Dandy walker malformation - Hội chứng Dandy Walker - Hypoplasia of Vermis, Megacisterna magna, Võ Tá Sơn

1. Dandy Walker malformation
Bs. Võ Tá Sơn
Bệnh viện Phụ sản – Nhi Đà Nẵng
HCM 12.01.2017

2. Posterior fossa anomalies
• It is at least possible to differentiate posterior
fossa anomalies into two broad categories:
• (1) cystic malformations, characterized by the
presence of an apparent CSF collection in the
posterior fossa due to fourth
ventricle/cisterna magna dilatation, or to true
arachnoid loculations;
• (2) non-cystic malformations, in which there is
no apparent CSF collection

3. Cystic posterior fossa
• The presence of an apparent CSF collection in the
posterior fossa and/or by the fourth ventricle
opening posteriorly and apparently
communicating with the cisterna magna.
• The failed closure of the fourth ventricle is
characteristic of Dandy–Walker malformation
(DWM), Blake’s pouch cyst (BPC), and vermian
hypoplasia.
• An apparent CSF collection can also be due to
mega cisterna magna (MCM) and a true
arachnoid loculation (arachnoid cyst).

4. Dandy–Walker malformation
• (1) complete or partial agenesis of the vermis;
• (2) cystic dilatation of the fourth ventricle that
fills the posterior fossa and extends into the
cisterna magna;
• (3) enlarged posterior fossa with upward
displacement of the tentorium;
• (4) upward rotation of the partial agenetic
vermis (usually more than 45 degree).

5. Dandy–Walker variant (DWv)
• Hypoplasia/partial agenesis of the postero-
inferior part of the vermis.
• Rotation of the vermis (usually not exceeding
45 degree).
• Mildly enlargement of the fourth ventricle
without substantial enlargement of the
posterior fossa.

6. Prevalence
• Dandy-Walker malformation (DWM) is
relatively rare, with an estimated prevalence
of approximately 1 in 30,000 births, and is
associated with 4% to 12% of infantile
hydrocephalus.

7. Causes
• Clinical history/genetics: May appear sporadically,
or may show autosomal-recessive or X-linked
inheritance.
• Risk of chromosomal anomalies: This is high, with
up to 35% of cases being associated with
aneuploidy, mainly trisomies 18 and 13.
• Teratogens: Congenital infections.
• Embryology: The Dandy–Walker syndrome
develops in the 5th to 6th week after conception.

8. Ultrasound diagnosis
• On axial transcerebellar view, a triangular or
square-shaped open fourth ventricle apparently
communicating with cistern magna can be seen.
An expansion of the posterior cranial fossa is also
evident.
• On the median view, a small vermis with a normal
or abnormal configuration (absence of fastigium
and/or fissures) may be present. While an
abnormal configuration usually indicates partial
agenesis, a small vermis with a normal
configuration indicates hypoplasia. However, the
distinction between these two entities is difficult.
The upward rotation of the small vermis usually
exceeds 45° and a superior displacement of the
torcular/tentorium is also present.

9. Ultrasound diagnosis

10. Ultrasound diagnosis

11. Differential diagnosis
• The DWM should be differentiated from other
cystic anomalies of the posterior fossa.
• A median view of the fetal head is mandatory
for an accurate assessment of the position and
features of the vermis and of the
characteristics of the CSF collection of the
posterior fossa (fourth ventricle and cisterna
magna).

12. Differential diagnosis
• The presence of a apparent communication between
the fourth ventricle and cisterna magna (open fourth
ventricle) associated with a normal vermis is indicative
of BPC. In this case, the rotation of the vermis is usually
less pronounced.
• The presence of a apparent communication between
the fourth ventricle and cisterna magna (open fourth
ventricle) associated with the hypoplastic vermis,
normally inserted tentorium/torcular, and no expanded
posterior fossa is indicative of vermian hypoplasia.
In this case, the rotation of the vermis usually does not
exceed 45°.
• In case of mega cisterna magna, the cisterna magna is
large but the cerebellum is intact and the fourth
ventricle is closed.

