Dandy-Walker syndrom

Dandy-Walker syndrome (DWS), or Dandy-Walker complex, is a congenital brain malformation involving the cerebellum and the fluid filled spaces around it. A key feature of this syndrome is the partial or even complete absence of the part of the brain located between the two cerebellar hemispheres (cerebellar vermis).[1] The Dandy-Walker complex is a genetically sporadic disorder that occurs one in every 25,000 live births, mostly in females.

Classification

The term Dandy-Walker represents not a single entity, but several abnormalities of brain development which coexist. There are, at present, three types of Dandy-Walker complexes.

They are divided into three closely associated forms: DWS malformation, DWS mega cisterna magna and DWS variant.

Malformation

The DWS malformation is the most severe presentation of the syndrome. The posterior fossa is enlarged and the tentorium is in high position. There is partial or complete agenesis of the cerebellar vermis. There is also cystic dilation of the fourth ventricle, which fills the posterior fossa. This often involves hydrocephaly and complications due to associated genetic conditions, such as Spina Bifida.

Mega cisterna magna

The second type is a mega cisterna magna. The posterior fossa is enlarged but it is secondary to an enlarged cisterna. This form is represented by a large accumulation of CSF in the cisterna magna in the posterior fossa. The cerebellar vermis and the fourth ventricle are normal.

Variant

The third type is the variant, which is less severe than the malformation. This form (or forms) represents the most wide-ranging set of symptoms and outcomes of DWS. Many patients who do not fit into the two other categories of DWS are often labeled as variant. The fourth ventricle is only mildly enlarged and there is mild enlargement of the posterior fossa. The cerebellar vermis is hypoplastic and has a variably sized cyst space. This is caused by open communication of the posteroinferior fourth ventricle and the cisterna magna through the enlarged vallecula. Patients exhibit hydrocephalus in 25% of cases and supratentorial CNS variances are uncommon, only present in 20% of cases. There is no torcular-lambdoid inversion, as usually seen in patients with the malformation. The third and lateral ventricles as well as the brain stem are normal.