DMS 221 CHAPTER 60

fetal neural axis

CNS arises from ectodermal neural plate around __ gestational days

18

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cephalic neural plate develops into ____

forebrain

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forebrain continues to develop into ____

prosencephalon

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midbrain becomes ____

mesencephalon

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hindbrain forms ____

rhombencephalon

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cephalic end of neural tube bends into shape of C (cephalic flexure ) at end of ____ week

third

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another bend, cervical flexure appears between hindbrain and spinal cord by beginning of ____ week

fifth

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prosencephalon divides into ____ and ____

telencephalon; diencephalon

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____ becomes cerebral hemispheres

telencephalon

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____ eventually develops into:

• epithalamus

• thalamus

• hypothalamus

• infundibulum

diencephalon

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____ subdivides into metencephalon and myelencephalon

rhombencephalon

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____ becomes cerebellum and pons

metencephalon

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____ transforms into medulla

myelencephalon

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primitive spinal cord divides into ____ regions

two

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two regions of primitive spinal cord

alar plate region

basal plate region

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____ region matures into sensory region of spinal cord

alar plate

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____ region develops into motor region of spinal cord

basal plate

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____ and ____ extend the length of the body

spinal cord; vertebral column

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neural fx begins at __ weeks of gestation

6

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most common neural tube defect

anencephaly

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also known as aprosencephaly and atelencephaly

anencephaly

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characterized by a lack of development of the cerebral and cerebellar hemispheres and cranial vault

anencephaly

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anencephaly is ____ with life

incompatible

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etiology of anencephaly is ____

widely unknown

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____ may result from a syndrome, such as Meckel-Gruber (ex. cystic kidneys, occipital encephalocele and/or polydactyly)

anencephaly

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risk for anencephaly is increased in pts with ____

diabetes

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____ means absence of the brain

anencephaly

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____ is caused by a failure of the cranial end of the neural tube to close

anencephaly

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with anencephaly, mechanical and chemical influences of amniotic fluid on the exposed brain cause the brain to disintegrate and both ____ and ____ fail to fully develop

cerebral hemispheres; skull

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base of the skull and facial structures are preserved, but there is a complete or partial absence of the cranium

anencephaly

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the remnant brain with anencephaly is covered by a thick membrane called ____ or ____

angiomatous stroma; cerebrovasculosa

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sonographic findings of ____:

• absence of brain and cranial vault

• rudimentary brain tissue characterized as the cerebrovasculosa

• bulging fetal orbits, giving fetus a frog-like appearance

• incidence varies with geographic location

anencephaly

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differential considerations of anencephaly:

• microcephaly

• acrania

• cephalocele

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polyhydramnios, coexisting spina bifida and cleft lip and palate are some other sonographic findings of ____

anencephaly

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lethal anomaly; also known as exencephaly

acrania

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manifests as absence of cranial bones with presence of complete, although abnormal, development of cerebral hemispheres

acrania

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____ may be associated with other anomalies:

• spinal defects

• cleft lip and palate

• talipes

• cardiac defects

• omphalocele

• amniotic band syndrome

acrania

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____ is a term used to describe herniation of meninges and brain through calvarium defect; associated with Meckel-Gruber syndrome

encephalocele

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____ describes herniation of only meninges

cranial meningocele

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sonographic appearance of ____ depends on location, size, involvement of brain structures

cephalocele

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cephaloceles are classified as ____ cephaloceles when the defect lies between the lambdoid suture and the foramen magnum

occipital

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____ cephaloceles occur between the bregma and the lambda

parietal

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____ cephaloceles lie between the anterior aspects of the ethmoid bone

anterior

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the ____ cephaloceles are always external lesions that occur near the root of the nose

frontal

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____ cephaloceles are internal lesions that occur within the nose, the pharynx, or the orbit

basal

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another sonographic finding of a cephalocele is ____

polyhydramnios

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coexisting anomalies of ____ include:

• microcephaly

• agenesis of corpus callosum

• facial clefts

• spina bifida

• cardiac anomalies

• genital anomalies

cephalocele

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cephaloceles may be confused with ____, although lack cranial defect

cystic hygromas

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____ means there is a cleft, or opening, in the spine

spina bifida

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when covered with skin or hair, referred to as spina bifida ____

occulta

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spina bifida ____ means “open”

aperta

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spina bifida ____ has three forms:

• meningocele

• myelomeningocele

• mieloschisis

aperta

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spina bifida ____ is extremely difficult to detect in fetus

occulta

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when spina bifida defect involves only protrusion of meninges, it is termed ____

meningocele

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spina bifida ____ is more common; both meninges and neural elements (spinal cord) protrude through defect, usually within a meningeal sac

meningomyelocele

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if spina bifida defect is very large and severe, it is termed ____

myelocschisis

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several variants include an adipose tissue component in addition to meningeal and/or neural components and are termed ____ and ____

lipomyelomeningocele and lipomeningocele

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open neural tube defects are commonly associated with increased ____

maternal serum AFP

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fetuses with myelomeningoceles often present with cranial defects associated with the ____ which is identified in 90% of pts

Arnold Chiari II malformation

pg 1529

____ changes the shape of the cerebellum, giving it a “banana” appearance

Arnold Chiari II malformation

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• leads to obliteration of cisterna magna

• caudal displacement of cranial structures causes scalloping of frontal bones of skull, making fetal head resemble a lemon

