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ANSWERS
CASE 12
Central Nervous System Arteriovenous
Malformation
1. D and E
2. D
3. C
4. B
References
Lee TH, Shih JC, Peng SS, et al: Prenatal depiction of angioarchitecture of
an aneurysm of the vein of Galen with three-dimensional color power
angiography. Ultrasound Obstet Gynecol 2000; 15(4):337-340.
http://www.ncbi.nlm.nih.gov/pubmed/10895457 (Accessed on May 30,
2012.)
Li AH, Armstrong D, terBrugge KG: Endovascular treatment of vein of
Galen aneurysmal malformation: management strategy and 21-year experience in Toronto. J Neurosur g Pediatr 2011; 7(1):3-10.
http://www.ncbi.nlm.nih.gov/pubmed/21194279 (Accessed on May 30,
2012.)
Kurihara N, Tokieda K, Ikeda K, et al: Prenatal MR ndings in a case of
aneurysm of the vein of Galen. Pediatr Radiol 2001 31(3):160-162.
http://www.ncbi.nlm.nih.gov/pubmed/11297077 (Accessed on May 30,
2012.)
Cross-Reference
Ultrasound: The REQUISITES, 2nd ed, pp 381, 391, 393, 398.
could be considered. These cysts lie between the frontal horns
of the lateral ventricle and are usually midline. Cystic neoplasm
may be considered in the differential diagnosis, but these neoplasms usually have solid components and are asymmetric.
They are very rare in utero. Finally, vein of Galen aneurysms or
fetal cerebral AVMs are the most likely differential diagnoses in
this case after power Doppler is used.
Ultrasound Findings
Three different types of congenital cerebral aneurysms have
been described: arteriovenous stula, AVM with ectasia of the
vein of Galen, and varix of the vein of Galen. Arteriovenous
stula may be seen in the fetus and manifests in the neonatal
period with cardiac failure. All of these anomalies may be identied as an elongated anechoic area at the level of the cistern
of the vein of Galen (Figure A). With color and pulsed Doppler imaging, there is evidence of turbulent venous and arterial ow (Figure B). Occasionally, the vascular malformation
may show increased echogenicity if a clot has formed within
it. Cerebral architecture is usually intact, but ventriculomegaly
and porencephaly may develop if there is associated infarction.
Signs of fetal hydrops from cardiac overload may be present,
including cardiomegaly, soft tissue edema, and polyhydramnios, which eventually lead to overt hydrops. MRI may be useful to identify the anomaly in utero (Figure C).
Comment
Differential Diagnosis
The differential diagnosis for a midline intracranial cyst includes
an arachnoid cyst. This is a smooth-walled cyst located anywhere within the brain and may have associated mass effect.
Agenesis of the corpus callosum with an interhemispheric cyst
Prognosis and Management
Serial in utero scans are used to monitor the cardiovascular
condition of the fetus and identify early signs of fetal hydrops.
Delivery may be planned depending on fetal lung maturation
and development of early hydrops. After delivery, management includes various endovascular techniques, such as different embolization agents and different novel approaches.
26
CASE 13
A
History: Ultrasound is performed on an asymptomatic
woman with a late second-trimester pregnancy.
1. What is the diagnosis in the cervical region?
A. Circumvallate placenta
B. Succenturiate lobe
C. Placental abruption
D. Placenta previa
2. Which of the two images (Figures A and B) is a better
performed image for the diagnosis and why?
A. Figure B, in which the maternal bladder is empty
B. Figure A, in which the maternal bladder is full
C. Figure A for the image of the cervix
D. Figure B for the image of the cervix
3. Which type of ultrasound study is known to be a problem
in making this diagnosis?
A. Transabdominal with a full bladder
B. Transabdominal with an empty bladder
C. Translabial with an empty bladder
D. Transvaginal with an empty bladder
4. Which of the following is not a complication of placenta
previa?
A. Hemorrhage
B. Placenta accreta
C. Intrauterine growth restriction
D. Macrosomia
B
27
ANSWERS
CASE 13
Placenta Previa
1. D
2. A
3. A
4. D
References
Mabie WC: Placenta previa. Clin Perinatol 1992; 19(2):425-435.
http://www.ncbi.nlm.nih.gov/pubmed/1617885 (Accessed on May 20,
2012.)
