3. Introduction
• Central nervous system (CNS) malformations are some of the most
common of all congenital abnormalities.
• Neural tube defects are the most frequent CNS malformations and
amount to about 1–2 cases per 1000 births.
• The incidence of intracranial abnormalities with an intact neural tube
is uncertain as probably most of these escape detection at birth and
only become manifest in later life.
• Long-term follow-up studies suggest however that the incidence may
be as high as one in 100 births
4. Introduction
• Ultrasound has been used for nearly 30 years as the main modality to
help diagnose fetal CNS anomalies.
• The scope of these guidelines is to review the technical aspects of an
optimized approach to the evaluation of the fetal brain in surveys of
fetal anatomy, that will be referred to in this document as a basic
examination
5. Introduction
• Detailed evaluation of the fetal CNS (fetal neurosonogram) is also
possible but requires specific expertise and sophisticated ultrasound
machines.
• This type of examination, at times complemented by three-
dimensional ultrasound, is indicated in pregnancies at increased risk
of CNS anomalies.
6. Introduction
• In recent years fetal magnetic resonance imaging (MRI) has emerged
as a promising new technique that may add important information in
selected cases and mainly after 20–22 weeks although its advantage
over ultrasound remains debated
7. General Considerations
Gestational age
• The appearance of the brain and spine changes throughout gestation.
• To avoid diagnostic errors, it is important to be familiar with normal
CNS appearances at different gestational ages.
• Most efforts to diagnose neural anomalies are focused around
midgestation.
• Basic examinations are usually performed around 20 weeks'
gestation.
8. • The advantage of an early fetal neuroscan at 14–16 weeks is that the
bones are thin and the brain may be evaluated from almost all angles.
• Usually, a satisfying evaluation of the fetal CNS can always be
obtained in the second and third trimesters of pregnancy.
• In late gestation, visualization of the intracranial structures is
frequently hampered by the ossification of the calvarium
9. Ultrasound transducers
• High frequency ultrasound trandsucers increase spatial resolution but
decrease the penetration of the sound beam.
• The choice of the optimal transducer and operating frequency is influenced
by a number of factors including maternal habitus, fetal position and the
approach used.
• Most basic examinations are satisfactorily performed with 3–5-MHz
transabdominal transducers.
• Fetal neurosonography frequently requires transvaginal examinations that
are usually conveniently performed with transducers between 5 and 10
MHz
• Three-dimensional ultrasound may facilitate the examination of the fetal
brain and spine
10. Basic Examination
Qualitative evaluation
• Transabdominal sonography is the technique of choice to investigate
the fetal CNS during late first, second and third trimesters of gestation
in low risk pregnancies.
• The examination should include the evaluation of the fetal head and
spine.
11. Basic Examination
Qualitative evaluation
• Two axial planes allow visualization of the cerebral structures relevant
to assess the anatomic integrity of the brain
• These planes are commonly referred to as the transventricular
plane and the transcerebellar plane.
• A third plane, the so-called transthalamic plane, is frequently added,
mostly for the purpose of biometry
• Structures that should be noted in the routine examination include
the lateral ventricles, the cerebellum and cisterna magna, and cavum
septi pellucidi.
• Head shape and brain texture should also be noted on these views
12. Sonographic examination of the fetal central nervous system: guidelines for performing the ‘basic examination’ and the ‘fetal neurosonogram’
Ultrasound in Obstetrics and Gynecology
Volume 29, Issue 1, pages 109-116, 3 JAN 2007 DOI: 10.1002/uog.3909
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13.
14. Fetal Neurosonogram
• It is commonly accepted that dedicated fetal neurosonography has a
much greater diagnostic potential than that of the standard
transabdominal examination, and is particularly helpful in the
evaluation of complex malformations.
• However, this examination requires a grade of expertise that is not
available in many settings and the method is not yet universally used.
• Dedicated fetal neurosonography is useful in patients with an
increased risk of CNS anomalies, including cases in which the basic
examination identifies suspicious findings.
