Module 11: Fetal Neural tube pathology Flashcards
What is the pathway of flow for CSF? 6
- Lateral ventricles
- Interventricular foramen (foramen of monro)
- 3rd ventricle
- Cerebral aqueduct (aqueduct of sylvius)
- 4th ventricle with two foramen (magendie and luschka)
- Spinal chord
What is the Magendie? What does it connect to?
- Medial aspect of the 4th ventricle
- Connects to the spinal cord
What produces cerebral spinal fluid?
Choroid Plexus
Where is CSF located?
In the body of the ventricles but not the horns
What is the Luschka? What does it communicate with?
- Lateral aspect of the 4th ventricle
- Communicates with the meninges of the brain
What does the Luscka allows?
Allows CSF into the subarachnoid space of the meninges
What is the upper limit for measurement for the lateral ventricles?
<10mm
Where do we place the caliper for ventricles?
On to on
Where is the normal 3rd ventricle located?
Between the thalami and inferior to the corpus callosum
Is the normal 3rd ventricle thick or thin?
thin
Where is the normal 4th ventricle located?
At the anterior and inferior edge of the cerebellum
What is hydrocephalus?
Increase in the CSF that results in enlargement of the ventricular system
What is usually a cause of hydrocephalus? 2
- Usually do to obstruction along the pathway of CSF
- Usually intraventricular and extraventricular
What is the most common cranial anomaly?
Hydrocephalus
What is symptoms of aqueduct stenosis? What does this do to the 3rd ventricles? What about the 4th?
- When the CSF can not flow from 3rd ventricle to 4th ventricle
- This results in lateral and 3rd ventricles are enlarged
- 4th ventricle is normal
What is another name for aqueduct stenosis?
Intraventricular obstructive hydrocephalus
What is Extraventricular obstructive hydrocephalus also called?
Communicating hydrocephalus
What happens with spina bifida?
CSF can not flow normally through spinal canal and backs up in the ventricle of the brain
What ventricles are affected with spina bifida?
All ventricles are affected
What do we see with extraventricular obstructive hydrocephalus? 3
- Excess CSF (less common, Excessive secretions from a choroid plexus papilloma)
- Dandy walker malformation
- Sacral tumors
How do we evaluate ventricular size?
Measure ventricular atrial diameter
When do we measure ventricular atrial diameter?
15-35 weeks
What is the typical ventricle measurement? 2
- Typical around 7mm
- 10 mm is upper limit of normal
What is the distance from medial ventricle wall to choroid?
<3mm
Should the choroid plexus dangle in atria of ventricle?
No
The choroid always rests how?
In a gravitationally dependent position
What are some causes of true hydrocephalus?
CSF obstruction vs ventriculomegaly resulting from brain atrophy
What are some true hydrocephalus causes? 3
- Aqueduct stenosis
- Neural tube defect (NTD)
- Dandy walker malformation
How does ventriculomegaly happen?
Brain atrophy results in a smaller brain allowing ventricles more room to expand
How many additional anomalies occur in cases with hydrpcephalus?
70% to 80%
What are some posterior fossa views we might see for hydrocephalus? 3
- Cisterna magna and cerebellum
- Banana sign
- Skull deformities
What is the lemon sign?
caving in of the frontal bones of the skull
What is the banana sign?
Deformed cerebellum looking like a banana
What is arnold chiari II?
Downward displacement of the brain in the skull as a result of spina bifida
What is spina bifida? What does it result in?
A defect in the spine resulting in tethering of the cord (abnormal attachment) as a result of myelomeningocele
What does this image demonstrate?
Arnold chiari type II symptoms
What does the banana sign look like?
Obliterated cisterna magna
When is Arnold Chiari II usually seen?
Second trimester
With Arnold Chiari II when does the lemon sign disappears?
3rd trimester
What does this image demonstrate?
