Cystic Dilatation of the Cistern of the Velum Interpositum

Three peculiar cases with cystic dilatation of the “cavum Veli interpositi” have been observed. This structure contains a narrow subarachnoid space; dilatation of this cistern was rarely found in conditions interfering with normal drainage of the subarachnoidal pathways. We describe the clinical and MR findings due to this very uncommon condition; correlative anatomy and differential diagnosis are also discussed.