ARRT PENNY BOOK CHAP 24

Lissencephaly

"Smooth brain"; condition where there is little to no gyri or sulci within cerebral cortex

falx cerebri

-A double fold of dura mater located within midline of the brain. Echogenic linear formation coursing through the midline of the fetal brain. Separates the cerebral hemispheres.

Neural plate

-The early embryologic structure that develops into the central nervous system

Sonographic findings of porencephaly

1. cystic mass that communicates with the lateral ventricle 2. most often unilateral

The interthalamic adhesion (mass intermedia) passes through the:

3rd ventricle

The cerebellum

A large structure of the hindbrain that controls fine motor skills. Located in the posterior fossa of the cranium. Consist of 2 hemispheres; right and left. Seen as dumbbell shaped figure or 8 shaped structure in the posterior cranium of the fetus.

Median cleft lip

A subdivision within the middle of the lip. associated with holoprosencephaly

Anophthalmia

Absence of eyes. associated with holoprosencephaly

The "sunburst" of the cerebral sulci is a sonographic finding of:

Agenesis of the corpus callosum

The most severe form of holoprosencephaly:

Alobar

The most common cause of hydrocephalus in utero is:

Aqueductal stenosis

Arnold chiari II malformation and spina bifida

Arnold-chiari II or Chiari II malformation is a group of cranial abnormalities associated with the neural tube defect spina bifida. Spina bifida may result in a mass that protrudes from the spine. This mass can be referred as meningocele or myelomeningocele, depending of its contents.

The anechoic midline brain structure located between the frontal horns and the lateral ventricles is the:

CSP

what cerebral malformation is a result of agenesis or hypoplasia of the cerebral vermis?

DWM

"Dangling choroid" sign

Describes the echogenic choroid plexus, hanging limp, and surrounded by CSF, within the dilated lateral ventricle. Associated with ventriculomegaly

Neural tube

Embryologic formation that results from fusion of two folded ends of neural plate

Ventriculomegaly

Enlargement of the ventricles beyond 10mm.

arachnoid granulations

Extensions of the arachnoid mater that allow excess CSF to be absorbed by the dural sinuses. Also referred as arachnoid villi

The most accurate measurement for estimating the gestational age is:

HC

Intracranial hemorrhage

Is a common worry for premature infants weighting less than 1500 g and those born before 32 weeks gestation but it occurs less in utero. Most often the origin of intracranial hemorrhage is within the germinal matrix.

Fetal head shape and associated anomalies

Lemon- chiari II malformation strawberry - trisomy 18 cloverleaf- thanatophoric dysplasia microcephaly- TORCH infections, trisomy 13, trisomy 18, Meckel- gruber syndrome, fetal alcohol syndrome macrocephaly- hydrocephalus, hydranencephaly, intracranial tumors, familial inheritance, Beckwith-Wiedemann syndrome brachycephaly- craniosynostosis, trisomy 21, trisomy 18 dolichocephaly- craniosynostosis

The lack of sulci within the fetal cerebrum is a reliable indicator of:

Lissencephaly

Head circumference (HC)

Measured at the same level as BPD, around outer perimeter of the calvarium Head circumference is not affected by head shape

The development of fluid filled cleft within the cerebrum is consistent with:

Schizencephaly

Doppler of the middle cerebral artery

Shown effective at evaluating hypoxia in a fetus that is measuring small for date. The resistance pattern of the MCA should be greater than of the umbilical artery and this should be compared when fetal shunting is suspected.

Choroid plexus cysts

Small cysts within the choroid plexus. (common), they often regress but there is a slight association with trisomy 18.

The most common intracranial tumor found in utero

Teratoma

The thalamus

a brain structure that allows communication between the senses; also performs many other functions. The 2 lobes of the thalamus are located on both sides of the 3rd ventricle. The massa intermedia or interthalamic adhesion passes through the 3rd ventricle to connect the 2 lobes of the thalamus. The thalamus should not be confused with the cerebral peduncles which are more inferiorly positioned in the brain.

Proboscis

a false nose situated above the orbits. associated with holoprosencephaly

The germinal matrix

a group of thin walled pressure sensitive vessels located in the subependymal layer of the ventricles.

cistern

a prominent space within the skull that contains cerebrospinal fluid; a cistern is created by the separation of the arachnoid membrane and pia mater.

Porencephaly

a rare condition in which a cyst communicates with the ventricular system. It can occur after the fetus has experience hemorrhage within one or both of the cerebral hemispheres. It can be caused by ischemic events or vascular occlusion,

Corpus callosum

a thick band of tissue that provides communication between the right and left halves of the brain.

