2nd & 3rd Tri: Central Nervous System Flashcards
When is the neural tube closed by?
6 menstrual weeks
pg. E 120
What plane is best to evaluate for spina bifida?
transverse
pg E 120
What should be shown in the trransverse plane of the spine?
location of ossification centers
musculature of back
skin line
pg. E 120
What should be shown in the sagittal/coronal plane of the spine?
cervical and lumbosacral curvatures
sacral tapering
configuration of vertebral ossification centers
pg. E 120
At what level is the BPD taken?
level of thalami, CSP, and anterior horns of lat ventricle
pg. E 121
What is a normal measurement for the atrium of lateral ventricle?
< 10 mm
pg. E 121
What fills in the lateral ventricles?
choroid plexus
pg. E 122
What is taken at an axial section of the brain?
CSP thalami lateral ventricles choriod plexus BPD HC pg. E 121
What is taken at an oblique axial section of the brain?
cerebellum
brain stem
cisterna magna
pg. E 123
What is a normal measurement of the cisterna magna?
> 3 mm and < 10 mm
pg. E 123
Why do neural tube defects occur?
when neural tube fails to close by 6 weeks
pg. E 124
Where do neural tube defects occur at?
anywhere along cranium or spine
allow cerebrospinal fluid to escape into the amniotic fluid
pg. E 124
What lab is elevated with neural tube defects?
MSAFP
pg. E 124
Why would an amniocentesis be performed?
when MSAFP values are high and ultrasound did not detect a neural tube defect
pg. E 124
What does an amniocentesis detect?
acetylcholinesterase is elevated in the amniotic fluid when there are neural tube defects
pg. E 124
What can be done to decrease the risk of neural tube defects?
supplement folic acid
pg. E 124
What is anencephaly?
congenital absence of the cerebral hemispheres and cranial vault
pg. E 124 O 390
What is the most common neural tube defect?
Anencephaly
pg. O 390
Why does anencephaly occur?
cephalic end of the neural tube fails to close by 24 days gestation
pg. E 124 O 390
What is elevated with anencephaly?
AFP
pg. E 124 O 390
What is associated with anencephaly?
polyhydramnios
spina bifida
pg. E 124
What are the sonographic findings of anencephaly?
absent cranial vault and cerebral hemispheres
frog-like facial appearance
polyhydramnios
pg. E 124
What is acrania?
cranium partially or completely absent with development of abnormal brain tissue
pg. E 125
What is elevated with acrania?
MSAFP
pg. E 125
What are the sonographic findings of acrania?
presence of brain tissue as early as 12 weeks -16 weeks
lack of ossified cranium
pg. E 125
What is exencephaly?
acrania
pg. E 125
What is an encephalocele?
herniation of brain and meninges or meninges and CSF through a cranial defect
pg. E 125 O 390
What syndrome is an encephalocele associated with?
Meckel-Gruber syndrome
pg. E 125
Where are encephaloceles located?
midline
occipital (most common)
frontal or lateral
pg. E 125
What are the sonographic findings of encephalocele?
cystic extracranial mass (meningocele) solid mass in cranium (cephalocele) hydrocephalus polyhydramnios pg. E 125
What is another name for encephalocele?
cephalocele
pg. E 125
What is spina bifida?
lack of closure of the vertebral column
pg. E 126 O 390
Where is the most common place for spina bifida?
lumbosacral
pg. E 126
What is a meningocele?
herniation of the meningese and CSF through a spinal defect
pg. E 126
What is meningomyelocele?
herniation of the meninges and spinal cord through the spinal defect
pg. E 126
What are the transverse findings of spina bifida?
splaying of posterior elements into a U or V configuration
cystic structure extending from back
pg. E 126
What are the sagittal findings of spina bifida?
splaying of parallel ossification centers
soft tissue defect
pg. E 126
What are some intracranial findings associated with spina bifida?
