CNS , NEURAL TUBE Flashcards
1
Q
Fetal neural axis
A
OUTLINE
mbryology
nencephaly
\crania
Cephalocele
Spina Bifida
Dandy-Walker Malformation
Holoprosencephaly
Agenesis of the Corpus Callosum
Aqueductal Stenosis
Vein of Galen Aneurysm
Choroid Plexus Cysts
Porencephalic Cysts
Schizencephaly
Hydranencephaly
Ventriculomegaly (Hydrocephalus)
Microcephaly
2
Q
Sonographic Findings
Absence of brain and cranial vault
Froglike appearance
Cerebrovasculosa
A
TABLE 60-2
Differential Considerations for Central Nervous System Anomalies
Anomaly
Differential Considerations
Distinguishing Characterist
Anencepha
*Microcephaly
*Acrania
*Cephalocele
No calvarium above vault orbits
3
Q
Hydranencephaly
A
Communication with ventricie
Absence of brain tissue
Fluid-filled brain
Absent or partially absent falx
** Hydrocephaly
Holoprosencephaly
**Lack of intact falx
No rim of brain tissue
4
Q
• Most common neural tube defect
A
Anencephaly
Or
• Also known as aprosencephaly and atelencephaly
5
Q
Significant recurrence
A
Significant recurrence risk (2% to 3%) for woman with history of prior pregnancy with open neural tube defect
6
Q
Anencephaly
A
Up to 50% of cases end in fetal demise
•Remainder die at birth or shortly thereafter
• Prenatal diagnosis often made with sonography following referral for high maternal serum alpha-fetoprotein (AF) levels
7
Q
Anencephaly causes
A
@Causes
© Meckel-Gruber
• Chromosomal (T-13, T-18)
•Diabetes
Environmental and dietary factors
• Amniotic band syndrome
8
Q
(cerebrovasculosa),
A
Rudimentary brain tissu
(cerebrovasculosa).
In Anencephaly
9
Q
Anencephaly
A
A. Anencephaly identified in fetus with < B. a radial ray defect
10
Q
Anencephaly • Other sonographic findings
A
@Polyhydramnios
Coexisting spina bifida and/or craniorachischisis
© Cleft lip and palate ~ Hydronephrosis
Diaphragmatic hernia
© Cardiac defects
Omphalocele
• Gastrointestinal defects
• Talipes
11
Q
Acrania
A
Acrania = cranium absem
brain tissue presens
Is lethal anomaly; also known as exencephaly
12
Q
Acrania
A
Manifests as absence of cranial bones with presence of complete, although abnormal, development of cerebral hemispheres
©Occurs at beginning of fourth gestational week
13
Q
Acrania when occure
A
Occurs at beginning of fourth gestational week
© Mesenchmal tissue fails to migrate and does not allow bone formation over cerebral tissue.
14
Q
Acrania confused with
A
May be confused with anencephaly
@Presence of significant brain tissue and lack of froglike appearance should establish diagnosis.
15
Q
© Other disorders may mimic acrania:
A
Hypophosphatasia
Osteogenesis imperfecta
© Identification of additional findings, such as long bone fractures, help to distinguish these disorders from acrania.
16
Q
Acrania
A
• The presence of brain tissue without the presence of a calvarium.
17
Q
Acrania
A
Disorganized brain tissue, absent skull bones, herniated ventricl and sulcal markings.
18
Q
Acrania May be associated with other anomalie:
A
• Spinal defects
Cleft lip and palate
Talipes
• Cardiac defects
Omphalocele
• Amniotic band syndrome
19
Q
Cephalocele
A
Neural tube defect in which meninges alone or meninges and brain herniate through defect in calvarium
20
Q
CEncephalocele
A
CEncephalocele is term used to describe herniation of brain through defect
© Cranial meningocele describes herniation of meninges
only.
21
Q
CEncephalocele
A
© Commonly involves occipital bone
Ols located in midline in 75% & cases
• May also involve:
• Parietal
Frontal
Temporal regions
• Other bones of calvarium
22
Q
© Sonographic appearance depends on location, size, involyement of brain structures
A
Cephaloceles containing:
• Meninges only -meningocele
Brain tissue only -encephalocele
Meninges and brain tissue -encephalomeningocele
• Meninges, brain tissue, lateral ventricles-encephalomeningocystocele
23
Q
• Cephalocele
• Are classified according to site of lesion
A
• Are classified according to site of lesion
• Occipital cephaloceles occur when defect lies between the lambdoid suture and foramen magnum.
