OB CHP. 24
The cerebellum grows at a rate of what per week between what weeks?
1 mm per week between 14 and 21 weeks
The normal lateral ventricle does not typically measure more than what at the level of the atrium?
10 mm
The biparietal diameter measurement is typically done when?
13 and 14 weeks
The corpus callosum forms late in gestation but should be completely intact between when?
18 and 20 weeks
The fourth ventricle has how many apertures?
3
The ventricular system is composed of how many ventricles? What is the function?
4, provide cushioning for the brain
By what week does the neural plate develop?
4.5 weeks
The skull consists of how many cranial bones?
8
The corpus callosum functionally provides what?
A pathway for communication between the hemispheres and is completely formed by 18 weeks
What are the sonography findings of acrania / anencephaly?
Absent cranial Vault, some cerebro tissue may be present, frog like faces or bulging eyes
What is the most severe form of holoprosencephaly?
Alobar
What are the three main types of holoprosencephaly?
Alobar, semilobar, lobar
How does the cave of septum pellucidum appear?
Anechoic box shaped structure in the axial scan plane
What are the sonography findings of choroid plexus cyst?
Anechoic round smooth walled cyst located within the choroid plexus of the lateral ventricle
The most severe form of holoprosencephaly
Anencephaly
Acrania can be further divided into what two subtypes?
Anencephaly and exencephaly
What are the most common neural tube defects?
Anencephaly and spina bifida
The absence of the eyes
Anophthalmia
cavum septum pellucidum can be identified where?
Anterior portion of the brain between the frontal horns of the lateral ventricles
The fourth ventricle is located where?
Anterior to the cerebellum within the midline of the brain
The abnormal narrowing of the cerebral aqueduct
Aqueduct stenosis
Benign cyst within the brain that do not communicate with the ventricular system
Arachnoid cyst
Arachnoid Villi AKA?
Arachnoid granulations
Nodular structures located along the falx cerebri that reabsorb cerebrospinal fluid into the venous system
Arachnoid granulations
What are responsible for the reabsorption of CSF into the venous system?
Arachnoid granulations AKA arachnoid villi
The middle layer of the meninges
Arachnoid membrane
A group of cranial abnormalities associated with spina bifida
Arnold Chiari 2 malformation
For lateral ventricle measurement where are the calipers placed?
At the level of the glomus of the choroid plexus
What is the formula used to calculate the cephalic index?
BPD /OFD x 100
A group of nuclei within the brain that function in several ways including information processing and emotional response
Basal ganglia
Where are the locations of coronal suture, sagittal suture, lambdoidal suture, squamosal suture, metopic suture?
Between the frontal and two parietal bones, between the two parietal bones, between the parietal bones and occipital bones, between the parietal bones and temporal bones, located within the frontal bone along the midline of the forehead
What could be the causes of hydranencephaly?
Bilateral occlusion of the internal carotid arteries with subsequent destruction of cerebral hemispheres
Where is the location and when does the closure of the following frontanelle: Anterior or frontal, posterior or occipital, anterolateral or sphenoidal, posterolateral or mastoid
Bordered by frontal and parietal bones by 18 months, bordered by occipital and parietal Bones by 6 months, bordered by frontal parietal and sphenoid Bones by 2 years, bordered by mastoid and occipital bones by 2 years
Where are the paired lateral ventricles located?
Both sides of the falx cerebri within the cerebal hemispheres
Where are the two lobes of the thalamus located?
Both sides of the third ventricle
The lower part of the brain composed of the pons, midbrain, medulla oblongata
Brain stem
Encephalocele will have what content of the mass?
Brain tissue only
The anterior fontanelle when completely filled with bone is referred to as what?
Bregma
Close-set eyes hypothyroidism and a nose with a single nostril
Cebocephaly
The ratio used for assessing fetal head shape
Cephalic index
What are protrusions of the inter-cranial contents through a defect in the skull?
Cephalocele
The portion of the cerebellum located within the midline of the brain that connects it's two hemispheres
Cerebellar vermis
The duct that connects the third ventricle of the brain to the fourth ventricle AKA Aqueduct of sylvius
Cerebral aqueduct
Paired structures located anterior to the cerebral aqueduct
Cerebral peduncles
The protective and nourishing fluid of the brain and spinal cord produced by the cells of the choroid plexus
Cerebrospinal fluid
The brain can be divided into what two parts?
