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OB Pathology > Chapter 59, The Fetal Neural Axis > Flashcards

Chapter 59, The Fetal Neural Axis Flashcards

1
Q

Many of the congenital malformations of the CNS result from

A

incomplete closure of the neural tube

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2
Q

A wide range of defects resulting from incomplete closure of the neural tube may affect what?

A

the spine and/or brain

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3
Q

What is anencephaly?

A

neural tube defect characterized by the lack of development of the cerebral and cerebellar hemispheres and cranial vault

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4
Q

T/F: anencephaly is compatible with life?

A

false

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5
Q

What is the most common neural tube defect?

A

anencephaly

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6
Q

What is the overall incidence of anencephaly in pregnancies in the US?

A

1 in 1,000

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7
Q

Where is there a much higher prevalence of anencephaly?

A

the U.K.

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8
Q

Prevalence of gender and race related to anencephaly?

A

female prevalence of 4 to 1, white to black of 6 to 1

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9
Q

What is the cause of anencephaly?

A

failure of closure of the neural tube at the cranial end…result is the absence of the cranial vault, complete or partial absence of the forebrain (Which may partially develop then degenerate,) and the presence of the brain stem, midbrain, skull base, facial structures.

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10
Q

Up to ____% of cases of anencephaly result in fetal demise?

A

50%, remainder die at birth or shortly after

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11
Q

T/F: With anencephaly, early diagnosis is preferred?

A

True

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12
Q

T/F: Maternal serum alpha-fetoprotein levels are extremely high with anencephaly?

A

True, because of the absent skull and exposed tissue

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13
Q

Anencephaly may result from what?

A

Meckel-Gruber syndrome or a chromosomal abnormality like trisomy 13

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14
Q

T/F: There is an increased risk of anencephaly in patients with diabetes?

A

True

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15
Q

Environmental and dietary factors that may increase the prevalence of neural tube defects include:

A
  • hyperthermia
  • folate and vitamin deficiencies
  • teratogenic levels of zinc
  • amniotic band syndrome
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16
Q

Sonographic features of anencephaly include:

A
  • absence of brain and cranial vault
  • rudimentary brain tissue characterized as the cerebrovasculosa
  • bulging fetal orbits, giving a froglike appearance
  • polyhydramnios (may not be present until after 26 weeks.)
  • coexisting spina bifida and/or craniorachisschisis
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17
Q

Related anomalies of anencephaly include:(7)

A
  • cleft lip and palate
  • hydronephrosis
  • diaphragmatic hernia
  • cardiac defects
  • omphalocele
  • GI defects
  • talipes
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18
Q

Acrania is AKA:

A

exencephaly

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19
Q

What is acrania?

A

a lethal anomaly that manifests as complete or partial absence of the cranial bones with the presence of complete, although abnormal, development of the cerebral hemispheres

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20
Q

When does acrania occur?

A

the beginning of the 4th gestational week

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21
Q

T/F: Acrania is rare?

A

True

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22
Q

Disorders that may mimic acrania:

A
  • anencephaly
  • hypophosphatasia
  • osteogenesis imperfecta (result in hypomineralization of the cranium.)
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23
Q

Sonographic features of acrania:

A
  • presence of brain tissue without the presence of a calvarium
  • disorganization of brain tissue
  • prominent sulcal markings
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24
Q

What is cephalocele?

A

A neural tube defect in which the meninges alone or meninges and brain herniate through a defect in the calvarium

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25
Q

What is encephalocele?

A

used to describe herniation of the meninges and brain through the defect

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26
Q

What is cranial meningocele?

A

The herniation of only meninges

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27
Q

Cephaloceles occur at a rate of

A

1-3 in 10,000 live births

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28
Q

In 75% of cephalocele cases:

A

the cephalocele involves the occipital bone and is located in the midline, although it may also involve the parietal and frontal regions

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29
Q

The prognosis for the infant with a cephalocele varies based on:

A
  • size
  • location
  • involvement with other brain structures
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30
Q

The sonographic features of cephaloceles include:

A
  • an extracranial mass which may be fluid filled or contain solid components
  • a bony defect in the skull
  • ventriculomegaly (usually w/ encephalocele)
  • polyhydramnios
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31
Q

Coexisting anomalies of cephalocele include:

A
  • microcephaly
  • agenesis of the corpus callosum
  • facial clefts
  • spina bifida
  • cardiac anomalies
  • genital anomalies
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32
Q

Chromosomal anomalies and syndromes ID’d with cephaloceles include:

A
  • Trisomy 13

- Meckel-Gruber syndrome

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33
Q

What is Meckel-Gruber syndrome?