Separate prital and occipital bones
• Parietal cephaloceles occur between bregma and lambda.
• Anterior cephaloceles lie between anterior aspect of ethmoid bone.
24
Q
© Anterior cephaloceles
A
© Anterior cephaloceles further classified into frontal and basal varieties
25
• Frontal cephaloceles are
Frontal cephaloceles are alwavs external lesions that occur near root of nose.
26
© Basal cephaloceles
Basal cephaloceles are internal lesions that occur within the nose, pharynx, and orbit.
27
• Cephalocele
• Cephalocele
Sonographic features
Sonographic features
• Extracranial mass, which may be fluid-filled (crania meningocele) or contain solid components (encephalocele)
© A bony defect in skull
© Ventriculomegalv; is more commonly identified
with encephalocele
• Another sonographic finding is polyhydramnios.
• Coexistine anomalies include microcephaly, agenesis of corpus callosum/ facial clefts / spina bifida/ cardiac anomalies/and genital anomalies.
28
© Chromosomal anomalies and syndromes have been identified with cephaloceles,
including trisomy 13 and Meckel-Gruber syndrome.
29
Meckel-Gruber syndrome
kel-Gruber syndrome.
lethal, genetic disorder, characterized by renal cystic dysplasia,
) CNS malformations (occipital encephalocele), polydactyly
• hepatic developmental defects, and pulmonary hypoplasia due to oligohydramnios.)
30
Cephalocele
Encephalocele
) The sac protruding from the cranium contains fluid and solid components.
31
Cephalocele
) May be confused
with cystic hygromas, (lack cranial ‹ defect)
Anencephaly difficult to distinguish from encepgaloceles of significant size;
32
© Frontal encephaloceles difficult to
© Frontal encephaloceles difficult to distinguish from facial teratoma
33
incephaly difficult to distinguish from ence ignificant size;
34
Ancephaly difficult to distinguish from encephalocele snificant size
o presence of cranial vault with encephalocele should establish diagnosis
35
4 / Spina Bifida
• Wide range of vertebral defects that result from failure of neural tube closure
• Meninges and neural elements may protrude through defect.
• Defect may occur anywhere along vertebral column but most commonly along lumbar and sacral regions
36
Embryogenesis of spina bifida
© Defects of spinal canal occur in first 8.5 weeks of life as fetal nervous system develops.
© Neural tube and subsequent spinal cord arise frot ectodermal cells.
© Surface ectoderm separates from neural tube, wit mesoderm coming to lie between neural tube and ectoderm.
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Spina Bifida
• Term spina bifida means there is cleft, or opening, in spine.
38
spina bifida occulta; this
© When covered with skin or hair, referred to as spina bifida occulta; this anomaly associated with normal spinal cord and nerves and normal neurologic development
39
O Spina bifida occulta extremely difficult to detect in fetus
• Defect is covered by skin
• Maternal serum AF level will be normal.
40
A, Spina bifida occulta. About
• A, Spina bifida occulta. About 10% of people have this vertebral defect in L5 and/or S1
41
The types illustrated in B through D are often referred to collectively as spina bifida cystica because of the cystic sac that is associated with them.
B, Spina bifida with O meningocele.
C, Spina bifida with meningomyelocele.
D, Spina bifida with myeloschisis.
42
meningocele :
• When defect involves only protrusion of meninges, termed meningocele
43
• Meningomvelocele
• Meningomyelocele is more common; both meninges and neural elements protrude through defect
44
rachischisis
•If defect very large and severe, termed rachischisis
45
•Fetuses with
myelomeningoceles often present with
•Fetuses with myelomeningoceles often present with cranial defects associated with Arnold-Chiari (type ll)
malformation.
46
(
Chiari (type malformation.
pina Bifida
Changes shape of cerebellum, giving it "banana"
appearance
LeadS to obliteration of cisterna magna
Caudal displacement of cranial structures causes scalloping of frontal bones of skull, making fetal he resemble lemon
47
• spina Bitiaa
• Management includes serial ultrasound
• Management includes serial ultrasound examinations to monitor progression and extent of ventriculomegaly and to follow fetal growth.