15. Fetal Neurosonogram
• The basis of the neurosonographic examination of the fetal brain is
the multiplanar approach, that is obtained by aligning the transducer
with the sutures and fontanelles of the fetal head
• When the fetus is in vertex presentation, a
transabdominal/transvaginal approach can be used.
• In fetuses in breech presentation, a transfundal approach is used,
positioning the probe parallel instead of perpendicular to the
abdomen.
16. Fetal Neurosonogram
• Vaginal probes have the advantage of operating at a higher frequency
than do abdominal probes and therefore allow a greater definition of
anatomical details.
• For this reason, in some breech presenting fetuses an external
cephalic version may be considered in order to use the transvaginal
approach.
• Evaluation of the spine is a part of the neurosonographic examination
and is performed using a combination of axial, coronal and sagittal
planes.
17. Fetal Neurosonogram
• The neurosonographic examination should include the same
measurements that are commonly obtained in a basic examination:
• the biparietal diameter, head circumference and the atrium of the
lateral ventricles.
• The specific measurements obtained may vary also depending upon
the gestational age and the clinical setting.
18. Fetal brain
• Whether the exam is performed transvaginally or transabdominally, proper
alignment of the probe along the correct section planes usually requires
gentle manipulation of the fetus.
• A variety of scanning planes can be used, also depending upon the position
of the fetus
• A systematic evaluation of the brain usually includes the visualization of
four coronal and three sagittal planes.
• In the following, a description of the different structures that can be
imaged in the late second and third trimesters is reported.
• Apart from the anatomic structures, fetal neurosonography should also
include evaluation of the convolutions of the fetal brain that change
throughout gestation
19. Fetal brain
• Coronal planes
• The transfrontal plane or Frontal-2 plane.
• The visualization of this plane is obtained through the anterior
fontanelle and depicts the midline interhemispheric fissure and the
anterior horns of the lateral ventricles on each side.
• The plane is rostral to the genu of the corpus callosum and this
explains the presence of an uninterrupted interhemispheric fissure.
• Other structures observed are the sphenoidal bone and the ocular
orbits.
20. Sonographic examination of the fetal central nervous system: guidelines for performing the ‘basic examination’
and the ‘fetal neurosonogram’
Ultrasound in Obstetrics and Gynecology
Volume 29, Issue 1, pages 109-116, 3 JAN 2007 DOI: 10.1002/uog.3909
http://onlinelibrary.wiley.com/doi/10.1002/uog.3909/full#fig3
21. Fetal brain
• The transcaudate plane or Mid-coronal-1 plane
• At the level of the caudate nuclei, the genu or anterior portion of the
corpus callosum interrupts the continuity of the interhemispheric
fissure.
• Due to the thickness of the genu in coronal planes it is observed as a
more echogenic structure than the body of the corpus callosum.
• The cavum septi pellucidi is depicted as an anechogenic triangular
structure under the corpus callosum.
• The lateral ventricles are found at each side surrounded by the brain
cortex. In a more lateral position the Sylvian fissures are clearly
identified.
22. Fetal brain
• The transthalamic plane or Mid-coronal-2 plane
• Both thalami are found in close apposition but in some cases the third
ventricle may be observed in the midline with the interventricular
foramina and the atrium of the lateral ventricles with the choroid
plexus slightly cranial on each side (Mid-coronal-3 plane).
• Close to the cranial base and in the midline the basal cistern contains
the vessels of the circle of Willis and the optic chiasma.
23. Fetal brain
• The transcerebellar plane or Occipital-1 and 2 plane.
• This plane is obtained through the posterior fontanels and enables
visualization of the occipital horns of the lateral ventricles and the
interhemispheric fissure.
• Both cerebellar hemispheres and the vermis are also seen in this
plane.
24. Fetal brain
• Sagittal planes
• Three sagittal planes are usually studied: the midsagittal; and the
parasagittal of each side of the brain.
