Down s Syndrome: Ultrasound Screening

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Hilary Hochberg

Advanced Radiology Clerkship

Dr. Gillian Lieberman

Down’s Syndrome:

Ultrasound Screening

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Gillian Lieberman, MD

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.

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Screening for Down syndrome by maternal serum

markers:

THE TRIPLE SCREEN

AFP

HcG

UE3

Absolute

58 ng/ml

97.36 ju/ml

28 ng/ml

Relative

1.93 MoM

3.12 MoM

0.42 MoM

Pt M.C.

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http://www.fetalmedicine.com/11-14scanbook/Figures/fig01-04.htm

Maternal age-related risk for

chromosomal abnormalities

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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;13:167–70

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Ultrasound Screening of

Down’s Syndrome

•

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

•

Ideally, perform at age when confirmatory diagnosis can be made, safe

termination can be offered

Image:http://anatomy.med.unsw.edu.au /cbl/embryo/sysnote.htm

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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 + – + + – – – – – + + – + – – + – – – – – + – + – + + – – – + + + + + – – – – –

Sonographic

finding

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http://www.fetalmedicine.com/nuchal.htm

Unclear physiological basis of fluid accumulation

1. Increased risk of associated cardiac abnormalities

2. Increased hyaluronanidase in ECM

Nuchal translucency >

3mm abnormal

NUCHAL TRANSLUCENCY:

1

st

Trimester

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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):15-9.

*

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Nuchal Fold: 2

nd

Trimester

•

Thickened nuchal skin

foldÆOuter skull table to

outer skin surface

•

>6 mm abnormal at 19-24

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, 1987.

*

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Choroid Plexus Cysts

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Present in 2% of normal pregnancies

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Folding of neuroepithelium

Æ

accumulate CSF

•

Most resolve by weeks 26-28.

http://www.thefetus.net/sections/articles/Technique/chapter-10/aneuploidies.html

Must be imaged in 2

orthogonal planes and

> 3 mm.

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12 Gillian Lieberman, MD

Echogenic Bowel

http://www.thefetus.net/sections/articles/Technique/chapter-10/aneuploidies.html

•

0.5% normal fetuses

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Usually no significance

•

Cause unknown

Hypoperistalsis

Meconium fluid content

Gut ischemia

Also found in cases of:

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fetal viral infection, ex: CMV

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small bowel atresia/volvulus

•

growth retardation

•

cystic fibrosis

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http://brighamrad.harvard.edu/Cases/bwh/images/35/Laing12US.GIF

Duodenal Atresia

Double-bubble sign

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1/10,000 births

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5-8% Down’s Syndrome fetuses

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30% of fetuses with duodenal

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14 Gillian Lieberman, MD

Echogenic

Intracardiac

Focus

Image 1 Image 2

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Single foci quadruples risk of Down’s syndrome

•

3-8 % normal 2nd trimester ultrasounds

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Image1:http://www.thefetus.net/sections/articles/Technique/chapter-10/aneuploidies.html

Image2: Winter, Thomas C, MD et al. Echogenic Intracardiac Focus in 2nd_{-Trimester Fetuses with Trisomy 21: Usefulness}

as a US Marker. Radiology 2000; 216; 450-456.

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Atrioventricular Septal Defect

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AKA endocardial cushion defect; 7% CHD; 1/3000 births

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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.

•

ASD+VSD

Î

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):104-8

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http://www.tmc.edu/thi/canal.html

http://www.acuson.com/cme/pdf/quiz30.pdf

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Images: http://www.thefetus.net/sections/articles/Technique/chapter-10/aneuploidies.html

Short femur

Mild renal pelvic dilatation

(

>4 mm at <33 wks abnormal)

Sandal gap

Other sonographic

features

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.

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Dilated Pelvis

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Ultrasound screening

for Down’s syndrome

Useful information

Confusion

Many trisomy 21 findings overlap with

normal fetus findings

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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

2

1

Callen, PW. Ultrasononography in Obstetrics and Gynecology. 4th edn. WB Saunders CO. Philadelphia 2000.

Score > 2

82% DS (4%

false positive)

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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.

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References

Bradley K. Femur length and trisomy 21: impact of gestational age on screening efficiency.

Ultrasound Obstet Gynecol 2000; 16:142-145.

Callen, PW. Ultrasononography in Obstetrics and Gynecology. 4th edn. WB Saunders CO. Philadelphia 2000.

Devore, GR. Trisomy 21: 91% detection rate using second-trimester ultrasound markers.

Ultrasound Obstet Gynecol 2000; 16:133-141.

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): 303-319.

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 18-23 week scan. The Parthenon Publishing Group: New York, 1999.

Simpson J. Cardiac echogenic focus. 1999 Prenat Diagn 19:972-975.

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): 1044-1055.

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: 510-514.

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: London, 1999.

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Acknowledgments

•

Dr. Gillian Lieberman

•

Pamela Lepkowski

es: http://www.thefetus.net/sections/articles/Technique/chapter-10/aneuploidies.html