M5: Fetal Neuro Tube Pathology Flashcards
where is CSF produced
choroid
found on the floor of lat ventricles
roof of 3rd ventricle
post wall of 4th
landmarks for lat ventricles
CSP
antrum of ventricles
V of ambient cistern
Parietal-occipital fissure
How would you angle the probe from the posterior fossa view p the see the 4th ventricle
inferior
What is hydrocephalus
What commonly causes it?
An increase in CSF that results in enlargement of the ventricles
Usually due to obstruction long the path of the CSF
What is the most common cranial anomaly
Hydrocephalus
What is true hydrocephalus
CSF obstruction
What are the causes of true hydrocephalus
Neural tube defect
Aqueduct stenosis
Dandy walker malformations
What causes ventriculomegaly
Caused by brain atrophy which allows the ventricles more room to expand… NOT DUE TO OBSTRUCTION
What happens in aqueduct stenosis?
- CSF can’t flow from the 3rd to the 4th ventricle
- lateral and 3rd ventricles are enlarged
- 4th ventricle is normal
- larger ventricles lead to hardly any brain mantel developing
What is a cause of intraventricular obstruction that leads to hydrocephalus
Aqueduct stenosis
How will the choroid appear w/ aqueduct stenosis
Posterior choroid will be dangling
Anterior choroid will be resting on mid line
3 causes of extraventricular obstruction that lead to hydrocephalus
Spinal bifida
Excess CSF
Dandy walker malformation
How can spinal bifida cause extracellular obstruction hydrocephalus
Which ventricles does it effect
CSF can’t flow normally through the spinal canal and backs up into the ventricles
Effects all ventricles
Where do we measure the ventricles
What is the upper limit of normal
At the atria or parietal occipital fissure
Upper is 10mm
What should the measurement from the medial ventricle wall to the choriod be?
<3mm
If you see hydrocephalus, which view of the brain should you assess
The posterior fossa view
Look at cisterna magna and cerebellum to assess for:
- obliterated cisterna magna
- deformed cerebellum (banana)
- lemon sign
When would the lemon sign be seen
2nd trimester
When does the lemon sign occur
Results when cranial contents are pulled towards the spine w/ Arnold chiari II malformations
How does the lemon sign appear of US
Frontal bones caved in
When does the lemon sign disappear
In 3rd trimester due to the resulting hydrocephalus from the enlarging ventricles of the blocked CSF
What type of Arnold chiari do we see on ultrasound
Type 2… other types are so lethal that fetus will die very early on
what is the banana sign
cerebellum in the shape of a banana and no cisterna magna
Describe dandy walker malformation. What characteristics should you look for
- enlarged cisterna magna and absent cerebellar vermis
- cisterna magna communicates w/ the 4th ventricle through the defect in the cerebellum (absent vermis)
- ventricles can be enlarged due to pressure in the posterior fossa
What is a dandy walker variant
Partial agenesis of the vermis w/ smaller cisterna magna and minimal dilation of the ventricles
-associated w/ many syndromes
What is DWM associated w/
-Intellectual impairment and fetal death
- agenesis or corpus callosum
- heart defects
- genitourinary defects
- polydactyly
The risk of DWM increases w/ what 3 things?
viral infection
Alcohol
Type 1 diabetes
What’s the differential diagnosis for DWM and how does it appear
Arachnoid cyst in posterior fossa
-fluid collection in the layers of the arachnoid membrane
norm value for cisterna magna
<10mm
cerebellar view must include what
CSP
peduncles
cerebellum
what should you try to prove w/ DWM
cisterna magna communicating w/ 4th ventricle
partial or full absence of vermis
enlarged ventricles
when does the corpus callosum start to develop, when is development complete
how does it develop/grow
12 wks, not complete until 20 wks
anterior to posterior
can the absence of corpus callosum be partial or complete
yes
2 causes for an absent corpus callosum
developmental: interruption in formation
acquired: damage that causes atropy of the CC
an absent corpus callosum is associated w/ what other abnormalities
- absent CSP (first clue)
- other CNS abnormalities - DWM and gyral dysplasia (no folds/grooves on the brain due to lack of development)
- `anomalies of the face. limbs and genitourinary sys
how will the anterior horns look w/ an absent corpus callosum
occipital horns?
