Dandy Walker Syndrome

Question 1

what is embryology of Dandy Walker?

Answer 1

In Benda’s pathologic analysis of six cases, it was concluded that DWM is directly related to the persistence of the posterior medullary velum, which remains as a thick arachnoid and ectodermal membrane.5 The cerebellar vermis is also at least partially absent.

Question 2

The rhombencephalon divides into the metencephalon (future pons and cerebellum) and myencephalon around the ? week of gestation

Answer 2

5th

Question 3

Cerebellar development begins in the ? week, when the cerebellar hemispheres develop from the rhombic lips, subsequently fusing to form the vermis.

Answer 3

9th

Question 4

Cerebellar development begins in the ? week, when the cerebellar hemispheres develop from the ?, subsequently fusing to form the vermis.

Answer 4

9th, rhombic lips

Question 5

The choroid plexus of the fourth ventricle and the foramina of Luschka and Magendie form around the ? week of gestation from the ??. Cerebrospinal fluid (CSF) then accumulates within the fourth ventricle, forming this space

Answer 5

tenth, rhombic vesicle

Question 6

when do the cerebellar lobules develop completely and why is that important?

Answer 6

Subsequently, the cerebellar lobules develop in an anterior-to-posterior direction and are completely formed by week 18. Because it develops more slowly than the cerebral hemispheres, the cerebellum appears smaller at 20 weeks’ gestation relative to the large posterior fossa CSF spaces, leading to a potential overdiagnosis of vermian hypoplasia by antenatal ultrasonography.

Question 7

embryologic basis for DWM has been attributed to dysgenetic development of the ?

Answer 7

anterior membranous area of the rhombencephalon

Although commonly seen, developmental failure of the foramen of Magendie is not necessary for the development of DWS

Question 8

what are the 6 characteristics of dandy walker malformation?

Answer 8

1) a large posterior fossa cyst communicating with the fourth ventricle; (2) absence of a portion of the inferior vermis; (3) hypoplasia, anterior rotation, and upward displacement of the remaining vermis; (4) absence or flattening of the angle of the fastigium; (5) a large posterior fossa with torcular elevation; and (6) anterolateral displacement of the cerebellar hemispheres.12

Question 9

characteristics of Dandy Walker Variant?

Answer 9

Dandy-Walker variant (DWV) milder spectrum of DWS-like signs that were not congruent with the classic definition, but a clear clinical separation has not been defined. DW V consists of an inferior cerebellar vermian defect and communication between a normal-sized cisterna magna and fourth ventricle.

Dandy-Walker complex (DWC) is another term coined to describe a continuum of posterior fossa anomalies categorized from mild (mega–cisterna magna only) to moderate (mild hypoplasia of vermis, enlarged fourth ventricle) to severe (agenesis of vermis, dilation of posterior fossa cyst and fourth ventricle).

Question 10

what is the difference between dandy walker variant and dandy walker complex?

Answer 10

Dandy-Walker variant (DWV) milder spectrum of DWS-like signs that were not congruent with the classic definition, but a clear clinical separation has not been defined. DW V consists of an inferior cerebellar vermian defect and communication between a normal-sized cisterna magna and fourth ventricle.

Dandy-Walker complex (DWC) is another term coined to describe a continuum of posterior fossa anomalies categorized from mild (mega–cisterna magna only) to moderate (mild hypoplasia of vermis, enlarged fourth ventricle) to severe (agenesis of vermis, dilation of posterior fossa cyst and fourth ventricle).

Question 11

what is this?

Answer 11

Axial T1-weighted magnetic resonance image showing Dandy-Walker variant with a fourth ventricle communicating with a retrocerebellar cyst (white arrow), absence of the inferior vermis, absence of the corpus callosum (black arrow), and lissencephaly.

Question 12

what is this?

Answer 12

Cerebellar vermis hypoplasia/atrophy. Note the normal size of the posterior fossa and absence of the hydrocephalus.

Question 13

what is this?

Answer 13

Retrocerebellar cyst with anterior shift of cerebellum, which has resulted in obstruction of cerebrospinal fluid (CSF) outflow and hydrocephalus.

Question 14

what is this?

Answer 14

Mega–cisterna magna. Note enlarged size of the posterior fossa but normal size of the cerebellum.

Question 15

Answer 15

Blake’s pouch cyst. Note CSF collection in the fourth ventricle that is contiguous (arrow) with a collection inferior to the cerebellum (asterisk). Small arrowheads show upward mass effect from fluid. In none of these conditions is the fourth ventricle significantly enlarged or upwardly rotated.

Question 16

when do most pts with dany walker malformation present?

Answer 16

DWS has been reported to occur in 1 of 25,000 to 30,000 newborns17 with the majority of patients presenting in the first year—in most in whom hydrocephalus develops, it has done so by 3 months.

The most common postnatal presentation is macrocrania. Other signs and symptoms in this age group include the sunset sign, a large posterior fossa, seizures, spasticity, lethargy, delayed milestones, respiratory failure, apnea, deafness, visual problems, increased intracranial pressure, and hydrocephalus.

Question 17

how do older kids present with DWS?

