Dandy-Walker malformations

Toddler with
cervical adenopathy with an incidental finding on a neck CT exam. Sagittal T1 MRI without contrast of the brain (upper left) shows an enlarged posterior fossa containing a dilated fourth ventricle resulting in a large midline cyst that is causing elevation of the superior cerebellum and torcular inversion. Axial (upper right) and coronal (below) T1 MRI without contrast of the brain show agenesis of the cerebellar vermis. A mild-moderate amount of hydrocephalus is present.The diagnosis was Dandy Walker Malformation.
pediatricimaging.org • CC-by-nc-sa 4.0
Dandy-Walker
malformation in methylmalonic acidemia: a rare case report. Magnetic resonance imaging of the brain demonstrated cerebellar vermis hypoplasia, enlargement of the fourth ventricle and supratentorial hydrocephalus. Axial T1 weighted imaging (A), Axial T2 weighted imaging with fat and fluid suppression (B), Sagittal T1-weighted imaging (C), Coronal T2 weighted imaging with fat and fluid suppression (D)
bmcpediatr.biomedcentral.com • CC-by-4.0
Dandy-Walker
malformation • Dandy walker syndrome with giant occipital meningocele - Ganzer Fall bei Radiopaedia
Alsmair, A. Dandy walker syndrome with giant occipital meningocele. Case study, Radiopaedia.org. (accessed on 23 Oct 2022) https://doi.org/10.53347/rID-90662 • CC by-nc-sa 3.0 (modified)
Radiopaedia • CC-by-nc-sa 3.0 • de

Dandy-Walker malformation (DWM) is the most common posterior fossa malformation, characterized by the triad of:

  • hypoplasia of the vermis and cephalad rotation of the vermian remnant
  • cystic dilatation of the fourth ventricle extending posteriorly 
  • enlarged posterior fossa with torcular-lambdoid inversion (the torcula lying above the level of the lambdoid due to abnormally high tentorium)

Terminology

This article focuses on the "classic" presentation of Dandy-Walker malformation, please refer to Dandy-Walker continuum for a discussion on other related posterior fossa malformations.

The term “classic Dandy-Walker malformation” and others like “Dandy-Walker variant” or “Dandy-Walker complex”, were created to differentiate those malformations that do not meet the criteria for Dandy-Walker malformation, however, some authors recommend to avoid them as they have a lack of specificity that may create some confusion. Instead, a more detailed anatomic description is recommended .

Epidemiology 

The estimated prevalence of a Dandy-Walker malformation and related variants is about 1 per 30,000 live births and accounts for ~7.5% (range 4-12%) of the cases of infantile hydrocephalus. It is known as the most common posterior fossa malformation .

Clinical presentation

Clinical presentation is dependent on the severity of the abnormality. In a classic Dandy-Walker malformation, patients usually manifest in the first year of life with symptoms of hydrocephalus and associated neurological symptoms. Macrocephaly is the most common manifestation and in ~80% of cases, the diagnosis is made by the first year of life. Despite severe cerebellar abnormalities, cerebellar signs are not common.

Pathology

Many have a sporadic inheritance with some possibly having an autosomal dominant or X-linked inheritance.

Associations

Radiographic features

Ultrasound

Antenatal sonographic features that would suggest the diagnosis include the combination of :

Antenatal ultrasound may falsely overdiagnose the condition if performed before 18 weeks, as the vermis has not properly formed.

MRI

MRI is the modality of choice for assessment of Dandy-Walker malformation, although both CT and ultrasound will demonstrate the pertinent features.

Classically Dandy-Walker malformation consists of the triad of:

  • hypoplasia of the vermis and cephalad rotation of the vermian remnant
  • cystic dilatation of the fourth ventricle extending posteriorly; usually the cerebellar hemispheres are displaced anterolaterally, but with a normal size and morphology
  • enlarged posterior fossa with torcular-lambdoid inversion (torcular lying above the level of the lambdoid due to abnormally high tentorium)

In 75-90% of patients, obstructive hydrocephalus is evident by three months of age , in many cases due to aqueduct stenosis . CSF flow study is recommended to better assess the hydrodynamic changes and identify eventual aqueductal stenosis association, which cannot be treated by cystoperitoneal shunt placement .

Treatment and prognosis

A Dandy-Walker malformation carries a high mortality rate, ~70% in live-born fetuses, often due to associated abnormalities . It is thought to carry a poorer prognosis if diagnosed prior to 21 weeks of gestation and a better prognosis if diagnosed postnatally . A cystoperitoneal shunt could be considered in situations where hydrocephalus is significant problem. Even in the absence of any associated syndromes, there is a recurrence risk of ~2.5% (range 1-5%) in subsequent pregnancies.

History and etymology

It was initially described by Blackman and Dandy in 1914 .

Differential diagnosis

The differential is that of other causes of an enlarged CSF retrocerebellar space (and mimics thereof) including:

On antenatal ultrasound, also consider technical and timing factors such as:

  • too steep insonation angle
  • a scan performed too early in gestation, i.e. prior to 18 weeks
Siehe auch:
und weiter:
Assoziationen und Differentialdiagnosen zu Dandy-Walker-Syndrom:
Mega Cisterna
magna
pediatricimaging.org • CC-by-nc-sa 4.0
Arachnoidalzysten
der hinteren Schädelgrube
Wikipedia • CC BY-SA 4.0
Dandy-Walker
variant
pediatricimaging.org • CC-by-nc-sa 4.0
Dandy Walker
continuum
Wikipedia • CC BY-SA 3.0
vermis
hypoplasia
ojrd.biomedcentral.com • CC-by-2.0
pädiatrische
Erkrankungen des Liquorsystems
insightsimaging.springeropen.com • CC-by-4.0