A

an autosomal-recessive disorder characterized by encephalocele, polydactyly and polycystic kidneys

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34
Q

What is spina bifida?

A

encompasses a wide range of vertebra defects that result from failure of neural tube closure (there is a cleft or opening in the spine)

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35
Q

What may protude through spina bifida?

A

the meninges and neural elements

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36
Q

What is a form of spina bifida that is covered with skin or hair?

A

spina bifida occulta

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37
Q

What is spina bifida occulta associated with?

A

a normal spinal cord and nerves and normal neurologic development

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38
Q

T/F: Spina bifida occulta is extremely difficult to detect in the fetus?

A

True

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39
Q

T/F: because spina bifida occulta is covered by skin, the maternal serum alpha-fetoprotein level will be normal.

A

True

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40
Q

When the defect involves only protrusion of the meninges it is termed ______.

A

meningocele

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41
Q

When the meninges ad neural elements protrude through the defect, this is called ____.

A

meningomyelocele

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42
Q

If the defect is very large and severe, it is termed _______

A

rachischisis

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43
Q

Meningoceles, meningomyeloceles, and rachischisis are commonly associated with:

A

increased maternal serum alpha-fetoprotein

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44
Q

Spina bifida is associated with varying degrees of neurologic impairment which may include

A

minor anethesia, paraparesis, or death

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45
Q

Fetuses with myelomeningoceles often present with

A

cranial defects associated with Arnold-Chiari (type 2) malformation

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46
Q

Describe Arnold-Chiari (type 2) malformation

A

presents invariably with hydrocephalus because of the cerebellar vermis, which becomes displaced into the cervical canal, giving the cerebellum a banana appearance and obliterates the cisterna magna. Also, caudal displacement of the cranial structures causes scalloping of the frontal skull bones, resulting in a lemon shape.

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47
Q

Sonographic findings of spina bifida include:

A
  • splaying of the posterior ossification centers with a V or U configuration.
  • protrusion of a saclike structure that may be anechoic or contain neural elements
  • a cleft in the skin
  • talipes
  • cephaloceles
  • cleft lip and palate
  • hypotelorism
  • heart defects
  • genitourinary anomalies
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48
Q

What should be documented once a spinal defect has been ID’d? (3)

A
  • the level and extent of the defect
  • the presence of absence of neural elements contained in the protruding sac
  • associated intracranial findings
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49
Q

Associated sonographic cranial findings of spina bifida include:

A
  • lemon-shaped head
  • obliteration of cisterna magna
  • inferior displacement of cerebellar vermis, giving cerebellum a banana shape
  • ventriculomegaly
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50
Q

T/F: The lemon sign is specific to spina bifida.

A

False, seen in other CNS malformations like encephalocele and non-CNS malformations like thanatophoric dysplasia

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51
Q

Spina bifida has been associated with

A
  • trisomy 18
  • maternal diabetes
  • hyperthermia
  • folic acid deficiency
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52
Q

What does Dandy-Walker malformation manifest with?

A

Agenesis or hypoplasia of the cerebellar vermis with resulting dialation of the fourth ventricle.

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53
Q

When is Dandy-Walker thought to occur?

A

before the 6th or 7th week

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54
Q

What is thought to cause Dandy-Walker?

A

abnormal embryogenesis of the roof of the fourth ventricle

55
Q

What % of the time is Dandy-Walker associated with other intracranial anomalies?

A

50%

56
Q

What intracranial anomalies are associated with Dandy-Walker? (8)

A
  • agenesis of the corpus callosum
  • aqueductal stenosis
  • microcephaly
  • macrocephaly
  • encephalocele
  • gyral malformations
  • heterotopias
  • lipomas
57
Q

What chromosomal anomalies are associated with Dandy-Walker?

