fetal brain us in the second trimester - espr · characteristics of the fetal brain in the second...
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FETAL BRAIN US IN THE SECOND TRIMESTER
C . G A R E L
D E P A R T M E N T O F R A D I O L O G Y , H Ô P I T A L D ’ E N F A N T S A R M A N D - T R O U S S E A U ,
P A R I S , F R A N C E
ESPR Helsinki 20191
CHARACTERISTICS OF THE FETAL BRAIN IN THE SECOND TRIMESTER
• Most developmental abnormalities involving the midline structures
and the posterior fossa are present in the 2nd trimester
• Some disorders may not be present in the 2nd trimester, due to:
• brain maturation
• late growth of certain structures
• late onset of certain developmental disorders
• late growth of certain abnormalities
• late onset of acquired disorders
ESPR Helsinki 20192
MIDLINE STRUCTURES
• The cavum septi pellucidi
• Visible from 15 WG and in all fetuses by 18 WG (US >> MR)
• Numerous normal variants
ESPR Helsinki 2019
shape size echogenicity septations3
ABSENCE OF SEPTUM PELLUCIDUM
ESPR Helsinki 2019
24 WG+4
31 WG + 5 34 WG + 2 2 months 25 d
Absence of septum
pellucidum
+ opercular dysplasia
and polymicrogyria
Diagnosis in the late 2nd T
or 3rd T
Other fetus
4
THE CORPUS CALLOSUM
ESPR Helsinki 2019
17.5 WG 20 WG 21 WG19 WG
22 WG
The corpus callosum is complete by 22 WG
23 WG
Morphology
US>> MR
5
AGENESIS OF THE CORPUS CALLOSUM
24 WG + 3
Complete agenesis
of the corpus callosum
Diagnosis in the 2nd T6
PARTIAL AGENESIS OF THE CORPUS CALLOSUM
23 WG + 5 29 WG + 6 32 WG + 6
32 WG + 6 6 months
Diagnosis in the 2nd T
7
AGENESIS OF THE CC + ASSOCIATEDABNORMALITIES
33 WG + 3
4 months
Partial agenesis
of the corpus
callosum +
subependymal
nodular
heterotopia
Diagnosis in the
late 2nd T or 3rd T
8
AGENESIS OF THE CC + ASSOCIATEDABNORMALITIES
24 WG + 2
Right Left
Partial agenesis of the
corpus callosum and
abnormal gyration
Diagnosis in the 2nd T
9
AGENESIS OF THE CC + ASSOCIATEDABNORMALITIES
31 WG + 1 1st twin 2nd twin
Partial agenesis
of the CC with
delayed gyration
Diagnosis in the
3rd T
10
AGENESIS OF THE CC + ASSOCIATEDABNORMALITIES
32 WG + 4
6 months
Partial agenesis of the CC
with marked hypoplasia of
the olfactory bulbs
Diagnosis in the 3rd T
11
POSTERIOR FOSSA
23 WG
21 WG 33 WG
Same morphology in the 2nd and 3rd T
except for hemispheres foliation
Morphological analysis: MRI >> US
28 WG 12
DEVELOPMENTAL ABNORMALITIES OF THE POSTERIOR FOSSA
27 WG
24 WG
23 WG
35 WG
20 days20 WG
Dandy-Walker malformation
No changes in morphology over time
and whatever the technique
13
24 WG
DEVELOPMENTAL ABNORMALITIES OF THE POSTERIOR FOSSA
33 WG 28 WG
2 months
Blake’s pouch
Same morphology over time unless
late fenestration of the Blake’s pouch occurs
14
22 WG + 3
DEVELOPMENTAL ABNORMALITIES OF THE POSTERIOR FOSSA
34 WG + 2
11 months24 days 4 months
Retrocerebellar arachnoid cyst
Marked increase in size between
US at 2nd and 3rd T
15
DEVELOPMENTAL ABNORMALITIES OF THE POSTERIOR FOSSA
26 WG + 3 31 WG + 2
31 WG + 2 5 months
Partial
Rhombencephalosynapsis
Same appearance in the
2nd and 3rd T
16
ABSENT DISORDERS DURING THE 2ND T DUE TO BRAIN MATURATION
30 WG + 6Type I lissencephaly
Microcephaly
Insula like 21 WG
No sulci
Diagnosis in the 3rd T
17
ABSENT DISORDERS DURING THE 2ND T DUE TO BRAIN MATURATION
27 WG 31 WG + 6 35 WG + 2
3 months
Partial agenesis of the CC
+ curvilinear pericallosal
lipoma
Non visibility of the lipoma
on fetal MRI
Diagnosis with US in the
3rd T, often missed in the
2ndT when small lipoma
18
ABSENT DISORDERS DURING THE 2ND T DUE TO BRAIN MATURATION
33 WG
34 WG + 1 4 days
Subependymal pseudocysts
secondary to involution of the
germinal matrix
Diagnosis mostly in the 3rd T
May be present in the 2nd T
mainly in case of damage of
the germinal matrix
19
CMVEARLY DAMAGE OF THE GERMINAL MATRIX
23 WG
24 WG
20
LATE GROWTH OF CERTAIN STRUCTURES
34 WG
Transverse cerebellar diameter = 30 mm, << 3rd centile
Normal TCD in the 2nd T
Growth of the cerebellum is particularly rapid in the 3rd T
Cerebellar hypoplasia may be overlooked in the 2ndT
21
LATE ONSET OF CERTAIN DEVELOPMENTAL DISORDERS
34 WG
34 WG + 2
Two cases of pontocerebellar hypoplasia
Small TCD
Small pons (no bulge or small bulge)
+/- small vermis
Normal PF in the 2nd T+++
Late onset of PCH
Most cases are discovered after birth
22
LATE GROWTH OF CERTAIN ABNORMALITIES
32 WG + 5 34 WG + 5 34 WG + 5
Immature teratoma of the roof of the
3rd ventricle
33 WG + 4
ATRT of the 4th ventricle
In both cases, normal US in the 2nd T
23
LATE ONSET OF ACQUIRED DISORDERS
35 WG + 2
Born at
36 WG + 4
2 days
Grade IV haemorrhage, may occur at any time during the
pregnancy. Normal US in the 2nd T 24
LATE ONSET OF ACQUIRED DISORDERS
Monochorionic diamniotic twin pregnancy. IUFD of the 2nd twin at 22 WG.
Normal US before 22 WG
27 WG
left right
29 WG
Bilateral ischaemic lesions of the white matter,
may occur at any time during the pregnancy. 25
MESSAGES
• Due to normal chronology of the cerebral development:
• Some abnormalities may be depicted as well in the 2nd or 3rd T (midline and some
abnormalities of the posterior fossa)
• Some abnormalities may not be present in the 2nd T (late development of the
cerebellum)
• Some abnormalities are not visible in the 2nd T (gyration and migration disorders)
• Moreover:
• Some developmental disorders may be visible very late, even after birth (ex
pontocerebellar hypoplasia)
• Some lesions may develop late and are not visible in the 2nd T (ex tumours)
• Some lesions may occur at any time of the pregnancy (ex haemorhage, ischaemic
damage)
26
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