2. Congenital Malformations: Failure to Form - Dandy Walker and Friends

Question 1

Answer 1

“Classic” Dandy Walker

there 3 findings which are consistently Reliable

Often identified on OB screening US.

Otherwise, presents with symptoms of increased intracranial pressure (prior to month 1)

Most Common Manifestation = Macrocephaly (nearly all cases within the first month)

Associations; Hydrocephalus (90%), Additional CNS malformations (~ 40%) (agenesis of the corpus callosum, encephaloceles, heterotopia, polymicrogyria, etc…).

Question 2

Answer 2

“Classic” Dandy Walker

Non-specific appearance of an enlarged posterior fossa CSF space.

It can look like a retrocerebellar cyst on axial only (although it’s not a cyst
- it’s the expanded 4th ventricle).

Question 3

“TORCULAR-LAMBDOID INVERSION”

Answer 3

describes the torcula (confluence o f venous sinuses) above the level of the
lambdoid suture, secondary to elevation of the tentorium

It’s worth mentioning that this inversion is often NOT seen in the “variant” version of Dandy Walker

Question 4

Dandy Walker and frieends

Answer 4

Question 5

Mega Cisterna Magna

Answer 5

Normal Variant

FOCAL enlargement of the Retrocerebellar CSF space

Question 6

Black Pouch

Answer 6

Sac like cystic protrusion = foramen of Magendie into the infra/retro cerebellar region.

Normally formed

UPWARDLY DISPLACED

Dilated 4th ventricle

+Hydrocephalus

Question 7

“Variant” Dandy-Walker Malformation

Answer 7

Hypoplastic vermis + Dilatation of the 4th ventricle

Hypopalstic Vermis (less severe)

Hypoplastic Cerebellar hemisphere

+ Hydrocephalus - 25% of teh cases