In five patients authors used the Stereoplan Plus programme with a PC work station and Zamora- no-Dujovny stereotactic device for virtual planning of cystocisternostomy or cystoventriculostomy in cysts with a masse effect. The accuracy of this system was plus minus 1 mm for navigation of the endoscope into the cyst or lateral ventricle for intervention. Duration of intervention was 20 - 30 minutes. The communication was effected by a balloon-expandible stent.

        Key words: navigation - virtual reality - stereotaxy - minimal invazivity - cerebral endoscopy - cystocisternostomy or cystoventriculostomy - stent