6 fetal skull dr ahmed esawy FETAL SKULL Microcephaly Teratogens Associated with Microcephaly Drugs (Alcohol, amniopterin, hydantoin) Maternal PKU Radiation exposure Infections ( Rubella, CMV, toxoplasmosis) congenital microcephalus and megalencephally lemon sign Lemon sign and Ventriculomegaly Binder syndrome Apert syndrome Trigonocephaly fetal craniosynostosis dolicocephaly-fetal Pfeiffer syndrome Saethre–Chotzen Syndrome Anencephaly Acrania Cephalocele Types: – 1. Meningoceles: only CSF – 2. Encephaloceles: Brain • Locations: – Occipital (75 %) – Frontoethmoidal (13 %) – Parietal (12 %) cephalic index

1. Dr/AHMED ESAWY

2. Dr. Ahmed Esawy
MBBS M.Sc
MD
Dr/AHMED ESAWY

3. Dr/AHMED ESAWY
FETAL SKULL

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7. (a) Major sutures involved in craniosynostosis and (b) skull deformities based on the suture(s)
involved (figure adapted from Keating2).
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Microcephaly
Microcephaly may be caused by a teratogen, a chromosomal abnormality, or a genetic
defect. The diagnosis of microcephaly and its prognostic significance for intellectual
impairment is more likely to be accurate when the head circumference is 3 SD or more
below the mean for dates
Teratogens Associated with Microcephaly
Drugs (Alcohol, amniopterin, hydantoin)
Maternal PKU
Radiation exposure
Infections ( Rubella, CMV, toxoplasmosis)

16. microcephaly
• exposure to hazardous chemicals/substances
• · methylmercury poisoning
• · lack of proper vitamins and nutrients in the diet
• · cytomegalovirus, rubella, or varicella infection
• · prescription or illegal drug and alcohol consumption
• · untreated phenylketonuria
• head circumference (HC) more than 2 standard
devaition below the mean for age and gender. Some
academics advocate defining it as head circumference
more than 3 standard devaition
Dr/AHMED ESAWY

17. Classification of
congenital microcephalus
and megalencephally
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The lemon sign refers to the shape of the fetal skull at
ultrasonography (US) when the frontal bones lose their
normal convex contour and appear flattened or
inwardly scalloped.
This gives the skull a shape similar to that of a lemon .
The sign is seen on transverse sonograms of the fetal
cranium obtained at the level of the ventricles .

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Transverse cranial
sonogram of an
18-week-old fetus
demonstrates the normal
contour of a fetal skull

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Transverse cranial sonogram of a 20-
week-old fetus with spina bifida. Image
obtained at the level of the ventricles
demonstrates the lemonlike configuration
of the fetal skull due to biconcavity (arrows)
of the frontal bones.

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25. • Lemon sign and
ventriculomegaly at 13
weeks gestation. Axial
transabdominal US
image of the fetal head
shows bilateral frontal
indentation (arrows)
and ventriculomegaly, as
evidenced by a dangling
choroid plexus (C) and
convexity of the lateral
wall of the lateral
ventricle (arrowheads).
Dr/AHMED ESAWY

26. Lemon Sign: bilateral skull indentations just anterior to insula, due to
collapse of anterior calvarium. Seen prior to 24 weeks in 75-100% of
open NTD, then disappears in later gestation.Dr/AHMED ESAWY

27. Lemon sign in Chiari II malformation. There is indentation of
the frontal bones of the skull (arrows). There are also
associated ventriculomegaly present.
Dr/AHMED ESAWY

28. Axial scan shows the tipical features of
the Arnold-Chiari type II malformation
Dr/AHMED ESAWY

29. Binder syndrome
:Binder syndrome or maxillo-nasal dysplasia can be diagnosed in early gestation.
The prominent feature is the small nose with flattening of the fronto-nasal angle.
It is frequently associated with other anomalies affecting mostly the fetal skeleton,
malformations of the cervical spine, chondrodysplasia punctata and warfarin embryopathy
Dr/AHMED ESAWY

30. Apert syndrome
The combination of hypertelorism, a large metopic suture and finger
abnormalities is suggestive of Aper syndrome
Dr/AHMED ESAWY