•Fetuses are delivered early for ventricular shunting, usually by cesarean section to preserve motor function.
•Surgical repair of defects in utero
Risks incurred with procedure includespremature delivery, maternal morbidity, fetal mortality
48
• Rachischisis invariably lethal; higher
Higher lesion tend to have worse prognosis
• Surgical closure of defect performed to preserve existing neurologic function
49
© Sonographic examination of fetal spine should include methodical survey of spine in sagittal and tra@sverse planes.
© Normal fetal spine should demonstrate posterior ossification centers completing spinal circle
50
Spina bifida
Associated sonographic cranial findings includes
© Associated sonographic cranial findings include
Flattening of frontal bones, head "lemon" shape
•Obliteration of cisterna magna
Inferior displacement of cerebellar vermis giving cerebellum rounded, banana shape
@Ventriculomegaly
51
• Spina Bifida
Sonographic findings associated with spina bifide
• Talipes
Cephaloceles
Cleft lip and palate
Hypotelorism
Heart defects
Gencourinary anomalies
52
• Spina Bifida association
• Spina bifida has been associated with multiple syndromes and chromosomal anomalies, including trisomy 18.
© Fetuses exposed to teratogens, such as valproic acid
© Maternal diabetes, maternal obesity, hyperthermia, folic acid deficiency have been associated with spina bifida.
• Familv history of spina bifida or anencephaly is significant risk factor for occurrence of spina bifida.
53
Dandy-Walker Malformation
Dandy-Walker, malformation (DWM) is defect that may have varying degrees of severity.
Manifests with agenesis or hypoplasia of cerebellar vermis with resulting dilation on fourth ventricle and enlargement of posterior fossa.
54
© Dandy Walker Complex encompasses the three main types of posteriOr fossa malformations:
• DWM with an elevated tentorium
• Dandy-Walker variant (DWV) manifests with cvstic dilation of the fourth ventricle and hypoplasia of the cerebellar vermis without an enlarged posterior fossa.
• Mega cisterna magna (MCM) is defined as an enlarged cisterna magna.
55
Development of cerebellar vermis
begin during 9t week.
56
© Diagnosis of agenesis and hypoplasia of cerebellar vermis should
© Diagnosis of agenesis and hypoplasia of cerebellar vermis should not be made prior to week 18.
© Communications between fourth ventricle and cistern magna not complete until week
18 of gestation
O Diagnosis of agenesis and hypoplasia of cerebellar vermis should not be made prior to week 18.
57
Dandy-Walker Malformation
© Associated with other intracranial anomalies about 30% of time, including:
• Agenesis of corpus callosum
Aqueductal stenosis
Microcephaly
• Macrocephaly
• Encephalocele
• Gyral malformations
• Heterotopias
O Lipomas
58
• Chromosomal anomalies that may be associated
Dandy-Walker Malformation
• Chromosomal anomalies that may be associated include triscmies 13, 18, 21, triploidy.
© Associated with several syndromes:
• Meckel-Gruber, Walker-Warburg, Aicardi ©
Is linked to congenital infections and maternal diabetes
59
Dandy-Walker Malformation @ Prognosis depends on presence or absence of associated anomalies and on degree of
hypoplasia of cerebellar vermis, as correlates with severity of mental retardation.
Mortality depends highly on other anomalies.
©Many infants with isolated DWM have subnormal IQ; some may have normal function.
60
Dandy-Walker Malformation
•Sonographic survey may reveal extracranial anomalies
• Sonographic survey may reveal extracranial anomalies also associated with DWM:
• Cardiac anomalies
Polydactyly
Facial clefts
Urinary tract anomalies
• Posterior fossa cyst
Splaying of cerebellar hemispheres as result of complete or partial genesis of cerebellar vermis
• Enlarged cisterna magna caused by cerebellar vermis anomaly and posterior fossa cyst
@Ventriculomegaly
61
Dandy-Walker Malformation
© Differential considerations should include
© Differential considerations should include arachnoid cyst, but identification of splayed cerebellar hemispheres may help to confirm DWM.
• Cerebellar hypoplasia should also be included in the differential diagnosis when cistern magna enlarged.
