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Bilateral choroid plexus cysts in trisomy 21
Bilateral choroid plexus cysts in trisomy 21 Siegfried Rotmensch, MD, Jia-Sen Luo, MD, Jose A. Nores, MD, Miriam Schoenfeld Dimaio, MD, and John C. Hobbins, MD New Haven, Connecticut, and Taipei, Taiwan, Republic of China Whether karyotyping is indicated in a fetus with choroid plexus cysts who is otherwise structurally normal is still controversial. Many authors have suggested basing the decision on cyst size, bilaterality, persistence with advancing gestational age, and association with other anomalies. We report a case of large bilateral choroid plexus cysts in a fetus with trisomy 21 who had no evidence of congenital anomalies or ultrasonographic signs of Down syndrome. Cyst sizes diminished by half over a 3-week period of follow-up. It appears that diminishing size alone should not be considered sufficient reassurance about the normality of the fetal karyotype. A similar case has been previously reported, and it is conceivable that choroid plexus cysts are associated not only with trisomy 18 but also with trisomy 21. (AM J OBSTET GVNECOL 1992;166:591-2.)
Key words: Choroid plexus cyst, trisomy 21 The prenatal ultrasonographic finding of choroid plexus cysts has been described in fetuses with trisomy IS, as well as in those with normal chromosomes. Whether karyotyping is indicated in a fetus who otherwise appears to be structurally normal has been the subject of much recent debate. Only one case of antenatally diagnosed choroid plexus cysts in a fetus with trisomy 21 has been reported in the literature.! This fetus also had an atrioventricular septal defect. We present a case of trisomy 21 in which the only ultrasonographically apparent abnormalities were bilateral choroid plexus cysts. Case report A 35-year-old woman, gravida 4, para 3, presented for routine ultrasonographic examination at 16 weeks' gestation, before amniocentesis for karyotyping. Biometric measurements were consistent with gestational age. Gross fetal anatomy appeared normal, except for the presence of bilateral choroid plexus cysts of 10 mm diameter in each atrium of the cerebral ventricles. The four-chamber view of the heart showed no abnormality. The nuchal fold thickness measured 3 mm. The middle phalanx of the fifth digit was equal in size to the middle phalanx of the fourth finger. The expected-to-actual femur length ratio and the biparietal diameter/femur length ratio were within the mean. The maternal serum a-fetoprotein level was within normal limits. An amFrom the Section of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, and the Department of Human Genetics, Yale University School of Medicine, and the Department of Obstetrics and Gynecology, Tri-Service General Hospital, National Defense Medical Center. Received for publication March 5, 1991; revised March 21, 1991; accepted August 4, 1991. Reprint requests: Siegfried Rotmensch, MD, Yale Universitv School of Medicine, Department of Obstetrics and Gynecology, 333 Cedar St., PO Box 3333, New Haven, CT 06510-8063. 611133037
niocentesis was performed and 16 ml of clear fluid was obtained. The karyotype was 47 ,XX + 21. The patient was counseled about the implications of the karyotype and decided to terminate the pregnancy at 19 weeks' gestation by dilation and evacuation. A repeat ultrasonographic scan before termination reconfirmed normal fetal anatomy and bilateral choroid plexus cysts, each of which had shrunk to 5 mm in diameter. Comment
Cysts of the choroid plexus arise from neuroepithelial folds within the choroid plexus and are filled with fluid and cellular debris. They are found frequently on microscopic examination of fetal, newborn, and adult brains. The incidence of macroscopically apparent cysts in chromosomally normal subjects, however, has probably been overestimated because of the use of histologic criteria for the definition of their presence. The estimated incidence of ultrasonographically diagnosed choroid plexus cysts in a population of normal midtrimester fetuses is 0.3%. An association with trisomy IS has been suggested 2 ; however, the magnitude of this link is controversial. Choroid plexus cysts associated with trisomy 21 have so far been described in the literature in only one case.! This fetus also had an atrioventricular septal defect. In our case bilateral choroid plexus cysts were the only abnormal finding in a detailed anatomic survey. Whether the finding was incidental or linked to the chromosomal anomaly is difficult to determine. If such an association is assumed, it is probably not a very consistent one, because multiple series of fetuses with Down syndrome have not reported this finding. However, a review of 9S prenatally diagnosed cases of trisomy 21 in our institution revealed two such cases. Unfortunately, only one case had complete ultrasono-
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graphic documentation. Even if the association between cysts ofthe choroid plexus and trisomy 21 was 1 in 100, most women would still wish to be offered prenatal diagnosis. However, it would require 120,000 midtrimester ultrasonographic scans to demonstrate a prevalence of this magnitude within 95% confidence limits of 0.5% and 1.5%. It is intriguing that the choroid plexus cysts in our case displayed multiple characteristics that were associated with a trisomic karyotype by several authors. Chitkara et at. 2 suggested that a cyst diameter> 10 mm and a bilateral location, as observed in our case, are more likely associated with a trisomic fetus. This tends to suggest that the finding of choroid plexus cysts in this case was not incidental but was linked to the abnormal karyotype. Interestingly, we observed a 50%
February 1992 Am J Obstet Gynecol
decrease in cyst diameter within a 3-week period of follow-up. Therefore diminishing cyst size alone should not be considered sufficient reassurance about the normality of the fetal karyotype. Furthermore, this finding emphasizes that in spite of improved ultrasonographic visualization of anatomy with advancing gestational age early scans can occasionally contribute exclusive information. REFERENCES 1. Ricketts NM, Lowe EM, Patel NB. Prenatal diagnosis of choroid plexus cysts. Lancet 1987;1:213-4. 2. Chitkara U, Cogswell C, Norton K, Wilkins lA, Mehalek K, Berkowitz RL. Choroid plexus cysts in the fetus: a benign anatomic variant or pathologic entity? Obstet Gynecol 1988;72:185-9.
