Risk assessment of hemorrhage of posterior inferior cerebellar artery aneurysms in posterior fossa arteriovenous malformations

BACKGROUND: Posterior fossa arteriovenous malformations (AVMs) are associated with increased risk of rupture and severe consequences fromsuch rupture. The hemorrhagic risk of prenidal aneurysms (anr) on the posterior inferior cerebellar artery (PICA) may exceed that of the AVM in posterior fossa AVMs fed by PICA (PICA-AVM). OBJECTIVE: To characterize the relative risks of aneurysm and AVM hemorrhage in patients with posterior fossa AVMs. METHODS: We retrospectively reviewed patients diagnosed with AVM. Patients with posterior fossa AVMs were divided into 3 groups: PICA-AVM with prenidal aneurysm (PICA-AVM-anr group), PICA-AVMwithout prenidal aneurysm(PICA-AVMgroup), andAVMs without PICA feeder with/without aneurysm(AVM-only group). Patient and lesion characteristics and treatment outcomeswere compared. ANOVA and chi squared testswere used for statistical analyses. RESULTS: Our cohort included 85 patients. Mean age was 45.3 ± 18.1 yr, with 43(50.6%) female patients. Fifty-one patients (60.0%) had hemorrhagic presentation, and 27 (31.8%) experienced acute hydrocephalus. Patients in the PICA-AVM-anr group (n = 11) weremore likely to present with aneurysmal subarachnoid hemorrhage (SAH; P = .005) and less likely to have AVM rupture (P < .001). Ten (90.9%) patients presented with hemorrhage, 6 (60.0%) of which resulted from aneurysm rupture. Of these 6, 5 (83.3%) had acute hydrocephalus. No patients with AVM rupture had hydrocephalus. Eight (72.7%) received aneurysm treatment prior to AVMtreatment. Therewere no significant differences in posttreatment outcomes dependent on treatment order. CONCLUSION: In addition to relatively higher risk of AVM rupture from infratentorial location and prenidal aneurysm, a higher risk of aneurysmrupture rather thanAVMrupture was observed in patients with PICA-AVM-anr complex.