Fig. 1

Preoperative angiography. a Left vertebral artery angiography (VAG). The left PICA is agenesis (frontal view). b Right VAG (frontal view) The tentorial sinus is shown as the drainage route (arrow). The right PICA perfuses bilateral inferior cerebellar hemispheres. c Three-dimensional rotational angiography (3D-RA, lateral view) shows the distal posterior inferior cerebellar artery aneurysm(DPICAAn) located at the telovelotonsillar segment of the right PICA with a bleb (large arrow), with neck 3.7 mm and the maximum diameter 7.3 mm; in addition, the AVM feeders are from the left SCA and the right PICA (small arrows). The nidus of AVM is about 18 mm