A

Trisomies 13, 18, 21

58
Q

What syndromes are associated with Dandy-Walker?

A
  • Meckel-Gruber
  • Walker-Warburg
  • Aicardi’s
59
Q

Sonographic features of Dandy-Walker include: (4)

A
  • a posterior fossa cyst that can vary in size
  • splaying of the cerebellar hemispheres as a result of the complete or partial agenesis of the cerebellar vermis
  • enlarged cisterna magna
  • ventriculomegaly
60
Q

What does holoprosencephaly result from ?

A

abnormal cleavage of the prosencephalon

61
Q

What is the incidence of holoprosencephaly?

A

1 in 10,000 to 20,000 live births

62
Q

Holoprosencephaly is associated with chromosomal anomalies in ___% of cases

A

50%, But may also be a sporadic event or associated with syndromes, genetic factors and teratogens

63
Q

What are the three forms of holoprosencephaly in descending severity?

A
  • alobar
  • semilobar
  • lobar
64
Q

Alobar holoprosencephaly is characterized by:

A
  • singular monoventricle brain tissue that is small and may have a cup, ball, or pancake configuration
  • fusion of the thalamus
  • absence of the interhemispheric fissure, cavum septum pellucidum, corpus callosum, optic tracts, olfactory bulbs
65
Q

Semilobar holoprosencephaly presents with:

A
  • a singular ventricular cavit with partial formation of the occipital horns
  • partial or complete fusion of the thalamus
  • a rudimentary falx and interhemispheric fissure
  • absent corpus callosum, cavum septum pellucidum, olfactory bulbs
66
Q

Lobar holoprosencephaly presents with:

A

an almost complete division of the ventricles with a corpus callosum that may be normal, hypoplastic, or absent, although the cavum septum pellucidum will still be absent

67
Q

What chromosomal anomaly has been associated with holoprosencephaly?

A

Trisomy 13

68
Q

What syndromes have been associated with holoprosencephaly?

A
  • Meckel-Gruber
  • Aicardi’s
  • Fryns
  • hydrolethalus syndrome
69
Q

Teratogens reported to produce holoprosencephaly include: (5)

A
  • alcohol
  • phenytoin
  • retinoic acid
  • maternaal diabetes
  • congenital infections
70
Q

Sonographic features of holoprosencephaly include: (11)

A
  • common C-shaped ventricle that may be enlarged
  • brain tissue wth a horseshoe shape as it surrounds the monoventricle
  • fusion of the thalamus with absence of 3rd ventricle
  • absence of interhemispheric fissure
  • a dorsal sac with expansion of the monoventricle posteriorly
  • absence of the corpus callosum
  • absence of the cavum septum pellucidum
  • hydrocephaly
  • microcephaly
  • polyhydramnios
  • IUGR
71
Q

Holoprosencephaly is often associated with ___ anomalies.

A

facial

72
Q

Facial anomalies with holoprosencephy include: (5)

A
  • cyclopia
  • hypotelorism
  • an absent nose
  • a flattened nose with a single nostril
  • proboscis
73
Q

Cebocephaly consists of a combination of

A

hypotelorism with a normally placed nose with a single nostril

74
Q

Ethmocephaly consists of

A

severe hypotelorism with a proboscis superior to the eyes

75
Q

What facial clefts are most common with holoprosencephaly?

A

-median or bilateral

76
Q

What defects can be ID’d in the presence of holoprosencephaly?

A
  • renal cysts or dysplasia
  • omphalocele
  • cardiac defects
  • spina bifida
  • talipes
  • GI problems
77
Q

________ anomalies must be considered if holoprosencephaly is present

A

Chromosomal , esp Trisomy 13

78
Q

What is the corpus callosum?

A

a fibrous tract that connects the cerebral hemispheres and aids in learning and memory

79
Q

Dysgenesis of the corpus callosum describes:

A

a range of complete to partial absence of the callosal fibers that cross the midline, forming a connection between the two hemispheres

80
Q

Likely cause of agenesis of the corpus callosum?

