The Dandy-Walker complex is a rare congenital brain malformation characterized by cystic dilation of the 4th ventricle and partial or complete absence of the cerebellar vermis. It ranges from mega cisterna magna to Dandy-Walker variant to Dandy-Walker malformation based on severity. Associated anomalies are common. The cause is unknown but likely involves abnormal development of the hindbrain. Treatment involves managing hydrocephalus, often with shunt procedures. Prognosis depends on severity and associated anomalies, with higher mortality and developmental delays in more severe forms.

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SURESH BISHOKARMA, MS
MCH RESIDENT, NEUROSURGERY
NINAS
Dandy Walker Complex

2. The Dandy-Walker complex is a rare congenital intracranial malformation
that comprises a spectrum of abnormalities of the posterior fossa which are
classified as
1. Dandy-Walker malformation (cystic dilatation of the 4th ventricle,
complete or partial agenesis of the cerebellar vermis and an enlarged
posterior fossa)
2. Dandy-Walker variant (cystic posterior fossa mass with variable
hypoplasia of the cerebellar vermis and no enlargement of the posterior
fossa)
3. Mega cisterna magna (enlarged cisterna magna with normal cerebellar
vermis)
Dandy-Walker complex

3. It is a continuum of posterior fossa cystic abnormalities with varying
degrees of vermian agenesis.
Mega cisterna magna Dandy-Walker variant  Dandy-Walker
malformation

4. • DWM and DWV cases show so many similarities that a clear-cut
distinction is difficult.
• There was no significant difference in the spectrum of associated
anomalies and postnatal prognosis between DW and DWV cases

5. • Specific size criteria to denote a normal-sized posterior fossa and vermian
hypoplasia are not established in the literature.
• DWV: The cerebellar hemispheres may be small but morphologically
normal

6. • The severity of the diagnosis is based on the size of the posterior fossa,
the presence of cystic dilatation of the fourth ventricle, and the degree of
vermian hypoplasia.

7. • First described in 1914 by W Dandy and K Blackfan and was designated
as Dandy-Walker syndrome in 1954 by C Benda
History

8. • The precise aetiology is unknown. The reported incidence varies between
one per 2500 births to one per 100,000 births. Environmental factors
including viral infections, alcohol and diabetes have also been suggested
to play a role in the genesis of Dandy-Walker malformation but the
evidence is uncertain
Epidemiology

9. • The cerebellum is formed by 2 distinct germinal matrices; 1
periventricular and 1 along the rhombic lip, which gives rise to the
cerebellar hemispheres.
• The cerebellar vermis develops as a thickening of the midline
primordium of the rhomboencephalon during the 5th gestational week.
By 16 weeks, the vermis fold and begins to cover the roof of the fourth
ventricle. By 19 weeks of gestation the cranial/caudal length of the
vermis is equal to that of the cerebellar hemisphere.
Embryology

10. • The pathophysiological mechanism underlying the Dandy–Walker complex is not
clearly elucidated. Initially, it was proposed that congenital obstruction of the foramina
of Luschka and Magendie resulted in cystic dilatation of the fourth ventricle and the
resulting malformed posterior fossa. In later studies investigators have suggested that
it is a manifestation of abnormal development of the rhomboencephalon, with
incomplete formation of the vermis, or due to a defect within the tela choroidea, which
leads to cystic dilation of the fourth ventricle. Given its comparable appearance to
DWM, it is likely that DWV develops along the same embryological pathway. One is
embryonic arrest of the rhombencephalon, with failure of cerebellum fusion in the
midline between weeks 7 and 10 of gestation. This leads to persistence and interposes
itself between the hypoplastic vermis and the choroid plexus. Furthermore, the roof of
the fourth ventricle expands upward through an agenetic corpus callosum.
• Chromosomal abnormalities were observed in this study and included defects on
chromosomes 9, 11, 13, and 8. Deletions on chromosome 8; a long-arm deletion of
chromosome 3 was observed in a patient with DWV and associated craniofacial
anomalies; and partial trisomy 3 and monosomy 11 (a partial imbalance of
chromosomes 6 and 11) have also been described. The gene locus for DWM is 3q24.
• Trisomy-18, tri- ploidy and trisomy-13.
pathophysiology

