[Occasional disclosure of large arachnoid cysts in 2 subjects].

Two old men in whom the CT and MR scans had unexpectedly shown an enormous arachnoid cyst in the fronto-temporo-parietal region, underwent neuropsychological examination. This did not show any neuropsychological abnormality. This is in accordance with the hypothesis that the cyst represents a dysontogenetic disorder with very slow growth, leaving functionally normal the cerebral structures shifted.