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Ch 55 Fetal Head Neural Tube Defects
diagnostic medical sonography
79
Medical
Undergraduate 2
04/14/2012

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Term
4.5 weeks
Definition
By when does the neural plate develop
Term
neural plate
Definition
What develops into the CNS?
Term
neural tube
Definition
the neural plate gives rise to what?
Term
neural tube
Definition
what forms the spine and the brain?
Term
  • prosencephalon (forebrain)
  • mesencephalon (midbrain) 
  • rhombencephalon (hindbrain)
Definition
the brain is initially what 3 vesicles?
Term
first trimester
Definition
rhombencephalon is visualized when?
Term
6 weeks
Definition
neural function begins when?
Term
6months
Definition
sucking begins when?
Term
anencephaly
Definition
most common neural tube defect
Term
united kingdom
Definition
higher prevalence of anencephaly where?
Term
females
Definition
anencephaly happens more often in which sex?
Term
anencephaly
Definition
absence of brain; result of failure of closure of the neural tube at the cranial end
Term
AFP; open defect
Definition
anencephaly has high levels of what?why?
Term
10-14 weeks
Definition
when can anencephaly be detected?
Term
anencephaly
Definition
froglike appearance, bulging of fetal orbits is associated with what?
Term

acrania

(exencephaly)

Definition
absence of the cranial bones with the presence of complete, although abnormal development of the cerebral hemispheres
Term
4th week
Definition
when does acrania occur?
Term
acrania
Definition
this leads to anencephaly as the brain regresses due to exposure to amniotic fluid
Term
  • presence of brain tissue without cranial vault
  • Disorganization of brain tissue

 

Definition
sonographic features of acrania?
Term
cephalocele
Definition
neural tube defect; meninges alone or meninges and brain herniate through a defect in the calvarium
Term
calvarium
Definition
upper part of the brain, surrounds cranium
Term
meninges
Definition
membranes that protect the CNS; contains the dura mater archnoid mater, and pia mater
Term
encephalocele
Definition
term used to describe herniation of the meninges and brain through the defect
Term
cranial meningocele
Definition
describes the herniation of only meninges
Term
cephalocele
Definition
sonographically appears as an extracranial mass, bony defect in the skull, and ventriculomegaly
Term
spina bifida
Definition
encompases a wide range of vertebral defects; failure of nueral tube closure; miniges and neural elements may protrude
Term
lumbar and sacral regions
Definition
spina bifida most commonly occurs along where?
Term
spina bifida occulta
Definition
when covered with skin or hair, spina bifida is referred to as what?
Term
meningocele
Definition
protrusion of the meninges only
Term
meningomyelocele
Definition
protrusion of meninges and neural elements; tends to be large; more common
Term
spina bifida
Definition
banana shape cerebellum due to the pulling of the exposed neural elements is associated with?
Term
spina bifida
Definition
scalloping of the frontal bones making the lemon sign is associated with?
Term
spina bifida
Definition
splaying of posterior ossification centers of the spine froming "U" instead of "V" is associated with?
Term
dandy walker malformation
Definition
agnesis or hypoplasia of the cerebellar vermis with resulting dilation on the fourth ventricle
Term
dandy walker malformation
Definition
result of abnormal embryogenesis of the roof of the fourth ventricle
Term
6-7 weeks
Definition
thought for dandy walker malformation to occur before when?
Term
posterior fossa cyst
Definition
most common ultrasound finding with dandy walker malformation?
Term
  • posterior fossa cyst
  • splaying of the cerebellar hemispheres
  • enlarged cisterna magna caused by the cerebellar vermis anomaly and posterior fossa cyst
  • ventriculomegaly 
Definition
ultrasound findings of dandy walker?
Term
holoprosencephaly
Definition

results from abnormal development of the prosencephalon(forebrain)

 

Term
trisomy 13
Definition
holoprosencephaly is associated with what chromosomal anomaly?
Term
  • alobar (most severe)
  • semilobar
  • lobar (least severe)
Definition
what are the 3 forms of holoprosencephaly?
Term
alobar holoprosencephaly
Definition
  • small brain tissue
  • fusion of thalamus
  • absence of:
    • interhemispheric fissue
    • cavum septum pellucidum
    • corpus callosum
    • optic tracts
    • olfactory bulbe 
Term
semilobar holoprosencephaly
Definition
  • singular ventricle
  • partial or complete fusion of the thalamus 
  • absent corpus callosum
Term
lobar holoprosencephlay
Definition
may appear normal but cavum septum pelludicum with still be absent
Term
corpus callosum
Definition
what connects the cerebral hemispheres
Term
corpus callosum
Definition
aids in learning and memory
Term
agenesis of the corpus callosum
Definition

Sonographic findings of what?

