Fig. 4

Digital subtraction angiographies are shown. a Left carotid artery angiography in the late venous phase, (b) in the last part of the venous phase. c Left vertebral artery angiography in the early venous phase, (d) in the late venous phase. Cerebral venous blood flowed into inferior petrosal vein through sigmoid sinus (a), and subsequently flowed backward from the inferior petrosal vein into the cavernous (arrow) (b). Digital subtraction angiography revealed left hypoplastic transvers sinus (arrow head). Blood flow through left transvers sinus was delayed and not much due to left hypoplastic sinus (b, c). Venous blood flowed normally into bilateral transverse sinus in the early venous phase (c), and furthermore, into the basilar venous plexus due to left hypoplastic transverse sinus in the late venous phase (d)