Chapter 59: The Fetal Neural Axis

Differential Diagnoses for cephalocele

-Cystic Hygroma -Anencephaly

Anything with opening is going to have elevated AFP -

-Spina bifida -Anencephaly -gastroschisis -omphalocele

cephaloceles occur at a rate of 1 to 3 in _______ births.

1 to 3 in 10,000

Filly's Rule -If the atrium of the lateral ventricle and cisterna magna both measure less than or equal to ____mm there is a ____% negative predictive value for ANY CNS anomaly

10, 95%

chromosomal anomalies and syndromes have been identified with cephaloceles, including trisomy ___ and ______ syndrome, which is autosomal recessive disorder characterized by _____, ______ and _____ kidneys

13, Meckel-Gruber, encephalocele, polydactyly, and polycystic kidneys, ABS

Microcephaly -Small head that falls ___ standard deviations below the mean -occurs due to _______ in size of brain -Commonly caused by an associated anomaly with a prognosis that is always _____ -Diagnosis usually made after ____weeks -Sonographic Findings -small ____ and ____ (other parameters are normal) -Decreased _____ & _____ ratios -Poor cranial growth on serial sonograms

2, reduction, poor, 24, BPD and HC, AC/HC, HC/FL

Dandy Walker Malformation -Abnormal development of the roof of the ___th ventricle -Causes obstruction of the __th ventricle outflow and cystic enlargement of posterior______ -Sonographic Appearance -Large midline cystic structure in posterior fossa -dilated ___th ventricle -Cerebellar hemispheres may be separated (splayed 1and flattened due to the complete or partial absence of the vermis -Enlarged ________ -Ventriculomegaly -Polyhydramnios -Differential Diagnosis -_________

4, 4, 4, fossa, cisterna magna, arachnoid cyst

Arnold Chiari Type II Malformation -Type ____ is the most common form and is the type seen in OB ultrasound -A congenital anomaly associated with spina bifida cystica in which the cerebellum and brain stem are pulled down through the ___th ventricle, _______, and foramen _____ into the cervical spinal canal. There cerebellum distorts to a "_________"

4th, cisterna magna, magna, Banana sign

Anencephaly is lethal and ____% results in fetal demise

50

cephaloceles involve the occipital bone and are located at the midline in _____% of cases

75

Vein of Galen Aneurysm -Rare event demonstrating an enlarged vein communicating with a normal appearing artery (___ malformation) -AKA vein of Galen Malformation -Considered _______ event with a male predominance -Usually isolated but has been associated with _______, _______ and _______ -Prognosis -poor especially when associated with ________ or _________ -good when it presents in older children or adults -Sonographic Appearance -irregular shaped _______ space located midline and ________ to the 3rd ventricle -_______- flow with Doppler evaluation

AV, sporadic, congenital heart defects, cystic hygromas and hydrops, hydrops or cardiac failure, cystic, posterosuperior, turbulent

(Anencephaly) Remnant brain is covered by a thick membrane called ______ or cerebrovasculosa

Angiomatous stroma

Sonographic Findings of holoprosencephaly -___-shaped single ventricle -brain tissue- ______ shape -fused _____ -absent falx, cavum septum pellucidum, corpus callosum, optic tracts, and olfactory bulbs and 3rd ventricle -Facial anomalies -______, ______, _____ -_________- hypotelorism with flattened nose and a single nostril -________- several hypotelorism with proboscis -Chromosomal anomaly -Trisomy ____ (more commonly), Trisomy _____ and triploidy

C, horseshoe, thalami hypotelorism, cyclopia, facial clefts, cebocephaly, ethmocephaly, 13, 18

Ventriculomegaly -Dilation of the fetal ventricular system -secondary to increased amounts of _____ -ventriculomegaly is defined as lateral ventricular enlargement greater than ____mm -Hydrocephalus -___________ in the neonate with enlargement of head -abnormal accumulation of _____ in cerebral ventricles -frequent destruction of ______ tissue -Mortality rate _____

