RESUMEN
OBJECTIVE: The purpose of this study is to characterize the distribution of posterior inferior cerebellar artery (PICA) aneurysm, the computed tomography (CT) patterns of hemorrhage, and the clinical presentation thereof. METHODS: We reviewed the records 1050 patients with intracranial aneurysms treated at our institution between January 1999 and November 2003. Upon clinical review of radiological data and postoperative reports, we found 20 patients with PICA aneurysms. RESULTS: The incidence of PICA aneurysms was 1.9% of all intracranial aneurysms. The location of PICA aneurysms varied. Of the 20 PICA aneurysm cases, ruptured aneurysms accounted for 18 cases. Review of only these ruptured cases resulted in the following observations : Subarachnoid hemorrhage (SAH) was presented in 94.4% of cases. Isolated infratentorial and supratentorial SAH was present in 7 cases (38.9%) and 2 cases (11.1%), respectively. SAH involving the infratentorial and supratentorial region was present in 8 cases (44.5%). Intraventricular hemorrhage (IVH) with or without associated SAH was seen in 77.8% of cases, whereas isolated IVH was seen in only one case. Perimedullary large hematoma was present in 50% of cases, while the hematoma was consistently thicker on the aneurysm side. Hydrochephalus was present in 16 cases (88.9%). Although patients' postoperative outcomes were excellent or good in 70% of the above cases, initial angiograms failed to reveal ruptured PICA aneurysms in 3 cases. CONCLUSION: PICA aneurysm is rare in most aneurysm cases. However, awareness of a possibility of PICA aneurysm and its features are still nonetheless important. IVH and hydrocephalus are commonly presented with a ruptured PICA aneurysm and complete vertebral angiography is a required to recognize this condition.