Outcomes and Complications of Brainstem Arteriovenous Malformation (AVM) Embolization: A Systematic Review

Brainstem arteriovenous malformations (AVMs) are rare, high-risk lesions with controversial endovascular management. We systematically reviewed the literature to clarify obliteration rates, complications, and mortality related to embolization of intrinsic brainstem AVMs and to situate the technique within modern multimodal care. Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidance, PubMed and Scopus were searched without date limits using combined terms related to brainstem structures (midbrain, pons, medulla oblongata), arteriovenous malformations, and embolization. Original English-language reports that provided detailed clinical or radiographic outcomes after endovascular treatment were eligible. Two reviewers independently screened records, extracted data, and assessed quality with ROBINS-I or CARE. Due to heterogeneity, results were summarized descriptively. Nine studies (aged 13-79 years) met the criteria. Hemorrhage was the initial presenting event in 62%, followed by cranial nerve or long-tract deficits. Embolic agents used included n-butyl-cyanoacrylate, Onyx, glue, and coils; most lesions were treated in one (60%) or two sessions. Reported nidus obliteration ranged from 23% to 100%; complete angiographic cure was achieved in all patients in three small series that employed either the Pressure-Cooker Technique or adjunctive microsurgery/radiosurgery. Procedure-related morbidity included new neurological deficits (up to 24%), infarction (7%), and rebleed (10%). The 30-day mortality ranged from 0% to 5% across series. Median follow-up was 12 months (range 1-48), with a few late hemorrhages. Endovascular embolization can achieve meaningful flow reduction and, in selected cases, complete obliteration of brainstem AVMs, but success and safety vary widely.