Answer 17

Older children and adults may present like patients with posterior fossa tumors: symptoms may include headache, vomiting, cranial nerve palsies, nystagmus, and ataxia

Question 18

How often is DWS associated w other CNS anomalies? What imaging characteristic is associated only w DWS.

Answer 18

The incidence of associated anomalies in the CNS is variable but has been reported as high as 68%, with systemic abnormalities present in about one fourth of patients.

Historically, the only imaging characteristic consistent with DWS has been an elevated torcular Herophili visible on plain radiograph, known as Bucy’s sign

Question 19

Are CSF dynamic studies useful w DWS?

Answer 19

CSF dynamics are increasingly being utilized with flow studies and cine MRI sequences, which can often determine the etiology of hydrocephalus

Question 20

Is pre-natal MRI a slam dunk in terms of DWS dx?

Answer 20

No.

Because some parents may elect to terminate DWS pregnancies, it is vital that an accurate prenatal diagnosis be reached with advanced MRI imaging, characterization of associated anomalies, and cytogenetic evaluation.

Question 21

How common are chromosomal aberrations for DWS?

Answer 21

Chromosomal aberrations occur in about 50% of cases, with trisomy 13, trisomy 18, and triploidy being the most common.

Question 22

what are 3 major DWM associated loci?

Answer 22

Cytogenetic studies have revealed at least three major DWM-associated loci, implicating deletions or duplications of FOXC1 on chromosome 6p2535 and heterozygous deletions of the ZIC1/ZIC4 complex on chromosome 3q24.36 The latter association has been linked with DWM via both sonic hedgehog (Shh)–dependent and Shh-independent mechanisms (the Shh pathway is crucial to normal cerebellar development). Characterization of other cytogenetic abnormalities is ongoing, but DWM is clearly a disorder of genetic heterogeneity.

Question 23

Treatment options for DWS currently consist of

Answer 23

In general terms, cyst membrane excision, shunting, and neuroendoscopic intervention. Shunt is first line, how you shunt is complicated.

Mohanty and colleagues23 extensively reviewed changing trends in the treatment protocols of DWS, from cystectomy to various shunting procedures and finally to endoscopic fenestration, in a single institution between 1986 and 2002. Radiographically, ventricular size reduction was achieved in 88% of patients with VPS placement, compared with 38% of those with CPS placement. On the other hand, cyst size was significantly smaller in 88% of patients with CPS, compared with 62% of those with VPS. These researchers reported no significant difference in intellectual outcome between different treatments.

A later series of 45 patients treated with ETV plus choroid plexus cauterization for hydrocephalus due to DWM, DWV, or mega–cisterna magna showed a 74% success rate, defined as avoiding further interventions.44 The investigators suggested that surgeons consider endoscopic management of hydrocephalus as a primary treatment for patients with these conditions to avoid shunt dependence.

(more info below)

From current retrospective evidence, it would be difficult to establish a universal treatment algorithm for DWS. A current trend is to determine the most appropriate treatment on the basis of CSF dynamics, often via MRI and cine MRI, to assess aqueductal flow.12 Most authorities recommend starting with the safest and most effective treatment, which is usually a VPS for an infant younger than 1 year with progressive hydrocephalus. Endoscopic treatment in this age group remains controversial, but some writers have reported successful ETV in patients as young as 6 months.23,44,45 The cyst is usually treated secondarily by fenestration or shunting, with excision of posterior fossa membranes being reserved for refractory cases.19,46 The initial shunt system may be converted to a dual system in cases of failure. With the presence of aqueductal stenosis, a combined procedure of ETV and aqueductal stenting47 or a dual shunt may be considered as first-line treatment.

Question 24

Define one reasonable approach to DWM management

Answer 24

From current retrospective evidence, it would be difficult to establish a universal treatment algorithm for DWS. A current trend is to determine the most appropriate treatment on the basis of CSF dynamics, often via MRI and cine MRI, to assess aqueductal flow.12 Most authorities recommend starting with the safest and most effective treatment, which is usually a VPS for an infant younger than 1 year with progressive hydrocephalus. Endoscopic treatment in this age group remains controversial, but some writers have reported successful ETV in patients as young as 6 months.23,44,45 The cyst is usually treated secondarily by fenestration or shunting, with excision of posterior fossa membranes being reserved for refractory cases.19,46 The initial shunt system may be converted to a dual system in cases of failure. With the presence of aqueductal stenosis, a combined procedure of ETV and aqueductal stenting47 or a dual shunt may be considered as first-line treatment.

Question 25

what is intelectual dev like for kids with DWM?

Answer 25

In children who have successfully been treated for hydrocephalus, the prognosis mainly depends on the presence of associated conditions. Seizures, hearing or visual problems, and other systemic or CNS abnormalities are predictive of worse outcome.41 In patients without other abnormalities, some authorities have reported intelligent quotients (IQs) of 80 or more in 50% of long-term survivors, with normal IQs in 30%.41,49,50 In a later study, Boddaert and associates found 14 patients with normal IQs who had normal vermian lobulation without supratentorial anomalies as demonstrated by MRI.51 In contrast, the remaining, developmentally delayed patients with DWS had abnormalities in the vermis or the supratentorial compartment. The investigators concluded that vermian lobulation may be a useful prognostic factor of functional development.