pointed
enlarged (colpocephaly)
all other ventricles are norm
when do CPCs usually disappear
2nd trimester
CPCs are associate w/ what chromosomal abnormality
T18 (must see open hands, if not, T18 suspected)
at what size are CPCs significant
> /= 3 mm
What is acrania
Absent skull
What is Anencephaly
No or destroyed cerebral cortex
this is the more commonly used term
What is exencephaly
Some cerebral cortex but it’s abnormal
May be an early stage of anencephaly
(brain exposure to amnitic fluid destroys brain tissue)
What does acranial lead to?
Leads to exencephaly and then anencephaly
What are the US features of anencephaly
Facial structures and orbits are present No skull above the orbits Polyhydramnios (baby can’t swallow) Active fetus Frog like face
Exencephaly can’t be diagnosed before how many wks
prognosis?
12-13 wks
fatal
DDX for anencephaly
anmiotic band syndrome - look for other amputations, waving memebrane or fetus stuck to the uterus
large encephalocele - (herniation of brain and meningies outside of the skull)
What is hydraencephaly
Variable absence of the cerebrum and destruction of brain tissue
Essentially a stroke in utereo
Which structures are intact w/ hydraencephaly
Cranial vault and meninges
Most severe form of porencephaly
hydraencephaly
What causes hydraencephaly
Occlusion of ICA
Infection or hemorrhage
Destruction and resorption of brain matter
Is hydraencephaly rare?
Yes
What causes the hemorrhage that leads to hydraencephaly
Lack of 02
How do you remember which artery is typically occluded and causes hydraencephaly
ICA has an A, and so does hydraencephaly
Us appearance of hydraencephaly
Intact thalami which are never fused
May see brain stem
Falx cerebri may or may not be present
Irregular brain matter
Ddx for hydraencephaly
Severe hydro (smooth along the periphery of the cranium) Alobar holoprosencephaly (would have fused thalami)
Prognosis of hydraencephaly
Fatal
When do porencephalic cysts occur
When the brain tissue is destroyed by hemorrhage or infarct
Us appearance of porencephalic cysts
- Destroyed brain tissue that had become cystic
- Usually seen close to the lateral ventricle
- Cysts May or may not communicate with the ventricles
Ddx of porencephalic cysts
DWM
Arachnoid cyst
Hydrocephaly if cysts communicate w/ the ventricles
Prognosis of porencephalic cysts
Depends on degree of brain destruction
what are arachnoid cysts
where do they occur
fluid filled collections in the layers of the arachnoid membrane
can occur anywhere in the brain
are arachnoid cysts associated w/ any conditions
no
us appearance of arachnoid cysts
well defined cysts in the brain that may show the mass effect
DDX of arachnoid cysts
DWM variant in the posterior fossa
porencephalic cyst
prognosis for arachnoid cysts
good if the cysts dont destroy too much brain matter or block the ventricles
what is encephalocele
what tissue can it contain
herniation of intracranial structures through a defect in the cranium
only meninges or brain tissue also
where do most encephaloceles occur
midline of the occiput, but they can occur anywhere
if in the nasal area it can be hard to see
what lab value will be increased w/ encephalocele
AFP
encephalocele associations
isolated
Meckel Gruber syndrome
what is Meckel Gruber syndrome
an autosomal recessive lethal condition characterized by:
encephalocele
cystic renal dysplasia (lrg echogenid kidneys)
polydactyly
Us appearance of encephalocele if only the meninges are protruding
cystic structure w/ thin membrane
cranial defects
hydrocephalus due to CSF blockage
Us appearance of encephalocele if brain matter is protruding
encapsulated echogenic mass w/ cystic areas
cranial defects
hydrocephalus due to CSF blockage
DDX for encephalocele
