MR Imaging of the Fetal Cerebellar Vermis in Utero: Criteria for

MR Imaging of the Fetal Cerebellar Vermis in Utero: Criteria for

MR Imaging of the Fetal Cerebellar Vermis in Utero: Criteria for Abnormal
Development, with Ultrasonographic and Clinicopathologic Correlation
A Robinson, S Blaser, A Toi, D Chitayat, W Halliday, M Gundogan, S Pantazi, G Ryan
The Hospital for Sick Children Departments of Diagnostic Imaging, Clinical & Metabolic Genetics and Neuropathology
Mount Sinai Hospital Departments of Medical Imaging, Prenatal Diagnosis & Medical Genetics and Obstetrics & Gynaecology
The University of Toronto, Ontario, Canada
Early developmental arrest
Arrest at 12-14 weeks
Vermis incomplete
IV ventricle uncovered
US
MR at 20 weeks
cyst ovoid
congenital muscular
dystrophy
206-2122083
fetal demise
Arrest at 16 weeks
Inferior vermian hypoplasia
IV ventricle covered
US
MR at 25 weeks
Postnatal MR
cyst “keyhole”
vermis small
247-805226622*
inferiorly
cortical heterotopias
developmental delay
Dandy-Walker Spectrum: Degree of vermian dysplasia (not “cyst” size) determines prognosis
US
MR at 22 weeks
ovoid
Dandy-Walker
Malformation PLUS
trapezoid
Cerebellopontine
hypoplasia . . .
cyst ovoid
221-1041460
ongoing
pregnancy
ongoing
pregnancy
US
MR at 22 weeks
poor outcome expected
Classic Dandy-Walker
Malformation
trefoil
Vermis small & poorly
lobulated . . .
cyst trapezoid
US
220-1991156
fetal demise
but better outcome
than for fetus above
MR at 34 weeks
Dandy-Walker
Malformation MINUS
keyhole
Less vermian dysplasia
Posterior fossa “cyst” shape on US changes with reducing hypoplasia
Dandy-Walker Spectrum features:
•Vermian dysplasia or hypoplasia
•4th ventricle dilated or encysted
•Tegmentovermian angle increased
•Cisterna magna enlarged
normal
. . . even better outcome
cyst trefoil
339-2034481*
Postnatal MR
Postnatal CT
These three fetuses with “Dandy-Walker variant” had different
outcomes – the varying associated anomalies and genetic &
chromosomal abnormalities make counselling difficult
a
b
US
MR at 21 weeks
Dandy-Walker
“variant”
216-1935707*
This fetus (a) had
other congenital
anomalies
= Wolf-Hirschhorn
syndrome
cyst trapezoid
fetal demise
216-1935707
US
MR at 23 weeks
231-2093975*
c
cyst trapezoid
fetal demise
US
MR at 21 weeks
less218-2117359
dysplatic vermis
cyst trefoil
Dandy-Walker
“variant”
These 2 (b,c) had no
other anomalies
. . . neuropathology
and autopsy MRI
were normal
Postmortem MR
small gap inferiorly
– maybe normal
Pseudo Dandy-Walker variant
US scan plane too coronal gives false appearance
*Note: Rhombic lip forms
US
MR at 21 weeks
Postnatal US
small gap in inferior
vermis
minimally increased
angle, small gap
vermis “closed”
209-1267181*
normal
follow-up
cerebellum and cochlear
nucleus, rhombencephalon
induces otocyst.
deaf but otherwise
normal development
bilateral cochlear
dysplasia
∴cerebellar and labyrinthine
anomalies often coexist
Mega cisterna magna: vermis fully formed
fastigium & lobulation normal
US
MR at 36 weeks
“omega”
too coronal
Vermis fully
formed but
small
IV ventricle “closed”
Vermian fusion anomalies
Joubert’s
(Prototype for congenital vermian hypoplasia)
US Image for this case courtesy of Dr. Phyllis Glanc
Women’s College Campus, Sunnybrook and Women’s College Hospital, Toronto
US
MR at 20 weeks
IV ventricle wide &
abnormal shape
“molar tooth” shape
of brainstem
no200-2139750
fastigial point or
primary fissure
US
IV ventricle “closed”
cisterna magna
measures too large
356-805244372*
normal follow-up
Arachnoid cyst: vermis fully formed
fastigium & lobulation abnormal due to extrinsic compression
US
cyst crescentic
MR at 29 weeks
arachnoid cyst
293-2013523*
small transcerebellar
diameter
ongoing pregnancy
Rhombencephalosynapsis
Images for this case courtesy of Dr. Anne Michelle Fink
Department of Radiology, The University of Melbourne, Royal Children's and Royal Women's Hospitals, Melbourne, Australia.
Postnatal MR
MR at 28 weeks
US (axial view)
normal follow-up
micrencephaly
284-1947026
fetal demise
folia continuous
across midline
MR – (axial view)
MR at 26 weeks
no fastigial point or
primary fissure