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OB 2 > Fetal CNS Pt. 2 > Flashcards

Fetal CNS Pt. 2 Flashcards

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1
Q

What can polyhydramnios indicate?

A

CNS abnormality.

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2
Q

What test results can indicate a CNS abnormality?

A

High AFP from the Triple Marker test.

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3
Q

List factors related to polyhydramnios.

A
  • Gastrointestinal abnormalities that block fluid passage
  • Abnormal swallowing due to CNS or chromosomal issues
  • Twin-to-twin transfusion syndrome
  • Heart failure
  • Congenital infection acquired in pregnancy
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4
Q

Name some intracranial cystic abnormalities.

A
  • Hydrocephalus
  • Hydranencephaly
  • Holoprosencephaly
  • Dandy-Walker malformation
  • Vein of Galen aneurysm
  • Choroid plexus cysts
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5
Q

What is hydrocephalus?

A

Congenital dilatation of the ventricular system.

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6
Q

What are common abnormalities associated with hydrocephalus in a fetus?

A

CNS abnormalities:
* Neural tube defects (NTDs)
* Dandy-Walker malformation
* Holoprosencephaly

Craniofacial anomalies:
* Cleft lip and/or palate

Syndromes and genetic conditions:
* Meckel-Gruber syndrome
* Trisomy 21 (Down syndrome)
* Triploidy

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7
Q

What are the four etiological classifications of hydrocephalus?

A
  • Aqueductal stenosis: 43%
  • Communicating hydrocephalus: 38%
  • Dandy Walker: 12%
  • Idiopathic: 7%
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8
Q

What are the sonographic findings of hydrocephalus?

A
  • Normal ventricle configuration but dilated
  • Atrium of lateral ventricle > 10 mm
  • Dangling choroid plexus
  • Dense brain echogenicity
  • Other associated fetal anomalies
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9
Q

What is ‘Filly’s Rule’?

A

If the atrium of the lateral ventricle and the cisterna magna both measure less than 10 mm, there is a 95% negative predictive value for any CNS anomaly.

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10
Q

Differentiate between ventriculomegaly and hydrocephalus.

A
  • Ventriculomegaly: refers primarily to ventricle enlargement
  • Hydrocephalus: refers to the whole ventricular system’s dilatation due to outflow obstruction.
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11
Q

What does the “dangling choroid sign” indicate, and how is ventriculomegaly (VM) classified?

A
  • Dangling choroid sign: Suggests fetal ventriculomegaly (VM)
  • Normal ventricle measurement: 5–10 mm (from 15 weeks gestation)
  • Mild VM: 10–15 mm
  • Severe VM: >15 mm
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12
Q

What is aqueductal stenosis?

A

The most common cause of obstructive hydrocephalus in neonates due to narrowing of the aqueduct of Sylvius.

Communicating: CSF still flows freely between the ventricles

With aqueductal stenosis, both lateral ventricles and the third ventricle are dilated, while the posterior fossa and fourth ventricle are normal

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13
Q

What does a normal sagittal view of the fetal head at 22 weeks show in relation to aqueductal stenosis evaluation?

A
  • Cavum veli interpositi: Located posterior and inferior to the CSP
  • Fourth ventricle: Visible as a distinct structure
  • Cisterna magna: Identified by an open arrow
  • Cerebellum: Labeled as “c” in imaging
  • These structures help distinguish normal anatomy from aqueductal stenosis, where obstruction occurs at the Aqueduct of Sylvius.
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14
Q

What is hydranencephaly?

A

Total or near total absence of cerebral hemispheres with normal meninges and skull.

  • Caused by: Occlusion of the middle cerebral artery (MCA) or internal carotid arteries
  • Falx is present (helps distinguish from holoprosencephaly) - THIS IS HYDRANECEPHALY
  • Single ventricle or absent/partially present
  • No cerebral cortex visible
  • Brainstem preserved

Structures typically unaffected:
* Midbrain
* Cerebellum
* Thalami
* Basal ganglia
* Choroid plexus

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15
Q

What are associated abnormalities with hydranencephaly?