25. Sonographic examination of the fetal central nervous system: guidelines for performing the ‘basic examination’
and the ‘fetal neurosonogram’
Ultrasound in Obstetrics and Gynecology
Volume 29, Issue 1, pages 109-116, 3 JAN 2007 DOI: 10.1002/uog.3909
http://onlinelibrary.wiley.com/doi/10.1002/uog.3909/full#fig4
26. Fetal brain
• The midsagittal or median plane shows the corpus callosum with all
its components; the cavum septi pellucidi, and in some cases also
the cavum vergae and cavum veli interpositi, the brain stem, pons,
vermis and posterior fossa.
• Using color Doppler the anterior cerebral artery, pericallosal artery
with their branches and the vein of Galen may be seen.
• The parasagittal or Oblique plane depicts the entire lateral ventricle,
the choroid plexus, the periventricular tissue and the cortex.
52. The fourth ventricle, also called the IT, appears as an anechoic region with two horizontal echogenic borders,
allowing reliable identification: the anterior border of the IT is the posterior border of the BS, and the posterior
border of the IT is the choroid plexus (Chor. plex.) of the fourth ventricle.
The choroid plexus is a well-recognized structure floating in the fluid of the IT and the future cisterna magna (f.CM),
which are still connected to one another. The brainstem–occipital bone distance (BSOB) appears larger than does
the brainstem diameter itself. OB, occipital bone.
13 w fetus
53. Fetal spine
• Three types of scanning planes can be used to evaluate the integrity
of the spine. The choice depends upon the fetal position.
• Usually, only two of these scanning planes are possible in a given
case.
• In transverse planes or axial planes, the examination of the spine is a
dynamic process performed by sweeping the transducer along the
entire length of the spine and at the same time keeping in the axial
plane of the level being examined
• The vertebrae have different anatomic configurations at different
levels.
• Fetal thoracic and lumbar vertebrae have a triangular shape, with the
ossification centers surrounding the neural canal.
• The first cervical vertebrae are quadrangular in shape, and sacral
vertebrae are flat.
54. Sonographic examination of the fetal central nervous system: guidelines for performing the ‘basic examination’
and the ‘fetal neurosonogram’
Ultrasound in Obstetrics and Gynecology
Volume 29, Issue 1, pages 109-116, 3 JAN 2007 DOI: 10.1002/uog.3909
http://onlinelibrary.wiley.com/doi/10.1002/uog.3909/full#fig5
55. Fetal spine
• In sagittal planes the ossification centers of the vertebral body and
posterior arches form two parallel lines that converge in the sacrum.
• When the fetus is prone, a true sagittal section can also be obtained,
directing the ultrasound beam across the unossified spinous process.
• This allows imaging of the spinal canal, and of the spinal cord within
it
• In the second and third trimesters of gestation the conus medullaris is
usually found at the level of L2-L3
56. Sonographic examination of the fetal central nervous system: guidelines for performing the ‘basic examination’
and the ‘fetal neurosonogram’
Ultrasound in Obstetrics and Gynecology
Volume 29, Issue 1, pages 109-116, 3 JAN 2007 DOI: 10.1002/uog.3909
http://onlinelibrary.wiley.com/doi/10.1002/uog.3909/full#fig6
57. Fetal spine
• n coronal planes, one, two or three parallel lines are seen, depending
upon the orientation of the sound beam
58.
59. Phasesof Development
• Certain elements of the nervous systemare
quite mature at FT,other continue their
development throughout infancy and
childhood
60. EVENTSOF IMPORTANCE
EVENT TIME OF
OCCURRENCE
Organinduction 2 ½ - 8weeks 1-4 WEEKS:NTD
4-8 WEEKS:Holo
Neural Proliferation 2 – 5 months
Glial cell
Proliferation
6 mo prenatally to 6 mo
postantally
Myelination 2nd mo prenatally up to
3rd decade
Synaptogenesis 5 mo prenatally Through
learning all life
61. OrganInduction
• 16th day: embryo is 3 layers (ectod, mesod,
endo)
• 18th day: notochord mesod induces ectod
thickening in the central portion to form he
neural plate
• 28th day: complete neuraltube
62. EMBRYOLOGY
Nelson.