CSF, 10, ventriculomegaly, CSF, brain, high

Porencephalic Cysts Porencephaly -Cysts filled with _____ -communicated with ventricular system or subarachnoid space -May result from ________, ________, _______ or _______ changes in the nervous system -The affect brain undergoes ________, brain tissue is reabsorbed and a cystic lesion remains -no known associated anomalies -Sonographic Findings -cyst in the brain without mass effect -communication with ventricular system or subarachnoid space -midline shift due to reduction of affected hemisphere and _________ ventricular enlargement -may be confused with ________ cysts, although lack of a mass effect with _________ may help differentiate

CSF, hemorrhage, infarction, delivery trauma, or inflammatory, necrosis, contralateral, arachnoid, porencephaly

Lemon Sign -_________- overlapping of the front bones creating a lemon shaped fetal head -Also associated with ______ and ______

Frontal bossing, encephalocele and thanatophoric dysplasia

Causes of neural tube defects including anencephaly are numerous and may result from a syndrome such as ________, _______ abnormality, such as trisomy ____ and _____. Risk in patients with diabetes ________, environmental and dietary factors another cause is ______

Meckel-Gruber, chromosomal, 13, 18, mellitus, ABS

Sonographic Findings of Arnold Chiari -Sagittal and Transverse Survey -Splaying of posterior ossification centers into a ____ or ____ shape which is abnormal -Presence of protruding sac like structure -________- (anechoic or cystic) -________ (contains neural elements) -Cleft in the skin -The level and extent of the defect, presence or absence of neural elements and associated intracranial findings should be documented -Cranial Findings -Lemon sign, flattening of the frontal bones, obliteration of the cisterna magna, inferior displacement of the cerebellar vermis, gives the cerebellum a rounded "banana shape", _______

U or V, meningocele, meningomyelocele, ventriculomegaly

Sonographic features of anencephaly include:

absence of the brain and cranial vault, Rudimentary brain tissue characterized as the cerebrovasculosa, bulging fetal orbits, giving the fetus a frog like appearance and poly

also known as exencephaly is a lethal anomaly that manifests as absence of the cranial bones, with the presence of complete, although abnormal, development of the cerebral hemispheres

acrania

condition associated with anencephaly in which there is complete or partial absence of the cranial bones with the presence of complete, although abnormal development of the cerebral hemispheres.

acrania

most severe form of holoprosencephaly characterized by a single common ventricle and malformed brain; orbital anomalies range from fused orbits to hypotelorism, with frequent nasal anomalies and clefting of the lip and palate

alobar holoprosencephaly

sonographic features of cephaloceles include the following:

an extracranial mass, which may be fluid-filled or contain solid components a bony defect in the skull ventriculomegaly, which is more commonly identified with an encephalocele poly

acrania may be confused with

anencephaly

acrania usually progresses to ______ as the brain slowly degenerates as a result of exposure to amniotic fluid

anencephaly

neural tube defect characterized by lack of development of the cerebral and cerebellar hemispheres and cranial vault; this abnormality is incompatible with life

anencephaly

most common neural tube defect with an overall incidence of 1 in _____ pregnancies in the U.S. The incidence varies with geographic location, with a much higher prevalence in the _______. The incidence also varies with gender and race, with a female prevalence of ___ to ____ over males, and a prevalence of white over black of ___ to ___

anencephaly, 1000, United kingdom, 4-1, 6-1

means absence of the brain, is caused by failure of closure of the neural tube at the cranial end the result consists of absence of the cranial vault, complete or partial absence of the forebrain, which may partially develop and then degenerate, and presence of the brain _____, ______ skull ______ and facial ____.