A
  • Renal dysplasia
  • Heart defects
  • Trisomy 13
  • Polyhydramnios
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16
Q

What are the sonographic findings of hydranencephaly?

A
  • Macrocephaly: Large anechoic area in cranial vault
  • Polyhydramnios
  • Absent cortical mantle (gray matter)
  • Variable presence of 3rd ventricle
  • Occasionally small portions of occipital lobes may be seen
  • Midbrain, cerebellum, and basal ganglia are intact
  • Tentorium separates normal posterior fossa from anterior/middle fossae
  • Falx cerebri is present
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17
Q

What is holoprosencephaly?

A

Failure of the embryo’s forebrain to divide into two cerebral hemispheres, causing defects in brain structure and function.

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18
Q

What are the sonographic findings and associated anomalies of holoprosencephaly?

A

Single, midline ventricle (monoventricle)
Thin cerebral tissue mantle surrounding the ventricle
Craniofacial abnormalities
* Proboscis
* Cyclopia
* Cleft lip
Variable appearance depending on severity

Associated anomolies
* Trisomy 13
* Trisomy 18
* Congenital renal anomalies
* Congenital cardiac anomalies

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19
Q

Facial Anomalies – know these images
Proboscis and cyclopia

Study These Flashcards
A
Note the fused thalami, monoventricle, proboscis, & Hypotelorism
20
Q

What is holoprosencephaly and how is it classified? What is the prognosis?

Study These Flashcards
A

A forebrain diverticulation abnormality leading to a single midline ventricle (monoventricle or holoventricle)
Types:
1. Alobar – most severe
2. Semi-lobar
3. Lobar – least severe

Prognosis:
* Alobar: Often stillborn or dies within 6 months
* Semi-lobar or lobar: Over half live past one year if no major organ malformations are present

21
Q

Holoprosencephaly - Alobar (MOST SEVERE)

Study These Flashcards
A
Note the monoventricle & fused thalami
22
Q

What defines semi-lobar holoprosencephaly?

Study These Flashcards
A
  • Partial fusion of the left and right hemispheres
  • Fusion occurs specifically in the frontal and parietal lobes
23
Q

What defines lobar holoprosencephaly, the least severe form?

Study These Flashcards
A
  • Two lateral ventricles are present (right and left)
  • Fusion of the cerebral hemispheres occurs in the frontal cortex
24
Q

What is Dandy-Walker malformation?

Study These Flashcards
A

Cerebellar vermian dysgenesis with cystic filling of the posterior fossa. (the VERMIS in the crebellum is MISSING!!!)

Most common congential malformation of the human cerebellum
* 4th ventricle outflow obstruction
* Cerebellar cleft malformation

