Isolated fetal choroid plexus cysts
Overview: Isolated choroid plexus cyst(s) are common findings, seen in 1-2% of normal fetuses in the second trimester. When choroid plexus cyst(s) are identified, an experienced provider should perform a detailed fetal anatomic survey and assess for aneuploidy risk factors.
Diagnosis/definition: 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). A choroid plexus cyst is not considered a structural or functional brain abnormality.
Epidemiology/Incidence: 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.
Risk factors/associations: The only association of some significance between an isolated choroid plexus cyst and a possible fetal problem is with trisomy 18. 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%.o In the absence of associated sonographic abnormalities, the likelihood of trisomy 18 is extremely low in otherwise low-risk pregnancies.
- 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.
- More than 90% of choroid plexus cysts resolve, most often by 28 weeks. 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. Therefore, neither serial antenatal ultrasounds nor post-natal evaluation are clinically useful.