The impact of associated nidal lesions in outcome of brain arteriovenous malformations after radiosurgery with or without embolization

Abstract Background Radiosurgery is a valuable option to treat arteriovenous malformations. There are correlations between some morphological nidal features and final results, and the benefits of preradiosurgical embolization have not been well established thus far. Methods Analysis of a longitudinal cohort of 47 consecutive patients who underwent radiosurgery with or without previous embolization. Embolizations were performed exclusively with n-butyl cyanoacrylate. Radiosurgery was delivered either as a single or divided in up to 5 equal fractions. Clinical and radiological follow up of at least 36 months was obtained. Presence of nidal lesions, such as aneurysms, venous outflow stenosis, venous outflow ectasias and/or intranidal arteriovenous fistulas were evaluated and their relation with outcome and complications were studied. Results 68.1% of patients presented with hemorrhagic event; of these, 62.5 % harbored intranidal arteriovenous fistulas, 83.3% had venous ectasias and 90% had venous outflow stenosis. Occlusion rate of embolization plus radiosurgery was 46.1% and SRS alone was 52.4% (p = .671). Variables significantly associated with obliteration were lower nidus volume, lack of intranidal arteriovenous fistula, higher SRS dose and lower radiosurgical based AVM scale score. Conclusions An untreated arteriovenous fistula inside the AVM at the moment of SRS was associated with lower cure rates (p = .001). Embolization followed by radiosurgery was not superior to radiosurgery alone, although targeted embolization of intranidal arteriovenous fistulae in order to increase obliteration rates and to protect the patient from bleeding during the radiosurgery latency period should be considered.