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Holoprosencephaly/ACC
with US images
67
Anatomy
Undergraduate 2
03/12/2016

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Term
In normal brain development, the Prosencephalon (forebrain) develops in the ___ week.
Definition
5th
Term
What is the term for a severe defect/incomplete cleavage of forebrain into two hemispheres?
Definition
Holoprosencephaly
Term
How rare is Holoprosencephaly?
Definition
1/10,000 live births
Term
If the forebrain does not divide to form both hemispheres, it causes defects in the development of the ___ and ____ structure and function.
Definition
face & brain
Term
What is the most common cause of Holoprosencephaly?
Definition
Sporadic/Unknown
Term
Other than idiopathy, what are some other causes of Holoprosencephaly?
Definition
Chromosomal: Strong assoc. with Trisomy 13 (Patau Syndrome)

Teratogens: drugs, severe chemical exposure
Term
What are the three types of Holoprosencephaly?
Definition
Alobar, Semilobar, Lobar
Term
What is the most severe form of Holoprosencephaly?
Definition
Alobar
Term
Describe the brain anatomy involved with alobar holoprosencephaly.
Definition
Monoventricle with minimal amount of surrounding cerebral tissue

fused thalami

absent third ventricle, falx, CSP, and corpus callosum
Term
What facial abnormalities are associated with alobar?
Definition
hypotelorism, cyclopia, proboscis, midline facial clefts (absent nose)
Term
What is the term for close-set eyes?
Definition
hypotelorism
Term
What is the most severe facial defect associated with alobar holoprosencephaly?
Definition
cyclopia - 2 orbits fused into one eye
Term
What is the "false nose" visualized above the level of the eyes called?
Definition
proboscis
Term
T/F. Alobar holopresencephaly presents with normal lateral ventricles.
Definition
False - there are NO lateral ventricles
Instead, there is a monoventricle (horseshow shaped).
Term
What is the prognosis for alobar?
Definition
fatal
Term
How do the lateral ventricles and brain mantle appear in alobar vs semilobar?
Definition
very similar, both have:
-monoventricle (no lateral ventricles)
-cortex displaced/flattened

Semilobar may have a dorsal cyst

[image]
Term
How does the size of the head appear in alobar and semilobar?
Definition
variable - microcephaly, normal, or large
Term
This type of holoprosencephaly presents with more cortex and partial fusion of thalami.
Definition
Semilobar Holoprosencephaly
Term
Name the abnormal brain anatomy in semilobar holoprosencephaly.
Definition
resembles alobar
-missing midline structures
-variable development of falx/interhemispheric fissure
-more cortex
-partial fusion of thalamus
-absent 3rd ventricle
Term
What type of holoprosencephaly can be associated with a dorsal cyst?
Definition
Semilobar

Dorsal cyst is the extension of a ventricle posterior
Term
What facial defects are more common in semilobar?
Definition
cleft lip and palate
Term
What is the least severe type of holoprosencephaly?
Definition
lobar holoprosencephaly
Term
Describe the abnormal brain anatomy associated with lobar.
Definition
-fully developed cortex
-partial falx (2 hemispheres present)
-absent CSP
-absent/hypoplastic corpus callosum
-normal separation of thalamus
-normal 3rd ventricle
-separate lateral ventricles
Term
What facial abnormalities are associated with lobar holoprosencephaly?
Definition
none!
normal face
Term
[image]
Definition
1) lobar
2) alobar
3) normal
4) semilobar
Term
[image]
Definition
proboscis - assoc. with alobar
Term
[image]
Definition
monoventricle - assoc. with lobar & semilobar
Term
[image]
Definition
lobar holoprosencephaly
Term
[image]
Definition
hypotelorism - close-set eyes
Term
[image]
Definition
cleft nose and cyclopia - assoc. with alobar
Term
What is the bridge of tissue located within the midline of the brain that connects the cerebral hemispheres?
Definition
Corpus Callosum
Term
The corpus callosum forms the roof of the ________ ________.
Definition
lateral ventricles
Term
In normal development, the corpus callosum is completely formed at ___ weeks.
Definition
18 weeks
Term
The corpus callosum lies to CSP and lateral ventricles.
a. lateral
b. inferior
c. medial
d. superior
Definition
d.superior
[image]
Term
______________ is defined as the congenital lack of the corpus callosum.
Definition
Agenesis of the Corpus Callosum (ACC)
Term
T/F. ACC includes both partial and complete absence of corpus callosum.
Definition
True
Term
Why is an absent CC worrying?
Definition
allows the ventricles to ride up and become displaced and misshapen