“lemon sign” - head shape
“banana sign” - cerebellum shape
hydrocephalus
pg. E 127
What is associated with spina bifida?
Arnold-Chiari II malformation
pg. E 127
What is spina bifida aperta?
defect exposed completely
elevated AFP level
associated w/ cleft lip, cardiac defects, encephalocele, GI anomalies, and clubfoot
pg. O 390
What is spina bifida occulta?
defect is covered by soft tissue
normal AFP level
not as easily diagnosed w/ US
pg. O 390
What is iniencephaly?
rare malformation where the occiput is fused to the cervical spine
pg. E 127
What are the sonographic findings of iniencephaly?
hyperextended neck and head
occipital encephalocele/cervical spina bifida
pg. E 127
How does cerebrospinal fluid flow through the ventricles?
lateral ventricles –>3rd ventricle –> 4th ventricle
pg. E 128
What is ventriculomegaly?
dilatation of the ventricular system due to increase in volume of CSF
pg. E 128
When is ventriculomegaly considered hydrocephalus?
head enlarges and CSF spreads
can cause brain damage
pg. E 128
What is obstructive hydrocephalus?
aka non-communicating;
obstruction of CSF flow due to aqueductal stenosis, CNS anomaly, or tumor
E 129
What is aqueductal stenosis?
narrowing of the aqueduct of Sylvius due to inflammation or developmental process
pg. E 129
What is communicating hydrocephalus?
dilatation of all ventricles and subarachnoid space caused by an obstruction to CSF flow outside of the ventricular system
pg. E 129
What are the sonographic findings of hydrocephalus?
dilated ventricles > 10mm
dangling choroid plexus
brain echogenicity
pg. E 129
What are some other associated findings with hydrocephaly?
polyhydramnios abnormal fetal lie fetal ascites hepatomegaly meningomyelocele Dandy Walker Malformation encephalocele intracranial tumor pg. E 129
What is holoprosencephaly?
absent or incomplete division of the forebrain (prosencephalon) into the cerebral hemispheres and lateral ventricles
pg. E 130
What are the types of holoprosencephaly?
alobar
semi-lobar
lobar
pg. E 130
What is the most severe form of holoprosencephaly?
Alobar
pg. E 130
What are the sonographic findings of alobar holoprosencephaly?
1 ventricle
fused thalami
absence of falx cerebri
pg. E 130
What are the sonographic findings of semi-lobar holoprosencephaly?
partial separation of the ventricles and hemispheres
occipital lobe present
incompletely fused thalami
pg. E 130
What are the sonographic findings of lobar holoprosencephaly?
least severe
normal separation of the thalami, hemispheres, and ventricles
absent CSP and olfactory tracts
pg. E 130
What reasons can holoprosencephaly be caused by?
Sporadic - chromosomal abnormalities
maternal infection
pg. E 130
What are some associated findings with holoprosencephaly?
facial anomalies- cyclopia w/ proboscis
hypotelorism
facial clefts
pg. E 130
What is hydranencephaly caused by?
ICA occlusion or malformation
pg. E 131
What is hydranencephaly?
near total lack of cerebral hemispheres with normally developed meninges and skull
brain is replaced w/ CSF
pg. E 131 O 389
What anomalies are associated with hydranencephaly?
no associated anomalies or risk
pg. E 131
What are the sonographic findings of hydranencephaly?
macrocephaly fluid filled cranium absent cerebral tissue necrosis polyhydramnios pg. E 131
What is Dandy-Walker Malformation (DWM)?
complete or partial absence of cerebellar vermis and posterior fossa cystic dilatation
pg. E 131 O 389
What can cause DWM?
autosomal recessive syndromes maternal infection diabetes alcohol use Coumadin use pg. E 131 O 389
What are the sonographic findings of DWM?
enlarged posterior fossa complete or partial agenesis of the cerebellar vermis cisterna magna > 1.0 cm ventriculomegaly polyhydramnios pg. E 131 O 389
What do 80% of DWM fetuses have?
hydrocephalus
pg. E 131
When should the corpus callosum be developed by?
