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Arachnoid cyst

Arachnoid cysts are collections of cerebrospinal fluid between the soft meninges (fine surrounding layers of the brain), the so-called arachnoid leaves. This cyst may have an expansive effect and impose pressure on the neighbouhring brain and sometimes lead to an obstruction of the normal circulation of the cerebrospinal fluid. This causes symptoms such as epilepsy, headaches or even hydrocephalus.

In case of such symptomatic arachnoid cysts, surgical treatment is necessary. Endoscopic or microsurgical fenestration of the cyst will restore the normal CSF circulation.


Chiari malformation

Chiari malformation is a deformity of the posterior fossa which is too small. The Tentorium cerebelli stands steeply, and the cerebellar tonsils reach too deeply into the spinal canal (Chiari type I). A more complex form (Chiari type II) is encountered in association with a meningomyelocele.

Result of this malformation can be the so-called syringomyelia (an expansice cystic formation within the medulla, filled with cerebrospinal fluid) and also may result in neurological symptoms.



Dandy Walker malformation

The Dandy Walker malformation is a developmental disorder with hypoplasia of the cerebellar vermis and of the medial aspects of the cerebellar hemispheres. The fourth ventricle impresses here as a huge cyst. The Dandy Walker malformation often occurs together with hydrocephalus.