Module 5 : Fetal Neuro Pathology Flashcards
What produces CSF
Choroid plexus
Where are the choroid plexus located
- body of lat ventricle
- roof of third vent
- superior lateral walls of fourth vent
Flow of CSF through the brain
Choroid plexus»_space; lat vents»_space; interventricular foramen»_space; 3rd vent»_space; cerebral aqueduct»_space; fourth vent»_space; megendie ( spinal cord) and Lushka ( brain)
landmarks for lateral ventricle measurement
- CSP
- antrum of ventricle
- V of the ambient cistern
- parietal-occiptal fissure
Normal fourth vent location
- anterior and inferior edge of cerebellum
Hydrocephalus
- increase in CSF that results in enlargement of ventricular system
- usually due to obstruction along the pathway to CSF
- MOST COMMON CRANIAL ANOMALY
two causes of hydrocephalus
- true hydrocephalus \+ CSF obstruction - ventriculomegaly \+ resulting from brain atrophy \+ small brain, ventricles have space to enlarge into
three causes of true hydrocephalus
- neural tube defect NTD
- aquaductal stenosis
- dandy walker malformation
Intraventricular obstruction hydrocephalus - aqueduct stenosis
- csf can’t flow from 3rd vent to 4th vent
- lat and 3rd bent enlarged but 4th vent normal
Extraventricular obstruction hydrocephalus - spine bifida
- CSF can’t flow normally through the spinal canal and back up in ventricle of brain
- ALL ventricles effects s
Extraventricukar obstruction hydrocephalus - excess CSF
- less common
- excess secretion from a choroid plexus papilloma (tumor)
Evaluating ventricular size
- measure ATRIAL diameter \+ size doesn’t change much 15 - 35 \+ normal size 7mm \+ 10 mm upper limit of normal - < 3mm from medial vent wall to choroid
Dangling choroid
- always rests in a gravitationally dependent position
- sign of hydrocephalus
Where to look when hydrocephalus is suspected
- additional anomalies tend to occur with hydrocephalus
- posterior fossa views
+ cisterna magna and cerebellum
= obliterated cisterna magna
= deformed cerebellum (banana)
= lemon sign
Banana sign
- indicates obliterated cisterna magna
- often ARNOLD CHIARI
Lemon sign
- resulting when cranial contents are pulled toward spine with Arnold Chiari II malformation
+ associated with spina bifida - frontal bones caved in
- seen in second trimester
- lemon sign disappears in 3rd trimester due to resulting in hydrocephalus from enlarging ventricles of blocked CSF
Dandy walker malformation DWM
- enlarged cisterna magna and defect in the cerebellar VERMIS
- the cisterna magna communicates with the 4th vent through a defect in cerebellum
- ventricles can be enlarged due to pressure in the post fossa
Dandy walker variant
- partial agenisis of the vermis with a smaller cisterna magna and minimal dilation of the ventricles
- associated with many syndromes
DWM associated with
- intellectual impairment and fetal steam
- AGENISIS OF CORPUS CALLOSUM
- heart defects
- genitourinary
- polydactyly
- increase risk
+ maternal viral infection
+ alcohol consumption
+ maternal diabetes
Assessing DWM
- cisterna magna > 1cm abnormal
- cerebellar view must include
+ caveman septi pellucidi
+ peduncles
+ cerebellum - measure
What to prove for DWM
- cisterna magna communicates with 4th vent
- cerebbellaR VERMIS absent or partially absent
- enlarged ventricles
- DDx = arachnoid cyst in posterior fossa
when does the corpus callous begin and finish developing
- starts 12 weeks ends at 20 weeks
development of corpus callous
- anterior to posterior
absence of corpus callosum extent and cause
- complete or partial
- developmental or acquired
developmental absence of corpus callosum cause
- interruption in the formation
acquired absence of corpus callosum cause
- insults cause secondary atrophy of previous developed parts
absence of corpus callosum associated with what
- may be isolated
- CNS abnormalites
+ gyro dysplasia (smooth brain)
+ DWM - also associated with anomalies of the face limbs and genitourinary system
sonography of agenisis of corpus callosum ACC
- ABSENCE OF CSP
- enlargement of occipital horns only
6 steps to take if ACC suspected
- profile image
- image top of head in sagitall plane
- CC should be visualized in this plane
- hypo echoic structure that sits superior to CSP
- if CSP is absent the 3rd ventricle will be elevated or high riding in the head
- try EV if fetal head is low in pelvis
prognosis of ACC
- if isolated and partial may not effect function at all
- severity of deceased intellect depends on associated CNS abnormalities
Choroid plexus cysts CPC
- cysts in choroid plexus
- usually disappear in 2nd trimester
- associated with trisomy 18
+ 1 / 200 are associate with T18 - HAVE TO BE > 3MM
Acrania
- absent skull / cal aria
Anencephaly
- no or distorted cerebral cortex
Exenceohaly
- some cerebral cortex but abnormal
- early stage of anencephaly
- brain tissue exposed to amniotic fluid gets damages
- brain tissue in beginning (excencephaly) then by time fetus is imaged there is minimal tissue left so diagnosed anencephaly
Sonographic features of anencephaly
- facial structures present and orbits
- no calvaria (skull) above orbits
- image through face would resemble a frog
- polyhydroamnios (no swallowing)
- very active fetus
- can not be reliable diagnoses before 12-13 weeks
ddx for anencephaly
- amniotic band syndrome \+ look for other amputation \+ waving membrane \+ fetus stuck to side wall - large encephalocele \+ look for any sign of cranial bones
hydranencephaly
- variable absence of cerebrum
+ destruction of brain tissue - intact cranial vault and meninges
- most sever form of porencephaly
what causes hydranenchephaly
- occlusion of ICA
- infection r hemorrhage
