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Posterior fossa defects
Magda Sanz-Cortes
Maternal Fetal Medicine Research Group Hospital Clinic-University of Barcelona, Spain
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12th World Congress in Fetal Medicine
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Cerebellar hypoplasia
Romboencepahlosynapsis
Obliteration of the PF
Increased PF
Fetal Posterior fossa pathology Abnormal PF
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Examination
CEREBELLUM
POSTERIOR
FOSSA
CSP
SYMMETRIC
Axial plane: Transcerebellar
Measurements
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Examination
Axial plane: Transcerebellar
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Examination
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Structures
TENTORIUM
CEREBELLUM
MEDULLA
PONS CISTERNA
MAGNA
4th VENTRICLE
Posterior fossa
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Abnormal PF
If PF >10mm
Differential diagnosis:
MEGACISTERNA MAGNA
PF ARACHNOID CYST
BLAKE´S POUCH CYST
DANDY WALKER
MALFORMATION
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Abnormal PF MEGACISTERNA MAGNA
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Abnormal PF
Coronal plane Sagital plane
If isolated: Good prognosis
- PF>10mm
- Normal vermis
- Normoinserted tentorium
MEGACISTERNA MAGNA
Dror J Child Neurol 2009Bolduc Dev Med Child Neurol 2010; Long Prenat Diagn 2006
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Abnormal PF
PF ARACHNOID CYST
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Coronal plane
Abnormal PF
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Coronal plane Sagital plane
Abnormal PF
If isolated: Good prognosis
- PF>10mm
- Asymmetry
- Normal vermis
- Normal 4th ventricle
- Tentorium could be displaced
PF ARACHNOID CYST
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Abnormal PF BLAKE´S POUCH CYST
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Abnormal PF
If isolated: Good prognosis
Coronal plane Sagital plane
- 4th ventricle and PF communicated
- Normal vermis
- +/- Normoinserted tentorium
BLAKE´S POUCH CYST
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Abnormal PF DANDY WALKER MALFORMATION
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Abnormal PF DANDY WALKER MALFORMATION
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Coronal plane Sagital plane
Abnormal PF
Adverse prognosis
Rule out associated malformations
- PF>10mm
- Absence/Hypoplasic vermis
- Displaced tentorium
DANDY WALKER MALFORMATION
Long Prenat Diagn 2006
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Vermis
Normal
Tentorium
Suggestive US sign
Megacisterna
Magna
Nr
+
Isolated increased PF
PF arachnoid
cyst
Nr
+/-
Asymmetry
Blake´spouch
cyst
Nr
+/-
Hourglass sign
DWM
Absent/hypoplastic
-
Absent/hypoplasic
vermis
Abnormal PF If PF >10mm
Sonographic signs
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• If PF is > 10mm: Neurosonography for TV coronal and sagital planes.
Axial plane
Hourglass sign
Normal
vermis
Blake´s
pouch cyst Dandy Walker
malformation
Normal
Normal
vermis
Megacisterna
Magna
Asymmetry
cerebellar
hemispheres
Normal
vermis
Arachnoid
cyst
Absence/Small
vermis
Hypoplastic/
Absent vermis
Conclusions
Good prognosis Adverse prognosis
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Examination Sagital plane: Transcerebellar
Measurements