62
Porencephalic Cysts
• Is also known as porencephaly
• Cysts filled with cerebrospinal fluid that communicate with ventricular system or subarachnoid space
• May result from hemorrhage, infarction, delivery trauma, or inflammatory changes in nervous system
• Affected brain parenchyma undergoes necrosis, brain tissue is resorbed, and a cystic lesion remains
63
• Postnatal problems may include:
Porencephalic Cysts
• Seizures
• Developmental delays
• Motor deficits
• Visual and sensory problems
• Hydrocephalus
64
Porencephalic Cysts
Sonographic features
sonographic reatures
Sonographic features
• Cyst within brain parenchyma without mass effect
• Communication of cyst with ventricle or
subarachnoid space
• Reduction in size of affected hemisphere
• May cause midline shift and contralateral ventricular enlargement
65
Porencephalic Cysts
• May be confused with
Porencephalic Cysts
• May be confused with arachnoid cysts, although lack of mass effect seen with porencephaly may aid in differ&htiating
66
Schizencephaly
. Rare disorder characterized by clefts in cerebral cortex
67
Schizencephaly
Place
• Clefts unilateral or bilateral, open-lip or closed-lip defects,
and
usually in area of
Sylvian fissure
68
Schizencephaly
• Schizencephaly thought to result from abnormal migration of neurons.
• Clefts can extend from ventricle to outer surface of brain and are©ned with abnormal gray matter.
69
Schizencephaly associated with
• Cause remains unclear; has been linked with multiple assaults during pregnancy
• Associated with:
• Congenital infections
• Drugs
• Other toxic exposures
• Vascular accidents
• Metabolic abnormalities
• Also association yith aneuploidy
70
Schizencephaly
• Prognosis varies, with mild to severe outcomes
• Open-lip lesions and bilateral clefts carry worse prognosis
71
• Long-term effects Schizencenhalv
include blindness; motor Long-termovinclude spastic quadriparesis,
hemiparesis, hypotonia.
• Seizures, mental retardation, and language impairment are possible.
• Hydrocephalus may be progressive and require shunt placement.
72
Schizencephaly in US
Sonographic features
• Fluid-filled cleft in cerebral cortex extending from ventricle to calvarium
• Ventriculomegaly may be observed.
73
Schizencephaly
• Associated with absence of septum pellucidum and corpus callosum
• Septo-optic dysplasia may be present in addition to other abnormalities of brain.
Disorder of early brain development.
Disorder of early brain development.
Traditionally defined by 3 characteristic features: underdevelopment (hypoplasia) of the optic nerves, abnormal formation of structures along the midline of the brain, and pituitary hypoplasia.
• Hydrocephaly can be seen when ventriculomegaly present; microcephaly has been observed.
74
Septa optic displasia
Disorder of early brain development.
Traditionally defined by 3 characteristic features: underdevelopment (hypoplasia) of the optic nerves, abnormal formation of structures along the midline of the brain, and pituitary hypoplasia.
75
Hydranencephaly
• Destruction of cerebral hemispheres by occlusion of internal carotid arteries
• Brain parenchyma destroyed and replaced by cerebrospinal fluid
76
Hydranencephaly
• Posterior communicating arteries preserved
• Midbrain and cerebellum present
• Basal ganglia, choroid plexus, thalamus may be spared.
• Rare abnormality occurs with frequency of approximately 1 in 10,000 births.
77
Hydranencephaly • Cause involves congenital infection or ischemia
• Infections associated include cytomegalovirus and toxoplasmosis
• Brain ischemia may result from maternal hypotension, twin-to-twin embolization, or vascular genesis; has been associated with cocaine abuse
78
Hydranencephaly in US
Sonographic features o
• Absence of normal brain tissue with almost complete replacement by cerebrospinal fluid
• Absent or partially absent falx
• Presence of midbrain, basal ganglia, cerebellum
• Choroid plexus may be identified.
• Macrocephaly may occur.
79
Hydranencephaly • May be confused with severe
hydrocephaly, although presence of an intact falx and
surrounding rim of brain parenchyma may help to differentiate
• Holoprosencephaly with severe ventriculomegaly may have similar appearance.
• These three anomalies have extremely poor outcomes.
80
Ventriculomegaly (Hydrocephalus)
• Ventriculomegaly refers to dilation of ventricles within brain.
