Clinical relevance of associated aneurysms with arteriovenous malformations of the posterior fossa.

The aim of this study was to determine the frequency of aneurysms associated with arteriovenous malformations (AVMs) of the posterior fossa and their relation to hemorrhagic presentation in comparison to supratentorial AVMs. We performed a retrospective analysis of 474 patients with intracranial AVMs treated in our center from 1990 to 2010. Patients were analyzed for AVM size, drainage type and their clinical course with focus on vessel anomalies including AVM-associated aneurysms. Seventeen (30%) of 57 posterior fossa AVMs versus 46 (11%) of 417 supratentorial AVMs were associated with aneurysms. In six (10.5%) versus seven (1.7%) patients, respectively, flow-associated aneurysms were the source of hemorrhage. Infratentorial location of an AVM was a significant risk factor for the incidence (p < 0.001) and rupture (p < 0.001) of AVM-associated aneurysms. Feeding artery aneurysms in particular represented a risk factor for hemorrhage in the overall group of AVM patients, independently of the location (p < 0.001). The majority of patients with a posterior fossa AVM were treated by combined embolization and surgical removal within one procedure (n = 33, 58%). Feeding artery aneurysms were excluded by endovascular coiling or surgical clipping whenever feasible. Overall treatment-associated permanent morbidity in the subgroup of posterior fossa AVMs was 11% (n = 6) and mortality 4% (n = 2). Posterior fossa AVMs display a significantly higher frequency of associated aneurysms of the adjacent vessels that are correlated to the high bleeding rate compared to AVMs of the supratentorial compartment. We therefore recommend aggressive AVM treatment including the exclusion of associated aneurysms as a minimal therapeutic goal whenever possible.