Onyx Embolization Before the Surgical Treatment of Grade III Spetzler-Martin Brain Arteriovenous Malformations: Single-Center Experience and Technical Nuances.

Background: Grade III Spetzler-Martin brain arteriovenous malformations (AVMs) are a specific set of AVMs with high variability in terms of site, size, angioarchitecture, flow dynamics, and involvement of eloquent areas. Surgery preceded by preoperative embolization has been reported as a useful treatment option for these lesions. The aim of this study is to report outcomes and personal experience of combined preoperative Onyx embolization and surgical resection on a consecutive series of grade III brain AVMs.

Methods: Between 2005 and 2017, 27 grade III AVMs were treated by means of a staged Onyx embolization and subsequent surgical treatment. Site and size of the AVMs, embolization, and surgical specifics as well as complications and outcomes were retrospectively reviewed.

Results: All AVMs were supratentorial, 13 of which were hemorrhagic. Mean nidal volume was 19.5 mL. Average embolization sessions were 1.6. Mean embolization-related obliteration rate and morbidity were 28.8% and 3.7%, respectively. Surgery was performed within 3.7 days on average. In our experience, Onyx embolization made the nidus excision easier, facilitated the hemostasis, and contributed to the early identification of the lesion in cases of small or racemose nidus. The surgical obliteration rate was 92.6%. A good overall outcome (modified Rankin Scale score 0-2) was achieved in 70.4% of patients.

Conclusions: In our experience, preoperative Onyx embolization helped the surgical management of grade III Spetzler-Martin brain AVMs. Careful evaluation of the angioarchitecture, a tailored strategy in the embolization process, and full cooperation within the neurosurgical-neuroendovascular team are mandatory.