Stereotactic radiosurgery for noncavernous sinus dural arteriovenous fistulas: treatment outcomes and their predictors

OBJECTIVE Stereotactic radiosurgery (SRS) has emerged as a safe and effective treatment modality for dural arteriovenous fistulas (dAVFs), particularly cavernous sinus (CS) dAVFs. However, the long-term outcomes of non-CS dAVFs are not well known. This study aimed to evaluate the efficacy and safety of SRS for non-CS dAVFs and to investigate the risk factors for incomplete obliteration. METHODS Between 2007 and 2020, 65 non-CS dAVFs in 63 patients were treated using SRS at a single institution. Demographic characteristics, initial clinical presentations, clinical outcomes, and radiological findings were retrospectively reviewed. The procedure-related complications were assessed. Radiological outcomes were evaluated as complete obliteration, incomplete obliteration, and angiographic worsening, whereas clinical outcomes were evaluated for symptom recovery. RESULTS At a median follow-up of 17 months, the overall complete obliteration rate was 63.1%, and the cumulative obliteration rates were 24.6%, 60.0%, 70.0%, and 74.3% at 12, 24, 36, and 48 months, respectively. Six patients underwent retreatment due to angiographic worsening; in 5 of these patients, recruitment of arterial feeders was newly observed in the adjacent sinus, which was not treated in the initial SRS. In the multivariate analysis, high-flow shunt and venous ectasia were associated with incomplete obliteration. No adverse events occurred after SRS. CONCLUSIONS SRS for non-CS dAVFs is safe, and its efficacy is highly variable according to location. High-flow shunts may indicate greater radioresistance. In the retreated cases, new fistulas tended to be accompanied by sinus steno-occlusion and formed in the adjacent sinus segments.