Aqueduct of Sylvius

also known as cerebral aqueduct. is a duct that connects the third ventricle of the brain of the fourth ventricle.

dolichocephaly

also referred as scaphocephaly, denotes an elongated, narrow head shape

Most common neural tube defects?

anencephaly and spina bifida

The 4th ventricle is located

anterior of the cerebellar vermis

The 3rd ventricle communicated with the 4th ventricle at the:

aqueduct of Sylvius

What can be confused with porencephaly?

arachnoid cyst can be confused with porencephaly. It is important to note that arachnoid cyst will not communicate with the ventricular system.

Schizencephaly

associated with the development of fluid filled clefts within the cerebrum. Etiology is unknown but there may be an association with intrauterine exposure to some illicit drugs.

The 3rd ventricle is located

between the 2 lobes of the thalamus

The structure located between the 2 lobes of the cerebellum is the:

cerebellar vermis

Trisomy 8

chromosomal aberration in which there is a third chromosome, also referred as Warkany syndrome 2

Cebocephaly

close-set eyes (hypotelorism) and a nose with a single nostril. associated with holoprosencephaly

Enlargement of the frontal horns and narrowing of the occipital horns is termed:

colpocephaly

The condition in which the frontal horns are small and the occipital horns are enlarged is referred to as:

colpocephaly

Agenesis of the corpus callosum and cavum septum pellucidum

congenital lack of these structures. there can be partial or complete absence of the corpus callosum. With agenesis of the corpus callosum, the sulci tend to have a more perpendicular or radial arrangement and often appear to have a "spoke wheel" pattern.

The band of tissue that allows communication between the right and left cerebral hemisphere

corpus callosum

Hydrocephalus

dilatation of the ventricular system caused by an increased volume of CSF, resulting in increases intraventricular pressure. Can be communicating hydrocephalus when the obstruction lies outside the ventricular system. Noncommunication hydrocephalus is when the obstruction level is located within the ventricular system.

The double fold of dura mater that divides the cerebral hemisphere is the:

falx cerebri

Prosencephalon

forebrain. The primary brain vesicle. It eventually becomes the lateral ventricles, cerebral hemisphere, third ventricle, thalamus, hypothalamus, pineal gland and pituitary gland.

With what structure does the posterior fossa cyst associated with DWM communicate?

fourth ventricle

Apert syndrome

genetic disorder that includes craniosynostosis, midline facial hypoplasia, and syndactyly

Brachycephalic

head shape that is considered round or short and wide

What cerebral abnormality are atypical facial features most commonly associated with:

holoprosencephaly

The sonographic finding of a fluid filled cranium with absence of cerebral tissue is consistent with:

hydranencephaly

When is DWM suspected?

if the cerebellar vermis is absent and the fourth ventricle is enlarged

Hydranencephaly

is a fatal condition in which the entire cerebrum is replaced by a large sac containing CSF. The falx cerebri may be partially or completely absent, whereas the brain stem and basal ganglia are maintained and surrounded by CSF. Thalamus may be seen but there will be no cerebral cortex identified.

The cavum septum pellucidum (CSP)

is a midline brain structure located in the anterior portion of the brain between the frontal horns of the lateral ventricles. Appears as an anechoic "box shaped" structure in the axial scan plane. CSP does not communicate with the ventricular system and its absence is associated with multiple cerebral malformations, including agenesis of the corpus callosum.

Lateral ventricle measurement

measured in the transaxial plane at the level of the atrium of the lateral ventricle. the calipers are placed at the glomus of the choriod plexus. Normal measurement should not exceed more than 10mm.

A cisterna magna that measure 15mm and a normal appearing cerebellum is most likely:

mega cisterna magna

A normal shaped skull is called:

mesocephalic

What fetal suture is located within the frontal bone along the midline of the forehead?

metopic suture

Mesencephalon

midbrain. primary brain vesicle that eventually becomes the cerebral peduncles, quadrigeminal plate and cerebral aqueduct

Holoprosencephaly

midline brain anomaly that is associated with not only brain aberrations but also atypical facial structures. There are 3 types of holoprosencephaly: alobar, semilobar, and lobar. With holoprosencephaly, there will be evidence of a horseshoe-shaped monoventricle, and the lobes of the thalamus may be fused and echogenic in appearance.

mesocephalic

normal to medium sized skull

Biparietal diameter (BPD)

obtained in the axial plane at level of the CSP, thalamus and falx cerebri. this is the same level as the 3rd ventricle, which can be seen between the 2 lobes of the thalamus

Neural tube defects

occur when the embryonic neural tube fails to close. Among the list of tube defects are cephaloceles, various spinal dysraphisms, anencephaly and spina bifida. Studies have shown the a supplement of 0.4 mg of folate (folic acid) in a woman's diet significantly reduces the likelihood of her fetus developing a neural tube defect.