Predanic M, Perni SC, Baergen RN, et al: A sonographic assessment of
different patterns of placenta previa “migration” in the third trimester of
pregnancy. J Ultrasound Med 2005; 24(6):773-780.
http://www.ncbi.nlm.nih.gov/pubmed/15914681 (Accessed on May 20,
2012.)
Wu S, Kocherginsky M, Hibbard JU: Abnormal placentation: twenty-year
analysis. Am J Obstet Gynecol 2005; 192(5):1458-1461.
http://www.ncbi.nlm.nih.gov/pubmed/15902137 (Accessed on May 20,
2012.)
Cross-Reference
Ultrasound: The REQUISITES, 2nd ed, pp 488, 498-504.
Comment
Types of Placenta Previa
Implantation of the placenta over the cervix (Figures A and B)
is known as placenta previa. Placenta previa can be complete
(the internal os is covered by placenta), partial (partial coverage
of the os), or marginal (the placental edge is at the margin of
the os). A low-lying placenta (within 2 cm of the internal os)
does not reach the internal os but may be clinically important
because it can be incorporated into the dilated cervix at the
time of delivery, leading to hemorrhage. Placenta previa complicates about 0.4% of all third-trimester pregnancies. Risk factors include prior cesarean delivery, history of placenta previa
in a previous pregnancy, increasing parity, advanced maternal
age, prior uterine surgery, tobacco use, and multiple gestations.
Ultrasound Imaging of the Placenta
Many cases can be diagnosed with transabdominal ultrasound.
The bladder must be empty to make an accurate diagnosis. A
distended maternal bladder (Figure A) or uterine contraction
can cause a false-positive result by compressing the lower uterine segment and making a low-lying placenta appear as a placenta previa. Translabial and transvaginal imaging after bladder
emptying is often necessary to visualize the lower uterine segment adequately, particularly in the third trimester. The transvaginal probe should be inserted only partially to avoid direct
contact with the cervix. When complete placenta previa is
diagnosed at second-trimester screening sonography, it is less
likely to resolve in patients with previous cesarean delivery.
Complications of Placenta Previa
Other complications can occur in addition to hemorrhage.
An anterior placenta may invade the uterine wall (placenta
accreta), particularly in patients with a placenta previa,
advanced maternal age, and a history of cesarean section.
Fetal complications include intrauterine growth restriction
and subsequent development of cerebral palsy. A low-lying
placenta may increase the incidence of small-for-gestationalage fetuses.
Prognosis of Placenta Previa
Most cases diagnosed early in pregnancy resolve, probably
because of placental remodeling owing to poor blood supply
of the lower uterine segment. Follow-up imaging is required
in the third trimester (at approximately 30 weeks). A cesarean section is performed for persistent placenta previa. A
nal placental distance of less than 2 cm from the internal
os and a deceleration pattern of placental migration have
been signicantly associated with the need for a cesarean
delivery.
28
CASE 14
A
History: An asymptomatic patient with a second-trimester
pregnancy undergoes ultrasound.
1. What is the diagnosis for this fetus?
A. Hydrocephalus
B. Alobar holoprosencephaly
C. Anencephaly
D. Strawberry skull
2. When can this disorder be reliably diagnosed on ultrasound?
A. In the beginning of the third trimester
B. In the middle of the rst trimester
C. In the second trimester
D. Never
3. When in gestation does the neural tube close?
A. At the end of the rst trimester
B. At 24 days of fetal life
C. At the beginning of the third trimester
D. At 10 days of fetal life
4. Which maternal dietary deciency is associated with this
disorder?
A. Folic acid
B. Iron
C. Copper
D. Thiamine
B
29
ANSWERS
CASE 14
Anencephaly
1. C
2. C
3. B
4. A
Reference
Goldstein RB, Filly RA: Prenatal diagnosis of anencephaly: spectrum of
sonographic appearances and distinction from the amniotic band syndrome. AJR Am J Roentgenol 1988; 151(3):547-550.
http://www.ncbi.nlm.nih.gov/pubmed/3044042 (Accessed on May 30,
2012.)
Cross-Reference
Ultrasound: The REQUISITES, 2nd ed, pp 374-376.
