Down s Syndrome: Ultrasound Screening

Transcription

1 October 2001 Down s Syndrome: Ultrasound Screening Hilary Hochberg Advanced Radiology Clerkship Dr. Gillian Lieberman

2 Patient M.C. 32 year old female presents at 16 weeks gestational age with abnormal triple screen test Obstetrician referred M.C. for ultrasound evaluation to look for signs of Down s syndrome or other congenital anomalies. 2

3 Screening for Down syndrome by maternal serum markers: THE TRIPLE SCREEN AFP HcG UE3 Absolute 58 ng/ml ju/ml 28 ng/ml Relative 1.93 MoM 3.12 MoM 0.42 MoM Pt M.C. Trisomy 21 3

4 Maternal age-related risk for chromosomal abnormalities 4

5 Prevalence of trisomy 21 by maternal age and gestational age Snijders RJM, Sundberg K, Holzgreve W, Henry G, Nicolaides KH. Maternal age and gestation- specific risk for trisomy 21. Ultrasound Obstet Gynecol 1999;13:

6 Ultrasound Screening of Down s Syndrome Image: /cbl/embryo/sysnote.htm Trisomy 21: Most common chromosomal abnormality Average incidence 1:800 live births Current second-trimester ultrasound screening detects up to 60% of Down s syndrome fetuses * Helpful to correlate a large number of relatively nonspecific visual and biometric markers *Chitty LS: Antenatal screening for aneuploidy. Curr Opin Obstet Gynecol 10:91,1998. Ideally, perform at age when confirmatory diagnosis can be made, safe termination can be offered 6

7 Sonographic finding Trisomy 21 Trisomy 18 Trisomy 13 Triploidy Turner Skull/brain Strawberry-shaped head Brachycephaly Microcephaly Ventriculomegaly Holoprosencephaly Choroid plexus cysts Absent corpus callosum Posterior fossa cyst Enlarged cisterna magna Face/neck Facial cleft Micrognathia Nuchal edema Cystic hygromata Chest Diaphragmatic hernia Cardiac abnormality Abdomen Exomphalos Duodenal atresia Collapsed stomach Mild hydronephrosis Other renal abnormalities Other Hydrops Small for gestational age Relatively short femur Clinodactyly Overlapping fingers Polydactyly Syndactyly Talipes Pilu G, Nicolaides KH. Diagnosis of fetal abnormalities. The week scan. The Parthenon Publishing Group: New York,

8 NUCHAL TRANSLUCENCY: 1 st Trimester Most clinically useful marker for trisomy 21 Unclear physiological basis of fluid accumulation 1. Increased risk of associated cardiac abnormalities 2. Increased hyaluronanidase in ECM Nuchal translucency > 3mm abnormal 8

9 * * In one large series of 1015 patients, nuchal translucency thickness of 3mm, 4mm, 5mm, and > 6mm increased risk of trisomy 3x, 18x, 28x and 36x higher than respective risk expected based upon maternal age alone. Pandya PP, Kondylios A, Hilbert L, Snijders RJ, Nicolaides KH. Chromosomal defects and outcome in 1015 fetuses with increased nuchal translucency. Ultrasound Obstet Gynecol 1995 Jan;5(1):

10 Nuchal Fold: 2 nd Trimester Thickened nuchal skin fold Outer skull table to outer skin surface >6 mm abnormal at weeks (83% specificity)* 40% Down s fetuses have thickened fold * * Benacerraf BR, Gelman R, Frigoletto FD: Sonographic identification of second-trimester fetuses with Down s syndrome. NEJM 317:1371,

11 Choroid Plexus Cysts Present in 2% of normal pregnancies Folding of neuroepithelium accumulate CSF Most resolve by weeks Must be imaged in 2 orthogonal planes and > 3 mm. 11

12 Echogenic Bowel 0.5% normal fetuses Usually no significance Cause unknown Hypoperistalsis Meconium fluid content Gut ischemia For isolated bowel changes, risk for trisomy 21 7x Also found in cases of: fetal viral infection, ex: CMV small bowel atresia/volvulus growth retardation cystic fibrosis 12

13 Duodenal Atresia Double-bubble sign 1/10,000 births 5-8% Down s Syndrome fetuses 30% of fetuses with duodenal atresia have Down s Syndrome 13

14 Echogenic Intracardiac Focus Image 1 Image 2 Single foci quadruples risk of Down s syndrome 3-8 % normal 2nd trimester ultrasounds Most commonly single foci in LV, can be multiple and bilateral 14