• this decreases the size of BPD

spina bifida/arnold chiari II malformation

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management of spina bifida includes serial ultrasound examinations to monitor progression and extent of ____ and to follow fetal growth

ventriculomegaly

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surgical repair of ____ defects in utero:

• risks incurred with procedure include

  • premature delivery

  • maternal morbidity

  • fetal morbidity

spina bifida

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after spinal defect is identified, document:

• level and extent of defect

• presence or absence of neural elements contained in protruding sac

• associated intracranial findings

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sonographic findings associated with ____:

• talipes

• cephaloceles

• cleft lip and palate

• hypotelorism

• heart defects

• genitourinary anomalies

spina bifida

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manifests with agenesis or hypoplasia of cerebeller vermis with resulting dilation on fourth ventricle and enlargement of posterior fossa

dandy-walker malformation

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____ is associated with other intracranial anomalies about 50% of the time

dandy-walker malformation

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sonographic survey may reveal extracranial anomalies also associated with ____:

• cardiac anomalies

• polydactyly

• facial clefts

• urinary tract anomalies

dandy-walker malformation

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splaying of cerebellar hemispheres as result of complete or partial agenesis of cerebellar vermis

dandy-walker malformation

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enlarges cisterna magna caused by cerebellar vermis anomaly and posterior fossa cyst

dandy-walker malformation

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differential considerations should include arachnoid cyst, but identification of splayed cerebellar hemispheres may help confirm ____

dandy-walker malformation

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cerebellar hypoplasia should also be included in the differential diagnosis for dandy-walker malformation when ____ is enlarged

cisterna magna

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three forms of holoprosencephaly:

• most severe form classified as ____

• intermediate form as ____

• mildest as ____

alobar

semilobar

lobar

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singular monoventricle brain tissue that is small

alobar holoprosencephaly

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____ holoprosencephaly presents with:

• singular ventricular cavity with partial formation of occipital horns

• partial or complete fusion of thalamus

• rudimentary falx and interhemispheric fissure

• absent corpus callosum

• absent cavum septum pellucidum

• absent olfactory bulbs

semilobar

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multiple syndromes have been associated with ____, including:

• meckel-gruber syndrome

• aicardi’s syndrome

• fryns syndrome

• hydrolethalus syndrome

holoprosencephaly

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common C-shaped ventricle that may or may not be enlarged

holonoprosencephaly

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facial anomalies include:

• cyclopia

• hypotelorism

• absent nose

• flattened nose with single nostril

• proboscis

holoprosencephaly

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____ consists of combination of hypotelorism with normally placed nose with single nostril and common ventricle

cebocephaly

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____ consists of severe hypotelorism with proboscis superior to eyes

ethmocephaly

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____ is fibrous white matter tract that connects the cerebral hemispheres and aids in cognition and neurological functions

corpus callosum

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allows communication between the right and left cerebral hemispheres

corpus callosum

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agenesis of the ____ may be associated with other CNS malformations:

• hydrocephalus

• gyral anomalies

• heterotopias

• DWM

• holoprosencephaly

corpus callosum

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apert has been associated with agenesis of the ____

corpus callosum

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maternal diseases that are contributing factors for agenesis of the ____:

• diabetes

• infections

• alcohol abuse

corpus callosum

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sonographic features of ____:

• absence of corpus callosum

• dilated occipital horns (colpocephaly), giving lateral ventricles teardrop shape

• absence of cavum septum pellucidum (CSP)

• abnormal or absent pericallosal artery

• elevation and dilation of third ventricle

• widely separated lateral ventricular frontal horns with medial indentation of medial walls

agenesis of the corpus callosum

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CNS anomalies that are associated with ____:

• holoprosencephaly

• encephalocele

• microcephaly

• porencephaly

• cranial lipoma

• arnold-chiari malformation

• septo-optic dysplasia

• hydrocephaly

• dandy-walker malformation

• lissencephaly

agenesis of the corpus callosum

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other abnormalities associated with ____:

• cardiac malformations

• diaphragmatic hernia

• lung agenesis or dysplasia

• absent or dysplastic kidneys

agenesis of the corpus callosum

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most common cause of hydrocephalus in utero

aqueductal stenosis

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aqueductal stenosis results from obstruction, atresia, or stenosis of aqueduct of Sylvius, causing ____

ventriculomegaly

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____ connects third and fourth ventricles

aqueduct of sylvius

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sonographic features of ____:

• ventricular enlargement of lateral ventricles (may be severe)

• third ventricular dilation

• flexion and adduction of thumb (in X-linked form)

aqueductal stenosis

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also known as vein of Galen malformation

vein of Galen aneurysm

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vein of galen aneurysm is a rare ____ malformation

arteriovenous

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with vein of galen aneurysm, vein will be ____ and communicate with normal-appearing arteries

enlarged

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may present as anechoic mass within the midline of the brain with turbulent arterial flow

vein of galen aneurysm

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____ is considered a sporadic event

vein of galen aneurysm

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usually an isolated anomaly; has been associated with congenital heart defects, cystic hygromas, and hydrops

vein of galen aneurysm

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sonographic features of ____:

• cystic space - may be irregular in shape and located midline and posterosuperior to third ventricle

• turbulent flow with Doppler evaluation

• fetal cardiomegaly

• nonimmune hydrops

vein of galen aneurysm

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porencephalic cysts should be listed in differential cosiderations for ____

vein of galen aneurysm

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