Fetal Neural Tube Pathology Flashcards
What does the ventricles contain?
4 connecting cavities within the cerebral hemispheres of the brain stem
The ventricles are continuous with what?
The spinal cord cavity
The Cavum septi pellucidi are located where in relation top the thalamus?
Anterior and slightly superior
What does the cavum septi pellucidi separate?
The anterior horns of the lateral ventricles
What is the CSF flow pattern?
- Lateral ventricles
- Interventricular foramen (Munro)
- 3rd ventricle
- Cerebral aqueduct
- 4th ventricle
- Two foramen, Magendie and Luschka
What does the cavum septi pellucidi visualization signify?
Normal development of the frontal midline
The cavum septi pellucidi is a important landmark for what measurements?
BPD where the cranium is measured
What is the criteria for ventricular measurement? 3
- Measure ventricle farthest from the transducer
- Measure at the level of the parietal occipital fissure
- Perpendicular to the cavity, inner to inner or “on to on”
Label the difference between the two
The left box is the CSP and the right box is the Fornix
What does the normal 3rd ventricle look like? And where is it located?
- Thin
- Located between the thalami and inferior to the corpus callosum
Where is the 4th ventricle located?
Anterior and inferior edge of the cerebellum
What is hydrocephalus?
Increase in CSF that results in enlargement of the ventricular system
Hydrocephalus is usually due to what? 2
Obstruction along the pathway of the CSF
- Intraventricular
- Extra ventricular
What is the most common cranial anomaly?
Hydrocephalus
What are causes of hydrocephalus? 2
- True hydrocephalus
- Ventricularmegaly
What is true hydrocephalus?
CSF obstruction
How would we get ventricularmegaly? 2
- Brain atrophy
- Small brain, ventricle have space to enlarge into
What are causes of true hydrocephalus? 3
- Neural tube defect
- Aqueduct stenosis
- Dandy walker malformation
What causes aqueduct stenosis? What does the lateral and 3rd ventricles look like? What about the 4th?
- CSF can not flow from 3rd ventricle to 4th
- Lateral and 3rd ventricle are enlarged
- 4th ventricle is normal
What causes intraventricular obstruction?
Aqueduct stenosis
What are some extra ventricular obstruction? 4
- Spina bifada
- Excess CSF
- Dandy walker malformation
- Sacral tumors
What is spinda bifida?
CSF can not flow normally through spinal canal and backs up in the ventricle of the brain
Which ventricles are affected by spina bifida?
All ventricles are affected
Excess secretion of CSF causing extraventricular obstruction comes from where?
Excessive section from a choroid plexus
How do we evaluate ventricular size?
Measure ventricular atrial diameter
Ventricular diameter does not change much from which dates?
15-35 weeks
What is the typical ventricle measurement ?
Around 7mm
What is the upper limit of normal for ventricular size?
10mm
What is the distance from medial ventricle wall to choroid?
<3mm
Additional anomalies occur in what percentage of cases of hydrocephalus?
70-80%
What are some things we see with posterior fossa views? 2
- Cisterna magna and cerebellum
- Skull deformities
What do we assess for in the cistern a magna and cerebellum? (What signs do we look for) 2
- Assess for obliterated cisterna magna, Cerebullum right up against the posterior skull
- Banana sign
What is dandy walker malformation? 2
A condition having
- Enlarged cisterna magna
- A defect in the cerebeller vermis
With DWM the cisterna magna communicates with the 4th ventricule how?
4th ventricle through the defect in the cerebellum
With DWM the ventricles may appear how?
Enlarge due to pressure in the posterior fossa
The DWM variant occurs when there is what?
Occurs when there is partial agenesis of the cerebella’s vermin’s, with smaller cisterna magna, and minimal dilation of the ventricles
Both DWM and DWM variant is associated with what?
Many syndromes
DWM is associated with what conditions? 6
- Agenesis of the corpus callosum
- Heart defects
- Genitourinary anomalies
- Polydactyly
- Intellectual impairment is common
- Fetal death is common
What risk factors increase the incidence of DWM? 3
- Maternal viral infection
- Alcohol consumption
- Diabetes
In terms of DWM, how big does the cisterna magna have to be to be abnormal?
> 1cm is abnormal
The cerebeller view of DWM must include what? 3
- Cavum septi pellucidi
- Peduncles
- Cerebellum
When assessing DWM what do we try to prove? 3
- Is the cisterna magna communicating with the 4th ventricle
- Is the cerebeller vermis absent or partially absent
- Are the ventricles enlarged?
What is the DDX for DWM? 2
- Arachnoid cyst in posterior fossa
fluid collections in the layers of the arachnoid membrane
These cysts can occur anywhere in the brain - Mega cisterna magna
What are Choroid plexus cysts?
Cysts in the choroid plexus
When does CPCs disappear?
2nd trimester
What is CPC associated with?
Trisomy 18
What is the variation of incidence with T18 for CPC?
1 in 200 CPCs are associated with trisomy 18
One cause for Dolichocephaly is what?
Breech baby
What is the calculation for Cephalic index?
BPD / OFD and should be <75
What are craniosynotoses?
Bizarre fusion of the cranial sutures
What does craniosynostoses look like? Why?
Cloverleaf - all sutures fuse before the brain is finished growing
If the view of the brain is especially clear, you should consider what? 2
- Conditions which have poor mineralization
- Also, can the brain be compressed with slight pressure?
In osteogenesis imperfect and hypophosphatasia, the cranial bones are what?
Not ossified and the brain can easily be compressed
What is a acrania? How many children are affected?
- Absent cranium
- 1/1000 births
What is anencephaly?
No cerebral cortex - absent or destroyed
What is exencephaly? 3
- Some cerebral cortex, but is abnormal
- Brain tissue exposed to amniotic fluid damages the brain tissue
- May be early stage of anencephaly
On ultrasound, what does anencephaly look like? 3
- The facial structures and orbits are present
- No skull above the orbits
- Frog look
When can anencephaly be diagnosed? (weeks)
12-13 weeks