A single sheet of cells – midline ectoderm
Ectodermal plate enlarges
Neural folds become elevated and fuse forming
Neural tube
Fusion occurs in cervical region and proceed
both caudally and cephalic, by secondary
neuralization
Cephalic completed by 23rd day
Caudally completed by 28th day
Thus neural tube formation completed by 4th
week
67. Thecentral nervous system
(CNS)appears at the beginning
of the third week asaslipper-
shaped plate of thickened
ectoderm, the neural plate, in
the middorsal region in frontof
the primitivenode.
Its lateral edgessoon elevateto
form the neuralfolds.
68. Central Nervous System
Thecephalic end of the neural tubeshows
three dilations, the primary brainvesicles:
1. Theprosencephalon, orforebrain;
2. Themesencephalon,ormidbrain;
3. Therhombencephalon, orhindbrain.
Simultaneously it forms twoflexures:
A. Thecervicalflexureat the junction ofthe
hindbrain and the spinalcord.
B. Thecephalic flexurein the midbrainregion.
When the embryo is 5weeks old,the
prosencephalon consistsof twoparts:
i. The telencephalon,formedbya midportion
andtwo lateral outpocketings, theprimitive
cerebral hemispheres,
ii. Thediencephalon,characterized by
outgrowth of theoptic vesicles.
71. Spinalcord
• Develops from caudal
cylindrical part ofneural
tube
• Cavity of the tube
bounded by thick lateral
wall, thin roof andfloor
72. POSITIONAL CHANGES OFTHE
CORD
• In the third month of development the spinal cord extends
the entire length of the embryo, and spinal nerves pass
through the intervertebral foramina at their level of origin.
• With increasing age,the vertebral column and dura
lengthen more rapidly than the neural tube, and the
terminal end of the spinal cord gradually shifts to a
higherlevel.
• At birth,this end is at the level of the third
lumbarvertebra.
• As a result of this disproportionate growth, spinal nerves
run obliquely from their segment of origin in the spinal
cord to the corresponding level of the vertebralcolumn.
73. POSITIONAL CHANGES OFTHE
CORD• Thedura remains attached to thevertebral column
at the coccygeallevel.
• In the adult, the spinal cord terminates at the
level of L2to L3,
• Thedural sacand subarachnoid spaceextend to S2.
• Below L2to L3,athreadlike extension of the pia mater
forms the filumterminale, which is attached to the
periosteum of the first coccygealvertebra and which
marks the tract of regression of thespinal cord.
• Nerve fibers below the terminal end of the cord
collectively constitute the caudaequina.
• `
75. • During pregnancy, the human brain and spine
begin asaflat plate of cells, which rolls into a
tube, called the neural tube. If all or part of
the neural tube fails to close, leaving an
opening, this is known asan open neuraltube
defect, or ONTD.Thisopening may be left
exposed (80 percent of the time), orcovered
with bone or skin (20 percent of the time).
77. Disorders of closure of Neural
tubes
• 1-Anencephaly
• 2- Neural tube defect (spinal defect)
• 3- encephalocele
78. • ONTDs→95%-veFH
• ONTDsresult from acombination of genes
inherited from both parents, coupled with
environmental factors. For this reason,ONTDs
are considered multifactorial traits, meaning
"many factors," both genetic and
environmental, contribute to theiroccurrence
Open Neural TubeDefects ETIOLOGY:
81. TYPESOFNTD
SECONDARY
-5% of allNTD.
Abnormal development of lower sacral
segment during secondaryneuralization
•Skinis usually intact
•Involves lumbo-sacral region
Eg.SpinaBifida Occulta
Meningocele
82. SpinaBifidaOcculta
• Very mild & commonform.