associated with as many as 50-200 syndromes:
-Trisomy 18 & 13
-Dandy walker
-Holoprosencephaly
Term
Why does Agenesis of the Corpus Callosum result in an absent Cavum Septum Pellucida?
Definition
CC and CSP are formed at the same time
Term
This is a disorder that refers to disproportionate enlargement of the occipital horns of the lateral ventricles.
Definition
colpocephaly
Term
Is Colpocephaly is associated with partial or complete ACC?
Definition
Complete
Term
Describe the appearance of partial ACC.
Definition
Anterior portion is present
Posterior portion is absent
Term
What is the prognosis of ACC?
Definition
Seizures/ Low IQ
Term
Agenesis of the corpus callosum may be suspected by the absence of the ____ and the ‘teardrop’ shape of the _____.
Definition
absence of CSP

teardrop shape of lateral ventricles
[image]
Term
ACC is demonstrated in what view of the brain?
Definition
mid-sagittal view
Term
The "sunburst" or "spokeswheel" sign refers to what brain anatomy in ACC?
Definition
sulci & gyri
Term
[image]
Definition
sulci & gyri "sunburst" or "spokeswheel" sign
Term
[image]
Definition
Partial Agenesis of CC
Term
Name some sonographic signs of Agenesis of the CC.
Definition
-Lateral displacement of lateral ventricular walls
-Widely separated lateral ventricular frontal horns
-Tear drop shaped lateral vents
-Absent CSP
-Colpocephaly: small frontal horns and enlarged occipital horns
-Elevated and dilated 3rd ventricle
Term
[image]
Definition
Normal vs. ACC
Term
_______ events: Abnormalities related to vascular infarction or agenesis.
Definition
Ischemic
Term
Name the four types of Ischemic Events.
Definition
Porencephaly
Schizencephaly
Lissencephaly
Hydranencephaly
Term
What is the congenital disorder that results in “softening of the brain” and formation of cysts filled with CSF?
Definition
Porencephaly (Porencephalic Cysts)
-Cyst communicates with the ventricular system
-Caused by infection/trauma-hemorrhage within one or both of the cerebral hemispheres
Term
[image]
Identify the abnormality and prognosis.
Definition
Porencephaly (Porencephalic Cysts)

Prognosis: Neurological deficits (cerebral palsy)
Term
Describe the US appearance of Porencephaly.
Definition
Head size = OFTEN NORMAL (CAN be large or small sometimes)

Cystic mass that communicates with lateral ventricle in the brain parenchyma

Most often unilateral

Other cranial anatomy = Well Developed

Face = NORMAL
Term
[image]
This cyst is filled with CSF and communicates with the lateral ventricles.
Definition
Porencephaly
Term
Due to unknown cause, this destructive process creates a cleft in the cerebral cortex.
Definition
Schizencephaly
Term
Schizencephaly Prognosis
Definition
Seizures
developmental delay
mental retardation
motor impairment
Term
[image]
Definition
US Appearance of Schizencephaly

Cerebrum containing clefts filled with anechoic CSF

May be associated with agenesis of the CSP and Corpus callosum
Term
[image]
You can think of this as creating clefts while ice skating.
Definition
Schizencephaly
Term
Brain surface is smooth with no sulci and gyri; Means “smooth brain”
Definition
Lissencephaly
Term
US Appearance of Lissencephaly
Definition
Difficult to diagnose until 3rd trimester when you can visualize sulci and gyri

Sometimes ventriculomegaly
Term
[image]
Definition
Hydranencephaly
Most or all of the cerebrum is absent and the cranium is filled with fluid
Term
Causes of Hydranencephaly
Definition
-Bilateral occlusion of the Carotid arteries causing destruction of the cerebral hemispheres
-Infections: (Intrauterine) Herpes virus, cytomegalovirus, toxoplasmosis, cocaine abuse
-Trauma
Term
A severe brain abnormality where normal tissue is destroyed and replaced with fluid.
Definition
Hydranencephaly
Term
What structures of the brain are absent in Hydranencephaly?
Definition
Almost all structures above the brain stem and midbrain are absent

Cerebrum: ABSENT
CSP: ABSENT OR PARTIAL
Falx: ABSENT OR PARTIAL
3rd Ventricle: ABSENT
Thalamus: PARTIAL OR PRESERVED
Term
What part of the brain is normal with Hydranencephaly?
Definition
brain stem
[image]
Term
Hydranencephaly US Appearance
Definition
Enlarged head size (Macrocephaly)
Fluid-filled cranium
Absent or hypoplastic midline structures
No identifiable cerebral cortex
[image]
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