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Objective: The purpose of the study was to determine the incidence of isolated choroid plexus cysts in association with trisomy 18 and other abnormalities.
Study Design: All patients from June 1992 through December 1995 were followed up after a screening ultrasonography. Any patient with a choroid plexus cyst was offered genetic counseling and an amniocentesis. Screening ultrasonographic examinations were performed on 16,059 patients, and 301 patients had a fetus with a choroid plexus cyst. One hundred thirty patients elected to have an amniocentesis. Patients were followed up to delivery.
Results: Two hundred sixty-three patients had an isolated choroid plexus cyst. Thirty-eight patients had a choroid plexus cyst associated with additional risk factors. Risk factors included advanced maternal age, additional ultrasonographic abnormalities, past obstetric history, or family history. No abnormalities were noted in the group with an isolated choroid plexus cyst. Four patients had an abnormality when the choroid plexus cyst was associated with an additional risk factor, including two patients with trisomy 18 and one with trisomy 21.
Conclusion: An isolated choroid plexus cyst was not associated with a trisomy or other abnormalities in this study. When a choroid plexus cyst was associated with an additional risk factor, 10.5% of the patients had an abnormality. Amniocentesis is recommended when a choroid plexus cyst is found in association with additional risk factors. (Am J Obstet Gynecol 1997;176:1381-3.)
The choroid plexus is a large echogenic structure within the lateral ventricles. [1,2] The incidence of choroid plexus cysts as determined by ultrasonography in early pregnancy varies from 0.18% to 2.5%. [3,4] Cystic formations within the plexus have been associated with trisomy 18 [5-8] and less commonly with trisomy 21 [9] and other abnormalities. [10] Several authors have recommended amniocentesis be offered to patients with a choroid plexus cyst. [8,11-17] Other investigators have suggested evaluating the pregnancy for other risk factors before recommending an amniocentesis. [18,19] This study was proposed to ascertain the risk of trisomy 18 or other abnormalities in our patient population when an isolated choroid plexus cyst was noted during a second-trimester screening ultrasonographic examination.
Material and methods^
All obstetric patients at San Diego Kaiser Permanente Hospital have ultrasonographic screening offered in the second trimester. Approximately 95% of the patients have the ultrasonography performed. This study included all the obstetric patients from June 1992 through December 1995. A total of 16,059 patients were screened at 18 to 21 weeks of gestation by a certified ultrasonography technician. An Acuson (Mountain View, Calif.) model XP10 machine was used with either a 3.5 MHz linear, a 2.25 MHz sector, or a 3.5 MHz curvilinear scanner. Cysts were evaluated as to their size, whether they were unilateral or bilateral, and if any other fetal abnormality was noted by ultrasonography. A choroid plexus cyst was noted in 301 patients. Any patient with a choroid plexus cyst was advised of this finding and was offered an appointment with a genetic counselor. All patients were given information regarding possible association with trisomy 18 and other abnormalities and amniocentesis was offered to all patients; 171 of 301 (57%) declined amniocentesis. An amniocentesis was performed in 130 of 301 (43%). Ninety-two of these patients had an isolated choroid plexus cyst, and 38 patients had a choroid plexus cyst and at least one additional risk factor. Risk factors were defined as maternal age > 35 years at delivery, other abnormalities found at the screening ultrasonographic examination, or significant obstetric or family history for congenital abnormality. No patient with additional risk factors declined amniocentesis. Follow-up ultrasonography was performed on 176 patients. All patients with a choroid plexus cyst were followed up to delivery. Eight patients with isolated choroid plexus cysts were lost to follow-up.
Results^
Of the 16,059 patients having routine second-trimester ultrasonographic screening, 1.9% or 301 patients had a choroid plexus cyst. The cyst size ranged from 0.7 to 15.2 mm. The cysts were unilateral in 166 of 301 (55%) and bilateral in 135 of 301 (45%). Follow-up ultrasonography was done for 176 patients and the choroid plexus cyst was noted to have regressed in 90% by 25 weeks' gestation. Isolated cysts were seen in 263 patients and they were offered amniocentesis. Amniocentesis was performed on 92 patients and all had a normal karyotype. There were no fetal losses or complications. The 92 patients who had amniocentesis and the 171 who declined were followed up until delivery. No fetal abnormalities were detected at birth. A total of 8 patients with isolated choroid plexus cysts were lost to follow-up.
All 38 patients with choroid plexus cysts and additional risk factors elected to have an amniocentesis. Four of the 38 (10.5%) had an abnormality (Figure 1).
Comment^
Earlier publications suggested that all patients who had a choroid plexus cyst should be offered an amniocentesis. [8,11-17] More recent articles suggest that an isolated choroid plexus cyst is not an indication for amniocentesis. [18,19] There may be several reasons for the different conclusions the early authors reached compared with those of later publications. The later studies were larger and could include the earlier series in analyzing their data. The incidence of trisomy 18 is low. Occasional association with choroid plexus cyst is obviously even lower. Very large numbers will be needed to determine the actual risk of trisomy 18 when a choroid plexus cyst is noted. With better ultrasonography machines and a skilled ultrasonographer more structural abnormalities will be seen. The improved resolution with current equipment permits visualization of fetal morphologic features much more accurately than was previously possible. Subtle fetal abnormalities may not have been noted with earlier equipment. Therefore some of the choroid plexus cysts in these studies were probably not isolated but were associated with fetal abnormalities.
Informing a patient that her baby has a cyst within its brain is disconcerting. The word cyst is frequently interpreted by the patient as a tumor. This misconception is not uncommon in spite of genetic counseling. Then telling her that the cyst may be associated with the serious abnormality of trisomy 18 can be devastating for some patients. On the basis of the data from this study and others [18,19] a different approach may be considered. That is, an isolated choroid plexus cyst may not be associated with a significantly increased risk for trisomy 18 or 21. A choroid plexus cyst with a morphologic abnormality as seen by ultrasonography or with maternal age > 35 years may be significant, and prenatal diagnostic procedures should be offered. In conclusion, second-trimester ultrasonography was performed on > 16,000 women. A choroid plexus cyst was noted in 301 patients. Of the 263 patients with an isolated choroid plexus cyst, none had an abnormality. Four of the 38 patients (10.5%) with a choroid plexus cyst and other risk factors had a significant abnormality. We would recommend amniocentesis for patients with a choroid plexus cyst and additional risk factors.
We thank Carol Richards, LVN, for data collection; Jim McKowan, for data entry; Paula Weber, RN, Gloria Sanchez, MS, and Cheryl Dubbel-Knight, MS, for genetic counseling; Silverio Chavez, MD, Leslie Casper, MD, Nicholas Mortell, MD, and David Preskill, MD, for amniocentesis; and the Ultrasound Department at San Diego Kaiser Permanente for their expertise.
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