• Level - L5& S1.
• Asymptomatic which can only
detected by x-ray or
investigating a backinjury.
• May be associated with
tethered cord/ recurrent
meningitis ( dermal sinus)
83. • Usually associated with skin visible signson the back.
– Dimple
– Dermal Sinus
– lipoma /Pad of subcutaneous fat
– small hairgrowth
– Nevus flaminous (red spot) or portwine
87. Meningocele
• Least common form
• Sac contains meninges and
cerebro-spinal fluid. And covered
with skin
• Cerebro-spinal fluid protects the
brain and spinal cord.
• Thenerves are not badly damaged
and able to functionnormally.
• Small sacwhich increases on crying
• Limited disability ispresent.
88. Meningocele
Investigation:-
• MRI HEAD– exclude hydrocephalus/ dysgenesis
• MRI SPINE–exclude
(i)Diastematomyelia – division of spinal cord into two
halves by projection of fibrocartilagenous or bonyseptum
from post vertebralbody
(ii)Tetheredcord – slender threadlike filum terminale
attached to coccyxconus here is below L2instead L1
Treatment –
• Skinintact – surgery in infancy
• Skinlacerated – urgent treatment
• Look for recto vaginalfistula
89. Tetheredcord
• The spinal cord could be
caught against the
vertebrae
• Normal cord ends at lower
end of L1
• Motor weakness of lower
limbs
• Sphincteric problems such
as inefficient bladder
control.
91. • Most serious andcommon
• Thecyst not only contains
meninges and CSFbut alsothe
nerves and spinalcord.
• Thespinal cord is damaged or
not properly developedresulting
in motor and sensorydeficit.
• Majority have boweland
bladder problems.
92. • Myelomeningocele, is the most severeand
occurs when the spinal cord is exposed
through the opening in thespine, resulting in
partial or complete paralysis. and may have
urinary and bowel dysfunction.
93. Meningomyelocele
Sac + CSF + neural element +
discontinuous skin +
hydrocephalus(80%).
TYPE – 94% of all NTD - Lumbo sacral
- Area of well developed skin at
periphery With thin apex covered by
glistening arachnoid membrane
- Usually CSF oozing +
100. Prenataldetection ofNTD
Serum alpha-fetoprotein (AFP)
• Normal fetal glycoprotein (MW=70,000)
• Present normally in amniotic fluid and mother
serum start 12 week increase steadily till 32
week
• High maternal serum AFP > 2 multiples of
median for appropriate week of gestation is
diagnostic
• 91%sensitivity in spina bifida
101. • Measures the level of AFPin mothers'blood
during pregnancy.
• Abnormal levels of AFP-
Openneural tube defects(ONTD)
Down syndrome
Other chromosomalabnormalities
Defects in the abdominal wall of the fetus
Twins - more than one fetus is makingthe
protein
102. Ultrasound
Detect 90-95 % of cases of spina bifida
100% cases of anencephaly
In cases of elevated AFP diffrentiate NTD
fron non-neurological causes of elevatedAFP
e.g. omphalocele
104. • Anencephaly is atype of ONTDs
• Anencephaly and spina bifida are
the most commonONTDs
ANENCEPHALY
105. ANENCEPHALY
• Failure of closure of rostralneuropore.
• Largedefect of calvarium, meninges,scalp
associated with rudimentarybrain.
• Cerebral hemisphere and cerebellum
usually absent
• Die at birth or fewdays
• Etiology – genetic, environmental
toxins, nutrition
106. Symptoms
•In pregnancy:polyhydroamnios
At Birth:
• absenceof bony coveringover
the back of thehead
• missing bones around the front
and sides of thehead
•folding of theears
•Associated anomalies-
- cleft palate
- congenital heartdefects
• some basic reflexes, but
without the cerebrum,there
canbe no consciousnessand
the baby cannotsurvive
107. PrenatalDiagnosis
• U/S
• Maternal alpha-
fetoprotein -AFP
increased
• amniocentesis - atest
performed to
determine
chromosomal and
genetic disorders and
certain birth defects.