15. Associated with DWM
• DWM is frequently associated with other CNS
(ACC, holoprosencephaly, or encephalocele)
and non-CNS anomalies (polycystic kidneys,
cardiovascular defects, and facial clefts) and
genetic conditions. When isolated, the
outcome is variable. In antenatal studies,
approximately 50% of surviving infants are
reported to have normal intelligence, and
50% have variable degrees of
neurodevelopmental disability.

16. Associated syndromes
• These include Smith-Lemli–Opitz syndrome,
Jubert syndrome, Meckel–Gruber syndrome,
triploidy, trisomy 18, arthrogryposis, CHARGE
association, Fryns syndrome,
MURCSassociation.

17. • Walker–Warburg syndrome: look for → DWM +
eye anomalies (microphthalmia and cataract),
other CNS anomalies (lissencephaly, midline
anomalies, microcephaly, and cephalocele)
• Meckel–Gruber syndrome: look for → DWM +
encephalocele, polydactyly, and polycystic
kidneys
• Aicardi syndrome: look for → DWM + agenesis of
the corpus callosum and vertebral defects
• Neu–Laxova syndrome: look for → DWM +
lissencephaly, microcephaly, proptosis, diffuse
joint contractures, subcutaneous tissue edema,
and intrauterine growth retardation
Nonchromosomal syndromes

18. • Modified from Murray JC, Johnson JA, Bird TD:
Dandy-Walker
• malformation: etiologic heterogeneity and empiric
recurrence risk
• Clin Genet 28:272, 1985.
• AD, autosomal dominant; AR, autosomal recessive.
Modified from Murray JC, Johnson JA, Bird TD: Dandy-Walker malformation: etiologic
heterogeneity and empiric recurrence risk. Clin Genet 28:272, 1985. AD, autosomal dominant;
AR, autosomal recessive.

19. Vermian agenesis/hypoplasia
• Vermian agenesis/hypoplasia is characterized
by an absent or small cerebellar vermis with
a normal cisterna magna. This condition was
originally labeled Dandy-Walker variant, a
term that has fallen out of favor. Follow-up
studies of children with antenatally diagnosed
vermian agenesis or hypoplasia have reported
widely variable outcomes, ranging from
largely normal in some series, to a high
prevalence of neurologic compromise in
others.

20. Vermian hypoplasia
• Incidence: Unknown.
• Ultrasound diagnosis: It is characterized, on axial
transcerebellar view, by an open fourth ventricle
apparently communicating with the cisterna magna.
Posterior cranial fossa is not expanded. On median
view of the head, the vermis is small and upwardly
rotated (usually less than 45°). Tentorium and torcular
are positioned normally.
• Risk of chromosomal anomalies: High, especially if
associated with other anomalies.
• Risk of nonchromosomal syndromes: High, especially
if associated with other anomalies.
• Outcome: Vermian hypoplasia is frequently a part of
multiple anomalies and genetic syndromes. When
isolated it may be asymptomatic, but precise risk
figures are not available.

22. Vermian agenesis/hypoplasia

23. Joubert syndrome
• Joubert syndrome and related disorders are a
group of conditions characterized by hypoplasia
of the cerebellar vermis with a characteristic
neuroradiologic finding described as the molar
tooth sign, which refers to elongation of the
superior cerebellar peduncles (cuống) that gives
an appearance reminiscent (gợi lại) of a molar or
wisdom tooth (răng khôn).
• These CNS findings can be associated with a
variety of non-CNS anomalies and therefore may
constitute different syndromes, although all
generally share an unfavorable neurologic
outcome.

24. Joubert syndrome
• Joubert syndrome is a very severe albeit rare condition
featuring vermian hypoplasia in association with
dysgenesis of the isthmic portion of the brainstem at
the pontomesencefalic junction, a deep posterior
interpeduncolar fossa with thick elongated superior
cerebellar peduncles.
• The diagnosis can be made on MRI only, and the typical
aspect of the abnormal superior cerebellar peduncles
is referred to as “molar tooth sign”, evident on axial
MRI slices of the brain. Symptoms range from general
hypotonia with a froglike posturing, hyperpnea/apnea,
ataxia. Colobomas, nystagmus and strabismus are
associated.

25. Joubert syndrome

26. Joubert syndrome. The ‘molar tooth’ sign (arrow) is visualized on
axial brain MRI and results from the combination of a
hypoplastic cerebellar vermis, elongated and thickened superior
cerebellar peduncles, and a deep interpeduncular fossa.

