The "leaf" or extension of the chiasmatic cistern above the chiasma, which is separated from the optic recess of the third ventricle by the thin lamina terminalis, has been called the suprachiasmatic cistern. As spaces filled with freely circulating cerebrospinal fluid, cisterns receive little direct study, but are mentioned in pathological conditions. Cysts and tumors of the lamina terminalis extend into the suprachiasmatic cistern, as can pituitary tumors, or the cistern can be partially or completely effaced by injury and hematoma[1] or by blockage of the cerebral aqueduct.