A 55-year-old man, who had experienced a headache for two days and then suddenly lost consciousness, presented at our hospital. Computed tomography (CT) revealed a right side dominant subarachnoid hemorrhage mainly in the right basal cistern and posterior fossa. Both CT angiography and cerebral angiography revealed the pearl-and-string sign in the intracranial portions of the bilateral vertebral arteries (VAs), involving the origin of the posterior inferior cerebellar arteries (PICAs). Trapping of the dissecting aneurysm (DA) in the right VA with an occipital artery-PICA anastomosis was performed as an emergency surgery. The postoperative course was uneventful; however, he suddenly lost consciousness on the seventh postoperative day. Both CT and CT angiography revealed a hemorrhage and an increase in the size of the left VADA. The patient died 2 days later. The autopsy revealed a rupture of the left VADA. The increase in the hemodynamic stress to the contralateral VA had induced the VADA rupture. Thus, during surgeries involving the bilateral VADAs, it is important to not change the hemodynamic stress to the unilateral VA.