Posterior fossa brain arteriovenous malformations

Background Posterior fossa brain arteriovenous malformations (PFbAVM) are relatively rare brain disorders but have a high risk of hemorrhage. Endovascular embolization to reduce the lesion size before treatment may improve the outcome of PFbAVM. The purposes of this study were to identify risk factors associated with hemorrhage in PFbAVM and to assess clinical outcomes in patients receiving initial endovascular embolization. Material and methods From 1999 to 2013 a total of 63 patients with PFbAVMs were treated (31 males and 32 females, 14.1 % of all AVM cases). A retrospective examination of patient demographics, clinical presentation, angiographic features, treatment modalities, complications and outcomes was carried out. The re-hemorrhage rate, obliteration rate and modified Rankin scale (MRS) were used as measures of outcome. Results Of the 63 PFbAVM patients 54 (85.7 %) exhibited hemorrhage and 15 had confirmed aneurysms. The cerebellar location ( P = 0.007) and deep venous drainage ( P = 0.012) were independent predictors of hemorrhage in multivariate analyses. The mean estimated devascularization was 46.9 % (range 10–100 %) in the 20 patients (31.7 %) treated by endovascular embolization. The 16 patients with residual niduses were further treated by radiosurgery, microsurgery or embolization. Complete obliteration was attained in 12 patients (67 %) while 2 (5.7 %) were left with persisting neurological deficits and 1 had a re-hemorrhage 3 years later (annual rate of 4.6 %). Favorable outcome (MRS ≤ 2) was obtained in the 20 patients receiving initial endovascular embolization ( P = 0.039 versus preoperative MRS). Conclusion Cerebellar location and deep venous drainage are predictors of hemorrhage in PFbAVM. Adjuvant endovascular embolization is useful and safe for PFbAVM prior to microsurgery or radiosurgery.