- destruction and resorption of brain matter
sonography of hydranenchaply
- intact thalami with are never fused and brain stem
- may or may not have intact falx cerebri
- irregular brain matter at periphery
DDX of hydranencephaly
- sever hydrocephalus
+ smooth along periphery of cranium - alobar holoprosencephaly
+ would have fused thalami
prognosis of hydranencephaly
- fatal
Arachnoid cysts in post fossa
- fluid collections in the layers of teh arachnoid membrane
- cysts can occur anywhere in the brain
when do porencephalic cysts occur
- occurs when brain tissue is destroyed by hemorrhage or an infarct
what does porencephalic look like on ultrasound
- destroyed brain tissue becomes cystic
- usually along the periventricular halo
+ close to lateral ventricles - may or may not communicate with the ventricles
DDX of porenchepalic cysts
- dandy walker malformation
- arachnoid cyst
- hydrocephaly if it communicates
prognosis of porenchepalic cysts
- depends on degree of brain destruction
DDX of arachnoid cysts
- dandy walker variant if in posterior fossa
- porenchephalic cysts
prognosis of arachnoid cysts
- is good as long as cyst does not destroy too much brain tissue or block ventricles
what is encephalocele
- herniation of inter cranial structures through a defect in the cranium
what is contained in an encephalocele
- may contain only meninges
- or with brain tissue also
where do most encephaloceles occur
- midline occiput
- but can be anywhere if in nasal area difficult to see
what lab value will be increased with an encephalocele
- AFP
common syndromes associated with encephalocele
- isolated
- meckel-gruber syndrome
what is meckel - Gruber syndrome and what are 3 signs of it
- autosomal recessive lethal condition
- encephalocele
- cystic renal dysplasia (large echogenic kidneys)
- polydactyly
sonography of encephalocele - if only meninges protruding
- cystic structures within membrane
- cranial defect present
sonography of encephalocele - if brain is protruding
- encapsulated echogenic mass with cystic areas
- cranial defect present
what other brain anomaly will occur with encephalocele
- hydrocephalus due to CSF blockage
DDX of encephalocele
- cystic hygroma
+ should see septations in cystic area with hygromas - teratoma
prognosis of encephalocele
- depends
+ size of defect
+ amount of brain tissue involved
+ whether or not it is associated with meckel-gruber syndrome
what is schizencepahly
- symmetrical clefts in the parietal and temporal lobes that extend from the ventricles to the cortical surface
- brain is split into anterior and posterior segments of the brain
what is lissencephaly
- smooth brain
- ## no sulci or gyri due to abnormal migration of neutrons from the germinal matrix
in what trimester is diagnosis of lissencephaly possible
- third trimester
what is microcephaly and when in the pregnancy is it seen
- disproportionally small head compared to gestational age and abdominal circumference
- late pregnancy
how many standard deviations below average is considered microcephaly and what does this diagnosis imply about future brain development
- > 3
- implies failure of brain development
sonography of microcephaly
- profile would demonstrate a sloping forehead
- ventriculomegaly occurs due to less brain tissue
what other abnormalities are associated with microcephaly
- many other developmental abnormalities
causes of microcephaly
- asphyxia
- infections (cytomegalovirus CMV)
- drugs
- alcohol
- radiation
what is a vein of Galen aneurysm
- a variety of AV malformations drain into the vein of Galen and result in tis distention as a single dilated midline fluid collection
when does dilation of the vein of Galen occur
- third trimester
sonography of vein of Galen
- dilated midline collection posterior to the thalamus and midbrain between the posterior horns of the lateral ventricles
- easily diagnosed with color doppler
- neck vessels appear prominent
- signs of heart failure
+ cardiomyopathy due to AV shunting
DDX of vein of Galen
- arachnoid cyst
- porencephalic cyst
prognosis for vein of Galen
- poor unless all anastomosis can be cauterized
are congenital tumors of the brain common or rare
- rare
what is the most common tumor of the brain
- teratoma
+ large echogenic masses with cystic space and occasional calcifications
what is the prognosis of tumors in the brain
- dismal
3 different cranial shapes
- craniosynostoses
- dolichocephalic
- brachiocephalic
what does a craniosynostoses head look like
- bizarre fusion of the cranial sutures
- clover leaf appearance= all fuse before brain is finished growing
what does a dolichocephalic head look like
- BPD/OFD = CI (cephalic index)
- <75
- narrow head
- one cause is a breech baby
what does a brachiocephalic head look like
- BPD/OFD = CI
- > 85
- wide head
what is cranial mineralization
- if view of the brain is especially clear you should consider conditions which have poor mineralization
- also if brain can be compressed with slight pressure
in what 2 syndromes are the cranial bones not ossified and what can you do the the skull as a result
- osteogenesis imperfecta
- hypophosphatasia
- can compress the brain
three types of holoprosencepahly
- alobar
- semilobar
- lobar
characteristics of alobar holoprosencephaly
- little to no cortical mantle
- single HORSESHOE shaped ventricle
- fused thalami and absent 3rd ventricle and falx
characteristics of semilobar holoprocencephaly
- single horseshoe shaped ventricle with brain mantle
- incomplete fusion of thalami
- absent falx and third ventricle
characteristics of lobar holoprosencephaly
- fused anterior horns that are squared off
- incomplete falx and 3rd ventricle may be seen