15 Image1: Image2: Winter, Thomas C, MD et al. Echogenic Intracardiac Focus in 2 nd -Trimester Fetuses with Trisomy 21: Usefulness as a US Marker. Radiology 2000; 216; Simpson J. Cardiac echogenic focus Prenat Diagn 19:

16 Atrioventricular Septal Defect AKA endocardial cushion defect; 7% CHD; 1/3000 births Endocardial cushions form the lower atrial septum, the upper ventricular septum, the septal leaflet of the tricuspid valve and the anterior leaflet of the mitral valve. An ECD defect is due to abnormal development of these endocardial cushions. ASDVSD a common opening to all chambers of heart >50% of DS fetuses have CHD (44% have AVSD) 43% of fetuses with AVSD have DS* *Paladini D, Tartaglione A, Agangi A, Teodoro A, Forleo F, Borghese A, Martinelli P. The association between congenital heart disease and Down syndrome in prenatal life. Ultrasound Obstet Gynecol 2000 Feb;15(2):

17 AVSD

18 Other sonographic features Short femur Sandal gap Snijders RJM, Platt LD, Greene N, Carlson D, Krakow D, Gregory K, Bradley K. Femur length and trisomy 21: impact of gestational age on screening efficiency. Ultrasound Obstet Gynecol 2000; 16: Images: Mild renal pelvic dilatation (>4 mm at <33 wks abnormal) 18

19 Dilated Pelvis Normal Pelvis 19

20 Ultrasound screening for Down s syndrome Useful information Confusion Many trisomy 21 findings overlap with normal fetus findings 20

21 Sonographic Index for DS: 2 nd trimester fetus Findings Major anomaly Nuchal Fold >6mm Short Femur Short Humerus Pyelectasis >4mm Hyperechoic Bowel Echogenic Focus Score Score > 2 82% DS (4% false positive) Callen, PW. Ultrasononography in Obstetrics and Gynecology. 4th edn. WB Saunders CO. Philadelphia

22 Patient M.C. Ultrasound: normal. Obstetrician offered amniocentesis because calculated risk of fetus with trisomy 21 > risk of amnio complications. Patient expressed that she would not abort fetus regardless of amnio results; however, she and her husband wanted psychological preparation and requested karyotype analysis. 22

23 References Bradley K. Femur length and trisomy 21: impact of gestational age on screening efficiency. Ultrasound Obstet Gynecol 2000; 16: Callen, PW. Ultrasononography in Obstetrics and Gynecology. 4th edn. WB Saunders CO. Philadelphia Devore, GR. Trisomy 21: 91% detection rate using second-trimester ultrasound markers. Ultrasound Obstet Gynecol 2000; 16: Filly RA. Obstetrical sonography: the best way to terrify a pregnant woman. J Ultrasound Med 2000; 19: 1-5. Graupe M, Naylor C, Greene N, Carlson D, Platt L. Trisomy 21: Second-Trimester Ultrasound. Clinics in Perinatology 28 (2): Paladini D, Tartaglione A, Agangi A, Teodoro A, Forleo F, Borghese A, Martinelli P. The association between congenital heart disease and Down syndrome in prenatal life. Ultrasound Obstet Gynecol 2000 Feb;15(2):104-8 Pilu G, Nicolaides KH. Diagnosis of fetal abnormalities. The week scan. The Parthenon Publishing Group: New York, Simpson J. Cardiac echogenic focus Prenat Diagn 19: Smith-Bindman R, Hosmer W, Feldstein VA, Deeks JJ, Goldberg JD. Second-trimester ultrasound to detect fetuses with Down syndrome: A meta-analysis. JAMA 285 (8): Snijders RJM, Platt LD, Greene N, Carlson D, Krakow D, Gregory K, Sepkulveda W, Sebire NJ. Fetal echogenic bowel: a complex scenario. Ultrasound Obstet Gynecol 2000; 16: Pandya PP, Kondylios A, Hilbert L, Snijders RJ, Nicolaides KH. Chromosomal defects and outcome in 1015 fetuses with increased nuchal translucency. Ultrasound Obstet Gynecol 1995 Jan;5(1):15-9. Twining P, McHugo J, Pilling D. Textbook of Fetal Abnormalities. Churchill Livingstone: 23 London, 1999.

24 Acknowledgments Dr. Gillian Lieberman Pamela Lepkowski Larry Barbaras & Cara Lyn D amour 24