Surgical Outcomes in Brainstem Arteriovenous Malformations: A Systematic Review and Meta-Analysis

Abstract

Abstract INTRODUCTION Due to their propensity to hemorrhage and the surrounding eloquent tissue, brainstem arteriovenous malformations (BS-AVMs) carry significantly higher risk of morbidity and mortality compared to their supratentorial counterparts. In this study, we examined the literature for outcomes following microsurgery and performed an analysis to determine preoperative characteristics that can best predict outcome. METHODS We performed a Pubmed and Web of Science search using the terms “brainstem,” “AVM,” “arteriovenous malformation,” and “outcome.” We collected data on demographics, presentation, AVM characteristics, treatment modalities, angiographic obliteration, and functional outcome. We then ran a multivariate regression analysis to determine factors correlated to outcome. RESULTS We found 114 papers, of which 15 were included in our systematic review and 6 in our meta-analysis. There were 187 BS-AVM patients (59.7% male, mean age 37.8 yr, 70% hemorrhagic presentation) who underwent microsurgical resection. In total, 87% were <3 cm in size with 90% Spetzler-Martin III or less. The AVMs were located in the pons 44.5%, midbrain 38.7%, and medulla 16.8% of the time. Treatment methods included microsurgery alone 65.5%, radiation alone 10.3%, embolization alone 3.4%, microsurgery plus radiation 2.2%, microsurgery plus embolization 12%, radiation plus embolization 2.2%, and >3 modalities in 5.2% of cases. Postoperatively, 78% of AVMs were completely obliterated and 73% of patients were improved or unchanged in their functional outcome. Mean follow-up was 39.1 mo. Multivariate regression analysis showed hemorrhage (P < .001) to be significantly correlated with improved or unchanged functional outcome with medullary location (P = .067) and older age (P = .1) trending toward significance. CONCLUSION BS-AVMs occur in 20 to 50 yr old male patients and predominantly present with hemorrhage. They are most commonly located in the upper brainstem. Obliteration rates are favorable with nearly 3 quarters of patients improving or remaining unchanged in function. Factors associated with favorable functional outcome include hemorrhage, and to lesser degrees, medullary location and older age.