109. .Various types of brain herniation
due to abnormal ossification of the
skull.
110. Cephalocele
• adefect in the skull anddura
with extracranial herniation
of intracranialstructures
• Theycanoccur in isolation or
with varioussyndromes.
111. Cephalocele
The swelling is:
• soft to firm inconsistency,
• non pulsatile
• no impulse on crying.
• no discharge or leak from theswelling.
• the lesion remained static in sizeover
these years.
• Developmental milestones were normal
122. • Basedon its contents:
meningoencephaloceles, meningocele, atretic
cephaloceles & glioceles.
• Basedon the bone defects:
occipitocervical, occipital, parietal, frontal, te
mporal, frontoethmoidal, sphenomaxillary, sp
henoorbital, nasopharyngeal and lateral.
Occipital cephaloceles originate betweenthe
foramen magnum and the lambda They
contain dysplatic and gliotic brain tissue
within.
Cephaloceles Classification
123. Associatedanomalies/disorders
• absent corpus callosum,
• orofacial clefting,
• craniostenosis,
• Dandy-Walkerdefect,
• Arnold-Chiari defect
• Microcephaly,
• Epilepsy , MR, motor impairment,cortical
blindness in occipital encephaloceles
127. Midline malformation of the fetal brain
(4-8ws gestation)
Holoprosencephaly:
• Itisadisordercausedbythe failureof the prosencephalon (theembryonic
forebrain) to sufficiently dividein to the doublelobesof thecerebral
hemispheresresultin in asingle-lobedbrainstructure andsevere skullandfacial
defects.
128. Midline malformation of the fetalbrain
(4-8wsgestation)
Holoprosencephaly :
In most casesof holoprosencephaly, the
malformations are sosevere that babies die before
birth.
• In lesssevere cases,babies are born with normal or
near-normal brain development and facial
deformities that may affect the eyes,nose, and
upper lip.
129. Three classifications of
holoprosencephaly
• Alobar, in which the brain has not divided at all, is usually
associated with severe facialdeformities.
• Semilobar, in which the brain's hemispheres havesomewhat
divided, causesan intermediate form of thedisorder.
• Lobar, in which there is considerable evidence of separate
brain hemispheres, is the least severe form. In some casesof
lobar holoprosencephaly the baby's brain may be nearly
normal.
• Middle interhemispheric variant :hypoplasia of the middle
part of the corpus callosum & associated sts of medial side of ‘
hemisphere
132. Alobar HPE. (A) lack of separation of the two hemispheres.
Large dorsal cyst (dc) posteriorly. (B) reveals a midline
ventricle, a monoventricle (mv), that communicates posteriorly
with the dorsal cyst (dc).
133. Semilobar HPE. (C) separation of the hemispheres posteriorly
but not anteriorly. There is incomplete separation of the basal
ganglia. (D) reveals a lack of interhemispheric fissure
and a monoventricle (mv)
134. Lobar HPE. (E) reveals that two hemispheres are separated
by an interhemispheric fissure both anteriorly and
posteriorly. (F) documents incomplete separation of the
inferior frontal lobes near the midline.
136. These scans also show middle interhemispheric fusion defect. Note that there is a clear-cut midline both anteriorly and
posteriorly but in the coronal sections in the midline there is no separation between right and left.
140. Mother of a Stillborn Holoporencephalic Baby
• Sarah was warm and beautiful with her button nose, long perfect
fingers, and great big feet. It was so wonderful to have her in my
arms. I touched her face, played with her ears, marveled over her
little mouth, and kissed her tiny sweet face.
• The hard part came when I handed her back to the nurse to take
away.
• She told me I could have her back if I hadn't had enough time. But
there can never be enough time with your baby.
• Nothing short of taking them home to love forever is good enough.