A Vertebral Artery-Posterior Inferior Cerebellar Artery Junction Aneurysm : Report of a Case

The authors report the case of a 58-year-old woman with a severe subarachnoid hemorrhage (SAH) caused by a ruptured aneurysm at the junction of the vertebral artery (VA) and posterior inferior cerebellar artery (PICA), slightly distal to the site of the dural penetration. The patient had experienced a sudden onset of severe nuckal pain but showed no neurological deficits, and a CT scan taken on admission revealed that the SAH was mainly confined to the posterior fossa. Although the initial cerebral angiograms appeared to be normal, the patient became comatose on rebleeding. After conservative therapy was initiated, she became conscious and angiography was again performed 27 days after onset. This revealed left vertebral artery aneurysm just below the foramen magnum. Thus, a suboccipital craniotomy was performed and an aneurysm was seen at the VA-PICA junction ; this aneurysm was sited very low, slightly distal to the site of dural penetration. The aneurysm was successfully clipped without disturbing the lower cranial nerves. Postoperatively, the patient merely exhibited transient left hemiparesis and diplopia, presumably caused by a vasospasm. PICA aneurysms and related aneurysms of this region show a great variation in their site of origin from the VA. A PICA originates below the foramen magnum in 18% of cases, but a VA-PICA aneurysm that develops at the site of the dural penetration, as in this case, is extremely rare.