interpeduncular cistern interpeduncular cistern the interpeduncular cistern of sweeney is the subarachnoid cistern that encloses the cerebral peduncles and the structures contained in the interpeduncular fossa and contains the arterial circle of willis as well as the oculomotor nerve (cn3). interpeduncular cisterndiagram showing the positions of the three principal subarachnoid cisternæ. (interpeduncular cistern labeled at left center.)detailsidentifierslatincisterna interpeduncularis, cisterna basalista98a14.1.01.212ta25397fma83718anatomical terms of neuroanatomy