Cerebrum and cerebellum
Specialized cells within the ventricular system responsible for cerebrospinal fluid production
Choroid plexus
A prominent space within the skull that contains cerebrospinal fluid, a cistern is created by the separation of the arachnoid membrane and Pia Mater
Cistern
What is the largest cistern in the head? How does it appear sonography?
Cisterna magna, anechoic fluid-filled space posterior to the cerebellum between the cerebellar vermis and the interior surface of the occipital bone may have septations
the abnormal lateral ventricle shape in which there is a small frontal horn and enlarged occipital horn
Colpocephaly
What are the two main types of hydrocephalus?
Communicating and noncommunicating
The obstruction of cerebrospinal fluid from a source outside of the ventricular system
Communicating hydrocephalus
A thick band of white matter that provides communication between right and left halves of the brain
Corpus callosum
Dolichocephaly head shape is associated with what anomaly?
Craniosynostosis
The premature close of the cranial sutures with subsequent Fusion of the cranial bones
Craniosynostosis
Brachycephaly head shape is associated with what anomaly?
Craniosynostosis, trisomy 21, 18
Fusion of the orbits
Cyclopia
A spectrum of posterior fossa abnormalities that involve the cystic dilation of the cisterna magna and fourth ventricle
Dandy-Walker complex
Congenital brain malformation in which there is an enlargement of the cisterna magna, agenesis of cerebellar vermis and dilation of fourth ventricle
Dandy-Walker malformation
A sonographic sign associated with hydrocephalus when the choroid plexus is noted hanging freely within the dilated lateral ventricle
Dangling choroid sign
What is the prognosis of hydranencephaly?
Death usually in the first year of life
What is the most common location of spina bifida?
Distal lumbosacral region
With a cephalic index of less than 75 it denotes what? More than 85 denotes what?
Dolichocephalic shape, brachialcephalic shape
Scaphocephaly AKA?
Dolichocephaly
An elongated narrow head shape AKA scaphocephaly
Doliochocephaly
A form of acrania and which the entire cerebrum is located outside of the skull
Exencephaly
A double fold of dura mater located within the midline of the brain
Falx cerebri
What are the sonography findings of hydranencephaly?
Fluid-filled Cranium, absent or partial absence of falx cerebri, maintained brainstem and basal ganglia, no identifiable cerebal cortex
A vitamin that has been shown to significantly reduce the likelihood of neural tube defects AKA folic acid
Folate
The opening in the base of the skull through which the spinal cord exits
Foramen magnum
What are the several notable changes that occur with spina bifida in the brain and skull?
Frontal bones become flattened and will yield a lemon shape, cerebellum will become displaced inferiorly and posteriorly and appear curved in a presents like banana sign, the cisterna magna is completely obliterated, lateral ventricles distorted, frontal horns will be small in slit like
What are the six cerebral lobes?
Frontal lobe, two temporal lobes, two parietal lobes, occipital lobe
Each lateral ventricle consist of what?
Frontal, temporal, occipital horn
Herniation of abdominal contents through a right-sided Periumbilical abdominal abdominal wall defect
Gastroschisis
A group of thin-walled blood vessels and cells within the subependymal layer of the fetus brain responsible for brain cell migration during fetal development
Germinal Matrix
The largest part of the choroid plexus
Glomus
What are the bilateral brain structures?
Hemispheres of cerebellum and cerebrum, lobes of the thalamus, Foreman of Monroe, lateral ventricles, choroid plexus
A group of brain abnormalities consisting of varying degrees of fusion of the lateral ventricles absence of the midline structures and Associated facial anomalies
Holoprosencephaly
Name the midline brain anatomy
Hulk cerebri, interhemispheric fissure, corpus callosum, cavum septum pellucidum, third ventricle, Aqueduct of sylvius, fourth ventricle, cerebellar vermis, cisterna magna, interthalamic adhesion
A fatal condition in which the entire cerebrum is replaced by a large sac containing cerebrospinal fluid
Hydranencephaly
An abnormal accumulation of fluid in at least two fetal body cavities
Hydrops
How do fetal sutures appear sonographically?
Hypoechoic spaces between the bone
Incomplete growth of a structure or organ
Hypoplasia
Reduced distance between the orbits
Hypotelorism
A shortage of oxygen or decreased oxygen in the blood
Hypoxia
Groove within the midline of the brain that divides the two cerebral hemispheres
Interhemispheric fissure
The falx cerebri is located within where?
