Ch 59 Fetal Neural Axis Flashcards
Remnant brain with anencephaly is covered by a thick membrane called
Angiomatous stroma or cerebrovasculosa
_____ usually progresses to anencephaly as the brain slowly degenerates as a result of exposure to amniotic fluid
Acrania {may be a precursor to anencephaly}
Causes of anencephaly include
- Meckel - Gruber
- Chromosomal anomaly
- Increased risk with diabetes mellitus
- Enviromental & dietary factors
- Amniotic band syndrome
Neural tube defect in which the meninges alone or the meninges and brain herniated through a defect in the calvarium
Cephalocele
Herniation of meninges and brain through a calvarium defect
Encephalocele
Herniation of meninges ONLY
{has a 60% chance of normal mentation}
Cranial meningocele
What is the most common open neural tube defect?
Anencephaly
Complete/ partial absence of the forebrain; With the presence of the brain stem, midbrain, skull base, and facial structures. {Frog like appearance}
Anencephaly
Autosomal-recessive disorder characterized by encephalocele, polydactyly, polycystic kidneys
Meckel-Gruber Syndrome
Lack of closure of the vertebral column {a cleft or opening in the spine}
Spina Bifida
Spina bifida most commonly occurs in the ______ and ______ regions of the spine
Lumbar & Sacral
Open neural tube defect WITHOUT external abnormalities
{normal spinal cord, nerves, & normal neurologic developemnt} {spinal defect covered by skin or hair}
Spina bifida occulta
Open neural tube defect WITH external abnormalities and neurological complications
Spina bifida cystic or aperta
Most severe form of spina bifida
Spina bifida cystic or aperta
Only meninges through a defect
Meningocele
Meninges and neural elements through a defect
Meningomyelocele
Increased AFP with spina bifida {T/F}
TRUE
A congenital anomaly associated with spina bifida CYSTICA in which the cerebellum and brain stem are pulled down through the 4th ventricle, cisterns magna, and foramen magna into the cervical spinal cord; the cerebellum distorts to a “banana sign”
Arnold-Chiari Malformation
Most common form of Arnold-chiari malformation {this is the type seen in OB ultrasound}
Type II
Banana sign is associated with dilated ______ and______, and meningomyelocele
3rd & lateral ventricles & meningomyelocele
The banana shaped cerebellum is create by an obliterated _________
Cisterna magna
Lemon sign is associated with ______ and ______
Encephalocele & thanatophoric dysplasia
Abnormal development of the roof of the 4th ventricle which causes obstruction of the 4th ventricle outflow & cystic enlargement of the posterior fossa
Dandy walker malformation
Differential diagnosis of dandy walker malformation
arachnoid cyst
Sonographic appearance of _______ :
- large midline cystic structure in posterior fossa {dilated 4th ventricle}
- cerebral hemisphere might be splayed and flattened due to complete or partial absence of the vermis
- enlarged cisterna magna
- ventriculomegaly
- polyhydramnios
Dandy walker malformation
Most severe form of holoprosencephaly
Lobar holoprosencephaly
________- SMALL BRAIN
- single venticle
- incompletely fused thalami
- no midline brain structures
Semi lobar holoprosencephaly
mildest form of holoprosecephaly {rarely detected on ultrasound}
Lobar holoprosencephaly
Hypotelorism with flattened nose and a single nostril
Cebocephaly
Severe hypotelorism with proboscis
Ethmocephaly
Sonographic findings:
- C-shaped single ventricle
- Horseshoe shape brain tissue
- Fused thalami
- Absent falx, cavum septum pellucidum, corpus septum pellucidum, corpus callosum, optic tracts,olfactory bulb, & 3rd ventricle
Sonographic findings for holoprosencephaly
Broad transverse nerve track connecting the 2 cerebral hemispheres; thought to involve vascular disruption or inflammatory lesion before 12 weeks {sporadic condition}
agenesis of the corpus callousum
Sonographic findings:
- Absent cave septi pellucidum & corpus callosum
- Elevation and dilation of the 3rd ventricle
- Lateral ventricle displaced upward & outward
- dilated occipital horns {colpocephaly}
* ^ gives lateral ventricle a tear drop shape
agenesis of the corpus callousum
Results from stenosis, atresia, or obstruction of the aqueduct of sylvius which causes ventriculomegaly
Aqueduct stenosis
The aqueduct of sylvius connects the …..
3rd & 4th ventricles
Aqueduct stenosis may result from intrauterine infections such as…. {3}
- Cystomeglovirus
- Rubella
- Toxoplasmosis
Primary aqueduct stenosis is usually ___-linked
X-linked
Rare event demonstrating an enlarged vein communicating with a normal appearing artery {AV malformation}
Vein of Galen malformation
Vein of galen aneurysm {malformation} is usually isolated but has been associated with… {3}
- congenital hear defects
- cystic hygromas
- hydrops
Sonographic findings:
- Irregular shaped cystic space located midline and poster-superior to the 3rd ventricle
- turbulent flow with doppler evaluation
Vein of galen aneurysm
Represents the most common intracranial “abnormality” reported prenatally
Choroid plexus cyst
Choroid plexus cyst usually resolve by…
22-16 weeks
Choroid plexus cysts contain ____ and ____
cerebral spinal fluid & cellular debris
Large choroid plexus cysts { >1 cm} carry greater risk for an underlying chromosomal anomaly, especially ______
Trisomy 18 - edwards
RARE disorder characterized by clefts in the cerebral cortex
Schinzencephaly
This disorder is associated with congenital infections, drugs, and other toxic exposures, vascular accidents, and metabolic abnormalities
Schinzencephaly
Sonographic appearance:
- fluid-filled cleft in cerebral cortex extending from ventricle to calvarium
- ventriculomegaly
Schinzencephaly
What is the destruction of cerebral hemispheres by bilateral occlusion of the internal carotid arteries; the cerebral hemispheres are replaced by cerebral spinal fluid
Hydranencephaly
Sonographic findings:
- CSF, no normal brain tissue
- absent or partially absent falx
- presence of the midbrain, basal ganglia, & cerebellum
- possible identification of the choroid plexus & possible macrocephaly
Hydranencephaly
Ventriculomegaly is defined as lateral ventricular enlargement of ____
greater than 10 mm
Ventriculomegaly in the neonate with enlargement of the head
Hydrocephalus
is Anencephaly is more common in females or males? / Whites or blacks?
Females, Whites
{also more common in the UK}
Filly’s rules:
If the atrium of the lateral ventricle and the cisterna magna BOTH measure ______, there is a 95% negative predictive value for any central nervous system anomaly
Equal to or greater than 10 mm
