, Norton K, Wilkins IA, Mehalek K, Berkowitz RL. Choroid plexus cysts in the fetus: a benign anatomic variant or pathologic entity? Report of 41 cases and review of the literature. Obstet Gynecol. 1988;72(2):185-189.
14. Bernier FP, Crawford SG, Dewey D. Developmental outcome of children who had choroid plexus cysts detected prenatally. Prenat Diagn. 2005;25(4):322-326.
15. Digiovanni LM, Quinlan MP, Verp MS. Choroid plexus cysts: infant and early childhood developmental outcome. Obstet Gynecol. 1997;90(2):191-194.
16. DiPietro JA, Costigan KA, Cristofalo EA, et al. Choroid plexus cysts do not affect fetal neurodevelopment. J Perinatol. 2006;26(10):622-627.
Dr. Fuchs is an assistant clinical professor in the Division of Maternal-Fetal Medicine, Columbia University Medical Center, New York, New York.
This opinion was developed by the Publications Committee of the Society for Maternal-Fetal Medicine with the assistance of Karin M. Fuchs, MD, and was approved by the Executive Committee of the Society on February 11, 2013. Neither Dr. Fuchs nor any member of the Publications Committee (see the list of 2013 members at www.smfm.org) has a conflict of interest to disclose with regard to the content of this article.
(Disclaimer: The practice of medicine continues to evolve and individual circumstances will vary. Clinical practices may reasonably vary. This opinion reflects information available at the time of acceptance for publication and is not designed nor intended to establish an exclusive standard of perinatal care. This publication is not expected to reflect the opinions of all members of the Society for Maternal-Fetal Medicine.)