Nonaneurysmal perimesencephalic subarachnoid hemorrhage: CT and MR patterns that differ from aneurysmal rupture. - Rinkel,G.JE.; Wijdicks,E.FM.; Vermeulen,M.; Ramos,L.MP.; Tanghe,H.LJ.; Kasan,D.; Meiners,L.C.; Gijn,J van. (AJNR, 1991)