Isolated fetal choroid plexus cysts: not an indication for genetic diagnosis?

Offering invasive prenatal cytogenetic testing in cases of isolated choroid plexus cysts is controversial. To give a contribution to this discussion we recorded prospectively the course of 41 fetuses with cysts of the choroid plexus diagnosed in 4,326 pregnancies sonographically scanned in our center between January 1994 and August 1995. The fetuses were all in the 13th to 24th week of gestation, with an average of 19.3 weeks. Only 1 of these fetuses (with large bilateral choroid plexus cysts) had further sonographically visible malformations (renal and cardiac anomalies, malposition of the hands). 34 fetuses had bilateral and 7 one-sided plexus cysts. 38 of the 41 patients decided on invasive diagnosis; karyotyping was successful in all these cases. The complete follow-up until 5 days after birth is known in 38 fetuses, including 3 without genetic diagnosis. A chromosomal aberration was detectable only in 1 fetus (trisomy 18, this fetus had the additional malformations described above), the other fetuses all displaying neither chromosomal nor morphological abnormalities. All fetuses, excluding 1 (the pregnancy was terminated due to trisomy 18) were re-examined before the 25th week of gestation, plexus cysts only still being visible in 3 fetuses. By the 30th week of gestation in these 3 fetuses the cysts had also disappeared. Furthermore, 20 pregnancies with confirmed trisomy 18 diagnosed between 1990 and 1996 were analyzed retrospectively. In 19 cases heart defects had been detected by prenatal ultrasound, cervical hygroma being less common (6 cases) and other malformations still rarer. Choroid plexus cysts had, however, been seen only in the 1 case described above. There was no case of isolated choroid plexus cysts in this group. From our data and current literature we conclude that isolated choroid plexus cysts are not an absolute indication for fetal karyotyping. In our opinion a detailed ultrasound assessment to seek for further malformations in a specialized center would be necessary if fetal choroid plexus cysts have been diagnosed, and only if additional fetal malformations are indeed detectable a fetal karyotype should be recommended.