Comment
Common Neural Tube Defect
With an overall frequency of 1 in 1000, anencephaly is one of
the most common neural tube defects. The incidence varies in
different parts of the world. The cerebral cortex and skull are
absent; orbits, brainstem, and skull base are present. In some
cases, “angiomatous stroma,” or vascular, dysmorphic tissue,
may cover the brainstem. As in other central nervous system
anomalies, polyhydramnios is also often present, particularly
later in the gestation period. Anencephaly is incompatible with
life. A deciency of maternal folic acid has been shown to
increase the risk of neural tube defects. It is recommended
that women begin folic acid supplementation before becoming
pregnant to decrease the risk of anencephaly and other neural
tube defects.
Ultrasound Imaging of Anencephaly
Ultrasound shows the absence of a calvaria and brain above
the orbits (Figures A and B), cephalad to the brainstem.
Although this may be detected by 8 weeks’ gestation, it is diagnosed more reliably in the early second trimester.
Serum Alpha-Fetoprotein and Anencephaly
Routine screening of maternal serum alpha-fetoprotein (AFP)
is performed between 15 and 20 weeks’ gestation as part of
the serum triple screen (AFP, estriol, and human chorionic
gonadotropin). Serum AFP is usually elevated in anencephaly,
using either 2 or 2.5 multiples of median gestational age as
the cutoff for detection. It is important that the pregnancy be
dated accurately because the levels vary with gestational age.
The serum AFP level also is abnormal in multiple gestations
and obese women. The differential diagnosis for an elevated
maternal AFP in pregnancy includes other open defects, such
as gastroschisis, and fetomaternal hemorrhage, maternal hepatitis, and maternal hepatocellular carcinoma.
30
CASE 15
A
B
History: Axial scans through the upper abdomen in two
separatefetuseswiththesameabnormalitiesareshown.
1. What should be included in the differentialdiagnosis of
FigureAandFigureB?(Chooseallthatapply.)
A. Choledochalcyst
B. Duplicationcyst
C. Ovariancyst
D. Duodenalatresia
E. Renalcyst
2. Thedifferentialdiagnosisof the“doublebubble”signofa
dilatedstomachanddilatedduodenumwouldincludeallof
thefollowingexcept:
A. Malrotationwithmidgutvolvulus
B. Annularpancreas
C. Duodenalatresia
D. Hepaticcyst
C
Used with permission from Anderson Publishing Ltd., from Victoria T,
et al: Fetal MRI of common non-CNS abnormalities: a review. Appl
Radiol 40[6]8-17, 2011. © Anderson Publishing Ltd.
3. Which of the following statements concerningduodenal
atresiaisfalse?
A. Approximately 40% of fetuses with trisomy 21 have
duodenalatresia.
B. The presence of duodenal atresia andanendocardial
cushiondefectisaverystrongindicatorof trisomy21.
C. Thereisanincreasedriskofotherintestinalatresiawith
duodenalatresia.
D. There is increased incidence of associated skeletal
deformitieswithduodenalatresia.
4. Allof thefollowingaretruestatementsconcerningduode-
nalatresiaexcept:
A. Diagnosis is usually not evident until after 20weeks’
gestation.
B. Polyhydramniosisatypicalndingof duodenalatresia.
C. Concurrentcardiacanomalies,especiallycoarctationof
theaorta,occurring withduodenalatresiaareastrong
indicatorof trisomy21.
D. Overall mortality of duodenal atresia is greater than
20%.
31
ANSWERS
CASE 15
Duodenal Atresia
1. B,C,andD
2. D
3. A
4. C
References
ChoudhryMS,RahmanN,BoydP,etal:Duodenalatresia:associatedanom-
alies,prenataldiagnosisandoutcome.Pediatr Surg Int 2009;25(8):727-730.
http://www.ncbi.nlm.nih.gov/pubmed/19551391(AccessedonMay30,
2012.)
DankovcikR,JirasekJE,KuceraE,etal:Prenataldiagnosisofannularpan-
creas:reliabilityof thedoublebubblesignwithperiduodenalhyperechogenicband.Fetal Diagn Ther 2008;24(4):483-490.
http://www.ncbi.nlm.nih.gov/pubmed/19047797(AccessedonMay30,
2012.)
NybergDA,NeilsenIR:Abdomenandgastrointestinaltract.InNybergDA,
McGahanJP,PretoriusDH,etal(eds):Diagnostic Imaging of Fetal Anomalies.