anencephaly, stem, midbrain, base, structures

an abnormality or congenital malformation

anomaly

Hydranencephaly -Destruction of cerebral hemispheres by bilateral occlusion of the internal ________ arteries -total or near total absence of ______hemispheres -replaced by ________ fluid -Sonographic Findings -CSF no normal brain tissue -absent or partially absent ______ -presence of the ______, basal _____, and ______ -possible identification of the _____ and possible ________

carotid, cerebral. CSF, falx, midbrain, ganglia, cerebellum, choroid plexus, macrocephaly

form of holoprosencephaly characterized by a common ventricle, hypotelorism, and a nose with a single nostril

cebocephaly

neural tube defect in which the meninges alone or the meninges and brain herniate through a defect in the calvarium. ______ is the term used to describe herniation of the meninges and brain through the defect, _____ describes the herniation of only meninges.

cephalocele, encephalocele, cranial meningocele

Banana Sign -banana shaped ______ created by an obliterated cisterna _____ -associated with dilated ___rd and lateral ventricles, _________

cerebellum, magna, 3rd, meningomyelocele

Agenesis of the Corpus Callosum -Fibrous tract that connects the ______ -aids in learning and memory -Thought to involve vascular disruption or inflammatory lesion before 12 weeks -sporadic -Sonographic Findings -absent _____ and _____ -elevation and dilation of the __rd ventricle -lateral ventricles displaced upward and outward -dilated ______ horns (colpocephaly) -giving lateral ventricles a ______shape

cerebral hemispheres, cavum septum pellucidum, corpus callosum, 3, occipital, teardrop shape

Schizencephaly -Rare disorder characterized by _____ in cerebral cortex -Unilateral or bilateral -Associated with _______ infections, _____, and other _____ exposures, _______ accidents, and ______ abnormalities -Sonography Findings -fluid filled ______ in cerebral cortex extending from _______ to _______ -Ventriculomegaly

clefts, congenital, drugs, toxic, vascular, metabolic, cleft, ventricle, calvarium

severe form of holoprosencephaly characterized by a common ventricle, fusion of the orbits with one or two eyes present, and a proboscis (maldeveloped cylindrical nose)

cyclopia

an increase in size of the jugular lymphatic sacs caused by abnormal development

cystic hygroma

Sonographic Findings of Ventriculomegaly -Normal ventricular configuration just ______; compression and frequent destruction of brain tissue -Presence of excess fluid in lateral ventricles measuring greater than ____mm -Dangling________ -Enlarged head circumference for gestation age -Possible dilation of the __rd and ___th ventricles -Frontal _____

dilated, 10, choroid plexus, 3, 4, bossing

Holoprosencephaly -Incomplete cleavage of the ________ -_______ holoprosencephaly- most severe -midfacial abnormalities, _______ -large single ventricle -fused ______ -no midline brain structures -frequent nasal anomalies and ______ and palate -Associated with Trisomy _____ -Semilobar holoprosencephaly- small brain -single ventricle -incompletely fused ______ -no midline brain structures -Lobar holoprosencephaly- _______ form -rarely detected on ultrasound

forebrain, alobar, hypotelorism, thalami, cleft lip and palate, 13, thalami, mildest

a range of abnormalities from abnormal cleavage of the forebrain

holoprosencephaly

congenital absence of the cerebral hemispheres caused by an occlusion of the carotid arteries; midbrain structures are present, and fluid replaces cerebral tissue

hydranencephaly

ventriculomegaly in the neonate; abnormal accumulation of cerebrospinal fluid within the cerebral ventricles, resulting in compression and frequently in destruction of brain tissue

hydrocephalus

Choroid Plexus Cysts -Represent the most common _________abnormality reported prenatally -Round or ovoid cysts within ________ -contains CSF and cellular debris -Usually isolated finding -usually resolve by ______weeks -Sonographic Findings -generally small, range from _____cm in size -unilateral or bilateral, solitary or multiple -ventricular enlargement with large cysts -larges cysts greater than ____cm carry a greater risk of an underlying chromosomal anomaly, especially trisomy _____