Foramen magnum

opening in the base of the cranium through which the spinal cord passes

Cyclopia

orbits are fused and contain a single eye. associated with holoprosencephaly

Rhombencephalon

primary vesicle of the embryonic brain also known as the hindbrain, eventually becomes the pons, cerebellum, and medulla

choriod plexus

produces CSF. located within the atria of the lateral ventricles

Cephalocele

protrusion of the brain from the cranial cavity. The most common location is in the occipital region.

hypotelorism

reduced distance between the orbits. associated with holoprosencephaly

"Banana sign"

refers to the shape of the cerebellum when a spinal defect is present (cerebellum is pulled downward into the foramen magnum)

Cisterna magna measurement

should not measure more than 10mm or less than 2mm in the Transcerebellar plane. Measurement of over 10mm is consistent with mega cisterna magna and dandy walker syndrome whereas measurement less than 2mm is worrisome for Arnold-Chiari II malformation.

A cloverleaf shaped skulls is related to

thanatophoric dysplasia

Colpocephaly

the abnormal lateral ventricle shape in which there is a small frontal horn and enlarged occipital horn

Transcerebellar measurement

the cerebellum grows at a rate of 1mm per week between 14 and 21 weeks, thus correlate agreeably with the gestational age of the fetus. i.e. at 16 weeks, the cerebellum should be approximately 16mm.

Agenesis of corpus callosum

the congenital absence of corpus callosum which may be partial or complete

Most common location for spinal bifida?

the distal lumbosacral region

cisterna magna

the largest cistern in the skull; located in the posterior portion of the skull

Aqueductal stenosis

the most common cause of hydrocephalus in utero. The cerebral aqueduct (aqueduct of Sylvius), located between the 3rd of 4rth ventricles of the brain may be narrowed, thus preventing the flow from the 3rd to the fourth ventricle. This obstruction level will cause the 3rd ventricle to expand, whereas the 4th ventricle remains normal.

Craniosynostosis

the premature fusing of the skull bones

cephalic index

the ratio used for assessing fetal head shape. BPD/OFD x 100. A cephalic index of less than 75 denotes a dolichocephalic shape, whereas an index of more than 85 denotes a brachiocephalic.

What chromosomal aberration is most often associated with holoprosencephaly?

trisomy 13

What can present in 50-70 % of fetuses diagnosed with holoprosencephaly?

trisomy 13 or Patau syndrome.

Strawberry shaped skull is commonly associated with:

trisomy 18

The choroid plexus cyst could be associated with an increase risk of

trisomy 18

Dangling choroid sign is associated with:

ventriculomegaly

Sonographic findings of ventriculomegaly

1. Atrium of the lateral ventricle measures >10mm 2. atrial measurement > 15mm is considered moderate to marked ventriculomegaly 3. dangling choroid sign 4. dilation of any part of the ventricular system

Sonographic findings of Aqueductal stenosis

1. Atrium of the lateral ventricle measures >10mm. 2. atrial measurement > 15mm is considered moderate to marked ventriculomegaly 3. dangling choroid sign 4. dilation of the lateral ventricles and the 3rd ventricle; the fourth ventricle remains normal

Sonographic findings of Schizencephaly

1. Fluid-filled clefts within the cerebrum 2. agenesis of the CSP and corpus callosum (50% of the time) 3. ventriculomegaly

Sonographic findings of agenesis of the corpus callosum and cavum septum pellucidum

1. Partial or complete absence of the corpus callosum and absence of the CSP (after 18 weeks) 2. "sunburst" sign- radial arrangement of the sulci which produces a "spoke wheel" pattern. 3. colpocephaly- small frontal horns and enlarged occipital horns (teardrop-shaped lateral ventricles) 4. elevated and dilated 3rd ventricle.

Sonographic appearance of a choroid cyst

1. anechoic, round, smooth walled cyst located within the choroid plexus of the lateral ventricle.