A

a vascular disruption of inflammatory lesion before 12 weeks

81
Q

Agenesis of the corpus callosum is associated with other CNS malformations, including: (5)

A
  • hydrocephals
  • gyral anomalies
  • heterotopias
  • Dandy-Walker malformation
  • Holoprosencephaly
82
Q

Chromosomal anomalies that may accompany agenesis of the corpus callosum include:

A
  • Trisomies 13, 18, 8

- Triploidy

83
Q

What syndromes are associated with agenesis of the corpus callosum? (4)

A
  • Aicardi
  • Apert
  • Opitz
  • Joubert
84
Q

Sonographic findings of agenesis of the corpus callosum: (15-just kill me now)

A
  • absence of cavum septum pellucidum
  • widely seperated lateral ventricular frontal horns with medial indentation of media walls
  • elevation and dilation of 3rd ventricle
  • small frontal horns and dilated occipital horns (colpocephaly), giving lateral ventricles teardrop shape
  • holoprosencephaly
  • DWM
  • cranial lipoma
  • Arnold-Chiari malformation
  • septo-optic dysplasia
  • hydrocephaly
  • encephalocele
  • porencephaly
  • microcephaly
  • lissencephaly
  • “sunburst” of cerebral sulci
85
Q

What is colpocephaly?

A

small frontal horns and dilated occipital horns

86
Q

Abnormalities associated with agenesis of the corpus callosum

A
  • cardiac malformation
  • diaphragmatic hernia
  • lung agenesis or dysplasia
  • absent/dysplastic kidneys
87
Q

What does aqueductal stenosis result from?

A
  • obstruction
  • atresia
  • stenosis of the aqueduct of Sylvius causing ventriculomegaly
88
Q

The aqueduct of Sylvius connects

A

the 3rd and 4th ventricle

89
Q

Sonographic findings of aqueductal stenosis: (3)

A
  • ventricular enlargement of lateral ventricles
  • third ventricular dilation
  • flexion and adduction of the thumb
90
Q

What is a rare arteriovenous malformation?

A

an aneurysm of the vein of Galen

91
Q

T/F: Vein of Galen aneurysm is considered a sporatic event and has a male prodominance?

A

True

92
Q

What has a Vein of Galen aneurysm been associated with? (3)

A
  • congenital heart defects
  • cystic hygromas
  • hydrops
93
Q

Sonographic findings with Vein of Galen aneurysm: (4)

A
  • cystic space that may be irregular in shape and is located midline and posteriosuperior to the third ventricle
  • turbulent flow with Doppler evaluation
  • fetal cardiomegaly
  • nonimmune hydrops
94
Q

What are choroid plexus cysts?

A

round or oval anechoic structures found within the choroid plexus, containing cerebrospinal fluid and cellular debris that is trapped within the neuroepithelial folds

95
Q

When will choroid plexus cysts often resolve?

A

-22-26 weeks

96
Q

Choroid plexus cysts have been associated with:

A

aneuploidy, esp. trisomies 18 and 21

97
Q

Sonographic features of choroid plexus cysts: (5)

A
  • cysts ranging from 0.3 to 2 cm
  • unilateral or bilateral cysts
  • solitary or multiple
  • unilocular or multilocular
  • enlargement of the ventricle with large cyst
98
Q

What is porencephaly?

A

cysts filled with CSF that communicate with the ventricular system or subarachnoid space

99
Q

What can porencephalic cysts result from?

A

hemorrhage, infarction, delivery trauma, or inflammatory changes on the nervous system

100
Q

Sonographic features of porencephalic cysts include: (3)

A
  • a cyst within the brain parenchyma without mass effect
  • communication of the cyst with the ventricle or subarachnoid space
  • reduction in size of the affected hemisphere, may cause a midline shift and contralateral ventricular enlargement
101
Q

What is schizencephaly?

A

a rare disorder characterized by clefts in the cerebral cortex (clefts may be unilateral, or bilateral, open-lip or closed-lip defects.)

102
Q

What is schizencephaly associated with?