• Hydrocephalus occurs when ventriculomegaly coupled with enlargement of fetal head
• Incidence of hydrocephalus occurs in 0.3 to 1.5 per 1000 live births
81
Ventriculomegaly (Hydrocephalus)
• Enlargement of ventricles occurs with obstruction of cerebrospinal fluid flow.
• Obstruction may be caused by ventricular defect like aqueductal stenosis; is referred to as noncommunicating hydrocephalus
• Obstruction may be outside of ventricular system, such as with arachnoid cyst; is referred to as communicating hydrocephalus
82
Ventriculomegaly (Hydrocephalus)
* Enlarged ventricles may exert pressure on brain tissue, sometimes producing irreyersible brain damage.
83
ventriculomegaly (riyarocepnalus) associated with
• May be associated with anomaly, or cause may remain@nknown
• Abnormalities linked with ventricular dilation include:
• Aqueductal stenosis
• Arachnoid cysts
• Vein of Galen aneurysms
• Common causes of ventriculomegaly include spina bifida and encephaloceles
84
Common causes of ventriculomegaly
include spina bifida and encephaloceles
85
Ventriculomegaly (Hydrocephalus) may present with
• Dandy-Walker malformation, ACC, lissencephaly, schizencephaly, and holoprosencephaly may present with hydrocephalus.
• Intracranial neoplasm, such as teratoma, may cause ventricular dilation.
• Ventriculomegaly may be associated with musculoskeletal anomalies.
86
Ventriculomegaly (Hydrocephalus)
• May be manifestation of
syndrome or chromosomal abnormality
• Ventricular enlargement has been linked to congenital infections, such as toxoplasmosis and cytomegalovirus.
87
Ventriculomegaly (Hydrocephalus)
• Typically progresses from
•
occipital horns into temporal then to frontal ventricular horns
Quantitated by measuring ventricular atrium across glomus of choroid plexus
• Ventricle considered dilated when its
diameter exceeds 10 mm
88
Ventriculomegaly (Hydrocephalus)
Sonographic features
• Lateral ventricular enlargement > 10 mm
• "Dangling choroid sign," as gravity-dependent choroid plexus falls into increased ventricular
space
• Possible dilation of third and fourth ventricles
• Fetal head enlargement when biparietal and head circumference measurements exceed those for established gestational age
89
Ventriculomegaly (Hydrocephalus)
• In absence of other abnormalities, fetal therapy for shut placement may be an gotion.
• Cesarean delivery may also be necessary because of large size of fetal head.
90
Ventriculomegaly (Hydrocephalus) confused with
• Severe hydrocephaly may be confused with hydranencephaly and holoprosencephaly.
• Documenting a complete falx and the presence of choroid p¢exus in the lateral ventricles, as well as separate third and fourth ventricles, help differentiate severe ventriculomegaly from
other anomalies
91
Microcephaly
• May result from inheritance of either autosomal-dominant or autosomal-recessive pattern
• May also occur with chromosomal aberrations and various brain anomalies O
• Teratogens linked with microcephaly
92
Microcephaly in US
• Sonographic diagnosis depends on accurate assessment of fetal age.
• Biparietal diameter, occipitofrontal diameter, and headCircumference should be used.
• Ratios comparing head perimeter to abdominal perimeter and head perimeter to femur length are useful.
93
Microcephaly
• Impaired cranial growth should coincide
• Impaired cranial growth should coincide with appropriate growth of abdominal circumference and femur length.
• Serial measurements for fetus at risk for microcepkalus should be performed at monthly intervals.
• Because microcephaly may manifest later in pregnancy, diagnosis before 24 weeks of gestation may be impossible.
94
Microcephaly in US
Sonographic features
• Small biparietal diameter
• Small head circumference
• Abnormal head circumference/abdomen circumference and head circumference-to-femur length ratios
• Other sonographic findings associated may include disorganized brain tissue and ventriculomegaly.
• Thorough search for evidence of associated anomaly should ensue, including careful investigation of fetal heart.
• Cerebral calcifications may be identified with congenital infections.
• Fetus with encephalocele may have microcephaly because of amount of brain tissue protruding outside calvarium.
95
Microcephaly associated
• Associated with trisomies 13, 18, 21, 22 and with triploidy
• Syndromes that have been linked include:
• Meckel-Gruber
• Pena-Shokeir
• Neu-Laxova
