Fetal Brain anomalies Flashcards
Describe Hydranencephaly
-Its lethal -No cortex -Fluid filled cranium -Liquified brain due to vascular insult Work-up: -TORCH -Thrombophilia -R/O Renal dysplasia, heart defects -T13
Describe Porencephaly
One or more cystic cavities communicating with ventricles (associated with infarction to hemorrhage) Differs from arachnoid cyst because it is communicating with the ventricles
Describe Schizencephaly
Cleft connecting lateral ventricle to subarachnoid space (pia mater)
- Absent cavum septum pellucidum
- Developmental delay and seizures
Encephalocele
defect in skull allowing brain to protrude associated with Meckel Gruber
Lobar holoprosencephaly
- presence of interhemipheric fissure and gyral continuity which is better seen on MRI
- communication of ventricles across the midline
- absent cavum septum pellucidum
- fused fornix and frontal lobe
- thalami is seperated
***hard to diagnose, the only finding is typically absent csp
***assess about diabetes
***associated with Smith-Lemli-Opitz and velocardio-facial syndrome
Semilobar holoprosencephaly
- partial clevage of proseccephalon
- absent CSP and incomplete interhemispheric fissure
- fused frontal lobes but seperated occipital lobes
- incomplete fusion of thalami
Alobar holoprosencephaly
- single ventricle cerebrum (monoventricle)
- no corpus callosum
- fused thalami
Holoprosencephaly
Incomplete cleavage of the prosencephalon into left and right at 18th-28th day of gestation. Risk factors: DM, vitamin A exposure
Acrania-exencephaly/anencephaly
Acrania - flat bones in the cranial vault are either completely or partially absent
Excencephaly is the early manifestation of anencephaly
Anencephaly - a neural defect that occurs when the cephalic end of the neural tube fails to close usually between the 23rd and 26th days
Examine for diabetes
Agenesis of the corpus callosum
- Caused by vascular event, genetic component, metabolic disorder, alcohol exposure
- Starts to develop at 12 weeks and stops at 18 weeks -On ultrasound:
see absent CSP
rostral displacement of the roof of third ventricle
tear drop shaped ventricle
Arachnoid cyst
Benign non-communicating fluid collections within the arachnoid membrane. 80% normal development
Aneurysm of vein of Galen (cranium):
Midline cystic tubular structure posterior to the thalamus with blood flow . 55% - perinatal death rate. 15% alive with disability. 35% alive and normal.
What does the Rhombencephalon consist of:
It represents the hindbrain and consists of the medulla, pons and cerebellum. it appears as an anechoic structure in the first trimester, seen in the posterior part of the brain
What brain structures can be seen between 11 weeks and 13 weeks and 6 days?
Cranium
Frontal horn
Choroid plexus
Thalamus
Fourth ventricle
Brain stem
Intracranial lucency
Cisterna magna
What are the three axial planes which a fetal brain scan can be performed?
Transventricular
Transthalamic
Transcerebellar
What can be seen in the transventricular view?
This is the plane where the lateral ventricle is measured
What can be seen at the transthalamic plane of the fetal brain
this is where BPD and HC can be obtained
Fornix verses CSP
fornix is the line through the box where the csp is suppose to be. it is located inferior to the CSP
What can you see at the transcerebellar plane?
Amniotic band syndrome of the cranium:
What does CMV look like in the fetal brain?
Look for interventricular synechiae
Cavum veli interpositi cyst
if measuring more than 11mm then can be considered a cyst which is associated with ventriculomegaly
Dural Sinus Thrombosis of the fetus
Lissencephaly
absence of gyri and sulci
Agenesis of corpus callosum
Widened interhemispheric space
Tear drop shaped ventricles (colpocephaly)
3rd ventricle is displaced upwards
Absent CSP differential dx:
Mega cisterna magna ddx:
Blakes pouch
Dandy walker malformation
Blake’s pouch
Septo-Optic Dysplasia:
- absent cavum septi pellucidi
- frontal horns communicating
- the fornix is not fused
- in coronal view: frontal horn is square shape at the points and the whole thing comes to a point inferiorly indicating seperated fornices
- the optic chiasm is small
(hypothalamic hypopituitarism, delay)
Syntelencephaly:
- it is a variant of holoprosencephaly
- fusion of the posterior portion of the frontal and parietal lobes across the midline
- absent cavum septi pellucidi
