Venous outflow restriction as a predictor of cavernous sinus dural arteriovenous fistula obliteration after Gamma Knife surgery

OBJECTIVE: Gamma Knife surgery (GKS) obliterates 65%-87% of cavernous sinus dural arteriovenous fistulas (CSDAVFs). However, the hemodynamic effect on GKS outcomes is relatively unknown. The authors thus used the classification scheme developed by Suh et al. to explore this effect. METHODS: The authors retrospectively (1993-2016) included 123 patients with CSDAVFs who received GKS alone at the institute and classified them as proliferative type (PT; n = 23), restrictive type (RT; n = 61), or late restrictive type (LRT; n = 39) after analyzing their pre-GKS angiography images. Treatment parameters, the presence of numerous arterial feeders, and venous drainage numbers were compared across the CSDAVF types. Patients' follow-up MR images were evaluated for the presence of complete obliteration. A Kaplan-Meier analysis was conducted to determine the correlation between CSDAVF types and outcomes. RESULTS: The 36-month probability of complete obliteration was 74.3% for all patients, with no significant differences across types (p = 0.56). PT had the largest radiation volume (6.5 cm3, p < 0.001), the most isocenters (5, p = 0.015) and venous drainage routes (3, p < 0.001), and the lowest peripheral dose (16.6 Gy, p = 0.011) and isodose level coverage (64.3%, p = 0.006). CSDAVFs presenting with ocular patterns were less likely to be completely obliterated (hazard ratio 0.531, p = 0.009). After adjustment for age, CSDAVFs with more venous drainage routes were less likely to be completely obliterated (hazard ratio 0.784, p = 0.039). CONCLUSIONS: GKS is an equally effective treatment option for all 3 CSDAVF types. Furthermore, the number of venous drainage routes may help in predicting treatment outcomes and making therapeutic decisions.