Philadelphia:LippincottWilliams&Wilkins,2003,pp547-602.
Cross-Reference
Ultrasound: The REQUISITES,2nded,pp436-437.
Comment
Differential Diagnosis
This casepresents two differentialdiagnoses.Therstdifferentialdiagnosisincludesacysticmassintheupperabdomen such as gastric duplication cyst, choledochal cyst,
hepaticcyst,orovariancyst.Othercysticmassescouldalso
beconsideredinthedifferentialdiagnosis.Aseconddifferentialdiagnosticconsiderationisthe“double bubble”sign,
which usually is associated with duodenal atresia but can
includeanyintrinsicabnormalitiesof theduodenumcausing
obstruction,suchasduodenalstenosis,aduodenalweb,and
intestinalmalrotationorextrinsiccompressionontheduodenum(whichwouldberare).
Ultrasound Findings
Theultrasoundndingsofduodenalatresiaincludea double
bubblesign,aclassicsignof auid-lleddilatedstomach on
the left side of the abdomen accounting for one “bubble”
and thesecondportionofthebubblecorrespondingtothe
dilatedduodenalbulbtotherightof midline.Thissigniswell
delineatedinthiscase(FiguresAandB).Polyhydramniosmay
developinthesecasesbutusuallynotuntilthethirdtrimester.A
doublebubblesignisusuallynotdetecteduntillaterinthesecondtrimester,oftennotuntil24weeks,andmaybeseenwith
prenatalMRI(FigureC).Ultrasoundshouldshowtheconnectionbetweenthedilatedstomachandthedilatedduodenum.
Prognosis and Management
Managementdependsonassociatedndingsofduodenalatresia. Careful examination of the fetus should concentrate on
identifying other malformations, including skeletal, gastrointestinal, cardiovascular,and genitourinary malformations. As
mentionedbefore,many differentskeletalmalformationsare
associated with duodenal atresia, including vertebral andrib
abnormalities.Othertypesofatresia associated with duodenalatresiaincludeesophagealandsmallbowelatresiaandrectal atresia or imperforate anus.Biliary atresia and pancreatic
ductalatresia areassociated withduodenal atresia.It isprobablymostimportanttocheckforendocardialcushiondefects
in these fetuses.Ifanendocardialcushiondefectis present
withduodenalatresia,itisalmostpathognomonicoftrisomy
21. There is a highincidence of trisomy 21 in fetuses with
duodenal atresia. Amniocentesis is the accepted method of
prenatalchromosomalanalysis.Duodenalatresiabyitself has
amorefavorableprognosisthanduodenal atresia associated
withothermalformations.Mortalityinmostcasesof duodenal
atresiaisassociatedwithothermalformations,suchascardiac
anomalies.Because of signicantuid andelectrolyteimbalance,theatreticsegmentshouldbebypassedafterbirth.
32
CASE 16
History: A patient has a routine ultrasound scan in the second trimester that shows a nuchal thickness of 7 mm at 20
weeks.
1. What should be included in the differential diagnosis of
nuchal thickness of 7 mm at a gestational age of 20 weeks?
(Choose all that apply.)
A. Trisomy 21
B. 45X (Turner syndrome)
C. Triploidy karyotype
D. Trisomy 13
E. Trisomy 18
2. The most correct diagnosis for nuchal thickness in the second trimester would include a plane through all of the following except:
A. Cavum septi pellucidi
B. Cerebellar hemisphere
C. Body of the lateral ventricle
D. Cerebral peduncles
3. Which of the following statements concerning the measurement of nuchal thickness is false?
A. Nuchal thickening is a sensitive nonstructural abnor-
mality associated with trisomy 21.
B. Redundant skin at the back of the neck associated with
trisomy 21 was rst reported by Benacerraf.
C. A threshold of 6 mm or more is the measurement that
has been reported for increased risk of trisomy 21.
D. Cut-off of 5 mm or more of nuchal thickness may be
a better threshold measurement for detection of Down
syndrome.
4. Which of the following is not a subtle marker in Down syn-
drome (trisomy 21)?