20 weeks
pg. E 132
Why does the corpus callosum not develop?
chromosomal abnormality or translocation
failure of callosal fibers to form
pg. E 132
What are the sonographic findings of agenesis of the corpus callosum?
no CSP dilatation of the 3rd ventricle widely separated frontal horns of lateral ventricles with enlarged occipital horn teardrop shaped ventricles Colpocephaly "Sunburst sign" pg. E 132 O 388
What is a vein of Galen aneurysm?
rare arteriovenous malformation causing increased flow through the vein of Galen.
pg. E 132
What are the songoraphic findings of a vein of Galen aneurysm?
midline vascular structure superior and posterior to thalamus with turbulent arterial flow
pg. E 132
What is a choroid plexus cyst?
unilateral or bilateral single or multiple large or small cysts in ventricle pg. E 133
Are choroid plexus cysts common?
yes
pg. E 133
Are choroid plexus cysts associated with other anomalies?
normally isolated finding, but can be associated with aneuploidy (Trisomy 18 specifically)
pg. E 133
What would be the most common intracranial lesion?
teratomas
pg. E 133
What is lissencephaly?
brain lacks sulci and gyri, which make the brain appear smooth
pg. E 133
What is lissencephaly associated with?
ventriculomegaly
abnormal corpus callosum
pg. E 133
When can lissencephaly be diagnosed?
3rd trimester
pg. E 133
What is schizencephaly?
rare malformation with clefts in the cerebral hemispheres
pg. E 134
What is the sonographic appearance of schizencephaly?
typically bilateral and symmetric
brain appears split into anterior/posterior parts
pg. E 134
What is porencephaly?
presence of cysts within the cerebral parenchyma due to intracranial hemorrhage
pg. E 134
What is the sonographic appearance of porencephaly?
simple cystic structures within cerebral parenchyma
pg. E 134
What is microcephaly?
decreased head size (3 SD below mean) due to several etiologic disturbances: chromosomal craniosynostosis teratogens pg. E 134
What is a sacrococcygeal teratoma?
rare tumor arising from the embryonic cells of the sacrum/coccyx
pg. E 135
What are the sonographic findings of sacrococcygeal teratomas?
large complex mass external or internal polyhydramnios hydrops fetalis increased AFP pg. E 135
What is caudal regression syndrome?
spectrum of skeletal anomalies of the caudal end of the neural tube
pg. E 135 O 390
What is caudal regression syndrome associated with?
diabetes mellitus
sporadic
pg. E 135 O 390
What anomalies are associated with caudal regression syndrome?
sacral, lumbar or thoracic agenesis GI tract GU tract CNS heart pg. E 135
What is scoliosis?
abnormal curvature of spine
pg. E 135
What are the possibilities if the skull is not present?
anencephaly
acrania (exencephaly)
pg. E 136
What are the possibilities if the skull is not intact?
encephalocele
Meckel-Gruber
pg. E 136
What are the possibities if there is no falx cerebri present?
holoprosencephaly
pg. E 136
What are the possibilities if the thalami are not separate?
holoprosencephaly
pg. E 136
What are the possibilities if the lateral ventricles measure > 10 mm?
ventriculomegaly hydrocephalus Spina bifida DWM pg. E 136
What are the possibilities if the choroid plexus is not identified or normal?
hydranencephaly
choroid plexus cyst
Trisomy 18
pg. E 136
What settings should you use to evaluate for a vein of Galen aneurysm?
color Doppler
pg. E 136
If a fetus is positioned face up, what could you do to optimize visualization of the spine?
Lower frequency to increase the penetration
URR exam
At what age should a normal cranium be identified?
15 weeks
When is a head considered macrocephaly?
BPD and HC are 2+ SD above average
What might an asymmetric encephalocele raise suspicion for?
Limb-body wall complex
