A RARE CASE OF EXENCEPHALY
ABSTRACT ID- IRIA -1221
20 years old G2 A1 lady
 Presented at 18 weeks POG for anamoly scan
 Antenatal period uneventful till date

USG
Obstetric USG
 Deficient cranial vault
above the levels of
orbit
 Brain tissue seen
protruding out of the
defect
 Polyhydramnios
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Provisional diagnosis Exencepahaly
MRI

Patient taken up for MRI
same day
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To confirm presence of
exencephaly
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T2 HASTE sequences
were performed
Fidings
Supraorbital cranial vault
was absent
 Disorganised brain tissue
seen protruding out of the
defect
 Bilaterally prominent
orbits : Frog Eye sign
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FINAL DIAGNOSIS
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EXENCEPHALY
DISCUSSION
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ACRANIA- EXENCEPHALY- ANENCEPAHALY
SEQUENCE
Acrania is the absence of the calvarium; the skull base
may be intact
Exencephaly is acrania with protrusion of a substantial
portion of the CNS into the amniotic cavity
Anencephaly is acrania with absence of most or all of the
brain tissue
Anencephaly is classified anatomically as
merocrania when the defect does not involve the foramen
magnum
 holoacrania when the defect extends through the foramen
magnum;
 Holoacrania with rachischisis if spinal defects are
associatedType of Neural tube defect
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DISCUSSION
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Incidence is around 1:1000. There is a recognised
female predilection with a F:M of ~4:1.
As with many other malformations, a number of
associated abnormalities are recognised:
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other neural tube defects: spina bifida (especially cervical)
congenital heart defects
cleft lip/palate
diaphragmatic hernia(s)
spinal dysraphism
skeletal anomalies: e.g. clubfeet
gastrointestinal abnormalities: e.g. omphalocele
urinary tract abnormalities: hydronephrosis most common
EXENCEPHALY
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Exencephaly is characterised by calvarial absence
and loss of fetal brain tissue to variable degrees and
is considered a precursor to anencephaly in
the acrania-exencephaly-anencephaly sequence.
Absence of the cranial vault exposes the brain to
contact with the amniotic fluid. Initially, an excessive
growth of the encephalic structures occurs with a
normal development of eyes and cranial nerves
Susequently, destructive processes of the exposed
brain occur
The eventual result is anencephaly
Markers : maternal serum alpha feto protein
(MSAFP) levels are highly elevated
RADIOGRAPHIC FEATURES
Imaging features have some overlap with that of
anencephaly except that there is some brain
tissue presence:
 cranial vault is absent or poorly formed, cephalad
to orbits
 nasal bone may be absent in most cases
 brain tissue is herniating or dangling in amniotic
fluid
 brain tissue may be attached to the amniotic
membrane
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US is an extremely
accurate technique for the
diagnosis of acrania, with
almost 100% sensitivity.
Transvaginal US can be
useful when the fetal head
is low in the pelvis and not
easily visible
The calcification of the
bone structures of the
skull can be discerned at
the 10th week of gestation;
therefore, it is suggested
not to attempt a diagnosis
before this week
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The characteristic US
feature is represented
by absent visualization
of the cranial vault
above the orbits, which
appear prominent; the
thalami and ventricles
are not detectable
In anencephaly it is
difficult to recognize the
cerebral tissue, while in
exencephaly it is usually
possible to detect a
normal amount of
cerebral tissue
AMNIOTIC BAND SEQUENCE WITH
EXENCEPHALY
Amniotic bands are thin fibrous bands causing
regional constrictions, amputations and
disruption of cranial bone formation .The brain
tissue is covered by only a vascular layer of
epithelium, and can be slowly degraded by the
amniotic fluid and degenerate into anencephaly.
 MRI:
 Usually HASTE T2 or SSFSE sequence is used ,
which is very fast and thus prevents motion
artifacts
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PROGNOSIS
Exencephaly is a precursor to anencephaly, and
essentially a lethal condition
 Advise and counselling for abortion is to be given
to the parents.
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REFRENCES
1. Wilkins-haug L, Freedman W. Progression of
exencephaly to anencephaly in the human fetus--an
ultrasound perspective. Prenat. Diagn. 1991;11 (4):
227-33
2. Bianchi DW, Crombleholme TM, D'Alton ME.
Fetology, diagnosis & management of the fetal
patient. McGraw-Hill Professional. (2000)
3. Timor-tritsch IE, Greenebaum E, Monteagudo A etal. Exencephaly-anencephaly sequence: proof by
ultrasound imaging and amniotic fluid cytology. J
Matern Fetal Med. 5 (4): 182-5.
4. Papp Z, Csécsei K, Tóth Z et-al. Exencephaly in
human fetuses. Clin. Genet. 1986;30 (5): 440-4.
5. Merz E, Bahlmann F. Ultrasound in obstetrics and
gynecology. Thieme Medical Publishers. (2005)