Fact-sheet: Dandy-Walker malformation


Updated on 04/18/2018 at 3:51 PM

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Definition

Dandy-Walker complex is a group of cerebellar dysplasias encompassing agenesis, hypoplasia, or early cerebellar atrophy.
It includes the Dandy-Walker malformation, "Dandy-Walker variant," and mega cisterna magna.
True Dandy-Walker malformation:
- Enlargement of the posterior fossa with superior displacement of the tentorium
- Agenesis or severe hypoplasia of the vermis
- Cystic dilatation of the 4th ventricle not communicating with the subarachnoid spaces

This malformation is sometimes associated with:

  • a gyration abnormality
  • Agenesis of corpus callosum
  • hydrocephalus
  • cerebral atrophy

"Dandy-Walker variant": malformation not meeting all 3 criteria of true Dandy-Walker:

  • Vermian hypoplasia and cyst without enlargement of the posterior fossa
  • Incomplete agenesis of the vermis
  • Communication of the cystic dilatation of the 4th ventricle with the subarachnoid spaces

May be part of a polymalformative syndrome:

- brain malformations: encephaloceles, corpus callosum abnormalities, or neuronal migration disorders.

- systemic: cardiovascular, urogenital, digestive, facial abnormalities...

Clinical features

- Psychomotor developmental delay

- Seizures

- In adolescents or older children: progressive hydrocephalus with suggestive clinical findings, oculomotor signs, headaches, nausea, lethargy, ataxia, conductive hearing loss

- Decreased IQ in 50% of cases.

MRI

Midline cerebellar defect

Fourth ventricle:

- Deformed, roof not visible

- Communicates with a posterior cystic cavity, extending to the occipital squama and also from the foramen magnum to the tentorium cerebelli.

Vermis:

- Superior vermis elevated by the cyst

- Inferior vermis: Agenesis

High position of the tentorium cerebelli.

The cerebellar remnants are flattened against the petrous bones.

Brainstem flattened against the clivus

Enlarged posterior fossa

Thinning and bulging of the occipital squama

Noncommunicating supratentorial hydrocephalus

Occipital horns splayed due to elevation of the tentorium cerebelli.

Management

During pregnancy:

- In utero endoscopic intervention between 24 and 32 weeks to create a ventriculo-amniotic shunt, replaced at birth by a ventriculoperitoneal shunt.

- Watchful waiting, follow-up after birth

At birth:

- Shunt placement to prevent compression of cerebral structures due to the cyst or hydrocephalus

- Watchful waiting, intervention in case of cerebral distress

Differential diagnosis

Faced with a posterior occipital cystic collection:

Assess the fourth ventricle

- Dandy-Walker malformation if the vermis is abnormal

- Blake's pouch cyst if the vermis has normal morphology

- Mega cisterna magna if the fourth ventricle is not dilated

- Arachnoid cyst if the fourth ventricle is not dilated