Fetopathology and developmental pathology of the embryo and fetus: Arachnoid cyst

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Arachnoid cyst

Etiology

Congenital developement anomaly of arachonoid membrane.

The cysts are formed from splitting or the arachnoid membrane, the cysts are intra-arachnoid to be exact.

Aquired arachnoid cysts are different. These cysts develope following meningitis, hemorrhage, trauma or neurosurgary.

Macroscopic appearance

Smooth thin walled unilocular or septate cyst containing clear fluid
Approximately 50% are localized supratentorial in the Sylvian fissure 25% are infratentorial
spinal cysts are also common

Histology

Discontinuited meningotelial layer, connective tissue.