The lemon sign
Dandy walker malformation (DWM) is a condition having what? What does the enlarged vessel communicate with now? And how does this affect the ventricles?
- Enlarged cisterna magna
- A defect in the cerebellar vermis
- The cisterna magna communicates with the 4th ventricle through the defect in the cerebellum
- Ventricles may be enlarged due to pressure in the posterior fossa
What does this image demonstrate? why?
Dandy walker malformation, note the
1. Enlarged cisterna magna
2. Absent cerebellar vermis
3. Cisterna magna communicating with 4th ventricle
When does the Dandy walker variant occur? 3
When there is partial agenesis of the cerebellar vermis
1. With a smaller cisterna magna
2. Minimal dilation of the ventricles
Both dandy walker malformation and variant are associated with what?
Many syndromes
What symptoms is DWM associated with? 4
- Agenesis of the corpus callosum
- Heart defects
- Genitourinary anomalies
- Polydactlyly
What increases the risk of DWM? 3
- Maternal viral infection
- Alcohol consumption
- Maternal diabetes - type 1
What is the prognosis of survivability of DWM? And what is a effect of it?
- Intellectual impairment
- Fetal death common
What is the cisterna magna measurement for DWM?
Usually >1 - abnormal
What must be present with cerebellar view of DWM? 3
- Cavum septi pellucidi
- Peduncles
- Cerebellum
When assessing DWM try to prove what things? 3
- Is the cisterna magna communicating with the 4th ventricle?
- Is the cerebellar vermis absent or partially absent
- Are the ventricles enlarged?
What are choroid plexus cysts (CPC)?
Cysts in the choroid plexus
When does CPC usually disappears?
In the 2nd trimester
What is CPC associated with? And how many? 2
- Trisomy 18
- 1 in 200 CPCs are associated
What does this image demonstrate?
Choroid plexus cysts
What does Choroid plexus cysts look like?
Hypo to anechoic structure within the choroid plexus
When can we assess nuchal fold?
16 to 20 weeks
____% of infants with Trisomy 21 have _________ ________ in the _____ _______ of the neck
- 80%
- Redundant skin
- Posterior part
Mothers with gestational diabetes mellitus result in a fetus can be what?
LGA (Larger than average)
What will happen with fetus as a result of gestational diabetes mellitus?
The baby will be more fat in general, making nuchal fold thick
When does gestational diabetes mellitus affect the baby? Should we continue to measure the baby?
- After 20 weeks
- Yes, but continuing to measure the nuchal fold after 20 weeks in these patients would result in a large number of “positive markers”
What is the abnormal measurement of the nuchal fold?
_> 6mm is abnormal
How do we measure the nuchal fold?
Measure from outer skull table to outer skin surface
What is acrania?
When a fetus develops without a skull
How common is acrania?
1/1000 births
What is anencephaly?
Absent or destroyed cerebral cortex?
What is exencephaly? 2
- Some cerebral cortex, but is abnormal
- May be an early stage of anencephaly
In a fetus without a _____ (______) there may be brain tissue present in the beginning (_______). However, without the _____ protecting it, the brain tissue is exposed to ______ ______. Over time ________ _______ damages the brain tissue, resulting in ______ or ________ brain tissue. If by time the fetus is imaged there is minimal brain tissue visualized, the diagnosis of __________ is made
- Skull
- Acrania
- Exencephaly
- Skull
- Amniotic fluid
- Amniotic fluid
- Little
- poorly defined
- Anencephaly
What are some sonographic features of acrania? 5
- Facial structures and orbits present
- No calvaria (skull) above the orbits
- Image through the face would resemble a frog
- Usually polyhydraminos
- Very active fetus
Acrania can not be reliably diagnosed before when?
12 to 13 weeks
What does this image demonstrate?
The frog like face on the left and a normal profile on the right
What does these images demonstrate?
Anencephaly (frog like head babies)
What does this image demonstrate?
A Crown rump length measurement of anencephaly