27. Arachnoid cysts
• Arachnoid cysts of the posterior fossa are rare
and most frequently result in a mass effect on
the cerebellar structures. They may be difficult
to differentiate from mega-cisterna magna or
DWM and should be considered in the
differential diagnosis of cystic lesions of the
posterior fossa.

28. Arachnoid cysts
• Incidence. Unknown.
• Ultrasound diagnosis. Sonographically, a
retrocerebellar arachnoid cyst appears as a sonolucent
cystic mass. Compression on the cerebellum may be
detected on the midsagittal view, in case of large cysts.
• Large arachnoid cysts may obstruct the circulation of
CSF, leading to secondary obstructive hydrocephalus.
• Risk of chromosomal anomalies. Low.
• Risk of nonchromosomal syndromes. Low.
• Outcome. The overall prognosis is good.

29. Arachnoid cysts

30. Mega-cisterna magna
• Mega-cisterna magna, in which the diagnostic
criteria are clear-cut (the widely accepted
definition is a cisterna magna with
anteroposterior diameter measuring >10 mm
with normal-appearing cerebellum and
cerebellar vermis).

31. Mega-cisterna magna
• Incidence: Unknown.
• Ultrasound diagnosis: It is characterized by a CSF
collection in the posterior fossa. The vermis is
normal and the fourth ventricle is closed.
• Risk of chromosomal anomalies: Relatively high,
especially if associated with other anomalies.
• Risk of nonchromosomal syndromes: Relatively
high, if associated with other anomalies.
• Outcome: If isolated, the prognosis is good.
Fetuses with MCM associated with abnormal
cerebral findings were found to have neurologic
sequelae in about one-third of cases.

32. Mega-cisterna magna

33. Mega-cisterna magna

34. Blake pouch cyst
• Incidence: Unknown; it seems to be the most frequent
fetal posterior fossa cystic anomaly.
• Ultrasound diagnosis: On axial transcerebellar view it
is characterized by an open fourth ventricle apparently
communicating with the cisterna magna. On a median
view of the fetal head, a normal but upwardly rotated
cerebellar vermis is seen.
• Risk of chromosomal anomalies: Relatively high,
especially if associated with other anomalies.
• Risk of nonchromosomal syndromes: If associated
with other anomalies, it is relatively high.
• Outcome: If isolated, it seems to be a normal variant.
In less frequent cases associated with hydrocephaly,
the prognosis depends on hydrocephaly.

35. Blake pouch cyst

36. Blake pouch cyst

37. Cerebellar hypoplasia

38. Clinical management of DWM
• Further sonographic screening, including fetal
echocardiography.
• Karyotyping and search for infections (TORCH).
• Counseling with a neurosurgeon, neuropediatrician, or
neuropathologist. If the mother decides to continue
with the pregnancy, regular sonographic monitoring.
• Premature delivery should be considered if the
hydrocephalus enlarges rapidly. This option is disputed
because of bad prognosis. Prognosis is worsened if
agenesis of the corpus callosum is also detected. If the
diagnosis is uncertain, MRI during the pregnancy can
be useful in deciding the clinical management.
Bleeding within the cysts may occur, and this should be
borne inmind when choosing the mode of delivery.

39. Procedure after birth
• Normal postnatal care for the newborn. In most
infants with absence of intrauterine
hydrocephalus, development of hydrocephalus
occurs within 2months after birth. Treatment for
the Dandy–Walker cyst is only then indicated if
the child develops symptoms (difficulty in
swallowing, aspiration, a weak cry,
underdeveloped sucking reflex). The usual
management is placement of a cystoperitoneal
shunt.

40. Prognosis of DWM
• DWM is associated with late-onset hydrocephalus
in about 80% of cases. If hydrocephalus develops,
whether in utero or in the neonatal period, there
is a mortality rate of over 60%, with most
survivors having a low IQ.
• In most DWM series, approximately 40% of the
children were intellectually normal, 40% were
severely retarded, and 20% had borderline
mental retardation.
• However, a review of DWM outcome has shown
that isolated forms have a better intellectual
prognosis and lower mortality

41. Thank you