Lecture on normal and abnormal spectrum of neuro-imaging findings in posterior fossa with focus on pattern recognition and clinico-radiological correlations.

1. A simplified approach…
felice.d’arco@gosh.nhs.uk

2. Summary
Case based Presentation
 Normal and Abnormal anatomy of the Posterior fossa
 Cystic Malformations of the Posterior Fossa
 Other cerebellar malformations
 Malformations involving cerebellum and brainstem
 Pattern recognition approach

4. Developmental
delay
1. both Normal
2. both abnormal
3. left abnormal
4. right abnormal
OK BUT WHY??

5. Length of
pons in
sagittal: 1.5
of midbrain
and medulla
Base of the IV
ventricle is a
straight line and
the fastigium is
acute and in
midpoint
Cerebellar
folia are
parallel to the
calvarium
(“onion-like”)
Fissures
radiating toward
cerebellar nuclei

6. Developmental
delay
Normal !

7. 6 yo, male, dev. Delay, shunted
hydrocephalus
10 yo, male, hydrocephalus
Diagnosis?
Differences?

8. 6 yo, male, dev. Delay, shunted
hydrocephalus
10 yo, male, hydrocephalusHypoplastic
vermis,
rotated.
Dilatation IV
ventricle,
fastigium
flattened
*
Enlarged
posterior
fossa
DANDY WALKER
MALFORMATION

9. 6 yo, male, dev. Delay, shunted
hydrocephalus
10 yo, male, hydrocephalusNormal
vermis, may
be rotated,
fastigium
present
Dilatation IV
ventricle
Normal
posterior
fossa
BLAKE’S POUCH CYST
Diagnostic Pearls:
- Both can have
hydrocephalus!
- Look at the

10. Normal Vermian Anatomy: 9 lobules
Diagnostic Pearl: 3D T1 WI is the choice

11. Cystic Malformation of the posterior Fossa
PF Arachnoid Cyst Mega Cisterna Magna
Severino et a. 2019
Poretti et al. 2016

12. What about so called “inferior vermis hypoplasia”?
Severino & Huisman 2019
Isolated inferior vermian hypoplasia and
apparent but not true enlargement of the fourth
ventricle (Botsemani et al 2015).

14. 3yo, dystonia, dev delay, clonus 23 mo, history of hypoglycemia at birth 4yo female, squint

15. 4yo female, squint
Unilateral Cerebellar
Hypoplasia
Non
progressive
Absent
widening of
the fissures
Disruptive
pre-natal
Origin
(hemorrhage
18-24 wks)

16. Global Cerebellar Hypoplasia
Global reduction of the
Volume of hemispheres and
vermis but normal shape
Absent
widening of
the fissures
Different
etiology (
consider
congenital
infection!)
Global Cerebellar Atrophy

17. 23 mo, history of hypoglycemia at birth
Isolated (“pure”)
Cerebellar atrophy in
Pz with CGD
Progressive
Widening of
the fissures
Wide
differential
(neurogenetic
conditions)

18. Poretti et al. Differential Diagnosis of Cerebellar Atrophy in Childhood: An Update
2015

19. “heterogeneous group of prenatal-onset neurodegenerative disorders,
mainly but not exclusively affecting the cerebellum and pons.”
Pontocerebellar Hypoplasia
11 types of so
called PCH
Can have non-
progressive course
Dragonfly vs Global
pattern

21. Pattern recognition
Scola et al. 2019
Progressive
cerebellar
atrophy
(“dragonfly”)
PVL like
changes
Thin corpus
callosum
Figure of 8
midbrian in
axial
PCH 9 due to AMPD2 mutation

22. Cb Cysts + normal
cerebrum &
dysplastic IV
CMD
Cb Cysts + Cobblestone Lis
& Z-shaped brainstem
LAMA1
Cb Cysts +
bilateral PMG
GPR 56
Blaser et al
2016
Pattern recognition: Cerebellar cysts

23. 2 y, perinatal history of difficulty in swallowing
Briguglio M, Pinelli L et al 2014
Pontine
Tegmenta
l Cap
Dysplasia

24. 7d old, dysmorphic features, abnormal eye movements
Rhomboencephalosynap
sis
Gomez Lopez
hernandez
Syndrome: RES +
scalp alopecia +
trigeminal
dysfunction
Control

25. 9yo old, female, developmental delay with absence
seizures
Molar tooth sign :
Joubert Syndrome

26. Joubert Syndrome is just a radiological
sign!
Romani, Micalizzi, Valente. Lancet 2013
Ciliopathies
Multiorgan
involvement
ocular,
retinal
hepatic,
skeletal
(polydactyly)
, and renal
abnormalitie
s

27. Putting pieces together: clue for the
diagnosis!
Poretti et al.
Orphanet Journal of
Rare Diseases 2012

28. 4 y male, delay in both cognitive and motor development, intractable
seizures
Dysmorphic,
asymmetric MCP
 Abnormal brainstem
“unusual
orientated/dysmorphic
basal ganglia
Abnormal corpus
callosum
Malformation of the
cortex
Cerebellar
hypoplasia/dysplasia
Radiological constellation of
findings consistent with
tubulinopathy
Bahi-Buisson N et al. Brain 2014

29. 1 y male, deafness, very mild motor delay, pre-natal diagnosis of
hydrocephalus
Partial agenesis
corpus callosum
 Frontal
polymicrogyria
Nodular heterotopia
Colopcephaly
Cerebellar
hypoplasia/dysplasia
Chudley-McCullough
Syndrome – GPSM2 mut
Doherty et al. AM J Hum Gen 2012

30. Take Home Messages
 Know what’s normal and you will know what’s not
 Cerebellar Atrophy vs Hypoplasia (difficult but useful)
 Connect the dots: pattern recognition
 Ask a friend … neurologists , geneticists, neuro-
metabolic specialists
 LOOK AT THE BIGGER PICTURES, POSTERIOR FOSSA
IS JUST A PART OF THE BRAIN AND BRAIN JUST A
PART OF THE BODY!!

31. felice.d’arco@gosh.nhs.uk
The Villa Poppaea is an ancient Roman
seaside villa situated between Naples and
Sorrento, in southern Italy.