intracranial, choroid plexus, 22-26, 0.3-2cm, 1cm, 18

Inencephaly -A rare lethal anomaly of the cranial development -Characterized by -exaggerated spinal ______ -Cervical ______ (defect in the occiput) -Occipital _______ -Sonographic Appearance -exaggerated, hyperextension of the fetal _____ -demonstration of cervical ______

lordosis, rachischisis, encephalocele, head, spina bifida

enlargement of the fetal cranium as a result of ventriculomegaly

macrocephaly

open spinal defect characterized by protrusion of the spinal meninges

meningocele

open spinal defect characterized by protrusion of meninges and spinal cord through the defect, usually within a meningeal sac

meningomyelocele

the bilobed brain in acrania is best identified in first trimester and is describe as ______ appearance

mickey mouse

other defects that may mimic anencephaly

microcephaly, acrania, cephalocele, ABS

coexisting anomalies include:

microcephaly, agenesis of the corpus callosum, facial clefts, spina bifida, cardiac anomalies, and genital anomalies

Etiology associated with Ventriculomegaly -usually ________ -Commonly associated with: (6 things) -communicating hydrocephalus -dilation of all ventricles caused by obstruction to ______ flow outside the ventricular system -Noncommunicating Hydrocephalus -obstruction within the _________ system -Idiopathic -cause _______

multifactorial -aqueductal stenosis -meningomyelocele -spina bifida -encephalocele -Dandy Walker -agenesis of the corpus callosum -holoprosencephaly CSF ventricular unknown

-Spina Bifida cystica or aperta -severe form -open defect with external abnormalities and ______ complications -__________- only meninges through defect -__________- meninges and neural elements -________- large and severe -elevated _____

neurological, meningocele, meningomyelocele, rachischisis, AFP

Additional anomalies to anencephaly include:

poly, spina bifida, cleft lip and palate, hydronephrosis, diaphragmatic hernia, cardiac defects, omphalocele, GI defects and talipes

sonographic findings of acrania

presence of brain tissue without presence of a calvarium, disorganization of brain tissue, prominent sucal markings

neural tube defect of the spine in which the dorsal vertebrae (vertebral arches) fail to fuse together, allowing the protrusion of meninges and/or spinal cord through the defect; two types exist: spina bifida occulta (skin-covered defect of the spine without protrusion of meninges or cord) and spina bifida cystica (open spinal defect marked by sac containing protruding meninges and/or cord)

spina bifida

closed defect of the spine without protrusion of meninges or spinal cord; alpha-fetoprotein analysis will not detect these lesions

spina bifida occulta

open defect without external abnormalities -normal spinal cord, nerves and normal neurologic development -spinal defect covered by ______ or _____ -difficult to detect _________ (normal AFP)

spina bifida occulta. skin or hair, antenatally

coexisting of ____ and _____ may be identified in fetuses with anencephaly

spina bifida, craniorachischisis

Lack of closure of the vertebral column - a cleft or opening in the spine ______ and neural elements may protrude through defect -Most commonly occurs in the _____ and _____ regions -Vary in ____ and severity according to type, size and location - means that there is a _____ or opening in the spine

spina bifida, meninges, sacral and lumbar, size, cleft

abnormal accumulation of cerebrospinal fluid within the cerebral ventricles resulting in dilatation of the ventricles; compression of developing brain tissue and brain damage may result; commonly associated with additional fetal anomalies

ventriculomegaly

Aqueductal Stenosis -Results from stenosis, atresia or obstruction of the aqueduct of sylvius -causes __________ -The aqueduct of sylvius connects the __rd and ___th ventricles -May result from intrauterine infections -_______, _______, _______ -Primary aqueductal stenosis is usually x linked and has a poor prognosis -Sonographic findings -enlargement of the _____ and ___rd ventricles -______ and ______ of the thumb (seen in the x-linked form)

ventriculomegaly, 3, 4, cytomegalovirus, rubella and toxoplasmosis, lateral and 3rd ventricles, Flexion and adduction