A. Absent nasal bone
B. Shortened limbs
C. Choroid plexus cysts
D. Sandal gap toes
33
ANSWERS
CASE 16
Nuchal Thickness in the Second Trimester
1. A, B, C, D, and E
2. C
3. B
4. C
References
Benacerraf BR, Gelman R, Frigoletto FD Jr: Sonographic identication
of second-trimester fetuses with Down’s syndrome. N Engl J Med 1987;
317(22):1371-1376.
http://www.ncbi.nlm.nih.gov/pubmed/2960895 (Accessed on May 30,
2012.)
Down JL: Observations on an ethnic classication of idiots. 1866. Ment
Retard 1995; 33(1):54-56.
http://www.ncbi.nlm.nih.gov/pubmed/7707939 (Accessed on May 30,
2012.)
Nyberg DA, Souter VL, El-Bastawissi A, et al: Isolated sonographic markers
for detection of fetal Down syndrome in the second trimester of pregnancy. J Ultrasound Med 2001; 20(10):1053-1063.
http://www.ncbi.nlm.nih.gov/pubmed/11587012 (Accessed on May 30,
2012.)
Cross-Reference
Ultrasound: The REQUISITES, 2nd ed, pp 394-395, 473.
Comment
Differential Diagnosis
The differential diagnosis for increased nuchal thickening
includes any of the trisomies and many other chromosomal
abnormalities. Nuchal thickening is one of the most sensitive
and important markers in detection of fetuses with trisomy
21 during the second trimester. Isolated nuchal thickening is
associated with risk of other malformations, chromosomal
abnormalities, and syndromes, but it is associated with a normal outcome in most fetuses.
Ultrasound Findings
The axial scan through the region of thalami and including the
cavum septi pellucidi, the cerebral peduncles, and the cerebellar hemisphere is the plane used for measurement of nuchal
thickness (see Figure). Nuchal thickness is usually measured in
the second trimester and was originally suggested to be a measurement after 15 weeks’ gestation by Benacerraf et al. This
measurement is determined from the outer portion of the bony
calvaria to the outer portion of the posterior scalp. Although
6 mm was used for the original measurement, some authors
believe 5 mm is a better threshold. Lowering the threshold
measurement to 5 mm improves the sensitivity at the expense
of decreased specicity; this could lead to increased detection
of trisomy 21 but at the expense of unnecessary alarm to the
parents, with an increased risk for additional amniocentesis.
Prognosis and Management
A nuchal thickness of 6 mm was the original measurement
used for detection of Down syndrome by Benacerraf et al.
Isolated increased nuchal thickening would increase the risk
for Down syndrome, which would be weighted against serum
screening, maternal age, and detection of other subtle ultrasound markers. Evaluation of the fetus should include not
only measurement of the nuchal thickness but also checking
for any cardiac defects and other subtle ultrasound markers, including renal pyelectasis greater than 4 mm, echogenic
bowel, echogenic cardiac focus, short femur, short humerus,
and ventriculomegaly. All of these results can be used in combination with either a triple marker screen or a quad marker
screen. A quad marker screen would include a maternal blood
sample to check for the following substances: alpha-fetoprotein,
unconjugated estradiol, human chorionic gonadotropin, and
inhibin A. Using all of these values and maternal age, a risk
assessment for potential chromosomal abnormalities such as
trisomy 21 can be made.
34
CASE 17
History: A pregnant patient presents with a high maternal
alpha-fetoprotein measurement.
1. What should be included in the differential diagnosis of a
lemon-shaped head? (Choose all that apply.)
A. Normal fetus
B. Trisomy 18
C. Myelomeningocele
D. Encephalocele
E. Alobar holoprosencephaly
2. Which of the following is not an associated intracranial nd-
ing of myelomeningocele?
A. Lemon sign
B. Mega cisterna magna
C. Banana sign
D. Ventriculomegaly
A
3. Which of the following would be considered in the differential diagnosis of a lumbosacral mass with a lemon sign
and a banana sign?
A. Open neural tube defect
B. Sacrococcygeal teratoma
C. Amniotic band syndrome
D. Limb–body wall complex
4. Which of the following is not a true statement concerning
myelomeningocele?
A. Sensitivity of the lemon sign and the banana sign is very
high in identifying spina bida.
B. Lipomeningocele may not be associated with the lemon
sign and spinal defects.
C. With proper diagnosis and treatment, the prognosis of
spina bida is excellent.
D. Ultrasound can predict the location and extent of spinal
defects with a high degree of accuracy.
B
C
35