Interhemispheric fissure
The mass of tissue located in the third ventricle within the midline of the brain which connects the two lobes of the thalamus AKA Massa intermedia
Interthalamic adhesion
The posterior fontanelle is referred to as what when completely filled with bone?
Lambda
Flow of CSF through ventricles
Lateral ventricles -> interventricular foramen -> third ventricle -> aqueduct of the midbrain -> fourth ventricle -> lateral apertures (Lushka) or median aperture (Magendie) -> subarachnoid space of brain and spinal cord
What are the sonographic findings of Arnold Chiari malformation?
Lemon sign, banana son, obliteration cisterna magna, Colpocephaly, enlarged Massa intermedia, hydrocephalus, open spinal defect
An enlarged head circumference
Macrocephaly
what is the most common risk factor for fetal intrauterine intracranial hemorrhage?
Maternal platelet disorders
A subdivision within the midline of the lip
Medial cleft lip
Measurement more than 10 mm of the cisterna magna is consistent with what? Less than 2 millimeters is worrisome for what?
Mega cisterna magna and Dandy-Walker complex,, Arnold Chiari 2 malformation
The coverings of the brain and spinal cord
Meninges
Meningocele will have what content of the mass?
Meninges only
Meninges herniation of the cranial or spinal meninges due to an open cranial or spinal defect
Meningocele
Meningocele the primary brain vesicle AKA midbrain, becomes the cerebral peduncles,quadrigeminal plate and cerebral aqueduct
Mesencephalon
Normal head shape
Mesocephalic
Small head
Microcephaly
Doppler of what artery has been shown effective at evaluating for hypoxia?
Middle cerebral artery
The early embryologic structure that develops into the central nervous system
Neural plate
Embryologic formation that results from the fusion of the two folded ends of the neural plate
Neural tube
Neural tube defects occur when what?
Neural tube fails to close
The neural plate will give rise to what?
Neural tube which will become the spine and brain
When is anencephaly considered?
No cerebral hemispheres present
The obstruction of cerebrospinal fluid from a source within the ventricular system
Non communicating hydrocephalus
When is exencephaly considered?
Normal amount of cerebral tissue
Arnold Chiari 2 malformation will have a sonographic finding of what as this is a posterior fossa abnormality?
Obliterated cisterna magna, banana shaped cerebellum, lemon shape skull
The most common location for a cephalocele is where?
Occipital region
Head circumference can be obtained by measuring the what diameter?
Occipitofrontal diameter
And anterior abdominal wall defect where there is a herniation of the fetal bowel and other abdominal organ into the base of the umbilical cord
Omphalocele
What are the sonography findings of cephalocele?
Open cranial defect, small or obliterated cisterna magna, complex Mass protruding from the cranium
The functional part of an organ
Parenchyma
What are the sonographic findings of agenesis of the corpus callosum and cavum septum pellucidum?
Partial or complete absence of the corpus callosum and absence of the cavum septum pellucidum after 18 weeks, Sunburst sign radial arrangement of the sulci, Colpocephaly small frontal horns and a large occipital horns, elevated and dilated third ventricle
A chromosomal aberration in which there is a third chromosome 13 AKA Trisomy 13
Patau syndrome
The innermost layer of meninges
Pia Mater
The primary brain vesicle AKA for brain becomes the lateral ventricles, cerebral hemispheres, third ventricle, thalamus, hypothalamus , pineal gland, pituitary gland
Prosencephalon
Initially the brain is separated into what three primary vesicles?
Prosencephalon, mesencephalon, rhombencephalon
The primary vein bicycle AKA hindbrain becomes the cerebellum, pons, medulla oblongata, fourth ventricle
Rhombencephalon
The cerebrum can be further divided into what?
Right and left hemisphere
A group of neural tube defects that describe some manifestation of incomplete closure of the spine
Spinal dysraphism
The normal cerebrum contains multiple what?
Sulci and gyri
The most common intracranial tumor found in utero is what?
Teratoma
a brain structure that allows communication between the senses as well as performing many other functions
Thalamus
The most common lethal skeletal dysplasia characterized by a Cloverleaf skull with frontal bossing and hydrocephalus
Thanatophoric dysplasia
The point at which the body, temporal horn, occipital horn meet is called what?