A

congenital infections, drugs and other toxic exposures, vascular accidents, metabolic abnormalities

103
Q

T/F: prognosis for patients with schizencephaly varies?

A

true

104
Q

Sonographic features of schizencephaly include:

A
  • a fluid-filled cleft in the cerebral cortex extending from the ventricle to the calvarium
  • ventriculomegaly
  • agenesis of the CSP and corpus callosum (50% of time)
105
Q

What is lissencephaly?

A

When the surface of the brain lacks normal sulci and gyri and appears smooth

106
Q

When can lissencephaly be diagnosed?

A

3rd trimester

107
Q

What can lissencephaly be associated with?

A

mild ventriculomegaly and abnormal corpus callosum

108
Q

What is hydraencephaly?

A

destruction of the cerebral hemispheres by occlusion of the internal carotid arteries. Brain parenchyma is destroyed, replaced by CSF.

109
Q

What parts of the brain are spared with hydraencephaly? (5)

A
  • midbrain
  • cerebellum
  • basal ganglia
  • choroid plexus
  • thalamus
110
Q

What causes hydraencephaly?

A

congenital infection or ischemia or cocaine abuse

111
Q

What can cause brain ischemia?

A
  • maternal hypotension
  • twin-to-twin embolization
  • vascular agenesis
112
Q

Sonographic features of hydraencephaly: (6)

A
  • absence of normal brain tissue, almost completely replaced by CSF
  • an absent/partially absent falx
  • presence of midbrain, basal ganglia, cerebellum
  • choroid plexus may be ID’d
  • macrocephaly may occur
  • polyhydramnios
113
Q

What is ventriculomegaly?

A

dilation of the ventricles within the brain

114
Q

What is hydrocephalus?

A

when ventriculomegaly is coupled with enlargement of the fetal head

115
Q

The incidence of hydrocephalus is

A

0.3 -1.5 per 1,000 live births

116
Q

Enlargement of the ventricles occurs with obstruction of

A

CSF

117
Q

Noncommunicating hydrocephalus is

A

an obstruction caused by a ventricular defect (ie. aqueductal stenosis)

118
Q

Communicating hydrocephalus is

A

when the obstruction may be outside of the ventricular system, such as with arachnoid cysts

119
Q

Rarely ventriculomegaly results from an overproduction of CSF by a

A

choroid plexus papilloma

120
Q

Common causes of ventriculomegaly: (2)

A

spina bifida and encephaloceles

121
Q

What may present with hydrocephalus? (5)

A
  • DWM
  • agenesis of corpus callosum
  • lissencephaly
  • schizencephaly
  • holoprosencephaly
122
Q

Sonographic features of ventriculomegaly:

A
  • lateraly ventricular enlargement exceeding 10 mm
  • a ‘dangling choroid sign’
  • possible dilation of the 3rd and 4th ventricles
  • fetal head enlargement when the BPD and HC measurements exceed those for the established gest. age
123
Q

What is microcephaly?

A

An abnormally small head that falls 2 standard deviations below the mean (occurs because the brain is reduced in size)

124
Q

What is the incidence of isolated microcephaly?

A

1 per 1,000 births

125
Q

About _____% of children with microcephaly are mentally retarded?

A

85%

126
Q

Son. diagnosis of microcephaly depends upon:

A

an accurate assessment of fetal age

127
Q

Diagnosis of microcephaly before ___ weeks of age is impossible.

A

24

128
Q

Sonographic features of microcephaly: (5)

A
  • small BPD
  • small HC
  • abnormal HC/AC and HC/FL ratios
  • disorganized brain tissue
  • ventriculomegaly
129
Q

Microcephaly is associated with: (5)

A
  • Trisomies 13, 18, 21, 22

- triploidy

130
Q

What syndromes have been linked to microcephaly? (3)

A
  • Meckel-Gruber
  • Pena-Shokeir
  • Neu-Laxova
131
Q

What is the most common intracranial tumor found in utero?

A

teratoma

132
Q

What do teratomas contain?

A

hair, sebum, fat

133
Q

teratomas appear as what?

A

complex masses that distort the normal architecture of the brain.

OB Pathology (16 decks)

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