  • absence of corpus callosum
  • enlarged lateral ventricles
  • absence of cavum septum pelucidum 
Term
aqueductal stenosis
Definition
results from obstruction, atresia or stenosis of the aqeduct of sylvius causing ventriculomegaly
Term
third and fourth ventricle
Definition
the aqueduct of sylvius connects what?
Term
aqueductal stenosis
Definition

ultrasound findings of what?

  • ventricular enlargement of lateral ventricles
  • third ventricular dilation 

 

Term
vein of Galen aneurysm
Definition
rare arteriovenous malformation
Term
vein of galen aneurysm
Definition

ultrasound findings of what?

  • cystic space tht may be irregular in shape and is located midline and posterosuperior to the third ventricle
  • turbulent flow with doppler 
Term
choriod plexus cyst
Definition
round or ovoid anechoic structures within the choroid plexus; common
Term
20-22 weeks
Definition
choroid plexus cyst often resolve when?
Term
aneuploidy; most commonly trisomies 18 & 21
Definition
choroid plexus cyst have been identified in associtation with?
Term
hydranencephaly
Definition

destruction of the cerebral hemispheres by occlusion of the internal carotid arteries; brain parenchyma is destroyed and is replaced by cerebrospinal fluid

poor prognosis

Term

congenital infection of ischemia:

  • cytomegalovirus(CMV) and toxoplasmosis

 

Definition
etiology of hydranencephaly inloves what?
Term
severe hydrocephaly, presence of an intact falx and surrounding rim of brain parenchyma may help differentiate
Definition
hydranencephaly may be confused with what?
Term
Definition

Ultrasound findings of what?

  • absence of normal brain tissue with almost complete replacement by cerebrosplinal fluid
  • absent or partially absent falx
  • presence of the midbrain, and cerebellum
  • choriod plexus may be identidfied
  • macrocephaly 
Term

hydrocephalus

(ventriculomegaly)

Definition

dilation of the ventricles within the brain; enlargement of the ventricles occurs with obtruction of cerebrospinal fluid flow

high mortality

Term

hydrocephalus

(ventriculomegaly)

Definition

ultrasound findings of what?

  • lateral ventricular enlargement exceeding 10mm
  • dangling choroid sign
  • possible dilation of the third and fourth ventricles
  • fetal head enlargement
Term
microcephaly
Definition
abnormality small head that falls 2 standard deviations below the mean; more commonly caused by an associated anomaly
Term
acrania
Definition
condition associated with anencephaly in chich there is complete or partial absence of the cranial bones
Term
alobar holoprosencephlay
Definition
most severe form of holoprosencephaly characterized by a single common ventricle and malformed brain; orbital anomalies range from fused orbites to hypotelorism, with frequent nasal anomalies and clefting of the lip and palate
Term
anencephaly
Definition
neural tube defect characterized by te lack of developmetn of the cerebral and cerebellar hemispheres and cranial vault; this abnormality is incompatible with life
Term
anomaly
Definition
an abnormality or congenital malformation
Term
cebocephaly
Definition
form of holoprosencephaly characterized by a common ventricle, hypotelorism, an a nose with a single nostril
Term
cyclopia
Definition
sever form of holoprosencephaly characterized by a common ventricle, fusion of the orbits with one or two eyes present, and a proboscis
Term
cystic hygroma
Definition
an increase in size of jugular lymphatic sacs because of abnormal development
Term
holoprosencephaly
Definition
a range of abnormalities from abnormal cleavage of the forebrain
Term
hydranencaphaly
Definition
congenital absence of the cerebral hemisperes because of an occlusion of the carotid arteries; midbrain structures are present, and fluid replaces cerebral tissue
Term
hydrocephalus
Definition
ventriculomegaly in the neonate; abnormal accumulation of cerebrospinal fluid within the cerebral ventricles, resulting in compression and frequently destruction of brain tissue
Term
macrocephaly
Definition
enlargement of the fetal cranium as a result of ventriculomegaly
Term
meningocele
Definition
open spinal defect characterized by protrusion of spinal meninges
Term
meningomyelocele
Definition
open spinal defect characterized by protrusion of meninges and spinal cord through the defect, usually within a meningeal sac
Term
spina bifida
Definition
neural tube defect of the spine in which the dorsal vertebrae fail to fuse together, allowing the protrusion of meinges and/or spinal cord through the defect; two types exist
Term
spina bifida occulta
Definition
closed defect of the spine without protrusion of meninges or spinal cord; alpha-fetoprotein analysis will not defect these lesions
Term
ventriculomegaly
Definition
abnormal accumulation of cerebrospinal fluid within the cerebral ventricles resulting in dilation of the ventrcles; compression of developing brain tissue and brain damage may result; commonly associated with additional fetal anomalies
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