Trigon or atrium of the lateral ventricle
Chromosomal aberration in which there is a third chromosome 13 AKA patau syndrome often associated with holoprosencephaly
Trisomy 13
Choroid plexus cysts are associated with a risk of what?
Trisomy 18
Chromosomal aberration in which there is a third chromosome 21 AKA Down syndrome
Trisomy 21
The cerebellum consists of how many hemispheres? Where are they located? What do they look like?
Two hemispheres, right and left, located under surface of cerebellum is the cerebellar tonsils, normal shape is dumbbell shape or Figure 8
the structure located between the two lobes of the cerebellum is the:
a. cerebellar vermis
the interthalamic adhesion (massa intermedia) passes through the:
a. third ventricle
dangling choroid sign is associated with:
a. ventriculormegaly
a lemon-shaped skull is related to:
b. Arnold-Chiari II malformation
which of the following will also typically be absent with agenesis of the corpus callosum? a. cerebellar vermis b. CSP (cavum septum pellucidum) c. third ventricle d. fourth ventricle
b. CSP
the "sunburst" of the cerebral sulci is a sonographic finding of:
b. agenesis of the corpus callosum
the most severe form of holoprosencephaly is:
b. alobar
the band of tissue that allows communication between the right and left cerebral hemispheres is the:
b. corpus callosum
which of the following should not be included in the correct level for an HC measurement? a. falx cerebri b. fourth ventricle c. thalamus d. CSP
b. fourth ventricle
which of the following would not be normally located within the midline of the fetal brain? a. CSP b. lobes of the thalamus c. third ventricle d. falx cerebri
b. lobes of the thalamus
Round skull shape
brachycephaly
absence of the skull is:
c. acrania
the fourth ventricle is located:
c. anterior to the cerebellar vermis
the third ventricle is located: a. anterior to the thalamus b. anterior to the cerebellar vermis c. between the two lobes of the thalamus d. superior to the corpus callosum
c. between the two lobes of the thalamus
enlargement of the frontal horns and narrowing of the occipital horns is termed:
c. colpocephaly
which of the following is located on both sides of the midline? a. interhemispheric fissures b. third and fourth ventricles c. lateral ventricles d. third ventricle and cerebral aqueduct
c. lateral ventricles
a cisterna magna that measures 15mm and a normal appearing cerebellum is most likely:
c. mega cisterna magna
a normal shaped skull is termed:
c. mesocephaly
what chromosomal aberration is most often associated with holoprosencephaly?
c. trisomy 13
a strawberry-shaped skull is commonly associated with:
c. trisomy 18
A normal midline brain structure identified in the anterior portion of the brain between the frontal horns of the lateral ventricles
cavum septum pellucidum
the anechoic midline brain structure located between the frontal horns of the lateral ventricles is the:
cavum septum pellucidum
the ______ is the largest part of the brain
cerebrum
the largest cistern in the skull; located in the posterior portion of the skull
cisterna magna
the cerebellum is measured in transverse at the same level as the
cisterna magna and thalamus
the cisterna magna should not exceed ______ in the transcerebellar plane
d. 10mm
the third ventricle communicates with the fourth ventricle at the:
d. aqueduct of Sylvius
the double fold of dura mater that divides the cerebral hemispheres is the:
d. falx cerebri
what fetal suture is located within the frontal bone along the midline of the forehead?
d. metopic suture
all of the following are sonographic findings of Arnold-Chiari II malformation except: a. enlarged massa intermedia b. hydrocephalus c. obliteration of the cisterna magna d. strawberry sign
d. strawberry sign
a cloverleaf-shaped skull is related to:
d. thanatophoric dysplasia
the choroid plexus cyst could be associated with an increased risk of:
d. trisomy 18
cranial bones:
ethmoid, frontal, occipital, parietal, sphenoid, and temporal
biparietal diameter (BPD)
fetal transverse cranial diameter at the level of the thalamus and cavum septum pellucidum
BPD is measured from
outer and inner
the cerebellum is located in the ______ ______ of the cranium
posterior fossa
Initially the brain is separated into three primary vesicles termed the
prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain)
BPD and HC are taken at the level of the
thalami and cave septum pellucidum and third ventricle
the ______ ventricle runs straight through the thalamus
third