cystic hygroma - would see septations in the cystic area
teratoma
prognosis for encephalocele
depends on size, amount of brain tissue involved, and if there’s an association w/ meckel gruber syndrome
what is schizencephaly
symmetrical clefts in the parietal or temporal lobes that extend from the ventricles to the cortical surface
the brain is split into anterior and posterior segments of the brain
what is lissencephaly
smooth brain… no sluci or gyri develope due to abnorm migration of neurons from the germinal matrix
when is lissencephaly diagnosed
not until 3rd trimester
what is microcephaly
when is it seen
disproportionately sm head compared to gestational age and AC… there is faliure of brain development
late preg
US appearance of microcephaly
sloping forehead
ventriculomegaly due to less brain tissue being present
microcephaly is associated w/ which type of abnormalities
developmental
causes of microcephaly
asphyxia infection drugs alcohol irradiation
what is a vein of galen aneurysm
a variety of AV malformations that drain into the vein of galen which leads to its distention
when does a vein of galen aneurysm occur
3rd trimester
US appearance of vein of galen aneurysm
single dilated, midline fluid structure posterior to the thalamus (mid brain) found b/w the posterior horns of the lateral ventricles
may have prominent neck vessels
signs of heart faliure (CMO due to AV shunting)
can you diagnose vein of galen aneurysm w/ colour doppler
yes
DDx for vein of galen aneurysm
arachnoid cyst
porencephalic cyst
prognosis for vein of galen aneurysm
poor unless the anastomoses can be cauterized
are congenital brain tumors rare
yes
most common type of congenital brain tumor
teratomas - lrg echogenic masses w/ cystic spaces, sometimes calcifications
prognosis for congenital brain tumors
poor
what is craniosynostoses
bizarre fusion of the cranial sutures
what is cloverleaf
type of craniosynostoses where fusion of all the cranial sutures occur before the brain is finished growing
what is doligocephay
narrow head, baby’s CI is < 75 percentile
causes are breech or oligohydramnious
what is bradycephaly
wide head, baby’s CI is > 85 percentile
what is poor cranial mineralization
skull bones arent ossified properly, brain structures will appear very easy to see
can the brain be compressed w/ slight pressure w/ poor cranial mineralization
yes
which 2 conditions have poor cranial mineralization and allow the brain to be compressed easily
osteogenesis imperfecta
hypophosphatasia
what are the 3 classifications of holoprosencephaly
which type is the most common
- Lobar - mild
- Semilobar
- Alobar - severe
alobar
describe alobar holoprosencephaly
- little to no cortical mantle
- single horseshoe ventricle
- fused thalami and no 3rd ventricle or falx
- no hemispheres
describe semilobar holoprosencephaly
- single horseshoe shaped ventricle w/ brain mantle
- no 3rd ventricle or falx
describe lobar holoprosencephaly
- fused anterior horns that appear square
- incomplete falx
- 3rd ventricle present, absent cavum septum pellucidi
describe the flow of CSF
- Lateral ventricles
- foramen of monro/interventricular foramen
- 3rd ventricle
- aqueduct of Sylvius/cerebral aqueduct
- 4th ventricle
- foramen of magendie - (1, medial) - to spinal cord
- foramen of luschka - (2, lateral) - to brain
what should you try to image if you suspect the corpus callosum is absent (ACC)
profile picture (hypo strucutre that sites superior to the CSP) 3rd ventricle evelated in the head
prognosis of ACC
-if isolated or partial, it may not effect function at all
severity of decreased intellect depends on associated CNS abnormalities
Which ‘sign’ will you see in the fetal head if there’s agenesis of the corpus callosum
Equal sign and not the box
