Patterns of hemorrhage with ruptured posterior inferior cerebellar artery aneurysms: CT findings in 44 cases

We intended to characterize the CT patterns of hemorrhage associated with ruptured posterior inferior cerebellar artery (PICA) aneurysms. CT scans of 44 cases of angiographically confirmed ruptured saccular PICA aneurysms (4) aneurysms at the junction of the vertebral artery and the PICA and three distal PICA aneurysms) were retrospectively reviewed. All scans had been obtained within 2 days of the subarachnoid hemorrhage (SAH) (day 0 [less than 24 hr], 35 patients; day 1, eight patients; day 2, one patient). Presence or absence of hemorrhage in specific subarachnoid, intraventricular, and intraparenchymal locations was noted, as were the presence and degree of hydrocephalus. Posterior fossa SAH was present in 95% of cases. Isolated posterior fossa SAH was present in 30% of cases, but in no case was isolated supratentorial SAH present. Supratentorial SAH was present in 70% of cases. SAH involving the sylvian fissure or the interhemispheric region was present in 25% and 23% of cases, respectively. SAH along the convexity was present in 2% of cases. Intraventricular hemorrhage (IVH) with or without associated SAH was seen in 95% of cases, whereas isolated IVH was seen in 5% of cases. Hydrocephalus was present in 95% of cases and was moderate to marked in 70%. Both IVH and hydrocephalus were present in 93% of cases. Ruptured PICA aneurysms almost always coexist with hydrocephalus and IVH, as seen in 93% of cases, and almost never coexist with SAH along the convexity. The most common pattern of hemorrhage associated with such aneurysms includes IVH and posterior fossa hemorrhage. Extensive supratentorial SAH, in conjunction with posterior fossa SAH, is a common finding in patients with ruptured PICA aneurysms. SAH isolated to the posterior fossa is present in a sizeable minority of cases.