Clinical findings of vein of Galen aneurysm (neonatal)

1. congestive heart failure

Clinical findings of acrania/anencephaly

1. elevated MSAFP

Clinical findings of Arnold chiari II

1. elevated MSAP

Sonographic findings of Arnold chiari II malformation

1. lemon sign- lemon shaped cranium with flattened frontal bones 2. banana sign- banana shaped cerebellum 3. obliterated cisterna magna 4. colpocephaly 5. enlarged mass intermedia 6. hydrocephalus 7. open spinal defect

Sonographic findings of cephaloceles

1. open cranial defect (typically posterior in location) 2. small or obliterated cisterna magna 3. complex or simple appearing mass protruding from the cranium

Clinical findings of cephaloceles

1. possible elevation of MSAP

Sonographic findings of Acrania/anencephaly

1.Absent cranial vault 2.Some cerebral tissue may be present 3.Frog like facies/bulging eyes Fatal condition

Sonographic findings of vein of Galen aneurysm

1.Anechoic mass within midline of brain Contains turbulent arterial and venous flow when interrogated with pulsed doppler 2.Fetal hydrops 3.Cardiomegaly (caused by cardiac overload)

Sonographic findings of Dandy walker malformation

1.Enlargement of cisterna magna >10 mm in anteroposterior dimension 2.communication of the enlarged cisterna magna with a dilated fourth ventricle 3.agenesis of the cerebellar vermis 4.varying degrees of ventriculomegaly

Sonographic findings of mega cisterna magna

1.Enlargement of the cisterna magna >10mm in the anteroposterior dimension 2. normal cerebellum and fourth ventricle

Sonographic findings of alobar holoprosencephaly

1.Horse shoe shaped monoventricle 2.fused echogenic thalami 3.absence of cavum septum pellucidum, falx cerebri, interhemispheric fissure, corpus callosum and third ventricle, 4.normal cerebellum and brain stem

Sonographic findings of Lissencephaly

1.Lack of sulci/gyri within cerebrum

Sonographic findings of hydranencephaly

1.fluid filled cranium 2.absent or partial absence of falx cerebri 3.maintained brain stem, basal ganglia and perhaps the thalamus. 4. no identifiable cerebral cortex

Posterior fossa abnormalities and their sonographic findings

Mega cisterna magna: enlargement of the cisterna magna > 10mm in the anteroposterior dimension. Normal cerebellum Dandy walker malformation: enlargement of the cisterna magna > 10mm in the anteroposterior dimension. Absent cerebellar vermis, enlarged fourth ventricle Arnold chiari II malformation: obliterated cisterna magna, banana-shaped cerebellum, lemon shaped skull.

Types of cephaloceces

Meningocele: meninges only Encephalocele: brain tissue only Encephalomeningocele: both meninges and brain tissue Encephalomeningocystocele: meninges, brain tissue and lateral ventricle.

subarachnoid space

an area locate between the arachnoid membrane and the pia mater

Fetal cranial findings with TORCH infections

intracranial calcifications

Dandy-Walker malformation (DWM)

is a spectrum of posterior fossa abnormalities that involve the cystic dilation of the cisterna magna and fourth ventricle. Is is thought to be caused by a developmental abnormality in the roof of the fourth ventricle

Vein of Galen aneurysm

is an arteriovenous malformation that occurs within the fetal brain. it is associated with congestive heart failure in the newborn.

The ventricular system

is composed of 4 ventricles. whose primary function is to provide cushioning for the brain. Each ventricle is lined by a membrane called the ependyma.

Occipitofrontal diameter (OFD)

is obtained at the same level of the BPD and HC. For the OFD, one caliper is placed in the anterior midline in the middle of the frontal bone, whereas the other is placed in the middle of the echogenic line of the occipital bone.

The cerebrum

is the largest part of the brain. the normal cerebrum contains multiple sulci and gyri. There are six cerebral lobes; the frontal lobe, two temporal lobes, two parietal lobes and the occipital lobe. The cerebrum can be further divided into a right and left hemisphere by the interhemispheric fissure.

Following a intracranial hemorrhage, a cyst is noted within the cerebrum that communicates with the lateral ventricle. this is referred as:

porencephaly

Acrania

the absence of the cranial vault above the bony orbits. can be divided into 2 subtypes, anencephaly and exencephaly. Anencephaly is considered when there is no cerebral hemispheres present and exencephaly denotes a normal amount of cerebral tissue. Nonetheless, the cranium is absent, making this condition fatal.

Fetal skull

the skull consist of 8 cranial bones , these bones are connected by structures known as sutures. frontal lobe-location; anterior parietal bones- location; superior and lateral temporal bones-location; inferior and lateral occipital bone-location; posterior sphenoid bone-location; lateral ethmoid bone- anterior (between orbits)

Effects of fetal infections on the brain

the sonographic intracranial findings consistent with intrauterine infections are the calcifications around the ventricles and ventriculomegaly.

Meninges

three protective membranes that surround the brain and spinal cord. The innermost layer of the meninges is the pia matter, the middle layer is the arachnoid membrane and the dense, outermost layer is the dura mater.