[Intraventricular arachnoid cyst. Case report].

Arachnoid cysts are found wherever the arachnoid membrane exists. Therefore, arachnoid cysts tend to occur extracerebrally. A case of an intraventricular arachnoid cyst in a 37-year-old female is reported. The cyst was found in the left lateral ventricle and arose from the choroid plexus. The cyst wall, histologically, consisted of the arachnoid cell lining. Light microscope examination showed the hypocellular membrane without glial tissue. Electron microscope examination showed that the cyst lining cells adhered by an interdigitation with desmosome and the cells had no microvilli. These findings were compatible with the features of an arachnoid cyst.