Key words: Choroid plexus cyst, trisomy 21 The prenatal ultrasonographic finding of choroid plexus cysts has been described in fetuses with trisomy IS, as well as in those with normal chromosomes. Whether karyotyping is indicated in a fetus who otherwise appears to be structurally normal has been the subject of much recent debate. Only one case of antenatally diagnosed choroid plexus cysts in a fetus with trisomy 21 has been reported in the literature.! This fetus also had an atrioventricular septal defect. We present a case of trisomy 21 in which the only ultrasonographically apparent abnormalities were bilateral choroid plexus cysts. Case report A 35-year-old woman, gravida 4, para 3, presented for routine ultrasonographic examination at 16 weeks' gestation, before amniocentesis for karyotyping. Biometric measurements were consistent with gestational age. Gross fetal anatomy appeared normal, except for the presence of bilateral choroid plexus cysts of 10 mm diameter in each atrium of the cerebral ventricles. The four-chamber view of the heart showed no abnormality. The nuchal fold thickness measured 3 mm. The middle phalanx of the fifth digit was equal in size to the middle phalanx of the fourth finger. The expected-to-actual femur length ratio and the biparietal diameter/femur length ratio were within the mean. The maternal serum a-fetoprotein level was within normal limits. An amFrom the Section of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, and the Department of Human Genetics, Yale University School of Medicine, and the Department of Obstetrics and Gynecology, Tri-Service General Hospital, National Defense Medical Center. Received for publication March 5, 1991; revised March 21, 1991; accepted August 4, 1991. Reprint requests: Siegfried Rotmensch, MD, Yale Universitv School of Medicine, Department of Obstetrics and Gynecology, 333 Cedar St., PO Box 3333, New Haven, CT 06510-8063. 611133037
niocentesis was performed and 16 ml of clear fluid was obtained. The karyotype was 47 ,XX + 21. The patient was counseled about the implications of the karyotype and decided to terminate the pregnancy at 19 weeks' gestation by dilation and evacuation. A repeat ultrasonographic scan before termination reconfirmed normal fetal anatomy and bilateral choroid plexus cysts, each of which had shrunk to 5 mm in diameter. Comment
Cysts of the choroid plexus arise from neuroepithelial folds within the choroid plexus and are filled with fluid and cellular debris. They are found frequently on microscopic examination of fetal, newborn, and adult brains. The incidence of macroscopically apparent cysts in chromosomally normal subjects, however, has probably been overestimated because of the use of histologic criteria for the definition of their presence. The estimated incidence of ultrasonographically diagnosed choroid plexus cysts in a population of normal midtrimester fetuses is 0.3%. An association with trisomy IS has been suggested 2 ; however, the magnitude of this link is controversial. Choroid plexus cysts associated with trisomy 21 have so far been described in the literature in only one case.! This fetus also had an atrioventricular septal defect. In our case bilateral choroid plexus cysts were the only abnormal finding in a detailed anatomic survey. Whether the finding was incidental or linked to the chromosomal anomaly is difficult to determine. If such an association is assumed, it is probably not a very consistent one, because multiple series of fetuses with Down syndrome have not reported this finding. However, a review of 9S prenatally diagnosed cases of trisomy 21 in our institution revealed two such cases. Unfortunately, only one case had complete ultrasono-
591
592
Rotmensch et al.
graphic documentation. Even if the association between cysts ofthe choroid plexus and trisomy 21 was 1 in 100, most women would still wish to be offered prenatal diagnosis. However, it would require 120,000 midtrimester ultrasonographic scans to demonstrate a prevalence of this magnitude within 95% confidence limits of 0.5% and 1.5%. It is intriguing that the choroid plexus cysts in our case displayed multiple characteristics that were associated with a trisomic karyotype by several authors. Chitkara et at. 2 suggested that a cyst diameter> 10 mm and a bilateral location, as observed in our case, are more likely associated with a trisomic fetus. This tends to suggest that the finding of choroid plexus cysts in this case was not incidental but was linked to the abnormal karyotype. Interestingly, we observed a 50%
February 1992 Am J Obstet Gynecol
decrease in cyst diameter within a 3-week period of follow-up. Therefore diminishing cyst size alone should not be considered sufficient reassurance about the normality of the fetal karyotype. Furthermore, this finding emphasizes that in spite of improved ultrasonographic visualization of anatomy with advancing gestational age early scans can occasionally contribute exclusive information. REFERENCES 1. Ricketts NM, Lowe EM, Patel NB. Prenatal diagnosis of choroid plexus cysts. Lancet 1987;1:213-4. 2. Chitkara U, Cogswell C, Norton K, Wilkins lA, Mehalek K, Berkowitz RL. Choroid plexus cysts in the fetus: a benign anatomic variant or pathologic entity? Obstet Gynecol 1988;72:185-9.