Isolated Choroid Plexus Cysts Rarely a Marker for Defects

OB/GYN News, Oct 15, 1999 by Guang-Shing Cheng

NEW YORK -- Choroid plexus cysts are not an indication for amniocentesis in the absence of other findings on fetal ultrasound, according to Dr. Beryl Benacerraf.

"It's very difficult to deal with when you identify a choroid plexus cyst because dearly they are associated with an increased risk of chromosomal abnormalities," Dr. Benacerraf said at a meeting on ob.gyn. ultrasound sponsored by the American Institute of Ultrasound in Medicine.

Clinicians who see a choroid plexus cyst on fetal ultrasound may consider doing an amniocentesis. The literature is extensive and covers both points of view, making it difficult for clinicians to decide.

In one study, Dr. Benacerraf, professor of ob.gyn. and radiology at Harvard Medical School, Boston, looked at 234 fetuses that had a choroid plexus cyst on ultrasound at 14-24 weeks. A total of 220 had no other findings, and the remaining 14 had other malformations.

Follow-up showed that of the 14 abnormal fetuses, 11 had trisomy 18, 1 had a triploidy, and 2 had multiple severe anomalies but normal karyotypes. Of note, the fetuses with trisomy 18 also had abdominal wall defects and facial cleft that raised the suspicion of a chromosomal abnormality. All 220 fetuses that had an isolated finding of choroid plexus cyst were normal at birth.

"The occasional fetus with trisomy 18 may have a choroid plexus cyst, but in our experience, most of these cysts are benign and lack clinical sequelae," Dr. Benacerraf said.

Because fetuses with trisomy 18 typically have a clenched fist, Dr. Benacerraf advised clinicians to get a good look at the hands. "The chances are that a fetus with isolated choroid plexus cyst that has no other findings and an open hand is not going to have trisomy 18," she said.

There have been reports of fetuses that have choroid plexus cysts and Down syndrome. "If that association is there, perhaps we have to rethink whether or not we should do amniocentesis," she said at the meeting. But because trisomy 21 and choroid plexus cysts are both relatively common, the association may be purely coincidental.

Dr. Benacerraf's group reviewed records of 34,503 fetuses and found that 473 had a choroid plexus cyst on second-trimester ultrasound; of these, 2 had Down syndrome. Excluding fetuses with trisomy 18, the overall incidence of choroid plexus cysts was 1.3% in the general study population. Of the 143 fetuses with Down syndrome, 2 had choroid plexus cysts, which translates to an incidence of 1.4%.

There was no significant difference in the incidence of choroid plexus cysts in Down syndrome patients and that of the general population, suggesting no direct association, and no increased risk of Down syndrome with a choroid plexus cyst, she contends.

"For that reason, I've held to our recommendation that we don't need to do an amniocentesis for an isolated choroid plexus cyst because trisomy 21 is not going to be an issue," Dr. Benacerraf commented.