The Significance of Venous Outflow Obstruction in Dural Arteriovenous Fistulas.

Background and objectives: The association between venous outflow obstruction (VOO) and cranial dural arteriovenous fistulas (DAVF) is well established; however, its impact on the natural history remains unclear. This article aims to characterize its clinical significance and further describe the natural history of DAVF.

Methods: A retrospective cohort study was performed at a tertiary neurosurgical center. Cohort characteristics were described with a focus on patients with VOO. Annualized event rates and risk factors for hemorrhage and nonhemorrhagic neurological events (NHNE) were also investigated.

Results: The cohort consisted of 108 patients, 74 of which had follow-up greater than 1 month including 24 low-grade (Cognard I-IIa) fistulas (21.7 lesion-years) and 50 high-grade (Cognard IIb-V) fistulas (60 lesion-years). 18 patients with concurrent VOO were identified; most (83.3%) were high-grade DAVF and had obstruction of the direct draining sinus. Annualized rates of hemorrhage and NHNE for high-grade DAVF were 4.6% and 10.6%, respectively. Those high-grade lesions presenting with hemorrhage had a 10.9% annual rate of recurrent hemorrhage, while those presenting with NHNE had a 22.3% annual rate of subsequent NHNE. Fifteen high-grade DAVF with VOO (15.7 lesion-years) had annualized hemorrhage and NHNE rates of 6.4% and 31.9%, respectively. High radiological grade, an aggressive index presentation, and the presence of VOO were the predictors of hemorrhage and NHNE (P < .05).

Conclusion: This study reports a novel association between VOO and a more aggressive clinical course. DAVF with high-grade angiographic features, an aggressive index presentation, or VOO should be considered for early treatment.