11. • Developmental Status
• Poor developmental outcome in association with posterior fossa
malformations is reported in 55–100% of patients.
• It is estimated that moderate-to-severe developmental delay is observed in
approximately one-third of patients with DWM, and
• of those 11–16% have a diagnosis of severe delay and require significant
assistance in their daily functioning.
• Hydrocephalus is common prenatally or during the neonatal period, although
this is a complication rather than part of the disease. Most cases are
diagnosed during infancy.
• Older patients might be asymptomatic, with normal or near-normal
neurological examinations. They usually pre- sent with neurological
manifestations such as developmental delay, spasticity, poor head control and
seizures.12 Some children present with symptoms suggestive of increased
intracranial pressure and posterior fossa tumour, like nystagmus, cranial
nerve palsy or truncal ataxia.
Clinical presentation

12. INTRACRANIALANOMALIES:
1. Brainstem dysplasia
2. Agenesis of corpus callosum
3. Holoprosencephaly
4. Occipital encephaloceles
Two thirds of patients have associated
central nervous system abnormalities.
Association
EXTRACRANIAL ANOMALIES
1. The incidence of extracranial
anomalies was 54% in DWV,
compared with the 12–86%
reported in patients with DWM
2. Genitourinary: polycystic kidneys
3. Musculoskeletal systems:
polydactyly
4. Gastrointestinal:
5. Ocular abnormalities
The severity of Dandy Walker syndrome depends on the presence of associated anomalies.
DWV has been associated with Menkes syndrome (kinky-hair disease), Coffin–Siris
syndrome, and Ehlers–Danlos syndrome, as well as neurocutaneous melanosis

13. Retrocerebellar arachnoid cyst
underlying brain is normal.
The cerebellar hemispheres are not
separated by a cystic mass,
rather displaced en-bloc.
Diagnosis
The diagnosis is challenging because of a lack of specific symptomatology.
Unless the syndrome is detected prenatally, by ultrasound or magnetic resonance imaging
or increased head circumference (prenatally or postnatally)
Definitive criteria have not been firmly established.
The prenatal differentiation between Dandy-Walker variant and mega-cisterna magna
should be made with caution, especially in the early second trimester because the
relatively large fourth ventricle and the incompletely formed inferior cerebellar vermis
may give a false impression of vermian defect and a follow-up scan at 18 weeks or later
should be done.
Cisterna magna:
Depth greater than
10 mm.
DWM:
thin communication
is found between
the fourth ventricle
and the cisterna
magna

14. • The treatment of Dandy Walker syndrome consists of dealing with
hydrocephalus by various approaches, although this is still controversial.
• Membrane excision was initially proposed by Dandy for the treatment of
DWM.
• The results using this form of therapy have been poor initially, with a high
failure rate. mortality rate of 10% and a failure rate of 70%.
• Few still advocate this treatment by way of cyst wall excision in children
aged over 3 years.*
• Endoscopic third ventriculostomy may be considered an acceptable
alternative, especially in older children, with the aim to reduce the shunt-
related problems.
• Endoscopic methods of transaqueductal placement of a single-catheter cyst-
ventriculoperitoneal shunt has also been noted to be with good results.
Treatment
* Udvarhelyi and Epstein

15. • The prognosis depends largely on the associated anomalies.
• The mortality rate ranges from 27% to 50%, and hearing and/or visual
problems are associated with poor intellectual development.
Prognosis

16. • Recurrence risk in subsequent pregnancies of 1-5% is suggested.
Genetic counselling

17. Thank you

NATIONAL INSTITUTE OF NEUROLOGICAL AND ALLIED SCIENCES, BANSBARI, KATHMANDU
DANDY-WALKER COMPLEX
NATIONAL INSTITUTE OF NEUROLOGICAL AND ALLIED SCIENCES, BANSBARI, KATHMANDU