What is the normal function of the Corpus Callosum (CC)?
Connects left and right cerebral hemispheres
Define Agenesis of the Corpus Callosum (ACC).
Complete or partial absence of the Corpus Callosum
What percentage of isolated cases of ACC result in neurodevelopmental delays?
~30%
Which syndrome is most commonly associated with ACC?
Dandy-Walker Syndrome
What is hydranencephaly?
Absence of cerebral hemispheres; preservation of midbrain & cerebellum
List the causes of hydranencephaly.
- Vascular occlusion (internal carotids)
- Severe hydrocephalus
- Infections (CMV, toxoplasmosis)
What is the prognosis for hydranencephaly?
Poor; usually fatal in infancy
Define porencephaly.
Cystic spaces in brain parenchyma that communicate with ventricles or subarachnoid space
What causes porencephaly?
Infarction or hemorrhage
What is the prognosis for porencephaly?
Variable; depends on size and location
What is schizencephaly?
Clefts connecting lateral ventricles to subarachnoid space
List the types of schizencephaly.
- Open-lip: Bilateral, filled with CSF
- Closed-lip: Unilateral
These are charateristics of what?
- Agenesis of cerebellar vermis
- Cystic dilatation of 4th ventricle
- Enlarged posterior fossa
characteristics of Dandy-Walker Malformation (DWM)?
What are the sonographic features of Dandy-Walker Malformation?
- Banana-shaped cerebellum
- Polyhydramnios
- Ventriculomegaly (70–90%)
- Posterior fossa cyst
What is the prognosis for patients with Dandy-Walker Malformation?
High mortality; >50% have neurodevelopmental delay
Define ventriculomegaly.
Lateral ventricle atrial diameter >10 mm
What distinguishes mild, moderate, and severe ventriculomegaly?
- Mild: 10–12 mm
- Moderate: 13–15 mm
- Severe: >15 mm
What is hydrocephalus?
a condition where cerebrospinal fluid (CSF) builds up in the brain’s ventricles, causing them to enlarge and put pressure on brain tissue. Caused by CSF flow obstruction
What is the most common cause of hydrocephalus?
Aqueductal stenosis
List the types of hydrocephalus.
- Communicating: Impaired absorption
- Non-communicating: Physical blockage
What is Chiari II Malformation (Arnold-Chiari) associated with?
Spina bifida
- Banana sign
- Ventriculomegaly
These are the major sonograhical sign of
Chiari II Malformation
Define holoprosencephaly.
Failure of the forebrain to properly divide into two hemispheres
List the subtypes of holoprosencephaly.
- Alobar: Most severe; single ventricle, no falx
- Semilobar: Anterior fusion, posterior separation
- Lobar: Mildest; separated hemispheres with some ventricle fusion