31. Trigonocephaly
:An abnormal shape of the skull with a triangular forehead and a premature
closure of the metopic suture is suggestive of trigonocephaly, a rare form of
craniostenosis that is frequently associated with other anomalies
Dr/AHMED ESAWY

32. Prenatal ultrasound diagnosis of fetal craniosynostosis
Lateral view of the fetal skull showing calvarial sutures. a, anterior fontanelle; b,
pterion; c, frontal bone; d, coronal suture.
Dr/AHMED ESAWY

33. dolicocephaly-fetal
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34. • (a) Pfeiffer syndrome at
24 weeks showing frontal
bossing
• and marked nasal bridge.
• (b and c) closed coronal
sutures (arrows).
Dr/AHMED ESAWY

35. • a) Saethre–Chotzen
syndrome at 12 weeks
showing flat facies and
high forehead. (b) Fetal
profile in Saethre–Chotzen
syndrome at 20 weeks
Dr/AHMED ESAWY

36. • Moderate dolichocephaly at 22
weeks’ gestation.
• (a) Sagittal view. (b) Axial view.
• (c) Closed sagittal suture at 32
weeks Dr/AHMED ESAWY

37. Anencephaly
• Absence of cranial vault (Acrania).
• Inability to determine BPD (absence of
cranial vault by 12-14 weeks).
• Associated anomalies (spina bifida-
meningocele - myelomeningocele).
• 100% mortality.
• DD: (microcephaly- deephy engaged
head).
Dr/AHMED ESAWY

38. Anencephaly
• The absence of the cranial vault
Dr/AHMED ESAWY

39. If early in pregnancy, brain tissue can be seen
Head has an irregular shape
There is no soft tissue seen above the orbits
Face – eyes appear “frog like”
Ultrasound Findings
Dr/AHMED ESAWY

40. Anencephaly
• Most Common Neural Tube Defect
• Cerebrovasculosa Replaces Hemispheres
• Fatal
• US Findings:
– 1. Absence of Cranial Vault
– 2. Cerebral Hemisphere above orbital level
Dr/AHMED ESAWY

41. Anencephaly
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43. Acrania and exencephaly at 12 weeks gestation
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49. Anencephaly throughout gestation
Anencephaly throughout gestation
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51. Cephalocele
• Protrusion through Bony
Calvarium Defect
– Brain
– CSF filled Sac
• Types:
– 1. Meningoceles: only CSF
– 2. Encephaloceles: Brain
• Locations:
– Occipital (75 %)
– Frontoethmoidal (13 %)
– Parietal (12 %)
Dr/AHMED ESAWY

52. Occipital cephalocele. There is a defect in the calvarium at the
occiput. Brain is seen herniating through the defect (arrow).
Dr/AHMED ESAWY

53. Encephalocele
A, Suboccipital bregmatic sonogram, with
anterior to the reader’s left, at 26 weeks shows
encephalocele (asterisk) but no CSP. The faint
hypoechoic structure seen anteriorly in the
midline (arrow) represents the fornix, a normal
structure caudal to the CSP that is commonly
mistaken for the CSP. The normal CSP must be
a boxlike fluid-filled structure that
is bordered on either side by the medial walls
of the frontal horns of the lateral ventricles
B, Axial follow-up sonogram,
with anterior to the reader’s left,
at 32 weeks shows colpocephaly
and absence of the CSP; note how
easy it is to miss absence of the
CSP unless one is specifically
looking for it.
Dr/AHMED ESAWY

54. • Encephalocele at 14 weeks
gestation..
Dr/AHMED ESAWY

55. Cephaloceles
:Cephaloceles
Dr/AHMED ESAWY

56. cephalic index
• cephalic index (CI) = bipareital diameter (BPD) / occipitofrontal
diameter (OFD) x 100
• The cephalic index gives an idea of the fetal head shape. It can
change according to various situations such as
• presentation : e.g. breech presentation
• ruptured membrances
• presence of a twin pregnancy
• Often the mean value is taken ~ 78 (range 74 – 83 )
• An grossly decreased cephalic index suggests dolicocephallywhile a
grossly increased one can suggest brachycephally.
Dr/AHMED ESAWY

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