25
What are associated abnormalities with Dandy-Walker malformation?
* Hydrocephalus * Other CNS anomalies * Cardiac anomalies * Cleft palate * Meckel-Gruber syndrome
26
What are the sonographic findings of Dandy-Walker Malformation (DWM)
* Enlarged cystic posterior fossa * Separated and flattened cerebellar hemispheres * **Hydrocephalus** in \~25% of cases * **Polyhydramnios** may be present * Differentiated from subarachnoid cyst by **continuity with 4th ventricle**
27
What is the difference between Holoprosencephaly and Dandy-Walker Malformation (DWM)?
**Holoprosencephaly**: * Neuronal migration disorder * **Failure of the forebrain (prosencephalon)** to divide into two hemispheres * **Posterior fossa structures are usually normal** **Dandy-Walker Syndrome (DWS)**: * Rare congenital malformation of the **cerebellum** * **Incomplete formation of the cerebellar vermis** (structure joining the two cerebellar hemispheres)
28
What is a Vein of Galen aneurysm?
An arteriovenous malformation in the mid portion of the fetal brain resulting in dilatation of the Vein of Galen.
29
What are the common abnormalities of a Vein of Galen aneurysm?
* High-output cardiac failure * Hydrocephalus ## Footnote Remember to always turn on color when you find any abnormality in the fetal brain!
30
What is the treatment for Vein of Galen aneurysm?
Embolization.
31
What is a dural sinus malformation?
A rare congenital malformation containing a dilated dural sinus pouch that communicates with other sinuses and drains cerebral veins
32
What percentage of congenital intracranial vascular anomalies does dural sinus malformation account for?
Less than 2%
33
What are choroid plexus cysts and what is their clinical significance?
* **Benign fluid collections** from abnormal folding of the choroid epithelium * Can be **unilateral or bilateral** * Seen in **1–2%** of mid-trimester fetuses * **Usually benign**, but **infrequently linked to aneuploidy** * **Genetic work-up may be recommended** * **Associated abnormality**: Trisomy 18
34
What should be looked for in addition to a Choroid Plexus Cyst to indicate Trisomy 18?
Other markers such as structural heart defect, clenched hands, clubbed feet, IUGR, and polyhydramnios
35
What is an Arachnoid Cyst?
A collection of cerebrospinal fluid located towards the back of the brain, covered by pia and arachnoid layers ## Footnote * We need to **differentiate between a Dandy Walker Malformation or an arachnoid cyst** when in the posterior fossa * Does not communicate with the ventricles, but rather displaces normal structures of the brain * Use color doppler and measure
36
Where is an Arachnoid Cyst most commonly located?
Left side of the brain
37
What characterizes Porencephaly?
An intracerebral cyst filled with cerebrospinal fluid that usually communicates with ventricles or subarachnoid space
38
What are the two types of Porencephaly?
* **True porencephaly (agenetic)** - a developmental anomaly * **Sporadic (destructive condition)**
39
What factors can lead to sporadic Porencephaly?
* Vascular incidents * Infectious conditions * Traumatic incidences * Maternal disease or sickness * Maternal diabetes * Maternal use of alcohol or drugs
40
What is the prognosis for children with Porencephaly?
Varies; some may be severely disabled, while others may have normal intelligence
41
What is Schizencephaly?
A rare developmental defect characterized by a unilateral or bilateral cleft between the ventricles and subarachnoid space Sonogrpahic Findings * **Unilateral or bilateral cystic defect** extending from the brain surface to the ventricular wall * **Absent cavum septi pellucidi (CSP)** Can **mimic**: * **Holoprosencephaly** * **Agenesis of the corpus callosum**
42
What are some associated abnormalities of Schizencephaly?
* Absent cavum septi pellucidi * Hydrocephalus
43
What are the key features and associated abnormalities of fetal intracranial tumors?
* **Rare in the fetus** * May appear **cystic, solid, or complex** * **Most are supratentorial** (located above the tentorium cerebelli) * **50% are teratomas** **Associated abnormalities**: * High-output cardiac failure * Hydrops fetalis * Abnormal cerebral artery Doppler flow patterns
44
What are the characteristics and prognosis of fetal intracranial teratomas?
* **Most common solid fetal intracranial tumor** (≈50% of cases) * **Rare overall**, but make up the majority of fetal brain tumors * Typically diagnosed in the **late second or third trimester** * Often **lack distinct ultrasound findings** * **Prognosis is poor** with survival rates **under 10%**
45
What are the typical sonographic findings of fetal intracranial tumors?
* **Large, complex, echogenic mass** within the brain * **Gross distortion** of normal intracranial architecture
46
What is fetal glioblastoma and how does it typically present?
* **Stage 4 glioma** (most aggressive form) * **Gliomas** are tumors from **glial cells** (neuroepithelial origin) * **Rare intracerebral tumor** in fetuses * Commonly presents with **polyhydramnios** and **hydrocephalus**
47
What are the key features and sonographic appearance of intracranial hemorrhage (ICH) in the fetus?
* **Bleeding into the fetal brain**, rare in utero * Caused by **cerebral hypoxic events** and pressure gradients * **Early appearance**: Homogeneous, brightly echogenic area (distinct from choroid plexus) * **Later appearance**: Becomes **heterogeneous** with: * **Echogenic rim** * **Sonolucent (dark) core** as clot breaks down

OB 2 (16 decks)

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